BREVES, J.P.; SPECKER, J.L.; University of Rhode Island; University of Rhode Island: Cortisol Stress Response of Juvenile Winter Flounder (Pseudopleuronectes americanus) to Predators

Depletion of wild stocks of winter flounder (Pseudopleuronectes americanus) in the Northwestern Atlantic has warranted stronger fishing regulations in the last decade. The rearing of juvenile fish in hatcheries for release in coastal waters has been viewed as a possible means to strengthen wild populations. Many fishery biologists are concerned that hatchery-reared fish are not behaviorally and/or physiologically equipped to survive in the wild due to a lack of predator interaction and conditioning under culture conditions. However, the physiological response of hatchery-reared winter flounder to predators has not been described. This study aimed to determine whether hatchery-reared juvenile winter flounder exhibited a stress response, as evidenced by an increase in whole-body cortisol concentrations, to cohabitation with predators. Predation by green crabs (Carcinus maenas) and sand shrimp (Crangon septemspinosa) have been implicated as a source of juvenile flounder mortality in laboratory and field studies and therefore they were chosen as the invertebrate predators. In addition, the summer flounder (Paralichthys dentatus) was selected as a predator because of its co-existence with young winter flounder in estuaries during early summer. Juvenile fish (n =12) were exposed to predators for 24 h in an arena. Results from radioimmunoassay indicate that juvenile winter flounder initiate a cortisol response to sand shrimp and summer flounder predation, whereas the presence of a green crab does not elicit such a response. This study represents the first step toward understanding the stress physiology of hatchery-reared juvenile winter flounder in response to predators. [Funded by NSF REU SURFO program and Rhode Island Sea Grant]