29 observations on the spawning development and rearing of the south african abalone haliotis midae linn

South African Journal of Marine Science ISSN: 0257-7615 (Print) (Online) Journal homepage: https://www.tandfonline.com/loi/tams19 Observations on the spawning, development and rearing of the South African abalone Haliotis midae Linn A B Genade , A L Hirst & C J Smit To cite this article: A B Genade , A L Hirst & C J Smit (1988) Observations on the spawning, development and rearing of the South African abalone Haliotis�midae Linn., South African Journal of Marine Science, 6:1, 3-12, DOI: 10.2989/025776188784480465 To link to this article: https://doi.org/10.2989/025776188784480465 Published online: 08 Apr 2010 Submit your article to this journal Article views: 507 Citing articles: 18 View citing articles Full Terms & Conditions of access and use can be found at https://www.tandfonline.com/action/journalInformation?journalCode=tams20 S Afr J mar Sci 6: 3-12 /988 OBSERVATIONS ON THE SPAWNING, DEVELOPMENT AND REARING THE SOUTH AFRICAN ABALONE HAL/OTIS MJDAE LINN A B GENADE*, A L HIRST*t AND OF c J SMIT* A description is given of the first successful controlled breeding of the South African abalone Ha/iotis midae Gametes of ripe abalone were obtained from spontaneous spawnings as well as by subjecting animals to spawning stimuli The larval period is five days at 20°C and seven days at 17,5°C The first respiratory pore is completed at a shell length of2,3 mm and the first shell ridge can be observed at approximately 2~ mm Benthic diatoms on fibreglass plates served as food for post-larval stages to a length of 5-8 mm Larger Juveniles were fed the seaweeds Plocamium spp and Ulvafasciata Shell pigmentation is affected by the food consumed Variable growth rates for individuals from the same spawning were observed 'n Beskrywing word gegee van die eerste suksesvolle gekontroleerde te1ing van die Suid-Afrikaanse perlemoen Haliotis midae Gamete is van ryp perlemoen deur spontane kuitings sowel as kuitprikkels bekom Die larwale periode is vyf dae teen 20°C en sewe dae teen 17,5°C Die eerste respiratoriese porie word voltooi op 'n skulplengte van 2,3 mm, terwyl die eerste skulprifby ongeveer23 mm waarneembaar is Bentiese diatomc op veselglasplate is as voedse1bron vir postlarvale stadia tot ongeveer'n lengte van 5-8 mm aangewend, waarna die seewiere Plocamium spp en Ulvafasciata gevoer is Die pigmentasie van die skulp word deur voeding beinvloed 'n Groot variasie in groei is vir individue afkomstig van dieselfde kuitgroep waargeneem Of the six South African abalones (Muller 1986), only Haliotis midae (locally known as perlemoen) occurs in quantities sufficiently extensive to warrant commercial exploitation It contributes substantially to the inshore fisheries and the present whole mass quota is 660000 kg (Chief Directorate Marine Development 1986) Strict conservation measures were implemented from 1965 to curb overfishing, peak production of 2,28 million kg being recorded in that year Because the present supply cannot meet the demand, commercial industry has shown an intense interest during recent years in the possibilities for controlled culture of H midae This need has been stimulated further by the advancement in abalone cultivation techniques overseas Japan is at present the acknowledged leader in developing techniques for the mass production of juveniles especially for restocking The number of seed abalone released from hatchery-produced seed in Japan has increased from 200 000 in 1970 to 10,7 million in 1978 (McCormick and Hahn 1983) Efforts to culture this economically valuable shellfish are now undertaken world-wide and, since the major contribution made by Ino (1952), research and development projects have been launched and production facilities established in Australia, the United Kingdom, Canada, Chile, France, Mexico, Taiwan and the United States (Ebert and Houk 1984) Whereas the production of juveniles so far has been aimed at augmenting the supply of natural seed, abalone producers in the United States are now investigating a market for small or cocktail abalone for the restaurant trade (Chew 1984) Various aspects of the biology of H midae of importance to fisheries management have been researched by Newman (1966, 1967a, b, 1968, 1969), and they cover mainly the migration, reproduction, growth and distribution of natural populations No successful rearing of H midae has been recorded to date, whereas most of the commercially important species in other countries have been cultured and larval and post-larval development documented (lno 1952, Leighton 1974) The purpose of this preliminary investigation is to demonstrate that spawning, larval development and further growth of H midae can be achieved under controlled and semi-controlled conditions Facilities, which were mainly utilized for bivalve culture, at the Aquaculture Unit of the Fisheries Development Corporation of South Africa Ltd at Knysna (Cape Province) were used for this study Knysna is about 500 km east of the main commercial exploitation area of abalone, Cape Hangklip to Quoin Point (Fig I) MA TERIALS AND METHODS Collection and transport Mature H midae larger than 110 mm shell length were collected during August and September 1981 and May and June 1985 from the exploitation area • Formerly Fisheries Development Corporation Aquaculture Unit, P.O Box 346, Knysna 6570, South Africa t Sea Fisheries Research Institute, Private Bag X2, Rogge Bay, 8012, South Africa - to whom all correspondence Manuscript received: March 1986 should be addressed 1988 South African Journal of Marine Science S 290 300 310 320 33 340 35 nG?01 Intensive exploitation 36 16 17 18 o 22 o 31 23 o 32 E Fig 1: The laboratory site and main area of commercial exploitation of Haliotis midae (Fig I) The animals were removed either by knocking off by hand those which had raised part of the foot (the method used by abalone for capturing drifting fragments of kelp) or by the conventional levering-off method used by commercial divers The captured animals were sexed by inspecting the colour of the gonad, which is dark green in females and cream in males Collection took place between IOhOO and I3hOO Immediately after delivery to the boat by SCUBA divers, each abalone was placed in a 10-1 plastic bag filled to one-third with seawater and inflated with oxygen before being sealed off The sex was recorded on the bag, which was then put into a polystyrene cool-box for the six-hour journey to the laboratory Animals collected during 1981 were placed 10 per aerated 600-1 tank at ambient temperature (± 17°C), and those collected in 1985 were put in shallow tanks with 19°C water filtered to ~m flowing at a rate of 1 per minute per animal In all cases the sexes were kept separate The tanks used for the 1985 groups were lined with clear plastic sheeting to facilitate subsequent removal of the animals Spawning The groups obtained during 1981 were not exposed to any additional stimulus, but those collected in 1985 were subjected to a stimulus procedure, more or less corresponding to that described by Chen (1984), the following morning These abalone were first exposed to air for one hour and then placed in tanks with flowing, 17°C seawater previously exposed to ultraviolet light (2,537 A) and filtered to ~m Sexes were still kept separate The water temperature was then increased by 1°C per hour for three hours, and then decreased over the same period to the original temperature Once spawning had commenced, the waterflow was reduced Fertilization and larval cultivation Spawned ova were collected by siphoning into 15-1 round fibreglass containers to a density that, when spread out, the ova would form a single layer on the bottom Because of their higher specific gravity than seawater, the ova would settle within approximately 10 minutes Siphoning was then easily accomplished The ova were fertilized by adding freshly released sperm (± I hour after spawning) at a concentration of ± 120000·ml-1 to the container after microscopic examination of their activity After gentle mixing, the ova were exposed to the sperm for 15 minutes, after which the water was topped up to 15 Decanting to remove the excess spenn,and debris began after most of the ova had settled Refilling with fresh seawater 1988 Genade et at.: Laboratory Spawning, Development and Rearing of Abalone and decanting was then repeated ten times, approximately every ten minutes After the final wash the ova were transferred to 240-t tanks for further development at either 20°C or ambient temperature (± 17,soC) As the larvae of the Haliotidae are lecithotropic (Leighton 1974), no food was added to the cultures until the settlement stage was reached Also, there was no water-flow or aeration during larval development The water was changed once per day after siphoning the larvae onto a 45-~m net Development stages were recorded according to the classification Leighton (op cit.) To test the effect of "GABA" (')I-aminobutyric acid), a neurotransmitter, on the settling rate of advanced veligers, the following experiment was designed, as used by Morse et al (1979) for H rufescens: 15 X 4-t Pyrex beakers were placed in a waterbath at 20°C, in groups of beakers each All the beakers were filled to t and treated with penicillin at 33 ppm "GABA" was then added to each group at increasing concentrations, i.e with no addition (control), at 10-6 molar, at 10-5 molar, at 10-4 molar and at 10-3 molar Some 000 advanced larvae (digitate cephalic-tentacle stage) were added per beaker and the reaction of the larvae was recorded and 18 hours later Settlement and juvenile cultivation Benthic diatoms scraped from the bottom of the outflow channel of the oyster nursery in the same laboratory were used to seed corrugated fibreglass plates of 25 X 30 em, which had been matured previously in seawater for three weeks A slurry was made after washing the diatoms (± 70 per cent Navicula) through a 50 ~m net The cleaned settling plates were suspended overnight in the diatom mixture, and the next morning, covered with a thin film of benthic diatoms, they were placed on the bottom of the 240-t tanks with advanced larvae "GABA" was added to the tanks at 10-6 molar After settlement, the plates were left in the tanks for a further five days, during which time the tanks received constant lighting, slight aeration and a daily water exchange To encourage further diatom growth, the plates were periodically removed and resuspended in a section of the oyster nursery which received a constant water flow No temperature control was administered, but regulating natural light by occasional screening with a shade mesh was necessary to control diatom growth At an approximate length of 5-8 mm, the seed abalones were transferred to tanks 2,0 m long X 0,5 m wide X 0,25 m deep, into which chopped pieces of seaweed about 1,0 cm2 were introduced daily at 17hOO.Initially, pieces of Plocamium sp., which was collected at low springtides on the coast and stored in a freezer, were used, but because of the distance from the nearest source, the feed was changed after a few months to Viva fasciata This species could be obtained easily from close to the laboratory Shelters, in the form of halved 100-mm PVC and ceramic pipes, which covered approximately 50 per cent of the bottom of the tanks, were also introduced into the tanks Unfiltered seawater of salinity 30-35 X 10-3 and ambient temperature (1O-27°C) was supplied at a flow rate of 61·min-l·tank-1 or 24 m£·min-1·animat' The tanks were also aerated Stocking density was ± 250 animals·m-2 (bottom surface) at a shell length of approximately 20 mm The outlets were screened with an appropriate mesh to prevent animals from escaping during night migration Food residues and faeces were siphoned off every second day At no stage was any attempt made to grade the abalones to prevent competition RESULTS Collection and transport Specimens knocked off by SCUBA divers experienced little or no damage, but the foot of those levered from the substratum was injured in more than 40 per cent In intact abalone, mortality was less than per cent two weeks after transfer Injured animals showed signs of extreme stress and more than 50 per cent mortality within the same period No injury was caused to the abalone when removed from the plastic bags because of the ease with which the plastic could be released from the adhering foot On arrival, oxygen concentration in the bags varied between 8,0 and 12,0 ppm and pH between 7,2 and 7,6 Spawning Natural spawning had commenced in the 1981 groups before 08hOO the morning after transfer and continued, in the August group, sporadically until IOh30 The temperature at spawning for the August group was 13,5°C and that of the September group 17,0°C, in both cases the ambient temperature Because of the number of abalone in each tank, no accurate estimate of the number that spawned could be made, though probably in excess of 80 per cent of both sexes spawned spontaneously The two groups collected during 1985 responded to stimulation as follows: May group - 40 per cent of the females reacted at South African Journal of Marine Science 6 Table I: Times at which developmental stages (after Leighton 1974) of H midae larvae were first observed at 20°C Stage When achieved after fertilization Description Hours I 10 II Hatching Free-swimming trochophore Cap-shell, early veliger' Infiatc-shell veliger, torsion Early operculate veliger, pre-eyespot Incipicnt cephalic tentacle, operculate veligcr Mid-formed cephalic tentacle Digitate (branched) cephalic tentacle Crawling, settling Total metamorphosis (loss of cilia, but no mouthparts or feeding yet observed) Peristomial growth June group - 14 22 24 31 ± Days 46 51 86 97 1/8 145 169 Ejaculation of ova and sperm occurred mainly through the first four respiratory pores In contrast to the ova, which settled to the bottom within a few minutes, the sperm stayed in suspension Egg counts were made of two females 150 mm long in the June spawning Both animals still had a substantial reserve after spawning and released I 245 X 106 and 0,750 X 106 ova respectively The spherical ova (Fig 2), which are enveloped by a relatively thick gelatinous membrane, varied in diameter between 212 and 222 J.lm (x 214 J.lm), and the yolk varied between 172 and 192 J.lm (x 181 J.lm) Fertilization II: Achieved stages of development of H midae larvae at different ambient temperatures Stage of development Day on which stage achieved 17,5°C 20°C M idformed cephalic tentacle Digital cephalic tentacle Crawling and settling I least slightly only after five hours All ova were prematurely released No males responded 20 per cent of the females reacted within three hours and produced well formed "mature" ova similar to those obtained during 1981 = Table 1988 = and early development A high rate of fertilization (± 80 per cent) was' obtained for the naturally spawning groups of August and September 1981 However, the June 1985 group showed a relatively low percentage, ranging from 11 to 25 per cent The addition of excess sperm to this group, ova of which already showed cleavage, did not improve the percentage successfully fertilized but rather resulted in the rupture of many egg membranes The progress in larval development is summarized in Table I No specific differences in larval features from those recorded by other authors for haliotid embryology (Ino 1952, Leighton 1974) could be observed (Fig 2b-f) The green pigmentation of the egg yolk is retained by the trochophores and veliger larvae This phenomenon has also been recorded for other species by Leighton (1972) The behaviour of trochophores and veligers is also typical of Haliotis Trochophores tend to concentrate at the surface of containers (negative geotaxis), and healthy veligers congregate in vertical columns, then tumble to the bottom where they scatter and regroup again to form new columns This cycle is repeated every few minutes Trochophores measure approximately 164 J.lm X 190 J.lm just after hatching and fully developed veligers 207J.lm X 265 J.lm Development from cleavage through to settlement at the two temperature regimes, 17,5 and 20,0°C, appeared to be quite normal A marked difference in rate of development was, however, recorded as shown in Table II Settlement and juvenile cultivation Settling of larvae was advanced and stimulated by addition of "GAB A ", as shown by the results in Table III Settlement was on the sides as well as at the bottom of the beakers Larvae held at 17,5°C in 240-£ tanks reacted well to the addition of "GABA" only on Day 7, with a maximum settlement of l·cm-2 on Day However, many larvae were still swimming actively at this stage Complete settlement was observed on Day (Fig 2g) Table III: Percentage settlement in 4-1 beakers at 20°C after addition of "GABA" to 4-day-old larvae Time After hours After 18 hours 10-3 molar 10-· molar 10 10 0 40 80 80 50 50 Control IO-l molar 10-6 molar 1988 Genade et al.: Laboratory Spawning, Development and Rearing of Abalone Fig 2: Developmental stages of Haliotis midas (a) fertilized eggs of ± 214 Ilm, sperm attached to membrane; (b) freshly hatched trochophore larva of 164 X 190 Ilm; (c) cap-shell veliger larva; (d) inflate-shell veliger (torsion) of 207 X 2651lm with retractor muscle; (e) operculate veliger (pre-eye spot); (f) operculate veliger (pre-eye spot) with retracted velum; (g) crawling and settling stage; (h) peristomial growth; (i) circular-shell post-larva of ± 600 Ilm; (j) whole shell pink with no respiratory pores; (k) juveniles showing dietary pigmentation; (I) juveniles of approximately year of age South African Journal of Marine Science 30 Vl UJ 1988 o 25 C>:: 0- >- 20 C>:: ~ C>:: c: 15 Vl UJ C>:: • 10 C>:: UJ a:l ~ ::::l Z ~ • ~~ "~ Open pores Closed pores ~ • • ~ ~ ~ • • Fig 4: Radial 10 LENGTH Fig 3: Relationship 15 20 on the shells of H midae specimen ± 36 mm) (largest (mm) between length and number of pores An extremely variable pattern of settlement took place over the plates Some features of post-larval development after transfer from the settling tanks and at different ambient temperature are given in Table IV Peristomial growth (Fig 2h) was apparent the first day after transfer to substrate with benthic algae At a size of 600 ~m, one juvenile could clear algae from an area of up to 16 mm2 in 24 hours and could move 1,0 cm At 700 ~m, the shells were fully round with a pink tint (Fig 2i, j) and movement of cm in hours was recorded under nursery conditions At this stage they were already extremely light-sensitive and would immediately move away from a bright stereo-microscope light In H midae, the notch stage is reached at a size of 2,1-2,2 mm and completion of the first pore at 2,3 mm, similar to that of the American west coast pink abalone H corrugata, but larger than for some Table IV: Post-larval ridges 25 other Baliotis species (Table V) The effect of temperature on growth (and pore formation) at this early stage was quite clear The August 1981 group took 65 days (I2-17°C ambient temperature) and the September 1981 group 48 days (I7-22°C ambient temperature) to display this feature Respiratory pores are continuously being formed and previous ones sealed off as growth advances (Fig 3) The first sealing off already starts at a size of mm, where just two of the three pores are functional At 25 mm a total of 27 pores would have been formed but only five of these were open for respiration A definite difference in pore formation in H midae from that of the smaller Japanese H diversicolor supertexta (Oba 1964) can be observed after a length of some 15 mm (Fig 3) Although the effect of light intensity on growth was not tested at any stage during development, it was observed that juveniles (2-3 mm long) on plates receiving less light were generally larger (by up to 50 per cent) than those exposed to brighter light The shell colour is affected by the food consumed For instance, when feeding on benthic algae, a development features after transfer to ambient temperature Description of stage Time taken to achieve stage (days) 12-I7°C Virtually fully round, length up to 600 11m Fully round, pink tint to shell, 700 11m Whole shell pink, no respiratory pore Development of first respiratory pore 2,1-2,3 mm Two respiratory pores ± 3,0 mm 17-22°C 22 26 40 65 79 48 55 Table V: Shell length of post-larval Haliotis spp at formation of first respiratory pore Species H rufescens H corrugata H.fulgens H sorenseni H diversicolor supertexta H midae Shell length (mm) Source 1,5-1,8 2,0-2,5 1,7-2,0 2,0-2,1 1,8-/,9 2,1-2,3 Leighton (1974) Leighton (1974) Leighton (1974) Leighton (1974) Dba (1964) This paper Genade et al.: Laboratory Spawning Development and Rearing of Abalone 1988 n=300 50 25 40 20 30 UJ ;:) '" 15 '« '" u ~ ' .• • Average 10 0" Maximum - "' Minimum , ' 50 (b) n=300 ;:) '" u 40 MAMJ J ASOND MONTH Fig: 6: Average monthly temperature of the nursery section of the aquaculture unit 30 20 10 :.:-:.:.:.:.: :-:.:.:.:.:.:-: = ~??~~) 10 20 30 SHELl LENGTH (mm) specimens, the shell surface would have an irregular corrugated surface, as described by Day (1974), as a result of the moulding of these ridges The size frequency (length) after one and two years is given in Figure From this Figure it is clear that a wide variation in growth rate, originating from a specific spawning group, can be expected under culture conditions After 12 months a size range of 5-30 mm was recorded (x Il,8 mm), and at an age of 24 months the range was 10-45 mm (x 34,4 mm) Another notable feature was the stunted growth displayed by certain animals These results vary from those obtained by Newman (1968, 1969) for natural populations at Stony Point near Cape Hangklip (estimated growth rate of 21,7 mm per annum) and Port Elizabeth (28,8 mm) Newman (1969) attributed this difference to variations in the mean annual temperature at the two sites, 15,8°C at Stony Point and I7,4°C at Port Elizabeth The mean monthly temperature (recorded by thermograph for the semi-closed nursery system used for ongrowing) is given in Figure The recorded mean for the II months February-December is identical to the annual mean for Port Elizabeth 40 Fig 5: Size frequency of H midae at (a) one and (b) two years of age turquoise pigmentation was produced, but when fed mainly on Plocamium spp., a brick-red colour was apparent (Fig 2k, I) The formation of radial ridges, which are formed parallel to the growing margin and are most probably used for shell strengthening, can be observed at a length of 23-24 mm Ridges are continuously being added thereafter, so that an abalone of 36 mm would have approximately five of these (Fig 4) In mature = South African Journal of Marine Science 10 1988 1.25 35 1.0 >- :r: Ij 30 w ~ ~ 0.75 UJ i13 0.5 25 0.25 E E :r: 20 >Ij 15 ~ :j w 20 SHELL LENGTH 25 30 ( mm) 15 :r: Fig 8: Relationship between shell length and shell weight of juvenile H midae