Predator avoidance of transgenic channel catfish containing salmonid growth hormone genes

Transgenic channel catfish (Ictalurus punctatus) containing salmonid growth hormone genes can grow 33% faster than normal channel catfish under aquacu lture conditions. However, before transgenic catfish are released and utili zed by the private sector, their genetic impact on the natural environment must be examined. Predator avoidance is one of the major fitness traits det ermining potential environmental risk. To determine the predator avoidance ability and growth performance of transgenic catfish in a natural habitat, various densities of transgenic and nontransgenic channel catfish were comm unally stocked in 0.04-ha earthen ponds without supplemental feeding. Large mouth bass (Micropterus salmoides) and green sunfish (Lepomis cyanellus) we re stocked as predators. Nontransgenic fry had better predator avoidance th an transgenic channel catfish when data were pooled (p < .01). When data we re not pooled, nontransgenic catfish had better predator avoidance in six t rials and transgenic individuals had better predator avoidance in four tria ls. There was no difference in predator avoidance in three trials. Overall predator avoidance was also better for nontransgenic individuals (p < .01) when the fish were evaluated as 3.5-g fingerlings, more clearly than as fry , as transgenic individuals were more vulnerable in 3 of 4 trials at this l ife stage. There was no significant difference in growth performance betwee n transgenic and nontransgenic channel catfish in ponds without supplementa l feeding. These findings indicate that transgenic channel catfish could be used for commercial aquaculture without affecting the natural environment. Although transgenic channel catfish may be released to nature by accident, any ecological effect would be unlikely because the increased susceptibili ty of transgenic channel catfish to predators would most likely decrease or eliminate the transgenic genotype.