Secondary stress responses to acute handling in striped bass (Morone saxatilis) and hybrid striped bass (Morone chrysops x Morone saxatilis).

OBJECTIVE

To test the hypothesis that, compared with pure striped bass, hybrid striped bass have reduced secondary physiologic responses to handling stress. A secondary objective was to determine whether not feeding fish for a 3-day period affected responses.

ANIMALS

Hatchery-reared adult striped bass (Morone saxatilis) and adult hybrids of striped bass with white bass (M chrysops), with mean length of 27.9 cm and mean weight of 487 g.

PROCEDURE

Fed and 3-day nonfed fish, in groups of 6, were held in dip nets above water for 3 minutes. Severity of response to handling was determined by measuring plasma glucose and chloride and blood lactic acid, sodium, and potassium concentrations. Terminal samples were taken from fish before handling (control), immediately after handling, and after 12, 24, and 48 hours of recovery.

RESULTS

Striped bass were hyperglycemic and lactacidemic after stress and for 12 to 48 hours afterward, whereas glucose and lactic acid values in hybrids were essentially unchanged. Blood sodium and chloride concentrations of hybrids decreased after stress, then returned to control values within 24 hours. Striped bass, however, had a greater decrease in values for these electrolytes and failed to recover in 48 hours. Blood potassium concentration remained unchanged in all test groups. Nonfeeding for 3 days before handling did not appear to affect stress response in striped bass or hybrids.

CONCLUSIONS AND CLINICAL RELEVANCE

Striped bass have an appreciably greater response to acute handling stresses, such as those that may be experienced in hatcheries and experimental laboratories, than do hybrid bass. Thus, pure striped bass require more care in handling. The usual practice of not feeding before handling does not affect physiologic responses.