Location: Warmwater Aquaculture Research UnitTitle: Effects of fry age-at-stocking on growth and survival of channel catfish Author
Submitted to: Journal of the World Aquaculture Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/15/2011
Publication Date: 2/15/2012
Citation: Mischke, C.C., Greenway, T.E., Griffin, M.J., Wise, D.J. 2012. Effects of fry age-at-stocking on growth and survival of channel catfish. Journal of the World Aquaculture Society. 43(1):135-139. Interpretive Summary: The study compared growth and survival of fingerlings harvested from nursery ponds that had been stocked as either sac fry, swim-up fry or hatchery fed fry. Results indicate that stocking younger fry would be too risky for commercial producers.While zooplankton inclusion in fry diets can provide benefits, this is negated if early stocked fry survival is low.
Technical Abstract: Large numbers of fry are required to supplystocking needs in the channel catfish, Ictaluruspunctatus, industry. In January 2009, fingerlings held on farms totaled 728 million (NASS 2009). Survival of fry after stocking into ponds in not well documented, and reported values range from about 55% (Hatch et al. 1987) to 80% (Moore and Waldrop 1994). Rearing catfishfrom the fry to fingerling stage is probably the least efficient phase of catfish production, and improvements in growth and survival during this phase should help to improve the overall sustainability of the catfish industry. Better utilization of natural forage organisms (i.e., zooplankton) and reducing the residence time of fry in the hatchery may be ways to improve fry production efficiency. Channel catfish fry readily consume zooplankton and selectively forage on larger zooplankton such as copepods, cladocerans, and ostracods (Mischke et al. 2003a). These larger zooplankton are excellent nutritional sources for fry as the composition of zooplankton meets or exceeds all nutritional requirements of channel catfish fry (Mischke et al. 2003b). Furthermore, zooplankton contain carotenoids that may influence fry survival (Torrissen and Christiansen 1995; Tachibana et al. 1997), immunity (Amar et al. 2001), and may have antioxidant properties (Lotocka and Styczynska-Jurewicz 2001). When catfish fry diets are supplemented with zooplankton, fry weight is increased 40–50% in just 19 d compared to fry fed only commercial diets (Mischke et al. 2009). 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. 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). The purpose of this study was to compare the growth and survival of fingerlings harvested from nursery ponds that had been stocked as either sac fry, swim-up fry, or hatchery-fed fry.