Three separate experiments were carried out to assess combined effects of temperature and salinity and induced stress on blood variables of Tra catfish (Pangasianodon hypophthalmus) fingerlings. Some hematological parameters included Haemoglobin concentration, glucose and pH levels which were tested in different conditions. The experiment 1 aimed to test how blood variables change in different temperature (24, 28-30, 32 oC) and salinity (0, 6 and 12 ppt) while the experiment 2 induced catfish fingerlings to different stress time (5, 15 and 30 min.).
AGU International Journal of Sciences – 2019, Vol (3), 37 – 46 COMBINED EFFECTS OF TEMPERATURE AND SALINITY AND INDUCED STRESS ON SOME HEMATOLOGICAL PARAMETERS OF TRA CATFISH (Pangasianodon hypophthalmus) FINGERLINGS Dang The Luc1 An Giang University, VNU - HCM Information: Received: 17/10/2018 Accepted: 08/07/2019 Published: 11/2019 Keywords: Pangasianodon hypophthalmus, temperature, salinity, Haemoglobin, glucose, stress ABSTRACT Three separate experiments were carried out to assess combined effects of temperature and salinity and induced stress on blood variables of Tra catfish (Pangasianodon hypophthalmus) fingerlings Some hematological parameters included Haemoglobin concentration, glucose and pH levels which were tested in different conditions The experiment aimed to test how blood variables change in different temperature (24, 28-30, 32 oC) and salinity (0, and 12 ppt) while the experiment induced catfish fingerlings to different stress time (5, 15 and 30 min.) Additionally, combined effects of all factors (temperature, salinity and induced stress) on fish blood parameters were also determined in the experiment Results showed that in normal condition, the mean Hb concentration and glucose levels of blood varied from 4.36 – 4.90 g/dL, and from 3.83 – 5.23 mmol/L, respectively and mean pH ranged from 7.73 – 8.20 The concentration of Hb, glucose and pH levels changed when temperature increased from 24 to 32oC After 30 stress minutes, there was only glucose levels influenced Moreover, there were significant interaction effects among temperature, salinity and stress level on blood variables The findings revealed that the physiology of Tra catfish fingerling could be affected after stress minutes at temperature of 24oC and 32oC with salinity of and 12 ppt All data of experiments showed that a positive correlation between Hb concentrations and glucose levels and negative correlation between Hb concentrations and pH levels were found Results also showed that changes in blood variables could cause stress for aquatic animal, especially Tra catfish fingerlings INTRODUCTION Catfish is one of the most important species cultured in the MeKong Delta, which brings the main income to An Giang farmers However, despite of climate change, there are some negative impacts on catfish farming, especially when temperature and salinity have changed levels and the interaction between temperature and salinity on fishes (Kemp, 2009; Wright and Tobin, 2011; Nguyen et al., 2015) These studies have all concluded that fish health including growth rates, survival rates and physiological responses could be negatively affected by significant changes Many previous studies have been carried out to assess effects of rising temperatures, salinity The increase of temperature could affect the metabolism of aquatic animals as well as the 37 AGU International Journal of Sciences – 2019, Vol (3), 37 – 46 growth rate of fish (Kemp, 2009) Modified salinity is a factor causing stress and affecting fish physiology (Fashina-Bombata & Busari, 2003; Konstantinov & Martynova, 1993; Partridge & Jenkins, 2002; Sink, 2010) Stress is a popular physiological status in fish or other species in order to deal with changes of the environment to survive and maintain internal balance of animals (Fuzzen et al., 2011) The study was carried out from December 2016 to October 2017 at the wetlab of An Giang University, Long Xuyen city, An Giang province 2.2 Experimental design The experiment 1: A two-factor designs, where three temperature (T) levels (24°C, 28°C – 30°C and 34°C) and three salinity (S) levels (0 ppt, ppt and 12 ppt) were tested in triplicate combinations (TxS) Previously, stress indicators included changes in plasma glucose and pH levels in fish, especially Tra catfish, were examined (Kirchhoff et al., 2014; Nguyen et al., 2014) In addition, Haemoglobin concentration is also considered as an indicator to evaluate overall physiology and general health in fish (Houston, 1997) However, it is necessary to fully collect more data on blood variables in Tra catfish's fingerlings in the condition of climate change in Mekong Delta, Vietnam In this experiment, with a density of 30 individuals/tank, fish fingerlings were accustomed gradually to required salinity rates by replacing freshwater in each tank with saline water in a stepwise fashion, which was 2‰ per day to prevent shock to fish, until all tanks had reached their target salinities Individuals were then kept within 24 hours to be stable Finally, the temperature levels were modified by ice and heaters in a stepwise fashion, which was not higher than 2°C per hours until all tanks had reached their target temperature levels Fish blood was immediately collected from the caudal veins within of sampling with mL heparincoated syringes after being anaesthetised at the following time intervals: 0h, 1h and 24h Therefore, the study “Combined effects of temperature and salinity and induced stress on some hematological parameters of Tra catfish (Pangasianodon hypophthalmus) fingerlings” was conducted to fully understand about Tra catfish fingerling’s health This also contributes to establish some blood variables’ baseline for Tra catfish, which helps to determine and manage fish health status more effectively As a result, the production cycle of Tra catfish could be enhanced and sustainably developed in the condition of climate change in Mekong Delta The experiment 2: According to Lopez-Patino et al (2014), fish was stressed by chasing (using hand-nets to catch up fish) within 5, 15 and 30 minutes After stressed time, fish blood was immediately collected from the caudal veins as in the experiment The experiment 3: Fish was challenged by a three-factor design which combined different temperature (T), salinity rates (S) and stress levels (St) in triplication This experiment included 27 treatments Temperature and salinity rates were adjusted as the experiment before fish was chased as in the experiment After that, fish blood was immediately collected from the caudal veins within of sampling with mL heparin-coated syringes after being anaesthetised MATERIALS AND METHODS 2.1 Experimental system and source of catfish Catfish fingerlings (25.96 ± 0.67 g/fish) were obtained from a hatchery farm located in Dong Thap province Fish were in good conditions and fed commercial feed (40% crude protein) during the experiment Individuals were acclimated for a month before transfered to 80L tanks in freshwater at 28-30°C (maintained by heaters) with a continuous supply of well-aerated water After the acclimatation period, fish were arranged 2.3 Sampling collection and analysis Fish fingerlings were anaesthetised by 0.3 ppm of MS-222 Fish blood was collected from caudal veins Each sample contained mL in heparinised into different experiments 38 AGU International Journal of Sciences – 2019, Vol (3), 37 – 46 Vacutainer® tube (BD, USA) All samples were stored with ice before being analysed time) and their interactions on blood variables All variances were homogenous by Levene's test Haemoglobin (Hb) concentration was determined by using a haemoglobin meter, ACON Mission® Hb Plus Meter (ACON Laboratories Inc., USA) Glucose concentration was determined by using a glucose meter test, ACON On Call Plus Meter (ACON Laboratories Inc., USA) Blood pH was determined by using a pH meter, Horiba 11 (LAQUAtwin, Japan) Relationships between blood variables were determined using all data and Spearman's rank correlation coefficients Homogeneity of variance was tested with Levene’s test and the means of blood variables were compared using Duncan test 2.4 Statistical analysis 3.1.1 Haemoglobin All data were analysed by SPSS 20.0 for Windows (SPSS Inc., Chicago, IL, USA) Means and standard errors were calculated for blood variables including Hb concentration, levels of glucose and pH The differences among treatments within experiment were determined by two-way and three-way analysis of variance (ANOVA) at a significance α=0.05 for significant main effects (temperature, salinity or stressed There was an interaction between temperature and salinity on Hb concentrations Hb concentrations were unstable during this study, especially there was an increase in Hb concentration at 24 0C, ppt after 24 hrs (shown in Table 1) when Hb concentration reached the highest concentration (6.03 ± 0.45 g/dL) The lowest one (2.90 ± 0.10 g/dL) was at 240C, ppt, hr The Hb concentration in a normal condition was in range of 4.36 – 4.90 g/dL RESULTS 3.1 The experiment Table Mean Hb concentrations (g/dL) between treatments in the experiment Treatment 0h 1h 24h 24C, ppt 3.33 ± 0.35ab 3.33 ± 0.35ab 6.03 ± 0.45d 24C, ppt 2.90 ± 0.10a 3.46 ± 0.45abc 3.36 ± 0.15ab 24C, 12 ppt 3.10 ± 0.30a 3.16 ± 0.32a 3.26 ± 0.35ab Control, ppt 4.36 ± 0.65bc 4.16 ± 0.25c 4.90 ± 0.10c Control, ppt 3.66 ± 0.85ab 3.93 ± 0.35bc 2.90 ± 0.10a Control, 12 ppt 3.86 ± 0.85ab 4.10 ± 0.40c 4.76 ± 1.15c 34C, ppt 4.85 ± 0.55c 4.90 ± 0.45d 4.20 ± 0.20bc 34C, ppt 3.30 ± 0.40ab 3.30 ± 0.30ab 4.25 ± 0.45bc 34C, 12 ppt 3.70 ± 0.50ab 3.63 ± 0.45abc 4.86 ± 0.95c Mean values having different letters within columns are significant difference (p