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 female x blue catfish male) was investigated at 0, 3, 6, and 9 ppt salinity. One-hundred percent mortality occurred at 9 ppt. Survivals were different (P b 0.05) by day 3 post hatch at 3 ppt, (P b 0.05) with blue catfish N hybrid catfish N channel catfish for salinity tolerance. Long-term survival of hybrid fry was better than that of the parent species at 0 ppt salinity, but highest for channel catfish at 3 ppt and 6 ppt with the hybrid being intermediate. NaCl had a negative effect on survival rate of yolk sac larvae starting at 3 ppt and for swim-up fry at 6 ppt. Genotype x 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. 6 ppt 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 relevance: The life stages of channel, blue and hybrid catfish were not previously studied for tolerance of sodiumchloride 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 3 ppt and growth of channel catfish was greatly enhanced at 3 ppt. Greater Ich resistance of hybrids compared to parents at 0 ppt contradicted earlier reports at older life stages. (C) 2016 Elsevier B. V. All rights reserved.