Motorboat noise impacts parental behaviour and offspring survival in a reef fish

Anthropogenic noise is a pollutant of international concern, with mounting evidence of disturbance and impacts on animal behaviour and physiology. However, empirical studies measuring survival consequences are rare. We use a field experiment to investigate how repeated motorboat-noise playback affects parental behaviour and offspring survival in the spiny chromis ( Acanthochromis polyacanthus ), a brooding coral reef fish. Repeated observations were made for 12 days at 38 natural nests with broods of young. Exposure to motorboat-noise playback compared to ambient-sound playback increased defensive acts, and reduced both feeding and offspring interactions by brood-guarding males. Anthropogenic noise did not affect the growth of developing offspring, but reduced the likelihood of offspring survival; while offspring survived at all 19 nests exposed to ambient-sound playback, six of the 19 nests exposed to motorboat-noise playback suffered complete brood mortality. Our study, providing field-based experimental evidence of the consequences of anthropogenic noise, suggests potential fitness consequences of this global pollutant.

Stress inhibition of reproductive endocrine processes in a natural population of the spiny damselfish Acanthochromis polyacanthus

Stress–reproduction interactions were assessed by in situ sampling and laboratory manipulation of fish from a natural population of A. polyacanthus. Mean plasma cortisol concentrations for fish sampled under water immediately after capture were <11 ng mL–1 (range <1 to 42 ng mL–1 ); the variation was not a function of disturbance before capture,with no differences in mean cortisol concentrations between 5 min time blocks for chase times of up to 30 min. Fish confined for 2 or 6 h after capture showed significant increases in plasma cortisol concentrations, and depression of plasma T and E 2 in females and T and 11KT in males in summer but not in winter. There was no correlation between plasma concentrations of cortisol and sex steroids at capture. Underwater treatment of fish with cortisol had no effect on brood-guarding behaviour.Injection of fish either at capture or 24 h afterwards with human chorionic gonadotropin or luteinizing hormone-releasing hormone analogue had no effect on plasma concentrations of gonadal steroids, which remained low. Incubation in vitro of ovarian follicles from these fish showed that gonadal tissue was still steroidogenically active. This study suggests that inhibition of reproduction by stress in spiny damelfish is above the level of steroid biosynthesis.