Non-consumptive effects of predatory three-spined sticklebacks (Gasterosteus aculeatus) on great crested newt (Triturus cristatus) embryos

Predatory fish have negative impacts on many amphibian populations, often through direct predation on embryos and larvae. The presence of predators during embryonic development may elicit adaptive responses in emerging larvae. This study examined the non-consumptive effects of predatory three-spined sticklebacks (Gasterosteus aculeatus) on great crested newt (Triturus cristatus) embryos under controlled conditions. Embryos raised in the presence of sticklebacks but in predation-proof enclosures suffered significantly higher mortality compared to control treatments in three independent trials over two years. Overall 26.9% of embryos hatched in stickleback treatments compared to 47.6% from controls. As sticklebacks were treated with fungicide before the experiments, this difference in mortality is unlikely to be due to fungal disease transmission. There were no significant differences in the date, stage of development or size at hatching in larvae raised with and without sticklebacks. The results suggest the potential for negative non-consumptive impacts of predatory sticklebacks on great crested newts during the embryonic stage.