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Effect of Sodium Chloride on Hatching Rate on Channel Catfish, Ictalurus punctatus, Embryos

Su, Baofeng, Perera, Dayan A., Mu, Xingjiang, Dunham, Rex A.
Journal of applied aquaculture 2013 v.25 no.4 pp. 283-292
Ictalurus punctatus, developmental stages, eggs, embryonic mortality, fungi, hatcheries, hatching, microbial growth, mortality, salinity, sodium chloride, yolk sac
Channel catfish, Ictalurus punctatus , eggs were hatched statically in 0, 2, 4, or 6 ppt salinity. Hatching rate was highest (P < 0.05) in 4 ppt treatments, 60%–82%. Hatching rate was 17%–52%, 46%–75%, and 32%–47% for 0, 2, and 6 ppt treatments, respectively. The high salt levels had adverse post-hatch effects as fry in the 4 and 6 ppt treatments had heavy post-hatch mortality and difficulty absorbing their yolk sac. The 0 ppt treatment experienced fungal infection, but no fungal growth was observed for the other treatments. Embryo mortality was observed between 24–48 hpf in the 6 ppt treatment, a time frame that may coincide with a developmental stage of the embryo that is sensitive to high salt concentrations as well as to other chemical treatments used to treat egg diseases. Developmental rate slowed with increasing salinity. The 2 ppt treatment appears to be the best treatment considering the post-hatch mortality in the 4 ppt treatment. Salinity levels between 2 and 4 ppt should be evaluated as well as variable treatment levels considering that 4 ppt had the most consistently high hatching rate, but heavy post-hatch mortality, which may require a reduction in salt level just prior to hatch to take advantage of the elevated hatch at 4 ppt. Partial budgeting indicated that the salt treatment for the eggs was economically beneficial, increasing net profit by $272,502 for a hatchery that is producing 10 million fry in 117 hatching troughs (379 L) without salt.