Abstract
Salinity tolerance of yolk-sac larvae and swim-up fry of channel catfish (Ictalurus punctatus), blue catfish (I. furcatus), and hybrid catfish (channel catfish ♀×blue catfish ♂) was investigated at 0, 3, 6, and 9ppt salinity. One-hundred percent mortality occurred at 9ppt. Survivals were different (P<0.05) by day 3 post hatch at 3ppt, (P<0.05) with blue catfish>hybrid catfish>channel catfish for salinity tolerance. Long-term survival of hybrid fry was better than that of the parent species at 0ppt salinity, but highest for channel catfish at 3ppt and 6ppt with the hybrid being intermediate. NaCl had a negative effect on survival rate of yolk sac larvae starting at 3ppt and for swim-up fry at 6ppt. Genotype×environment interactions occurred for growth as hybrids grew faster than channel catfish and blue catfish at 0ppt. Raising salinity to 3ppt 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. 6ppt was detrimental to yolk-sac larvae and swim-up fry. These results help identify the saline environments that might be suitable for long-term growth and disease resistance of ictalurid catfish, and reveals changes in salinity tolerance during development. Statement of relevanceThe life stages of channel, blue and hybrid catfish were not previously studied for tolerance of sodium chloride and genotype-environment interations were observed indicating the ideal environment for culture or disease treatment varies among these genetic groups.Heterosis of the hybrids almost disappeared at 3ppt and growth of channel catfish was greatly enhanced at 3ppt.Greater Ich resistance of hybrids compared to parents at 0ppt contradicted earlier reports at older life stages.
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