|Green, Bartholomew - Bart|
Submitted to: North American Journal of Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/5/2008
Publication Date: 2/2/2009
Citation: Green, B.W., Perschbaucher, P., Ludwig, G.M. 2009. Effect of threadfin shad as forage for channel catfish fed daily or every third day. North American Journal of Aquaculture. 71:46-51. Interpretive Summary: Catfish farmers strive to reduce production costs in response to low catfish prices or high raw material prices. Because feed represents the largest component of variable costs, improved feed management could result in lower feed expenditures. Reducing the amount of feed fed is one management strategy contemplated to reduce production costs. Providing catfish with a source of forage fish upon which they can prey may be another way to reduce the amount of feed required. Threadfin shad could be a good forage fish for use in channel catfish production ponds because it spawns throughout the growing season, young-of-year fish can mature and spawn in one season, and adults rarely exceed 6” in length, which allows them to pass through the seine net used to harvest catfish for market. The objective of this study was to determine whether threadfin shad stocked as a forage fish could supplement formulated feed when channel catfish were fed daily or every three days. We conducted the experiment form April-October in ¼-acre ponds stocked with catfish at a rate to simulate commercial production ponds. Catfish growth and production was affected by feeding frequency, but not by the presence or absence of threadfin shad. Catfish growth and yield was higher when fish were fed daily compared to every three day. However, catfish feed consumption was not affected by threadfin shad, which indicated they contributed little or nothing to catfish growth. Catfish fed every three days consumed 62% as much feed as fish fed every day, which reduced net total yield by 66% and slowed fish growth. Most of the fish that were fed every three days failed to reach market size and would require a third season to reach harvest weight. Stocking threadfin shad at the rate used in this experiment as a forage fish into channel catfish production ponds did not appear to be a viable substitute for formulated feed during the growing season.
Technical Abstract: We evaluated whether stocking threadfin shad (Dorosoma petenense) as a forage fish in multiple-batch channel catfish (Ictalurus punctatus) production ponds could substitute for formulated feed when catfish were fed daily or every three days. A completely randomized design in 2 x 2 factorial arrangement was used for the experiment, which was conducted in 12 0.1-ha earthen ponds. Pre-spawn adult threadfin shad were stocked at 404 kg/ha in half of the ponds. Channel catfish stockers (0.35 kg/fish) and fingerlings (28.2 g/fish) were stocked at 5,040 kg/ha and 14,820 head/ha, respectively. Catfish in each of 6 ponds were fed a floating 32% protein feed to apparent satiation daily or every 3 d. After 144 d, mean channel catfish total gross yield was unaffected by the presence of threadfin shad, but was significantly greater when fish were fed daily (12,406 kg/ha) compared to every 3 d (7,570 kg/ha). Mean fish weight at harvest also was greater in the daily feed treatment. Compared to the daily feed treatment, 62% as much feed was used in the every 3 d feed treatment, which reduced net total yield by 66% and slowed fish growth. Nearly 90% of the stockers in the every 3 d feed treatment failed to reach the 0.68 kg/fish market size and would require a third season to reach harvest weight. Stocking threadfin shad at the rate used in this experiment as a forage fish into channel catfish production ponds did not appear to be a viable substitute for formulated feed during the growing season.