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Abstract.— Channel catfish Ictalurus punctatus fry are typically held under hatchery conditions for 7 to 14 d after hatching to allow feeding and growth before they are stocked into nursery ponds to produce fingerling catfish. In an attempt to reduce hatchery operating costs, several catfish fingerling producers in Louisiana presently stock fry within 2 d after hatching before yolk absorption is complete. Fry at this stage of development are commonly referred to as “sac‐fry.” Although research has shown that fry can be stocked at the onset of yolk absorption with no detrimental effects on subsequent fingerling production, stocking sac‐fry has been reported to result in reduced fingerling survival. To further investigate this topic, production trials were conducted in experimental outdoor pools over the course of two growing seasons to evaluate the effect of stocking fry of three different ages (2‐, 7‐, and 14‐d post‐hatch, DPH) on survival, growth (weight and length), condition factor (K), yield, feed consumption, and feed conversion ratio (FCR) of fingerling catfish. Results from both trials indicated that the age at which fry were stocked had no effect on production characteristics with the exception of growth. Specifically, fingerlings reared from fry stocked at 2 and 7 DPH were significantly larger than fingerlings reared from fry stocked at an age of 14 DPH. These findings suggest that the practice of stocking sac‐fry may be a suitable alternative to the traditional procedure of holding and feeding fry under hatchery conditions prior to stocking. However, in order to fully evaluate the effects of early‐age stocking of catfish fry on fingerling production, additional studies must be conducted under pond conditions. Furthermore, these studies must be coupled with a rigorous economic analysis before the practice of stocking sac‐fry can be recommended to the catfish industry.

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A 1-year study was conducted from February 1999 to January 2000 to determine the effects of low levels of salinity on selected hematological parameters (total protein, hematocrit, leukocrit, and osmolality) and the health of channel catfish Ictalurus punctatus reared in ponds managed under the multiple cropping production strategy. We stocked 2,000 catfish into 15 ponds (0.08 ha each) that we subdivided into five replicate ponds per each of three NaCl (salinity) treatments: freshwater conditions (nominal salinity ϭ 0 g/L of water) or adjusted salinities of 1.5 or 3 g/L. Total protein, hematocrit, and plasma osmolality for fish reared at the NaCl-induced salinities were significantly higher than those for fish cultured in freshwater. Although the leukocrit of fish reared at a salinity of 3 g/L was significantly higher than that of fish reared in freshwater or at 1.5 g/L, all were within the normal ranges reported for channel catfish. Although two bacterial diseases known to routinely affect channel catfish (enteric septicemia of catfish and motile aeromonad septicemia) were observed at all salinity levels tested, columnaris disease was not observed during the study. Parasitic infections during certain months were less severe for fish reared in saline ponds than in freshwater. The results indicate that the hematological variables measured in this study were higher at increased salinities but within the ranges reported as normal for channel catfish.