Stress of capture and captivity in kahawai Arripis trutta (Bloch and Schneider) (Perciformes: Arripidae)

Abstract

Plasma cortisol in wild kahawai (Arripis trutta), an active pelagic marine fish, immediately after capture by hook and line was 8 ± 5 ng/ml (capture time, 4.9 ± 0.8 min, range 1–11 min). Capture by angling was accompanied by high levels of lactate in the white muscle (46.6 ± 2.8 μmol/g) and moderate plasma lactate levels (8.4 ± 1.0 mmol/l). Peak plasma cortisol concentration in fish after transport to shore in live tanks aboard a boat (1–2 hr post-capture) was 161 ± 31 ng/ml. Cortisol levels in wild-caught kahawai had returned to basal values within 3 days of introduction to a shore-based holding pool. Kahawai reacted violently to confinement in still water in darkened enclosed boxes. This prompted the design and construction of a swim tunnel for holding individual kahawai. Confinement of chronically cannulated kahawai in the swim tunnel resulted in a progressive increase in plasma cortisol; 2 hr after cannulation and confinement in the swim tunnel, plasma cortisol concentration was 112 ± 31 ng/ml. This increased to 233 ± 55 ng/ml after 2 days of confinement. Thus, confinement and cannulation do not appear to be suitable approaches for studying the physiology of this species.