Effect of brooder age and size on fry size variation in channel catfish.

Authors: Ott, Brian; Bosworth, Brian; TORRANS, EUGENE - Retired ARS Employee; Waldbieser, Geoffrey - Geoff

Submitted to: North American Journal of Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/5/2022
Publication Date: 4/7/2023
Citation: Ott, B.D., Bosworth, B.G., Torrans, E.L., Waldbieser, G.C. 2023. Effect of brooder age and size on fry size variation in channel catfish. North American Journal of Aquaculture. https://doi.org/10.1002/naaq.10280.
DOI: https://doi.org/10.1002/naaq.10280

Interpretive Summary: Groups of catfish harvested for processing often possess a wide range of body masses and can be too small or large for the preferred size of commercial processors. These catfish are typically purchased at reduced prices, resulting in decreased profits for farmers. All of the variables contributing to these size discrepancies are unknown, so scientists at the USDA-ARS Warmwater Aquaculture Research Unit worked together to determine if size variation is present when catfish hatch and if broodstock age or size impacts this variation. At hatch, catfish fry from five-year old brooders can be 54% larger than those from two-year old brooders and this discrepancy persists up to four days after they begin feeding, when farmers typically stock them into ponds. Age of the brooders appears to be a more important factor in determining fry size than brooder body mass. These data indicate that management of brooders and their fry are important first step in reducing size variation of food fish at their final harvest.

Technical Abstract: Variation in harvest size of ictalurid catfishes can be problematic for both catfish producers and processors, ultimately reducing profitability for both. While harvesting and grading techniques can reduce this variation, the biological underpinnings of these size discrepancies remain unknown. Fry from channel catfish (Ictalurus punctatus) brooders that were two-, three-, four-, and five-years old were measured to determine the amount of naturally occurring variation in body mass among sac and swim-up fry. Over two spawning seasons, older brooders consistently produced larger sac and swim-up fry than their younger counterparts. However, within spawn fry size variation was similar among all brooder ages measured. Broodstock body mass did not play a significant role in influencing fry body mass, whereas broodstock age did. These data reveal that brooder age is an important determinant of fry size and that this range of fry body mass may prove to be a factor relevant to understanding the causes for fry size variation and may play a role in improving production of ictalurid catfishes.