An Evaluation of Triploid Flathead Catfish

Abstract

The overall objective of this research was to develop an effective protocol to produce triploid flathead catfish, Pylodictis olivaris. To accomplish this goal, data was gathered depicting characteristics of flathead catfish provided by Georgia Department of Natural Resources and the fry produced from these fish. The gamete production of male and female flathead catfish, ovulation techniques, egg incubation methods, and characteristics of fry produced was examined. Eleven males and twenty eight females were used in this study. The average weight of the male catfish was 3.27 kg with the females averaging 4.55 kg. The mean grams of usable testes produced by male catfish were 1.24 g. Larger males produced a greater amount of usable testes demonstrating a strong positive correlation that exists between the traits. Females in this experiment produced an average of 350.0 g of eggs. The total number of eggs produced by each female was 10,826 eggs from strip spawning, and a linear relationship exists between egg number and body weight, r²=0.70. Relative fecundity of the females decreased with size with a linear regression equation with fecundity=3,511.1-209.89(female BW). Females that received a combination of implant and injection had a percent ovulation of 37.5 and 50% over ripe eggs. The implant only treatment had 33.3% ovulation. The percent of viable eggs that were not over ripe for this treatment was 83.3%. The mean latency of the implant only treatment, 81.3 hours was longer than that for the combination treatment, 63.3h. Two incubation techniques were used to assess any differences that may exist between the two treatments. The first technique utilizes a standard paddle wheel in a flow thru trough. The second technique utilized hatching jars to incubate the eggs. The mean percent hatch for the troughs was 12.4 % was lower than the mean percent hatch in the jars, 22.1. Five different pressure treatments, 5,500, 6,000, 6,500, 7,000, and 7,500 psi were administered. The pressure treatment of 6,500 psi was the most effective treatment with a % hatch of 16.7 and 100% triploidy The diploid fry grew over this entire period from a minimum of 4.6 to a maximum of 28.5 grams. This period produced triploid fry from a minimum growth of 3.9 and a maximum of 33.7 grams. These values were not proven to be significantly different from each other (P=0.72). Triploid fry appeared less aggressive during confinement in aquaria and trough with fewer deaths in their tanks being attributed to cannibalism.

Key words: flathead catfish, invasive species, triploidy, polyploidy, hydrostatic pressure, cannibalism, predatory, fry growth, super males, screw fly, spawning.