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Effects of Low Salinity on Growth, Survival, and Stress Response in the Longtooth Grouper, Epinephelus bruneus, and E. bruneus × E. lanceolatus Hybrid Grouper
Get PDFThis study investigated the effects of low salinity on growth, survival, and
stress response in longtooth grouper, Epinephelus bruneus, and the hybrid
grouper resulting from crossing E. bruneus females and E. lanceolatus males.
There were no significant differences in the hybrids for any of the above
growth values among different salinity groups, however the percent weight
gain was significantly lower in the 8 Practical Salinity Unit (psu) group than in
the other salinity groups. As for survival, only longtooth grouper in the group
reared at 8 psu died. The plasma cortisol levels tended to increase at lower
salinities in both the longtooth grouper and the hybrids. Plasma Na+, K+, Cl–
concentrations in the hybrid were not significantly different among the salinity
groups, while Na+ and Cl– concentrations in the longtooth grouper were
significantly lower in the 8 psu group than in the other treatments. The above
results indicate that both the longtooth grouper and the hybrid grouper
juveniles were highly adaptable to variations in salinity. The optimal salinity
for rearing longtooth grouper was found to be 24 psu, while the hybrids had a
larger tolerance range of 16-32 psu. Results therefore showed that the hybrid
grouper has a higher tolerance than the longtooth grouper for low salinity
Effect of Different Protein Source Diets on Growth, Sensory Parameters and Flesh texture of On-Growing Grass Carp (Ctenopharyngodon idellus)
Get PDFThe introduction of plant protein (PP) sources in aquafeed is regarded as an economic and environmental-friendly strategy for aquaculture. Our objective was to investigate the effects of pure PP diets on the growth performance and to analyze their effects on flesh quality of grass carp (357.2±0.7g). The study was performed using and comparing a control fish meal diet and two PP diets. Fish meal (FM), soybean meal (SBM), and rapeseed meal (RM) were served as sole protein source of corresponding feeds, respectively. The results suggested that the PP diets significantly impaired the growth performance of grass carp. In regard to flesh quality, the SBM and RM diets decreased the muscle lipid content, n-3 series of PUFA, EPA, DHA, and n-3/n-6 ratio at the nutritional level. However, from the consumer's perspective SBM significantly improved flesh firmness, and RM diets, and PP diets had no adverse effects on flesh flavor, amino acids composition, and sensory characteristics. Fish fed the RM diet displayed a higher water holding capacity (WHC) in the fillets than in the other groups. In summary, compared to the FM diet, both SBM and RM diets reduced fish growth and flesh lipid nutritive values, but improved the fillet firmness. Plant ingredient-rich diets do not have detrimental effects on muscle flavor because of the free amino acids composition and organoleptic attributes
Effects of Acute Copper Exposure on Physiological and Cytological Responses in Liver of GIFT Tilapia (Oreochromis niloticus)
Get PDFThis study was designed to evaluate the physiological and cytological responses in liver of GIFT tilapia (Oreochromis niloticus) to acute copper exposure. Fish were exposed to three Cu treatments at the following concentrations: 0 (control), 1.96 mg/L and 3.92 mg/L, and liver samples were collected after 96h of exposure. Observation of oil red O staining showed that acute copper exposure increased lipid accumulation in liver, which may due to changes of hepatic enzyme activities (malic enzyme, lipoprotein lipase, hepatic lipase, fatty acid synthetase, carnitine palmitoyltransferases l) and lesions of some organelles such as mitochondria and swollen rough endoplasmic reticulum of hepatocytes. This study indicated that acute copper exposure induced hepatic lipid metabolic disturbances and damaged hepatic organelle in GIFT tilapia
