Fisheries science JSFS , tập 76, số 6, 2010 11

Fish Sci (2010) 76:893–899 DOI 10.1007/s12562-010-0294-7 ORIGINAL ARTICLE Fisheries Measurement of swimming speed of giant jellyfish Nemopilema nomurai using acoustics and visualization analysis Kyounghoon Lee • Bong-Seong Bae In-Ok Kim • Won-Deuk Yoon • Received: 22 April 2010 / Accepted: 10 September 2010 / Published online: 23 October 2010 Ó The Japanese Society of Fisheries Science 2010 Abstract A species of giant jellyfish, Nemopilema nomurai, which has appeared only recently in the East China Sea, is an emerging nuisance in the northeastern region of Asia because of its extensive damage to fisheries Until now, the biomass estimates of these jellyfish have mainly been obtained using trawl sampling and sighting survey methods However, it is also necessary to determine the origin and diurnal migration patterns of these jellyfish Drawbacks of the trawl sampling method are that it is effective only in estimating the density of jellyfish population distributed throughout the entire water column and requires considerable time Another common analysis technique is the sighting method, which is effective only in the estimation of he density of jellyfish distributed in surface areas The sighting method can determine distributions over wide areas in a short time This method has limitations in investigating the vertical distribution and swimming behavior of jellyfishes In our study, we utilized an echo sounding method extensively and effectively to overcome K Lee (&) Fisheries System Engineering Division, Fundamental Research Department, National Fisheries Research and Development Institute, Busan 619-705, Korea e-mail: khlee71@nfrdi.go.kr B.-S Bae Aquaculture Industry Division, East Sea Fisheries Research Institute, Gangneung 210-861, Korea I.-O Kim Aquaculture Industry Division, West Sea Fisheries Research Institute, Incheon 400-420, Korea W.-D Yoon Fishery and Ocean Information Division, Research and Development Planning Department, National Fisheries Research and Development Institute, Busan 602-092, Korea these limitations Our method involved the use of a scientific echo sounder, acoustic camera, and conductivitytemperature-depth instrument during the drifting of a research vessel at various stations in the Yellow Sea The acoustical method of particle tracking velocimetry (PTV) was used to analyze the swimming speed according to the vertical distribution of N nomurai jellyfish Results of the scientific echo sounder indicated that the jellyfish were mainly present in the water column from the surface up to a depth of 40 m The mean swimming speed of the jellyfish was estimated as being 0.6 times the bell size (BS), with a tendency to maintain a certain speed Further, results of a Monte Carlo simulation showed that the swimming speed was in the range of 0.46–0.89 BS These results might be used as an index in a migration model, which may be useful to forecast the behavior and origin of the giant jellyfish entering inshore areas on a massive scale in northeastern Asia Keywords Giant jellyfish Á Nemopilema nomurai Á Swimming speed Á Vertical distribution Á PTV visualization analysis Introduction The giant jellyfish Nemopilema nomurai, which has appeared in the East China Sea only recently, is presumed to be damaging the Korean and Japanese fishing industries and causing a nuisance along the coasts of northeastern Asia Korea and Japan have recently undertaken research on the distributed density of the jellyfish by employing trawl sampling [1] and sighting methods They have also developed discharge devices for jellyfish to minimize the damage to the fishing industry [2, 3] It is very important to 123 894 understand the origin, migration, and behavior patterns of the jellyfish as they move toward shore [4–6] The spatial distribution of giant jellyfish has mainly been determined by midwater trawling and sighting surveys A drawback of the trawl sampling method is that it is effective only in the estimation of the density of jellyfish distributed in the main water column, and thus, it takes a considerable amount of time Additionally, while the sighting method provides a fast estimate of populations, it provides only an effective estimate of jellyfish density on the surface Recently, underwater acoustics has been utilized extensively and effectively to investigate the spatial and vertical distribution of jellyfish, as well as their swimming behavior patterns as biological information To estimate population density in a water column using hydroacoustic techniques, the sound-scattering characteristics of each kind of jellyfish need to be elucidated, and these characteristics should be differentiated from those of other scatterers in the same layer, such as zooplankton and nekton [7–9] Acoustic camera systems have recently been developed and used to measure and monitor the swimming behavior and speed of jellyfish and other types of fish [10, 11] The speed of fish with good swimming ability can be estimated without considering the current field; however, the speed of jellyfish needs to be extracted from the surrounding current field because jellyfish are not strong swimmers With this as background, this study observed the distributions of giant jellyfish moving with the current at sites in the Yellow Sea during the summer, when the thermocline layer is sufficiently developed; the observations were carried out in water columns, and the vertical distribution of giant jellyfish as a function of conditions in the column was confirmed Additionally, the moving speed of giant jellyfish was recorded using an acoustic camera system along with suspended particles in the water column Then, by assuming that the jellyfish move in the same direction as the suspended particles, i.e., the current direction, the swimming ability of the jellyfish was estimated by analysis of the two-dimensional (2D) observed velocity of the particles This analysis was done using the particle tracking velocimetry (PTV) technique, where visualization analysis was applied to a thin plane of the volume flow images that were acquired by the acoustic cameras Fish Sci (2010) 76:893–899 Fig Map of Yellow Sea showing survey area for giant jellyfish Fisheries Research and Development Institute, Korea, during the summer, when giant jellyfish are found in massive numbers mainly around northeastern Asia (Fig 1) The surrounding oceanographic data were collected at 10 stations concurrently with the acoustic monitoring surveys The water temperature and salinity were obtained using a conductivity-temperature-depth (CTD) instrument (SBE911, Sea-Bird, USA), and these data were compared with the vertical distribution of the jellyfish, which was determined using two frequencies of the scientific echosounder (EK60-38, 120 kHz, Simrad, Norway) installed on the research vessel at each station When the research vessel was drifting at night, the jellyfish were monitored constantly using an acoustic camera (DIDSON, Sound Metrics, USA) and scientific echosounder (EK60-120 kHz, Simrad, Norway), each installed on the side of the research vessel (Fig 2) The acoustic camera systems were used to analyze the swimming behavior of subject organisms The images of the jellyfish moved by the current were analyzed to determine their swimming ability in relation to their bell size (BS) This was done by applying the flow visualization technique Materials and methods Flow visualization analysis Survey area and data acquisitions Measurements in this study were conducted in the Yellow Sea using Tamgu (R/V 2, 180G/T) of the National 123 The PTV technique calculates particle displacement by analyzing the quantitative velocity field This technique was originally used to calculate average velocity in order to Fish Sci (2010) 76:893–899 895 Fig Experimental setup for measurement of moving speed of giant jellyfish; the setup consists of an acoustic camera and a 120 kHz split beam echosounder The swimming speed of the jellyfish is extracted from the current 2D velocity using PVT as shown in Fig ! When jellyfish move as vector A with a swimming tilt ! angle h against suspended particles moving as vector B , the swimming speed can be estimated by the BS of jellyfish acquired from the acoustic image data Then, the swimming tilt angle in relation to the current direction is represented by (?) and (-) in the case of upward and downward directions, respectively Additionally, it is certain that the moving behavior of the jellyfish is affected by the current; the jellyfish are considered to be moving faster or slower than the current speed depending on the current direction relative to the second image of particle "A" at time t (a) ( x2,y2) Δy compute direct correlation coefficient or the Fourier conversion for the scattered particles’ intensity distribution within the observed section of flow visuals [12] Hence, PTV calculates the cross-correlation function between observation sections using two visuals obtained from intervals of specific durations It assumes velocity by considering the peak value achieved through the calculation to be the average displacement (Fig 3a) The PTV software program used in this analysis was a Thinks 2D PTV program (T&Tech, Korea), which employs a twoframe cross-correlation algorithm to perform the visual analysis The cross-correlation function is shown in Fig 3b and expressed in Eq When this correlation condition is satisfied, the particle-movement vector values can be estimated The values of fi and gi are that of a pixel in the image, and the resolution of our acoustic camera image is cm/pixel Pn2 ðfi À fi Þðgi À gi Þ ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi q Cfg ¼ P i¼1 ð1Þ n2 Pn 2 i¼1 ðfi À fi Þ i¼1 ðgi À gi Þ first image of particle "A" at time t ( x1,y1) Δx (b) Fig Schematic diagram of particle tracking velocimetry (PTV) swimming direction of the jellyfish In this case, the cause can be considered in measured low values by resistance against the jellyfish’s bell in a hovering state as a physiological conservation of its energy so that it will be considered to any uncertainty of the mean swimming speed in 123 896 Fish Sci (2010) 76:893–899 Fig Swimming speed of jellyfish as measured from 2D current profiles relation to the jellyfish’s bell size A Monte Carlo simulation was performed to analyze the minimum, maximum, and mean swimming speeds of the jellyfish The simulation was performed by assuming a normal swimming speed distribution relative to the mean BS of the jellyfish The variation in the swimming speed was established to be within the range of ±5% Fig Vertical distribution of giant jellyfish as measured by a scientific echosounder Results Oceanographic environment and vertical distribution Typically, during the summer season, the nighttime water column in the Yellow Sea forms thermocline layers whose temperature differs with depth However, strong thermocline layers are generally formed at depths of 10–30 m with a water temperature difference of more than 13°C According to the salinity data, strong low-salinity troughs were formed around the surface layer (Fig 5) Their vertical distribution at each station was observed and analyzed by two frequencies of the scientific echo sounder (Fig 6), and the BS was obtained by bottom trawl sampling at each station (Fig 7) During the observation period in July 2007, the population of giant jellyfish following the Kuroshio current northward through the Yellow Sea was found to move day and night from the surface layer to a depth of 40 m at 10 stations There was not nearly distributed in the water Fig Variation of temperature (a) and salinity (b) of water column in survey area The box marks the median and the 25th and 75th percentiles of the oceanographic data; the whiskers show the 10th and 90th percentile plots of the oceanographic data 123 Fig Individual and averaged bell sizes of giant jellyfish sampled at each station using the bottom trawl net in 2007 columns deeper than 40 m depth with a stabilized water temperature and salinity The average BS of giant jellyfish was 0.30 m, and jellyfish with larger BSs had a higher density in the southern area than in the northern areas Fish Sci (2010) 76:893–899 897 Table Swimming speed in relation to bell size of N nomurai jellyfish Measured mean values Estimated values N nomurai Current Direction (°) Speed (m/s) Swimming speed (SS, m/s) SS/BS Bell size (BS, m) Speed (m/s) Direction (°) 0.245 0.497 11.0 0.497 -6.2 0.147 0.60 0.278 0.374 -15.8 0.553 -3.7 0.203 0.73 0.245 0.247 0.467 0.685 6.9 1.2 0.530 0.631 -5.4 9.1 0.123 0.106 0.50 0.43 0.283 0.500 2.4 0.441 -15.0 0.153 0.54 0.331 0.528 9.4 0.441 -14.9 0.222 0.67 0.647 1.186 -8.9 1.528 -2.9 0.370 0.57 0.680 1.430 2.8 1.627 -15.7 0.529 0.78 Average Swimming speed Table shows the relationship between the mean swimming speed (based on the mean moving speed of suspended particles) and the bell size of the jellyfish, obtained by measuring the velocity fields using the PTV analysis of data measured at each station and stored in the acoustic camera The swimming behavior of jellyfish in the open sea showed various tilt angles of hovering, which differed with the current When the current direction was along the horizontal axis in 2D vectors, the tilt angle was measured in the up-downward direction, as shown in Table These values were not considered in absolute terms because they were measured while the test vessel rolled and pitched owing to sea conditions In order to estimate the swimming ability of the jellyfish with high precision, the acoustic images were analyzed only under conditions where the jellyfish moved and hovered along the current direction Further, the detected jellyfish were only considered in the recorded data when they were captured over a sufficiently large temporal span by the acoustic camera In our analysis of the mean swimming speed of N nomurai jellyfish, the BS of jellyfish ranged from 0.24 to 0.68 m in two different current fields estimated by PTV analysis using suspended particles (Table 1) The maximum mean net swimming speed was 0.529 m/s (BS 0.680 m), whereas the minimum mean swimming speed was 0.106 m/s (BS 0.247 m) The mean swimming speed ranged from 0.43 to 0.78 BS, and the swimming speed was estimated to be 0.60 times the BS Discussion When the thermocline layer was strongly formed within the surface layer, the population of N nomurai jellyfish within 0.60 the first 10 m numbered 959, accounting for approximately 42.7% of the total observed population The population was mainly distributed (98.6%) in the depth range between the surface and 50 m This shows that the N nomurai jellyfish are distributed within a wide range of water temperatures, from to 26°C, despite the presence of a strong thermocline layer From a general ecological perspective, it is assumed that in water columns with rapidly changing temperatures, the distribution of organisms tends to be separated or limited to small zones; however, in our study, N nomurai jellyfish were observed to be passing through a strong thermocline layer Such results confirm that, in contrast to the expected results [13], N nomurai jellyfish are distributed even in low-temperature zones although their population density around Korea drops rapidly in areas where the temperature is below 12°C Moreover, we found that in high-temperature water columns and lowsalinity waters in the upper thermocline layer, almost all giant jellyfish were distributed at water depths shallower than approximately 40 m [1] In survey areas, N nomurai jellyfish are mainly distributed in water columns with salinities in the wide range from 28.6 to 34.7 psu Lowsalinity waters on the surface layer existed at stations 8–10 in the southern Yellow Sea These results differ from the expectation that the influence of water temperature and salinity variation on the vertical distribution of N nomurai is not significant It seems that these jellyfish can adapt well to widely ranging conditions in the oceanographic environment Thus, considering the fact that zooplankton is the major food source of most jellyfish, it is necessary to elucidate the distribution of zooplankton throughout the water column in relation to their diurnal vertical migration Further, additional experiments should be conducted to elucidate the distribution of zooplankton in wide water columns close to the surface, as well as midwater layers and bottom layers in 123 898 123 0.6 Net Swimming Speed (m/s) consideration of the different environmental factors that relate to jellyfish The swimming behavior of jellyfish has been determined by the seawater circulation model in the field of physical oceanography as a way of estimating movements of N nomurai along currents This study was conducted in order to estimate timings of jellyfish migrating to inshore areas by using particle tracking under the assumption that jellyfish have relatively slow swimming speed from a temporary point of origin Moreover, jellyfish movement, migration, and swimming speed are currently being analyzed using ultrasonic pingers along inshore areas of Japan [11] In general, it is difficult to estimate the swimming speed of jellyfish because it is influenced by the current field, which significantly affects the measured swimming speed Recently, acoustic camera systems have been used to analyze the swimming behavior of subject organisms They are convenient tools for distinguishing the speed and size of organism movement, but they require current information in survey areas It is therefore difficult to acquire actual information on swimming behavior Thus, PTV analysis, applied to the flow visualization technique, was used along with visual data acquired by acoustic cameras to analyze a 2D velocity field at the specific depth where jellyfish move This analysis was also used to estimate the swimming ability of the jellyfish relative to their BS The mean swimming speed was estimated to be 0.6 times the BS, as shown in Table This mean speed was estimated to be six times the swimming speed (approximately 0.1 BS), as measured by N nomurai jellyfish’s vertical migration attached by pingers [11] These lower measured values were possibly attributable to their vertical migration speed, including horizontal current vectors at the depth at which they were moving Considering the relation between swimming speed and BS size as shown in Table 1, we suggest that there are mainly two size domains centered around BSs of 0.25 and 0.65 m, and the swimming abilities of the jellyfish differ The correlation between the BS and swimming speed of N nomurai jellyfish can be estimated as shown in Fig (R2 = 0.92) Further, it was clear that the movements of jellyfish are affected by the current speed; the jellyfish were considered as moving faster or slower than the current speed In the latter case, the slower speed is probably caused by resistance to the current of the jellyfish’s bell in a hovering state in an effort to conserve energy physiologically In addition, the Monte Carlo simulation was performed to analyze their swimming ability in relation to BS and to subsequently consider the uncertainty of the mean Fish Sci (2010) 76:893–899 0.5 R = 0.92 0.4 0.3 0.2 0.1 0.00 0.20 0.40 0.60 0.80 Bell Size (m) Fig Relationship between swimming speed and bell size of Nemopilema nomurai jellyfish swimming speed in relation to the size of the jellyfish The results of jellyfish’s swimming ability were estimated over the entire range from 0.46 to 0.82 BS as shown in Fig The swimming performance of the jellyfish was analyzed by performing a comparison between the kinematics acquired from video recordings and those simulated using the hydrodynamic model of jellyfish The comparison showed the experimental values of the swimming speed were comparable to the body weight (BW, in kg) of moon jellyfish Aurelia aurita [14]: u ¼ À1:4 Á ðBWÞ0:17 where BW can be calculated from the length–weight relationship: BW ¼ 0:0003 Á ðBSÞ2:5364 [13] Therefore, the swimming speed of N nomurai jellyfish ranged from 0.44 to 0.78 BS The average swimming speed was estimated as being 0.67 BS While the morphological characteristics of swimming speed of A aurita jellyfish are different from those of N nomurai jellyfish, the acceleration reactions of their swimming behaviors are similar; therefore, this result obtained by applying the PTV analysis is reliable for estimating the swimming speed of jellyfish in the field This study proves that visualization analysis using the PTV technique is more accurate than other analysis techniques (e.g., current meter, underwater acoustic camera) in estimating the swimming speed of N nomurai jellyfish as distinct from the current speed The visualization analysis using the PTV technique is useful even when the test vessel’s pitching and rolling are significant This study suggests the usefulness of an index in forecasting the migration behavior and origin, with consideration of the Fish Sci (2010) 76:893–899 899 Fig Results of Monte Carlo simulation according to the uncertainty of swimming speed of Nemopilema nomurai jellyfish current fields, of jellyfish that are found to be moving inshore on a massive scale in northeastern Asia Acknowledgments We thank the officers and crews of the R/V Tamgu for monitoring jellyfish in the survey periods We are grateful to Dr T Arimoto, Dr Y Matsushita and two anonymous reviewers for insightful comments that greatly helped to clarify and refine the paper This study was partially supported by a grant (RP-2009-FE-014) from the National Fisheries Research and Development Institute of Korea and the YSLME Nemopilema nomurai jellyfish monitoring project (2008–2009) References Honda N, Watanabe T (2007) Vertical distribution survey of the giant jellyfish Nemopilema nomurai by an underwater video camera attached to a midwater trawl net Nippon Suisan Gakkaishi 73:1042–1048 Matsushita Y, Honda K (2005) Method of designing and manufacturing JET (jellyfish excluder for towed fishing gear) for various towed fishing gears Nippon Suisan Gakkaishi 71:965– 967 Kim IO, An HC, Shin JK, Cha BJ (2008) The development of basic structure of jellyfish separator system for a trawl net J Kor Soc Fish Tech 44:99–111 Uye S, Ueno S, Hiromi J, Shiomi K (2005) Jellyfish blooms— ecology, biochemistry and food science for utilization Nippon Suisan Gakkaishi 71:968–994 Honda N, Watanabe T (2007) Observation of the giant jellyfish Nemopilema nomurai using an underwater acoustic camera Nippon Suisan Gakkaishi 73:919–921 Lee KH, Kim IO, Yoon WD, Shin JK, An HC (2007) A study on vertical distribution observation of jellyfish (Nemopilema nomurai) using acoustical and optical methods J Kor Soc Fish Tech 43:355–361 Colombo GA, Mianzan GH, Madirolas A (2003) Acoustic characterization of gelatinous-plankton aggregations: four case studies from the Argentine continental shelf ICES J Mar Sci 60:650–657 Brierley AS, Axelsen BE, Boyer DC, Lynam CP, Didcock CA, Boyer HJ, Sparks CAJ, Purcell JE, Gibbons MJ (2004) Singletarget echo detections of jellyfish ICES J Mar Sci 61:383–393 Hirose M, Mukai T, Hwang DJ, Iida K (2005) Target strength measurements on tethered live jellyfish Nemopilema nomurai Nippon Suisan Gakkaishi 71:571–577 10 Rose CS, Stoner AW, Matteson K (2005) Use of high-frequency imaging sonar to observe fish behaviour near baited fishing gears Fish Res 76:292–304 11 Honda N, Matsushita Y (2009) In situ measurement of swimming speed of giant jellyfish Nemopilema nomurai Nippon Suisan Gakkaishi 75:701–703 12 Lee YH, Choi JW (1996) Principle and classification of PIV J Kor Soc Mech Eng 36:1146–1162 13 National Fisheries Research and Development Institute (NFRDI) (2005) Annual report of jellyfish research NFRDI, Busan, Korea 14 McHenry MJ, Jed J (2003) The ontogenetic scaling of hydrodynamics and swimming performance in jellyfish (Aurelia aurita) J Exp Biol 206:4125–4137 123 Fish Sci (2010) 76:901–907 DOI 10.1007/s12562-010-0285-8 ORIGINAL ARTICLE Biology Are environmental conditions in Finnish streams limiting to early life-history survival in the nonnative rainbow trout? Kai Korsu • Ari Huusko Received: June 2010 / Accepted: August 2010 / Published online: 17 September 2010 Ó The Japanese Society of Fisheries Science 2010 Abstract The nonnative rainbow trout Oncorhynchus mykiss has been an unsuccessful invader in North European streams, although it has been widely introduced Here we studied whether early life history stages (egg incubation and hatching, first overwintering) act as filters for the establishment of hatchery rainbow trout Survival of hatched alevins was approximately 80%, whereas only 47% of the embryos survived However, the latter value was impacted by the high number of unfertilized eggs Correlation coefficients with embryo survival rate and environmental variables (pH and temperature) were statistically insignificant In the overwintering experiments, the survival of rainbow trout was 93% The growth was generally slowed during the winter, but in the spring the growth of rainbow trout exceeded that of the native brown trout Our data demonstrated that the survival and growth of rainbow trout during early life-history stages were relatively high and comparable to those of the native brown trout Based on the variables considered in our study, our results suggest that environmental conditions during early life-history stages are not detrimental for rainbow trout in the study streams Keywords Biological invasions Á Egg incubation Á Hatching success Á Oncorhynchus mykiss Á Overwintering K Korsu (&) Department of Biology, University of Oulu, P.O Box 3000, 90014 Oulu, Finland e-mail: kai.korsu@oulu.fi A Huusko Finnish Game and Fisheries Research Institute, Kainuu Fisheries Research, Manamansalontie 90, 88300 Paltamo, Finland Introduction Invasions by nonnative organisms are recognized to be a major threat to global biodiversity, leading to species extinctions and worldwide homogenization of biota [1, 2] The establishment success of nonnative species in recipient systems has been relatively high, as up to 50% of species that have entered recipient ecosystems have subsequently become established [3, 4] An ability to predict which species will establish and become nuisance invaders is considered highly important for prioritizing management efforts such as prevention and eradication, which are likely to be effective only in the early stages of invasion [5–7] Salmonids are widely introduced fishes that have successfully established themselves in many parts of the world [8] They also have wide-reaching impacts on native species and the trophic organizations of native stream communities [9, 10] Subsequently, the World Conservation Union has listed two salmonids (the rainbow trout Oncorhynchus mykiss and the brown trout Salmo trutta) among the eight fish species included in the list of 100 of the world’s worst invasive species [11] Among the salmonids, rainbow trout is the most widely introduced species; nevertheless, its establishment success varies strongly among regions [12, 13] For example, in Europe, rainbow trout has become established primarily in southern regions, while the British Isles and northern regions have only a few self-reproducing populations [12–16] In Japan, New Zealand, and North America, established populations of rainbow trout have frequently affected native species negatively [10] The reason for the low establishment success of rainbow trout in North European streams has not been fully explained to date Fausch [15] suggested several influential factors, such as (1) high environmental resistance from 123 902 temperature and flow regimes, (2) high biotic resistance from native fishes or diseases, (3) rainbow trout domestication, and (4) high angling pressure Water pH may also affect establishment success in some regions, because rainbow trout is vulnerable to acidic water [17–19] Probably the most powerful explanation thus far is associated with environmental resistance: high floods during early summer may wash away newly emerged rainbow trout fry [12] However, climate change may alter the timing of floods due to earlier snowmelt, thus facilitating fry survival and subsequently the establishment of rainbow trout in northern regions [13, 20, 21] In general, environmental conditions during early life history stages have major effects on salmonid populations For example, a lack of swimming ability easily results in the displacement of hatched alevins under high-flow conditions, and a lack of adequate fat reserves may lead to fry starvation [15] Moreover, the early life-history stages are more vulnerable to acid water compared to adult fishes [18] Thus, any change in environmental conditions in spring or early summer may have a strong positive effect on the survival of rainbow trout in North Europe [13, 20] After being established in northern streams, rainbow trout might have severe effects on the survival and habitat use of the native brown trout [22] and various other stream organisms [9] Moreover, being a spring spawner, rainbow trout might superimpose their redds on those of the native autumnspawning salmonids, as has been observed in Japanese streams [23] Here, we explored the survival and growth of the nonnative rainbow trout during two critical early life-history stages: (1) egg incubation and hatching in the spring, and (2) the first overwintering We performed experiments in Finland, where rainbow trout has been extensively stocked for over 100 years [17], but reproduces only in a few streams in southern regions (Saura et al http://www.rktl.fi/ www/uploads/pdf/raportti289.pdf) The aim of the study was to examine whether low survival in the early lifehistory stages limits rainbow trout establishment in north European streams, where rainbow trout has thus far been an unsuccessful invader Materials and methods Fish Sci (2010) 76:901–907 regimes with snowmelt-induced floods that typically occur in April–May Each of these streams is known to support a self-sustaining population of the native brown trout [24], a species that spawns in autumn and for which the eggs hatch in spring By contrast, rainbow trout spawn in spring and the eggs hatch in late spring, approximately month after the spawning Rainbow trout eggs used in the experiment were fertilized in a local commercial hatchery (Savon Taimen http://www.savontaimen.fi) on 24 April 2008 In the absence of established populations of rainbow trout, egg and sperm were provided by hatchery fishes The fertilized eggs were transferred to the incubation sites of the study streams within 10 h after the fertilization Thirty eggs were placed in one plastic egg container (10 cm 10 cm cm) with abundant gravel mixture (5–30 mm in diameter) Regular water flow through containers was ensured by utilizing openings covered with plastic mesh (mesh size mm) Ten containers were placed in natural gravel beds of each stream (water velocity, 12–30 cm s-1; depth, 20–40 cm) Embryo survival, hatching, and the swimming ability of the hatched alevins were measured on two occasions: on 30 May and June Both times, five randomly selected containers per stream were examined Water temperature and pH were measured four times in each stream during the study At the end of the experiment, we stored the hatched alevins in a solution of ethanol and formalin and determined their total lengths and dry masses (24 h at 60°C) later in the laboratory At the end of the experiment, we also took a sample of hatchery alevins from the same strain that was used in our field experiment This was done to compare the sizes of the alevins reared in the controlled hatchery environment and the field environment We assume that a markedly smaller body size of the alevins in the study streams compared to those reared in the hatchery would indicate the influence of some sublethal environmental factor We used a paired t test to explore whether there was a difference between embryo survival on 30 May and June We also investigated the relationship between embryo survival and three explanatory variables (degree days, minimum pH, and pH at the end of the experiment) by Pearson’s correlation coefficient Because we had only four temperature measurements per stream, the degree days reported here are rough estimates Incubation experiment Overwintering experiments The experiment was conducted in five central Finland streams where rainbow trout have not become established The selected streams were: Arvaja, Kiertojoki, Ko¨nkko¨joki, Ko¨hnio¨npuro, and Rutajoki (see [24–26]) The study streams drain forested catchments and have natural flow 123 We studied the survival and growth of age-0 rainbow trout compared to the native brown trout Sympatric treatments were used because we assumed that the low invasion success of rainbow trout may result from its 1012 could be due to flux of superoxide radicals, which have been reported to inhibit CAT activity [30] Reduced GSH is the main nonprotein thiol and one of the main reductants found in cells GSH possesses antioxidant properties, and its protective role against oxidative stress-induced toxicity in aquatic animals is well established [31–33] Effects of insecticides on lipid peroxidation have been evaluated in several studies In the study of Gohary et al [33], the effect of deltamethrin on testicular apoptosis in rats and the protective effect of nitric oxide synthase inhibitor was investigated Plasma levels of both nitric oxide and lipid peroxides were measured as MDA, and the MDA levels were found to be significantly increased in deltamethrin-treated animals in this study Shadnia et al [34] studied genotoxicity and oxidative stress in workers who formulate organophosphorus pesticides Results indicated that chronic exposure to organophosphorus pesticides was associated with increased activities of CAT, SOD, and GSP-Qx in erythrocytes In the study of Akhgari et al [35], the effect of subchronic exposure to malathion in the production of oxidative stress was evaluated in male Wistar rats Administration of malathion (100, 316, 1,000, and 1,500 ppm) for weeks increased CAT and SOD activities, as well as MDA concentrations in red blood cells and liver Seth et al [36] studied the effects of propoxur on lipid peroxidation In that study they found that propoxur increased MDA levels and altered glutathione levels Gromov et al [37] investigated effects of deltametrin and dichlorvos on memory processes, and the activity of antioxidant enzymes such as SOD and CAT in brain and blood of female rats The enzyme activities were not significantly changed in blood, but CAT activity was lowered in brain h after administration Oxidative stress and lipid peroxidation were determined by measuring the MDA concentration [25] In the present study, MDA levels were found to increase with high concentrations These findings about MDA levels are compatible with other study results In addition, the durations of the active and rest periods in the control were significantly different, in agreement with the literature [38] The experiment revealed that the lasting presence of cypermethrin in the water also influences central neural regulation The mechanism of contraction and relaxation of the adductor muscles, forming the basis of the periodic activity, is controlled by the central nervous system, and the external influences resulting in the modulation of the opening and closing of the valves are exerted through neural mechanisms from the ganglia [20, 39] As the present experiment indicates, under cypermethrin exposure the regulatory mechanism operates first with reduction of the active periods and elongation of the rest periods Chronic application of cypermethrin may affect the central neural (possibly both membrane and 123 Fish Sci (2010) 76:1007–1013 synaptic) processes, which in turn results in alteration of the effector system regulating the contraction and relaxation of the adductor muscles, and leads to shortening of the active periods and elongation of the rest periods The effect of cypermethrin at concentrations of 10 lg/L or more can be interpreted in this experiment as depressive to the filtering behavior of mussels It is an adverse action: upon reduction of the filtering activity, the feeding, respiration, and excretory processes are reduced, affecting both the living processes of the mussels and their water-cleaning function, which is an important component with respect to the maintenance of a healthy aquatic ecosystem The USDA National Agricultural Pesticide Impact Assessment Program’s document reports that cypermethrin causes acute toxicity in fish in laboratory tests at an average concentration of 1.8–8.2 lg/L [5], for example, the 96 h values are 1.2 lg/L for Salmo trutta, lg/L for Salmo salar, 2.2 lg/L for Tilapia nilotica, and lg/L for Oncorhynchus mykiss Clark et al [8], examining cypermethrin toxicity in other aquatic organisms, reported a 96 h LC50 value of cypermethrin for the grass shrimp Palaemonetes pugio to be 0.016 lg/L In the present study, the 96 h LC50 value of cypermethrin for freshwater mussels was determined as 59.20 lg/L, and the toxicity of cypermethrin on mussels increased with increasing concentration However, the toxicity of cypermethrin on mussels did not increase with increasing times of exposure The results indicate that the insecticide cypermethrin has a harmful effect not only on fish [5] and nontarget aquatic arthropods [8], but also on mollusks, although the sensitivity of the freshwater mussel is less than that of fish The results obtained from this study show significantly increased lipid peroxidation (MDA) levels and decreased GSH and CAT activities in digestive glands and gills of freshwater mussels after exposure to increasing cypermethrin concentrations Negative correlations were observed between the MDA levels and the GSH and CAT activities This suggests a protective response in freshwater mussels toward exposure to an oxidative stress-inducing cypermethrin The experimental data obtained with freshwater mussels can be considered as a useful reference for comparisons with biomarker responses of organisms living in polluted environments It is concluded that cypermethrin contamination is dangerous to the ecosystem, and this fact should be taken into consideration when this insecticide is used in agriculture or in the control of mosquito populations References Casida JE, Gammon DW, Glickman AH, Lawrence LJ (1983) Mechanism of pyrethroid insecticides Annu Rev Pharmacol Toxicol 23:413–418 Fish Sci (2010) 76:1007–1013 Glickman AH, Lech JJ (1982) Differential toxicity of trans-permethrin in rainbow trout and mice II Role of target organ sensitivity Toxicol Appl Pharmacol 66:162–171 Hill IR (1989) Aquatic organisms and pyrethroids Pestic Sci 27:429–465 Polat H, Erkoc¸ FU, Viran R, Koc¸ak O (2002) Investigation of acute toxicity of beta-cypermethrin on guppies, Poecilia reticulata Chemosphere 49:39–44 US EPA (1989) Pesticide fact sheet number 199: cypermethrin Office of Pesticides 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Acta Biol Hung 29:173–180 123 Fish Sci (2010) 76:1015–1021 DOI 10.1007/s12562-010-0298-3 ORIGINAL ARTICLE Food Science and Technology Prebiotic effect of glycerol galactoside isolated from color-faded nori in rats Kenji Ishihara • Chiaki Oyamada • Yoko Sato Toshiyuki Suzuki • Masaki Kaneniwa • Hiromi Kunitake • Toshihiko Muraoka • Received: 19 July 2010 / Accepted: 24 September 2010 / Published online: 26 October 2010 Ó The Japanese Society of Fisheries Science 2010 Abstract Glycerol galactoside (GG; floridoside: 2-O-glycerol-a-D-galactopyranoside, and isofloridoside: 1-O-glycerola-D-galactopyranoside) is known to be a component of edible red seaweed nori Recently, we have found that lowquality nori (color-faded nori), which has a low protein content, contains a large quantity of GG From further studies, we have also found that GG has prebiotic characteristics in vitro In this study, we evaluated the in vivo prebiotic activity of GG in rats Dietary GG selectively increased the cecal Bifidobacterium count in rats Other indices of prebiotics, such as pH of cecal content, organic acid concentrations, and fecal weight, also supported the existence of prebiotic activity of GG The present data will also contribute to the development of a new method of utilizing color-faded nori as a health-promoting foodstuff Keywords Prebiotics Glycerol galactoside Á Floridoside Á Nori Á Abbreviations CFU Colony-forming unit FOS Fructooligosaccharide GG Glycerol galactoside K Ishihara (&) Á C Oyamada Á Y Sato Á T Suzuki Á M Kaneniwa Functional Biochemistry Section, Marine Biochemistry Division, National Research Institute of Fisheries Science, Yokohama 236-8648, Japan e-mail: hplc@affrc.go.jp H Kunitake Á T Muraoka Food Science Research Division, Kumamoto Prefectural Fisheries Research Center, 2450-2 Naka, Oyano, Kamiamakusa, Kumamoto 869-3603, Japan Introduction The red algae Susabinori Porphyra yezoensis and Asakusanori Porphyra tenera are processed into a sheet-like dried food called nori Nori is largely consumed in East and South-East Asia, and due to the recent popularity of sushi it is available now in many countries Nori contains many nutritionally functional components, such as b-carotene, porphyran and vitamin B12 [1] There are many papers that report the nutritional functions of nori and its components, such as their antitumor [2], immunostimulating [3], antiallergic [4], antioxidant [5], dioxin excretion enhancing [6] and antimutagenic [7] effects Glycerol galactoside (GG; floridoside: 2-O-glycerola-D-galactopyranoside, and isofloridoside: 1-O-glycerol-aD-galactopyranoside, Fig 1) is known to be a component of nori [8] Recently, we have found that low-quality nori (color-faded nori), which has a low protein content, contains a large quantity of GG [9] From further studies, we have also found that GG exhibits prebiotic characteristics in vitro GG was selectively utilized by Bifidobacteria, not digested by digestive enzymes, and not adsorbed in the small intestine according to an everted sac test [10] Prebiotics were first defined as ‘‘a non-digestible food ingredient that beneficially affects the host by selectively stimulating the growth and/or activity of one or a limited number of bacteria in the colon [11].’’ Prebiotics are generally recognized to be beneficial to health [12] If the prebiotic activity of GG can be improved, new applications of color-faded nori could potentially be found In this study, we have evaluated the in vivo prebiotic activity of GG in rats, and compared this activity to that of fructooligosaccharide (FOS), which is one of the most important prebiotics 123 1016 Fish Sci (2010) 76:1015–1021 Fig Structure of glycerol galactoside (floridoside and isofloridoside) Materials and methods Reagents Fructooligosaccharide (92% purity, Meioligo-W) was purchased from Meiji Seika Kaisha, Ltd (Tokyo, Japan) The mixed-bed ion exchange resin MB-4 was purchased from Organo Co Ltd (Tokyo, Japan) Primers and probes for cecal microflora analyses were commercially synthesized by BEX Co Ltd (Tokyo, Japan) Bacterial strains Bacterial strains used to calibrate analyses of cecal microflora were obtained from the Japan Collection of Microorganisms at the RIKEN Bioresource Center, and they are listed in Table All bacteria were spread onto GAM agar plates (Nissui Pharmaceuticals, Tokyo, Japan), and single colonies were picked up and cultured in GAM broth (Nissui Pharmaceuticals) Bacterial colony forming units (CFUs) were assayed on GAM agar plates All cultures were carried out under anaerobic conditions using an AnaeroPack jar and AnaeroPack Kenki (Mitsubishi Gas Chemical Company Inc., Tokyo, Japan) Preparation of GG Glycrol galactoside was extracted and purified from colorfaded nori A color-faded nori sample with a quality that was too low for commercial distribution was kindly provided by Mr Yamada of the Federation of Japan Fisheries Cooperatives, and Dr M Fujiwara of Kagawa Prefectural Fisheries Experimental Station Nori was shredded by a cross-cut shredder One liter of 75% ethanol was added to 150 g of a nori sample of low protein content The mixture was boiled for 30 in a 90°C water bath and filtered through a 5B filter (Advantec, Tokyo, Japan) The residue was extracted Table Bacterial strains used to calibrate the analyses of cecal microflora T type strain 123 times by the same procedure Each extract was concentrated to about 250 ml under reduced pressure at 35°C with a rotary evaporator, and defatted twice with 250 ml of diethyl ether The defatted extracts were combined and decolored by passing through an activated charcoal column (2.5 20 cm, Wako Pure Chemical Company, Osaka, Japan) The eluate was concentrated under reduced pressure at 60°C and made up to 100 ml The concentrate was deionized using a mixedbed ion exchange resin, MB-4 The resulting solution was freeze-dried The residual colorless crystal was identified as glycerol galactoside (a mixture of floridoside, L-isofloridoside and D-isofloridoside, in proportions of 11, 62 and 27%, respectively) by nuclear magnetic resonance [10], and purity was assessed by HPLC ([95%) [9] Animals Male Sprague–Dawley rats (4 weeks old) were purchased from Charles River Japan (Yokohama, Japan) Rats were individually housed in stainless-steel cages The animals were maintained in an air-conditioned room (temperature: 20–22°C; relative humidity: 55–65%, lighting: 06:00–18:00) All animal experiments were performed in accordance with the National Research Institute of Fisheries Science guidelines for the ethical treatment of laboratory animals Animal experiment After days of acclimation feeding, the animals were divided into groups (7 rats/group) Each group (control, FOS, and GG) was fed the experimental diet shown in Table for weeks From the 11th day to the 13th day of the experimental period, feces were collected Fecal weight was measured before and after drying At the end of the experimental period (14th day), the animals were killed by bleeding from the artery under ether anesthesia The cecum of each animal was excised and weighed, and its contents were collected Cecal contents were immediately frozen in liquid nitrogen and stored at -80°C until analysis Chemical analyses of cecal content The pH of the cecal contents was measured using a pH meter (Sartorius Docu Meter with a PI-P22 electrode, Sartorius Mechatronics Inc., Tokyo, Japan) After measuring Strain no Genus name Species name Used for calibration of JCM5803T Enterococcus faecalis Enterococcus spp JCM11019T Bacteroides fragilis Bacteroides fragilis group, total bacteria JCM1255T Bifidobacterium bifidum Genus Bifidobacterium JCM1291T Clostridium clostridioforme Clostridium coccoides group JCM1012T Lactobacillus delbrueckii Genus Lactobacillus Fish Sci (2010) 76:1015–1021 1017 Table Compositions of the experimental diets Ingredients Control FOS GG a-Cornstarcha 132 119 119 b-Cornstarcha 397 360 360 Sucrosea 100 100 100 a Casein 200 200 200 Cellulose powdera 50 50 50 Soybean oilb 70 70 70 3 2.5 2.5 L-Cystine b Choline bitartrateb 2.5 Mineralsa,c 35 35 35 Vitaminsa,c 10 10 10 t-Butylhydroquinoneb FOSd 0.014 0.014 50 GGe 0.014 50 Values are expressed as g/kg a Obtained from Oriental Yeast Co (Tokyo, Japan) b Supplied by Wako Pure Chemical Industry (Osaka, Japan) c AIN-93G formulation d Meioligo W (Meiji Seika Kaisha, Tokyo, Japan) e Purified from low-quality nori, as described in ‘‘Materials and methods’’ the pH, a portion of the cecal contents was added to an equal volume of water and vigorously vortexed The mixture was centrifuged at 10,0009g for 15 and the resulting supernatant was used for the following chemical analyses Ammonia concentration was measured using an Ammonia Test Wako kit (Wako) Lactic acid was quantified using a F-kit for L-lactate/D-lactate (Roche Diagnostics, Basel, Switzerland) Aliphatic organic acids (acetic, propionic and butyric acids) were measured by high-performance liquid chromatography (HPLC) as follows The supernatant was filtered through an ultrafiltration cartridge, Ultrafree (NMCO5K; Millipore, Billerica, MA, USA), and the filtrate was acidified by adding 1/20 volume of 2.5 mM sulfuric acid before being transferred to a high-performance liquid chromatography system (System 305 Programmable Pump; Gilson, Middleton, WI, USA) equipped with an ICSep ICECOREGEL-87H column (7.8 250 mm; Transgenomic, Omaha, NE, USA) The column temperature was set at 35°C and mM sulfuric acid was used as solvent (0.55 ml/min) The eluent was monitored with a UV–Vis monitor (no 119 UV/Vis detector, Gilson) set at 220 nm 450 ll of extraction buffer (100 mM Tris, 40 mM EDTA, pH 9) and added to 50 ll of 10% SDS, 500 ll of TE-saturated phenol (Nakarai Tesque, Kyoto, Japan), and 300 mg of glass beads (1 mm diameter) The mixture was shaken with a Shake Master (Biomedical Science, Tokyo, Japan) for After centrifuging at 10,0009g for min, 400 ll of the supernatant were collected and mixed with an equal volume of phenol/chloroform/isoamylalcohol (25:24:1) The mixture was centrifuged at 10,0009g for min, 250 ll supernatant were collected, and DNA was recovered by isopropanol precipitation The extracted DNA was dissolved in 100 ll of TE buffer and stored at -80°C until use Analyses of cecal microflora Cecal microflora was analyzed by quantitating 16S rDNA genes using genus- and cluster-specific primers and probes with a real-time polymerase chain reaction (PCR) system, the Thermal Cycler Dice Real Time System (Takara Bio Inc., Kyoto, Japan) Primers and probes used for the analyses, annealing temperature and PCR programs are listed in Table In the PCR reaction, Premix Ex Taq (Takara Bio) was used to quantitate total bacteria and Lactobacillus, SYBR Premix Ex Taq (Takara Bio) to quantitate Bifidobacterium, the Bacteroides fragilis group, the Clostridium coccoides group, and Enterococcus spp Quantitations were calibrated using the total DNA extracted from the standard bacterial strains listed in Table employing the same procedure as used for the cecal contents Bacteroides fragilis (JCM11019) was used to calibrate total bacteria Cecal bacterial content was expressed as log CFU/g cecal content The size and purity of the PCR products of the reaction mixture used for the quantification of Bifidobacterium, the Bacteroides fragilis group, the Clostridium coccoides group, and Enterococcus spp were checked via dissociation curve and electrophoresis Statistical analysis Statistical analyses were done using JMP version (SAS Institute, Cary, NC, USA) Data obtained in this report were analyzed by one-way analysis of variance When significant, the data were further analyzed by Tukey–Kramer test or Dunnett’s test The significance level was set at p \ 0.05 Extraction of DNA from cecal contents Results Bacterial DNA was extracted by the method described by Matsuki [13] with slight modifications Briefly, a 10 mg portion of the cecal contents was washed by suspending it in 0.5 ml of phosphate-buffered saline and centrifuging for at 9,0009g times The pellet was suspended in Growth, food intake, and relative organ weight and fecal weight Initial and final body weights, total food intakes, fecal weights and fecal water contents are shown in Table 123 1018 Fish Sci (2010) 76:1015–1021 Table Primers and probes used for the analyses of cecal microflora Name Specificity Primer Sequence or probe LAB1 Genus Lactobacillus F Product size 50 -GGCAGCAGTAGGGAATCTTCCA 174 LAB probe P -TGGAGCAACGCCGCGTGAGTGA R 50 -GTATTACCGCGGCTGCTGGCAC F 50 -CTCCTGGAAACGGGTG R 50 -GGTGTTCTTCCCGATATCTAC F 50 -ATAGCCTTTCGAAAGRAAGAT Genus Bifidobacterium g-Bifid-R g-Bact-F Bacteroides fragilis group R Clostridium coccoides group F -CCAGTATCAACTGCAATTTTA 50 -AAATGACGGTACCTGACTAA g-Ccoc-R R 50 -CTTTGAGTTTCATTCTTGCGA F 50 -GGATAACACTTGGAAACAGG R 50 -TCCTTGTTCTTCTCTAACAA F 50 -GGATTAGATACCCTGGTAGTC 1400r P 50 -TGACGGGCGGTGTGTACAAGGC 1512r R 50 -TACCTTGTTACGACTT Enterococcus spp Ent-R 785 Total bacteria A B [14] 549–563 55 B C [13] 501 50 B C [13] 438–441 50 B C [13] 366 50 B C [15] 727 52 A A [16] g-Bact-R g-Ccoc-F Ent-F 50 LAB2 g-Bifid-F PCR Ref Annealing PCR temp (°C) cocktaila programb no F forward primer, R reverse primer, P Taqman probe a PCR cocktail was composed of: A: 12.5 ll of Premix Ex Taq (Takara Bio), ll of template, 0.5 ll of 10 lM primers, 0.25 ll of 10 lM Taqman probe, 11.25 ll of H2O (total 25 ll); B: 12.5 ll SYBR of premix Ex Taq (Takara Bio), ll of template, 0.5 ll of 10 lM primers, 11.5 ll of H2O (total 25 ll) b PCR reaction was done under the following conditions: A: 30 s at 95°C to activate the Ex Taq enzyme, and 40 cycles of 10 s at 95°C, 10 s at 52°C, and finally 45 s at 72°C; B, 30 s at 95°C to activate the enzyme, and 40 cycles of s at 95°C, and finally 30 s at 60°C; C: 30 s at 95°C to activate the enzyme, and 40 cycles of s at 95°C, 10 s at 55°C, and finally 30 s at 72°C Final body weight and food intake were lower in the FOS and GG groups than in the control rats Fecal weight was significantly higher in the FOS group, and tended to be higher in the GG group than the control group Fecal water content was higher in FOS rats Cecal weight, pH and concentration of organic acids Cecal weight and cecal content weight increased and cecal pH fell when the rats were fed FOS and GG diets (see Table 5) Most of the cecal organic acid concentrations were elevated in rats fed the FOS and GG diets, with the exception of lactate and propionate in rats fed the GG diet Cecal microflora The cecal microflora in rats fed the FOS and GG diets was analyzed by a real-time PCR method (total bacteria, genus Lactobacillus, genus Bifidobacterium, the Bacteroides fragilis group, the Clostridium coccoides group, and Enterococcus spp.) and expressed as CFU/g of cecal content (Fig 2) The FOS and GG diets did not significantly alter the total bacterial count and those of Enterococcus spp and the Clostridium coccoides group The Bifidobacterium count was significantly increased compared to that of the control by feeding the rats FOS and GG diets [6.07 ± 0.32 log (CFU/g) for control, 8.69 ± 0.21 log (CFU/g) for FOS, 123 Table Body weight, food intake and fecal weight of rats fed control, FOS, or GG diets Control Initial body wt (g) 102.0 ± 1.6 FOS GG 102.0 ± 1.3 101.9 ± 1.3 Final body wt (g) 239.2 ± 4.9a 215.0 ± 5.7b 219.6 ± 5.7b Food intake (g/14 days) Fecal wt (g/days) a b 236.6 ± 8.3b Fecal water content (%) 276.3 ± 6.8 231.4 ± 9.8 1.68 ± 0.17a a 13.3 ± 0.89 2.54 ± 0.33b 27.5 ± 3.6 b 2.00 ± 0.13ab 21.3 ± 2.7ab Value are means ± SEM, n = Means in a row with superscripts without a common letter differ; p \ 0.05 by Tukey–Kramer test 7.16 ± 0.27 log (CFU/g) for GG, respectively] However, the increase in Bifidobacteria was greater in the FOS-fed animals than in the GG-fed ones The GG diet significantly increased Lactobacillus bacteria [8.65 ± 0.15 log (CFU/g) for control, 8.78 ± 0.06 log (CFU/g) for FOS, 9.11 ± 0.05 log (CFU/g) for GG, respectively] Discussion Nowadays nori is a commonly available foodstuff in many countries of the world Many studies of the nutritional components of nori, such as porphyran [1] and other Fish Sci (2010) 76:1015–1021 1019 Table Cecal weight, pH and concentration of organic acids in rats fed control, FOS, or GG diets Control Cecal wt (g) Cecal content wt (g) pH of cecal content FOS GG 2.98 ± 0.17a 7.74 ± 0.46b 7.33 ± 0.50b a 4.73 ± 0.49 b 5.02 ± 0.54b 5.44 ± 0.09 b 5.95 ± 0.18c 1.88 ± 0.15 a 7.13 ± 0.05 Cecal organic acids (mM) Lactate 2.5 ± 0.6a Acetate a Propionate Butyrate 16.9 ± 3.0 5.5 ± 0.5a 2.6 ± 0.4a 24.0 ± 5.6b 25.6 ± 4.6 a* 17.6 ± 6.0b 2.8 ± 0.9a 2.8 ± 1.1a 24.1 ± 4.7a 4.3 ± 0.6a 6.0 ± 0.9b Value are means ± SEM, n = Means in a row with superscripts without a common letter differ; p \ 0.05 by Tukey–Kramer test * Significantly different from control by Dunnett’s test at p \ 0.05 polysaccharides [17], peptide [18], vitamin B12 [19], carotenoids [7], and glycolipids [20], have been reported Glycerol galactoside (floridoside ? isofloridoside) is known to be a minor component of nori and other red algae [8] We recently found that color-faded nori contains large amounts of GG, more than 10% w/w in dry wt [9] In an in vitro study, we found that GG was a potential candidate for a prebiotic compound [10] Control FOS GG Fig Cecal microflora in rats fed control, FOS, or GG diets Values are means ± SEM, n = Different alphabet letters above columns indicate statistical differences between feeding groups at p \ 0.05 by the Tukey–Kramer test As reviewed by Kelly [12], there is now an extensive amount of evidence showing that intestinal microflora greatly affect host health It is generally thought that intestinal lactic acid bacteria, such as those of the genus Lactobacillus and the genus Bifidobacterium, have positive effects [11] Most prebiotics selectively increase the number of Bifidobacteria [12] We believe that if the prebiotic characteristics of GG can be proved, GG could be applied as a new prebiotic material This may also lead to more effective utilization of color-faded nori Therefore, in this study, we investigated the in vivo prebiotic effect of GG in rats FOS was used as a positive control to compare the prebiotic activity of FOS with that of GG, because FOS is one of the most commonly used and well-studied prebiotics Dietary GG selectively increased a number of cecal Bifidobacteria in rats Therefore, we can conclude that GG exhibits prebiotic activity in vivo Comparing the prebiotic activities of FOS and GG using the cecal number of Bifidobacteria as a distinguishable trait, the prebiotic activity of GG appears to be milder than that of FOS (Fig 2) Other indices of the prebiotic activity such as cecal weight, pH of cecal content, cecal concentration of organic acids, and fecal weight also support this suggestion (Tables 4, 5) Bifidobacterium produces acetate and lactate, while Lactobacillus mainly forms lactate GG increased Bifidobacterium and Lactobacillus in cecum (Fig 2) Thus, the GG diet was expected to increase cecal lactic and acetic acids However, GG only increased butyrate significantly, while the FOS diet increased the cecal concentrations of lactate, acetate and propionate (Table 5) The reasons for this inconsistency are unclear The GG diet possibly affected organic acid concentrations by modulating the cecal microflora species composition Many butyrate-producing bacteria have been identified and studied in human intestinal microflora [21] Among the above organic acids, butyrate is known to play an important role in colonic function Butyrate is known to be an important energy source for colon epithelial cells Butyrate suppresses colonic carcinogenesis and inflammation and decreases oxidative stress [22] Thus, the selective increase in cecal butyrate concentration caused by a GG diet may be an advantage of GG over FOS FOS is known to be present in edible plants such as onions, burdocks, and bananas [12] FOS is also synthesized enzymatically and sold Due to its prebiotic activity, FOS has been reported to promote intestinal mineral absorption [23], and to exhibit antiallergic activity [24], immunoenhancing activity [25], and many other positive activities [12] In the present results, GG was shown to exhibit prebiotic activity in vivo Even though the prebiotic activity of GG was lower than that of FOS, it suggests that some of the functionality of FOS can also be expected of GG 123 1020 To the best of our knowledge, GG has been found only in red algae Structurally, GG is composed of glycerol and galactose Galactose is combined with glycerol at the 1-position of galactose by a-configuration [26] Many prebiotic compounds have been found, such as fructooligosaccharide, xylooligosaccharide, galactooligosaccharide, and mannooligosaccharide [12] Most of these prebiotics are oligomers of monosaccharides Recently, O’Sullivan et al [27] reviewed prebiotics in marine macroalgae In their review, they referred to polysaccharides and their hydrolyzed oligosacchalides such as alginate, fucoidans, laminarin, agar, neoagaro-oligosaccharides, carrageenans and glycerol galactoside as candidate prebiotics Among these, prebiotics with a GG-like structure appear to be unique Therefore, GG could provide a new research material for prebiotic studies Nori is a major component of Japanese foods About 40,000 metric tons of nori are cultured annually in Japan A large amount of nori is also cultured in Korea and China It was reported that color-faded nori occurs under conditions where low concentrations of nutrient minerals are present during culture [28] The occurrence of color-faded nori is a heavy burden on the nori culture and processing industry In our previous study, color-faded nori was found to contain over 10% GG by weight on a dry weight basis [9] Although further human experiments are necessary to evaluate the prebiotic activity of GG in humans, we anticipate that the present data will contribute to the development of a new way of utilizing color-faded nori as a health-promoting foodstuff Acknowledgments We thank Mr T Yamada of the Federation of Japan Fisheries Cooperatives and Dr M Fujiwara of Kagawa Prefectural Fisheries Experimental Station for providing us with colorfaded nori samples We are also grateful to Prof T Kuda of the Tokyo University of Marine Science and Technology for useful discussions References Mumford TF Jr, Miura A (1988) Porphyra as food: cultivation and economics In: Lembi CA, Waaland JR (eds) Algae and human affairs Cambridge University Press, Cambridge, pp 91–93 Noda H, Amano H, Arashima K, Hashimoto S, Nisizawa K (1989) Antitumor activity of polysaccharides and lipids from marine algae Nippon Suisan Gakkaishi 55:1265–1271 Yoshizawa Y, Enomoto A, Todoh H, Ametani A, Kaminogawa S (1993) Activation of murine macrophages by polysaccharide fractions from marine algae (Porphyra yezoensis) Biosci Biotechnol Biochem 57:1862–1866 Ishihara K, Oyamada C, Matsushima R, Murata M, Muraoka T (2005) Inhibitory effect of porphyran, prepared from dried ‘‘Nori,’’ on contact hypersensitivity in mice Biosci Biotechnol Biochem 69:1824–1830 Zhang Q, Li N, Zhou G, Lu X, Xu Z, Li Z (2003) In vivo antioxidant activity of polysaccharide fraction from Porphyra haitanesis (Rhodophyta) in aging mice Pharmacol Res 48:151–155 123 Fish Sci (2010) 76:1015–1021 Morita K, Tobiishi K (2002) Increasing effect of nori on the fecal excretion of dioxin by rats Biosci Biotechnol Biochem 66:2306–2313 Okai Y, Higashi-Okai K, Yano Y, Otani S (1996) Identification of antimutagenic substances in an extract of edible red alga, Porphyra tenera (Asakusa-nori) Cancer Lett 100:235–240 Noda H, Amano H, Abo K, Horiguchi Y (1981) Sugars, organic acids, and minerals of ‘‘nori’’ the dried laver Porphyra spp Nippon Suisan Gakkaishi 47:57–62 Ishihara K, Oyamada C, Sato Y, Danno H, Kimiya T, Kaneniwa M, Kunitake H, Muraoka T (2008) Relationships between quality parameters and content of glycerol galactoside and porphyra-334 in dried laver nori Porphyra yezoensis Fish Sci 74:167–173 10 Muraoka T, Ishihara K, Oyamada C, Kunitake H, Hirayama I, Kimura T (2008) Fermentation properties of low-quality red alga susabinori Porphyra yezoensis by intestinal bacteria Biosci Biotechnol Biochem 72:1731–1739 11 Gibson GR, Roberfroid MB (1995) Dietary modulation of the human colonic microbiota Introducing the concept of prebiotics J Nutr 125:1401–1412 12 Kelly G (2008) Inulin-type prebiotics––a review: part Altern Med Rev 13:315–329 13 Ten Bruggencate SJM, Bovee-Oudenhoven IMJ, Lettink-Wissink LG, van der Meer R (2005) Dietary fructooligosaccharides increase intestinal permeability in rats J Nutr 135:837–842 14 Matsuki T, Watanabe K, Fujimoto J, Kado Y, Takada T, Matsumoto K, Tanaka R (2004) Use of 16S rRNA gene-targeted group-specific primers for real-time PCR analysis of predominant bacteria in human feces Appl Environ Microbiol 70: 7220–7228 15 Ezaki T, Xu H-X, Li Z-Y (1999) Quantitative amplification of anaerobic cocci and enterococci from normal human feces using light cycler (Chap 8) In: Mitsuoka T (ed) Molecular ecological detection and identification of intestinal microflora Japan Scientific Societies Press, Tokyo, pp 123–136 16 Lyons SR, Griffen AL, Leys EJ (2000) Quantitative real-time PCR for Porphyromonas gingivalis and total bacteria J Clin Microbiol 38:2362–2365 17 Kawadu D, Tanaka M, Fujii T (1995) Effect of polysaccharides of ‘‘Susabinori’’ Porphyra yezoensis on intestinal flora (in Japanese with English abstract) Nippon Suisan Gakkaishi 61:59–69 18 Suetsuna K (1998) Purification and identification of angiotensin I-converting enzyme inhibitors from the red alga Porphyra yezoensis J Mar Biotechnol 6:163–167 19 Takenaka S, Sugiyama S, Ebara S, Miyamoto E, Abe K, Tamura Y, Watanabe F, Tsuyama S, Nakano Y (2001) Feeding dried purple laver (nori) to vitamin B12-deficient rats significantly improves vitamin B12 status Br J Nutr 85:699–703 20 Eitsuka T, Nakagawa K, Igarashi M, Miyazawa T (2004) Telomerase inhibition by sulfoquinovosyldiacylglycerol from edible purple laver (Porphyra yezoensis) Cancer Lett 212:15–20 21 Louis P, Flint HJ (2009) Diversity, metabolism and microbial ecology of butyrate-producing bacteria from the human large intestine FEMS Microbiol Lett 294:1–8 22 Hamer HM, Jonkers D, Venema K, Vanhoutvin S, Troost FJ, Brummer R-J (2008) Review article: the role of butyrate on colonic function Aliment Pharmacol Ther 27:104–119 23 Fukushima A, Ohta A, Sakai K, Sakuma K (2005) Expression of calbindin-D9k, VDR and Cdx-2 messenger RNA in the process by which fructooligosaccharides increase calcium absorption in rats J Nutr Sci Vitaminol 51:426–432 24 Fujitani S, Ueno K, Kamiya T, Tsukahara T, Ishihara K, Kitabayashi T, Itabashi K (2007) Increased number of CCR4positive cells in the duodenum of ovalbumin-induced food allergy model Nc/jic mice and anti allergic activity of fructooligosaccharides Allergol Int 56:131–138 Fish Sci (2010) 76:1015–1021 25 Nakamura Y, Nosaka S, Suzuki M, Nagafuchi S, Takahashi T, Yajima T, Takenouchi-Ohkubo N, Iwase T, Moro I (2004) Dietary fructooligosaccharides up-regulate immunoglobulin A response and polymeric immunoglobulin receptor expression in intestines of infant mice Clin Exp Immunol 137:52–58 26 Bondu S, Kervarec N, Deslandes E, Pichon R (2007) Separation of floridoside and isofloridosides by HPLC and complete 1H and 13C NMR spectral assignments for D-isofloridoside Carbohydr Res 342:2470–2473 1021 27 O’Sullivan L, Murphy B, McLoughlin P, Duggan P, Lawlor PG, Hughes H, Gardiner GE (2010) Prebiotics from marine macroalgae for human and animal health applications Mar Drugs 8:2038–2064 28 Isagai H, Isobe T (2006) Effect on metal elements on fading laver in the Ariake Sea (in Japanese with English abstract) Bunseki Kagaku 55:999–1002 123 Fish Sci (2010) 76:1023–1028 DOI 10.1007/s12562-010-0297-4 ORIGINAL ARTICLE Social Science Conjoint analysis of consumer preference for bluefin tuna Masahiko Ariji Received: July 2010 / Accepted: September 2010 / Published online: 22 October 2010 Ó The Japanese Society of Fisheries Science 2010 Abstract Tuna is one of the most important marine products in Japan, but fishery productivity is decreasing, especially for bluefin tuna (Thunnus orientalis, Thunnus thynnus) because of strict capture limits implemented by regional fisheries management organizations (RFMOs) Such capture limitations are necessitated by a shortage of resources At the same time, full-cycle farming technology of Thunnus orientalis has recently been developed This technology is set to achieve productivity levels at an industrial scale In Japan, however, most consumers are believed to have a negative image of farmed products; therefore effective marketing is necessary This study employs conjoint analysis via an internet questionnaire to clarify consumer preferences and the determine the possibility of marketing through provision of information to consumers regarding bluefin tuna and the environmental background of the problem The results show that once consumers are provided with enough information about bluefin tuna, particularly in terms of the underlying resources problem, the willingness to pay (WTP) for fullcycle farmed fish is greater compared to conventionally farmed fish Furthermore, if the product has an ‘‘eco-label,’’ the WTP increases drastically Therefore, the informational process is important for marketing, and labeling can be an efficient marketing method Keywords Full-cycle farming Á Bluefin tuna Á Conjoint analysis Á WTP Á Marketing M Ariji (&) Department of Fisheries, Faculty of Agriculture, Kinki University, Nakamachi, Nara 631-8505, Japan e-mail: mariji@nara.kindai.ac.jp Introduction In Japan, tuna, which is often eaten raw (including from both frozen and fresh sources) in the form of sushi and sashimi, is one of the most consumed fishery products [1] Fisheries supply half of the total animal protein consumed by Japanese people, and tuna, whose consumption represents a large portion of this, is an important food that rivals even beef and pork [2] The global demand for tuna is growing, and international fishing pressures on tuna are intensifying [3] As a result, supplies of tuna are on a downward trend all over the world, and the Tuna Regional Fisheries Management Organization (RFMO) has been implementing increasingly stringent catch restrictions Meanwhile, stock from tuna farms is increasing significantly, and tuna supply composition is changing greatly [1] However, because these farms rely on natural young tuna as a raw material for tuna culture, they will be affected by the framework of resource management [1] Therefore, the establishment of production technology involving the complete process of cultivating eggs and hatchlings has become desirable as a means to have a stable and sustainable supply However, unless a consumer propensity for farmed tuna can be established, whereby the costs involved in such technology are covered by consumers, a sustainable supply and demand situation cannot be created in the market Currently, although there has been some early research on the consumption of tuna, it has not appropriately analyzed the situation from the perspective of additional value, which must be provided on the supply side where there are already concerns related to the production method, location, and environment, or from the perspective of consumer propensity, which will factor in to the added value However, in order for companies involved in production and 123 1024 Fish Sci (2010) 76:1023–1028 logistics to draft an optimal market strategy, it is necessary to have a clear understanding of the factors associated with consumers’ marginal willingness to pay (MWTP) as it relates to factors associated with bluefin tuna production This study uses a conjoint analysis based on an online survey to gauge consumer propensity for tuna with the background mentioned above as points of reference [6, 7, 12, 14] This study analyzes the difference in the utility from a consumer’s perspective with respect to the different production methods (wild-caught, conventional fish farms, or full-cycle farming) in order to formulate a strategy for selling tuna Also, understanding the difference in consumer utility with respect to the various geographical sources of bluefin tuna worldwide will help in the formulation of a sales strategy for domestically produced tuna Particularly, by clearly positioning domestic production vis-a`-vis consumer needs, I show the effect of presenting bluefin tuna as domestically produced and remark on effective combinations of factors for marketing The conjoint analysis conducted by Kitano [4] specifies affiliation with a production site, preservation method, and production method (as well as price); however, it is difficult to distinguish the difference in preservation methods, particularly for sushi, in actual levels of consumption Furthermore, because the recent development of ultra-low-temperature freezing technology (B1 freezing and other high-quality maritime freezing technologies) makes it very likely that freshness at the consumer level will be higher in cases of preservation through freezing [5], this factor is not included in this analysis What is essential here is to know what strategy would be best for supplying tuna to consumers in a way that maximizes utility Therefore, we need to establish the affiliation for factors we can actually control, such as the existence of eco-labeling [6, 7] and different kinds of information provided in the product display In addition, consumer recognition changes depending on the kind of information provided, so if the utility changes with respect to the consumers, then we must simultaneously consider the way in which the information is provided Therefore, this study uses a behavioral economics method to analyze the changes in consumer behavior depending on the information provided Based on the above considerations, the objectives of this analysis are as follows: Understand the difference in utility from a consumer’s perspective with respect to the production method Understand the positioning of domestically produced tuna with respect to consumer needs, while understanding that a large portion of the tuna is imported 123 Understand the effect of mentioning efforts taken to preserve the environment on labels Analyze the changes in knowledge and behavior following the provision of information Materials and methods The analysis was in the form of an online questionnaire As reaching consumers through direct mailing (DM) is difficult due to regulations regarding personal information protection, a survey targeting general consumers based on online panels was the main method of gathering information The online survey provided by Yahoo! Value Insight offers the largest number of panels in Japan, and this company frequently conducts online surveys for the government For these reasons, this research body was chosen to carry out this analysis In order to eliminate sampling bias as much as possible, target consumers were divided into two groups, the first group containing 20- to 30-year-olds, and the second group containing individuals who were 40 years and over, with an equal number of men and women from three regions— Tokyo, Osaka, and Fukuoka This sampling method is usually employed in Japanese internet surveys, and especially in this study, the pool data are used because the purpose of this study is to grasp the complete trends and behaviors of Japanese consumers [6] The survey was carried out in late March 2009 on 2,400 individuals, a relatively large number for a survey on consumer propensity There were five conjoint survey questions asked both before and after information was provided to respondents, for a total of 12,000 samples The direct purpose of this survey is to gauge the current tuna consumption trend in a large market while factoring in regional characteristics In Japan we have two styles of sushi bars: conveyor-belt sushi bars and table style, which is the traditional method It is said that the former has young people and low-income households as the target and the latter has households of middle or high income as their target [2] According to the average retail prices available on the Internet, table style and conveyor-belt sushi bars serve bluefin tuna for approximately 300–600 yen A practical approach was taken to match the samples considered and the actual price range The product affiliation in the conjoint analysis was determined as follows According to the random effect theory, consumer utility is believed to be composed of several important component effects that form a complete effect that regulates consumer behavior [9] (Fig 1) Conjoint analysis determines which important component effects are matched according to this Fish Sci (2010) 76:1023–1028 Fig Relationship between effect and affiliation 1025 Attribution Partial utility Production method Utility towards production method Production location Utility of production location image Existence of label Utility towards label Price Utility towards prices concept In this analysis, four effects are considered, namely the utility with respect to the production method, the effect of the production location image, the effect of the label [6, 7, 12, 14], and the utility with respect to the price In terms of the label, recently the eco-label has become one of the important factors in product display This has recently come under discussion in the FAO because it is necessary to create an international standard, and now there is a standard ‘‘FAO guideline of the labeling for responsible aquaculture.’’ This study narrowed the exercise to analyzing product affiliation with respect to production method, production location, the existence of a label, and price Because of the multiple choice test format, the choice of attributes was limited to these four to give respondents the feeling of a realistic situation Production methods (three levels) included wild-caught (fishery), farmed (relying on natural young tuna as a raw material for culture), and full-cycle farmed (creating stable young tuna production from cultured parental stock); locations (two levels) included domestic production and overseas production; labeling (two levels) was either with or without a label presenting the eco-friendly character of the product with the certification as to the production and chain of custody); and prices (four levels) were based on data available online and were set at 200, 300, 400, and 500 yen per piece of sushi A virtual label was designed that was very similar to a real eco-label, mainly describing the eco-friendly condition and the existence of a chain of custody to make the study as close to reality as possible [6, 7] Table shows the content of the conjoint survey that was drafted The questions were designed in the format of a direct arrangement table [9] The analysis examined differences in consumer response before and after information was provided The information provided included three sections: the exhaustion of tuna resources, tuna farms and resource management, and full-cycle farming of bluefin tuna (Table 2) Overall effect The theoretical background for the conjoint analysis designed above is explained below [9–11] To grasp the consumer propensity for bluefin tuna, this study used a selection test format within the conjoint analysis Regarding affiliation (production method, production location, existence of a label, and price), several types of products with different levels (profiles) were presented, and respondents were asked to select the most desirable product from among them The selection test format allows for realistic responses to be obtained from respondents to a survey The following is an explanation of the model used for the selection test format conjoint analysis [8–10, 13] The conjoint analysis calculates the consumer utility based on the random utility theory and, based on this, I hypothesized utility using a linear equation for product affiliation as follows: U is the utility if the respondent i selects j from selection J Uij ¼ Vij þ eij ¼ b0 xij þ eij ; j ¼ 1; ; J ð1Þ where V is the component that allows the measurement of utility, e is the probability component, x is the vector indicating affiliation level, and b is the parameter/vector of affiliation When the respondent i selects j, the utility increases more than in the case where another item was selected Therefore, the probability of selection j is expressed by À Á Probð jÞ ¼ Prob Uij [ Uim À Á ¼ Prob Vij þ eij [ Vim þ eim À Á ¼ Prob Vij À Vim [ eim À eij for all m 6¼ j ð2Þ Here, as long as the probability component of J falls within the extreme value distribution of the first kind, the probability of the individual i selecting j is expressed in the following equation: À Á À Á exp b0 xij exp Vij Probð jÞ ¼ PJ ð3Þ À Á ¼ PJ À Á j¼1 exp Vij j¼1 exp b xij By maximizing this likelihood function, the parameters of each individual affiliation can be estimated (maximum 123 1026 Fish Sci (2010) 76:1023–1028 Table Questionnaire likelihood method) [9, 13] Also, a conjoint analysis is different from the contingent valuation method (CVM) in that we can obtain the MWTP for each affiliation [9, 13] First, the observable component V of the aforementioned utility is expressed as the affiliation variable other than price x, price p, and parameter b X V ðx; pÞ ¼ bs xs þ bp p ð4Þ s From Eq 4, we can derive the following: 123 X oV s oxs dxs þ oV dp ¼ dV op ð5Þ Here, by making the utility level constant (dV = 0) and fixing the affiliations other than xt at the initial level (dxs = for all s = t), the desired amount of payment per each unit increase of affiliation xt (in other words, the amount people not mind paying extra if the price of an affiliation increases by one unit) or MWTP is obtained (Eq 6) Fish Sci (2010) 76:1023–1028 Table Information provided to consumers 1027 Category Description Exhaustion of tuna resources Currently, there is overfishing of tuna because of very high consumption and inadequate resource management, and the availability of bluefin tuna and others is decreasing significantly Some scholars have said that resources of these fish have drastically decreased Under such circumstances, regional fisheries management organizations (RFMOs) are restricting the quantity of bluefin that can be caught in open seas and are gradually decreasing the quota every year Unfortunately, even this does not create a trend toward recovery Tuna farms and resource management Presently, conventional farming of bluefin tuna meets about half of the total demand for tuna Living tuna are caught in the wild, fed on the farm until they have matured, and then are delivered to the market when they reach an appropriate size However, because these methods begin with tuna caught in the wild, the negative impact on resources is great and catch restrictions are becoming more stringent worldwide Full-cycle farming of Full-cycle farming of bluefin tuna as developed by Kinki University consists of an bluefin tuna integrated cultivation process from the production of eggs to maturity, without relying on tuna caught in the wild This breakthrough method will eliminate any worries pertaining to exhaustion of our natural resources Regarding food safety, because the feed is completely controlled, the accumulation of methyl-mercury as in natural stocks is not seen in full-cycle farmed tuna Flavor is also carefully controlled, with fat found throughout the body of the tuna for better flavor Flavor is currently reaching the point where this tuna can be served by luxury hotels in Japan and other countries MWTPt ¼ dp oV=oxt b ¼À t ¼À dxt oV=op bp ð6Þ By determining the relative MWTP, it becomes clear what points should be focused on when marketing a product In addition, ‘‘will not buy any’’ was added to the selection choices to eliminate any bias toward maintaining the current status and to estimate ASC, the constant component [13] This analysis was performed using TSP5.0 (TSP International), owned by Kinki University, Faculty of Agriculture, Fisheries Science and Economics Research Laboratory Results All analysis results were statistically significant McFadden’s quasi-R2 (a statistic that represents the goodness of fit when applying the estimate model) was 0.16 prior to information provision and 0.14 after This is relatively significant as a discrete selection analysis Moreover, the most important factor, the t statistics for each estimate, rejects the null hypothesis at a level of 1%; therefore, the estimated parameters are all statistically significant Schwartz B.I.C and log-likelihood are statistics that show model fitness, and they reached an acceptable value Therefore it can be said that this estimation can be used Table shows the estimate results prior to information provision Before information was provided, the MWTP for a bluefin tuna of wild-caught hand-formed sushi was 77 yen higher than full-cycle farmed tuna and 49 yen higher than farmed tuna This shows that there was no positive inclination toward full-cycle farmed tuna before information was provided Meanwhile, the MWTP was 109 yen for sushi with an eco-label and 159 yen for the one labeled as domestically produced tuna Table Estimated values prior to information provision Parameter Estimate Standard error t statistic P value MWTP Full-cycle farmed cultivation METHOD_A -0.656 0.048 -13.697 0.000 -77 Farmed Labels METHOD_C LABEL -0.414 0.927 0.049 0.032 -8.425 29.214 0.000 0.000 -49 109 159 Domestically produced PLACE Price PRICE Constant ASC 1.356 0.027 49.476 0.000 -0.009 0.000 -32.719 0.000 2.652 0.079 33.593 0.000 312 McFadden quasi-R = 0.16, number of observations = 12,000, number of choices = 48,000, log-likelihood = -13,931.5, Schwarz B.I.C = 13,959.7 123 1028 Fish Sci (2010) 76:1023–1028 Table After information provision Parameter Estimate Standard error t statistic P value Full-cycle farmed cultivation METHOD_A -0.532 0.039 -13.520 0.000 -81 Farmed METHOD_C -0.776 0.049 -15.833 0.000 -117 Labels LABEL 0.780 0.024 32.021 0.000 118 229 Domestically produced PLACE Price PRICE Constant ASC 1.510 0.031 48.872 0.000 -0.007 0.000 -30.386 0.000 1.763 0.071 24.811 0.000 MWTP 267 McFadden quasi-R = 0.14, number of observations = 12,000, number of choices = 48,000, log-likelihood = -14,361.1, Schwarz B.I.C = 14,389.3 After information was provided, the MWTP changed After information was provided, domestic production continued to be the greatest basis for trust to the consumer, with an MWTP increased to 229 yen (Table 4) There was no significant change in MWTP with or without a label (changed from 109 to 118 yen) The MWTP for farmed tuna was the opposite of that for fullcycle farmed tuna This was due to the increase in comprehension with respect to farms and full-cycle farming, and the relative increase in the position of fullcycle farming The result was a higher position for fullcycle farming in the eyes of consumers after information is provided Discussion An information provision strategy centered on marketing was investigated based on the aforementioned MWTP Increased value per production method after information provision was shown for domestically produced tuna and for tuna with labels, as was the case prior to information provision Also, because the willingness to pay increased overall, information provision can be seen as important for adding value in a marketing strategy Eco-labeling invoked a large MWTP, so it can be said that certification labeling offers significant value to consumers and can be reflected in prices This suggests that a labeling certification system is needed in the Japanese market to add value to the bluefin tuna Full-cycle farmed bluefin tuna should find a possible market when an eco-label is provided and consumers are given information about the resource problem and farming methodology This suggests that eco-friendliness and good resource management are key factors for consumers when choosing between wild-caught and farmed fish Full-cycle farming of bluefin tuna is set to reach industrial levels, and at the same time, there are other eco-friendly technologies, such as soy-based feed, that may offer solutions to create a sustainable supply that can meet the demand in the market 123 Acknowledgments This study is a part of the GCOE program of Kinki University I wish to thank Prof Seiichiro Ono of Kinki University for assistance References Kumai H et al (2010) Fullcycle farming of bluefin tuna Seizando, Tokyo Ono S (2008) The problem and view of tuna farming: logistics and economics of cultivated tunas––proximity based on the food system theory, chap Kinki 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Center, Fisheries Research Agency, Sapporo, Hokkaido 062-092 2, Japan e-mail: brochet@affrc.go.jp Present Address: I Shimizu National Research Institute of Fisheries Science, Fisheries Research Agency, Yokohama, Kanagawa 236-864 8, Japan Present Address: J Seki Eniwa, Hokkaido 061-137 2, Japan Present Address: E Hasegawa National Research Institute of Fisheries Engineering, Fisheries Research Agency, Kamisu,... coefficients, standard errors, and standardized coefficients, respectively brood-year effect: F( 3, 392) = 2.61 6, P [ 0.05; sex effect: F( 1, 392) = 4.89 9, P \ 0.05; brood-year 9 sex effect: F( 3, 392) = 2.39 0, P [ 0.05) For the 5–10CW, there was neither a brood-year effect nor a sex effect; however, there was significant interaction (two-way ANOVA, brood-year effect: F( 3, 392) = 1.21 6, P [ 0.05; sex effect: F( 1,. .. In: De Silva SS, Davy FB (eds) Success stories in Asia aquaculture Springer, NACA, and IDRC, Dordrecht, pp 133–149 8 Baras E, Slembrouck J, Cochet C, Caruso D, Legendre M (2010) Morphological factors behind the early mortality of cultured larvae of the Asian catfish, Pangasianodon hypophthalmus Aquaculture 298: 211 219 9 Slembrouck J, Baras E, Subagia J, Hung LT, Legendre M (2009) Survival, growth and... hypophthalmus, depending on feeding level, prey density and fish density Aquaculture 294:52–59 10 Poulsen AF, Hortle KG, Valbo-Jorgensen J, Chan S, Chhuon CK, Viravong S, Bouakhamvongsa U, Yoorong N, Nguyen TT, Tran BQ (2004) Distribution and ecology of some important riverine fish species of the Mekong River basin Technical paper no.10 Mekong River Commission, Phnom Penh 11 Nguyen TT, Nguyen ND, Vu VA, Truong... including Vietnam, Malaysia, Indonesia, Laos, Cambodia, and China [1–5] Vietnam, the largest sutchi catfish producing country in the region [6 ], produced 1,2 0 0,0 00 tons of catfishes in 200 7, of which 95–97% were sutchi catfish [7] Although sutchi catfish is an important species for aquaculture and the survival rate of reared larvae is low due to high levels of cannibalism [ 2, 3, 8, 9 ], no detailed ecological... 3-aminobenzoic acid ethyl ester (MS22 2, 200 ppm) and preserved in Bouin’s solution Specimens were embedded in paraffin, cut into 6-lm-thick sections, and stained with hematoxylin–eosin for histological examination [newly hatched larvae, 6 individuals; 1 day after hatching (1 day ), 6; 2 days, 10; 3 days, 9; 4 days, 7; 5 days, 5; 6 days, 6; 7 days, 5; 10 days, 5; 15 days, 5; 20 days, 5] Other specimens from the... Agency, Kamisu, Ibaraki 314-040 8, Japan H Saito School of Biological Science and Engineering, Tokai University, Sapporo, Hokkaido 005-860 1, Japan K Nagasawa Graduate School of Biosphere Science, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-852 8, Japan regulates brood-year strength Contrary to this expectation, the 2000 brood year had almost the lowest return rate Alternatively, a statistical... period, but fishes only lost mass in the small-scale experiment (Fig 2) In the spring period, however, both species started to grow: in the small-scale experiment, the % mass gains of the study species were almost identical (winter, t4 = -0.3 3, P = 0.758; spring, t4 = -0.17 6, P = 0.869 ), but rainbow trout tended grow slightly faster in the mesoscale experiment (winter, t2 = -3.2 5, P = 0.083; spring, t2... community ecology In: Resetarits WJ Jr, Bernardo J 907 30 31 32 33 34 35 36 37 (eds) Experimental ecology issues and perspectives Oxford University Press, New York, pp 3–26 Huusko A, Greenberg L, Stickler M, Linnansaari T, Nyka¨nen M, Vehanen T, Koljonen S, Louhi P, Alfredsen K (2007) Life in the ice lane: the winter ecology of stream salmonids Riv Res Appl 23:469–491 Kocik JF, Taylor WW (1995) Effect of juvenile... Distribution, migration, and abundance estimation of Asian juvenile salmon Salmon Rep Ser 45:83–103 24 Nagasawa K (2000) Winter zooplankton biomass in the subarctic North Pacific, with a discussion on the overwintering survival strategy of Pacific salmon (Oncorhynchus spp.) N Pac Anadr Fish Comm Bull 2:21–32 25 Fukuwaka M, Sato S, Takahashi S, Onuma T, Sakai O, Tanimata N, Makino K, Davis ND, Voklov AF, Seong