Effects of Stocking Sac‐Fry and Hatchery‐Fed Fry on Production of Fingerling Channel Catfish Ictalurus punctatus

Abstract

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.

Effects of Fry Age‐at‐Stocking on Growth and Survival of Channel Catfish

“…Total feed fed also increased with increased survival. In our study, overall survival rates were not as high as those reported by Tidwell et al (1995) (31-86%) or those reported by Weirich et al (2001) (72-92%), but were better than those reported by Reigh et al (2006) (4-13%).…”

“…Neither Tidwell et al (1995) nor Weirich et al (2001) found differences in survival of fingerling catfish stocked as either sac fry or hatchery‐fed fry. However, those studies were done in small 0.04‐ha ponds and 10,000‐L tanks, respectively, which may not represent commercial conditions.…”

“…In the Tidwell et al (1995) study and the Weirich et al (2001) study, fry were stocked into relatively small impoundments; in the Reigh et al (2006) study, using larger impoundments, survival was not different among ages of fry stocked, but was poor for all age groups.…”

“…Although the common hatchery practice is to hold fry in the hatchery and feed commercial starter diets for 7-10 d after the swim-up stage (Tucker and Robinson 1990), fry may be missing out on the benefits of zooplankton during this period. In previous studies, some authors have found no differences in survival among fry stocked at various ages (Snow 1962;Weirich et al 2001;Reigh et al 2006). Tidwell et al (1995) found swim-up fry stocked directly into nursery ponds had higher survival compared to fry fed for 7 d in the hatchery, and Weirich et al (2001) produced larger fingerlings by stocking 2 or 7 d post-hatch (DPH) fry compared to 14 DPH swim-up fry.…”

“…In previous studies, some authors have found no differences in survival among fry stocked at various ages (Snow 1962;Weirich et al 2001;Reigh et al 2006). Tidwell et al (1995) found swim-up fry stocked directly into nursery ponds had higher survival compared to fry fed for 7 d in the hatchery, and Weirich et al (2001) produced larger fingerlings by stocking 2 or 7 d post-hatch (DPH) fry compared to 14 DPH swim-up fry. Recently developed fertilization practices for channel catfish nursery ponds provide rapid growth of desirable zooplankton and may enhance the benefits of early stocking of fry (Mischke and Zimba 2004).…”