QUANTITATIVE COMPARISON OF THE STRESS-RESPONSE OF STRIPED BASS (MORONE-SAXATILIS) AND HYBRID STRIPED BASS (MORONE-SAXATILIS X MORONE CHRYSOPS AND MORONE-SAXATILIS X MORONE AMERICANA)

Striped bass (Morone saxatilis) exposed to a standardized confinement stress had markedly different clinical and endocrinologic responses, c ompared with hybrid striped bass exposed to the same stress. Plasma co rtisol concentration increased at a faster rate and appeared to reach a higher value in striped bass than in hybrid bass. Mean plasma cortis ol concentration was 742 +/- 43 ng/ml in striped bass, com pared with 490 +/- 37 and 531 +/- 40 ng/ml in striped bass x white perch (M ameri cana) and striped bass x white bass (M chrysops) hybrids, respectively , after a 45-minute net confinement. Plasma cortisol concentration als o remained significantly (P = 0.003) higher in striped bass for at lea st 48 hours after the net confinement. These hormonal differences were associated with a markedly lower survival and resistance to infection in striped bass, compared with the hybrids.