Comparisons Among Channel Catfish Ictalurus punctatus, Blue Catfish I. furcatus, Channel ♀ × Blue ♂ Hybrid Catfish and Transgenic Channel Catfish for Growth, Cold and Salinity Tolerance
Type of DegreePhD Dissertation
Fisheries and Allied Aquacultures
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Two studies were performed related to salinity tolerance and the potential effect of climate change on genetic choices for catfish farming. The first study examined the growth rate and survival rate among channel catfish (Ictalurus punctatus), blue catfish (Ictalurus furcatus), and channel catfish, I. punctatus, ♀ × blue catfish, I. furcatus, ♂ hybrid catfish at early life stages at 0, 3.0, 6.0, and 9.0 parts per thousand (ppt) salinity. No yolk sac larvae or swim-up fry survived for channel catfish, blue catfish, and hybrid catfish at 9.0 ppt for either stage of development. Channel catfish were more resistant to salinity than hybrid catfish and blue catfish. The resistance of (C×B) hybrid catfish to salinity was intermediate to that of channel catfish and that of blue catfish. NaCl had a negative effect on survival rate of yolk-sac larvae beginning at 3 ppt and for swim-up fry at 6 ppt. Genotype × environment interactions occurred for growth as hybrids grew faster than channel catfish and blue catfish at 0 ppt. Raising salinity to 3 ppt greatly increased the growth rate (50-75%) of channel catfish and blue catfish, but only slightly (10%) for hybrid catfish, which were still larger than the parent species. These results indicate the types of saline environments that might be used long-term for growth of juvenile ictalurid catfish, and the salinities that could be used for long-term disease treatment. This information could be increasingly important for aquaculture planning in the event of global climate change. The second study examined the survival of fingerlings of channel catfish, channel ♀ × blue ♂ hybrid catfish, channel catfish transgenic for the goldfish Carassius auratus glutamate decarboxylase 65 gene driven by the carp β-actin promoter (βA-GAD65) and channel catfish transgenic for the catfish growth hormone gene driven by the antifreeze protein promoter from an ocean pout Zoarces americanus (AFP-ccGH) at different temperatures (9.0 °C, 6.0 °C, 3.0 °C, 1.0 °C, 0.5 °C, 0 °C, and −0.5 °C) and different salinities (0 ppt, 2.5 ppt, 5 ppt, and 7.5 ppt). Survival was 98–100% for all genetic groups at all salinities between 0 °C and 9.0 °C. However, large differences were observed at −0.5 °C. At 0 ppt salinity, 100% of AFP-ccGH transgenic (T) fingerlings survived (P < 0.0001), but survival of all other genetic groups was 0–2%. Raising salinity to 2.5 ppt at sub-zero temperature had a strong positive impact on survival as survival rates of AFP-ccGH (T), AFP-ccGH control (C), channel catfish, βA-GAD65 (T), βA-GAD65 (C) and hybrid catfish were 100, 100, 98, 76, 100 and 18%, respectively with the hybrid having the lowest survival followed by βA-GAD65 (T) (P < 0.0001). Increasing salinity further to 5 ppt decreased overall survival, although it was still higher than at 0 ppt. Survival rankings were altered, as means for βA-GAD65 (T), βA-GAD65 (C), AFP-ccGH (T), AFP-ccGH (C), channel catfish and hybrid catfish were 69, 0, 15, 22, 0 and 0%, respectively with βA-GAD65 (T) having the highest survival (P < 0.05). Mortality was 100% in all genetic groups at −0.5 °C and 7.5 ppt demonstrating significant interaction between temperature and salinity.