The response to capture and confinement stress of plasma cortisol, plasma sex steroids and vitellogenic oocytes in the marine teleost, red gurnard

Abstract

Reproductively active female red gurnard Chelidonichthys kumu were captured on long‐lines, and placed in confinement tanks for 24, 48, 72 and 96 h to examine the effect of capture and confinement on reproductive parameters (experiment I). Plasma cortisol at the time of capture was elevated to levels typical of stressed fish in other species (53–125 ng ml−1). Final plasma cortisol levels in red gurnard confined for any length of time were not significantly different from one another (ranging from 17 to 43 ng ml−1), indicating that fish were chronically stressed when held in captivity for up to 96 h after capture. When initial and final plasma cortisol levels were compared within confinement groups, cortisol decreased significantly after 24 and 96 h of confinement indicating that some acclimation to captivity may have occurred. In contrast, plasma 17β‐estradiol (E2) and testosterone (T) levels decreased significantly to levels comparable to those in post‐spawned fish, after any period of confinement, and remained low throughout the experiment. Another group of fish was captured and confined in the same manner as experiment I but subjected to repeated blood sampling every 24 h, until 96 h post‐capture. In these fish, plasma cortisol levels decreased significantly from 127 ng ml−1 after 24 h confinement and thereafter showed no change (25–45 ng ml−1). Plasma E2 decreased significantly after 72 h of confinement while plasma T showed no change from levels at capture. Increased amounts of follicular atresia were found in vitellogenic oocytes of fish confined for longer periods of time in experiment I, indicating that capture and confinement stress affect reproduction negatively in captive wild fish.