Document Type

Honors Paper


Robert Askins

Publication Date



Marine bycatch is one of the most pressing issues that result from modern industrialized fishing. Scientists do not have good estimates of rates of cryptic mortality, which is the mortality of individuals that are not landed but die from interactions with fishing gear below the water surface. One of the main causes of cryptic mortality is depredation, which occurs after individuals have escaped through fishing equipment and are eaten by predators waiting close behind for an effortless meal. In this study the effects of scale loss, slime loss, and exhaustion on the startle response of zebrafish were examined. These stressors may lead to the depredation of escapees from trawls and other fishing equipment. To test this hypothesis, zebrafish in four treatment groups were first exposed to scale loss, slime loss, exhaustion or no stressor and then exposed to a model predator. There were two sets of experiments, one with individual fish, and the other with fish in schools. Descaled zebrafish travelled a significantly shorter distance than zebrafish in the control group. The distance to nearest neighbor was also significantly greater in the descaling group when compared to the control in the schooling trial. In the schooling trials, fish in the exhaustion and slime loss trials travelled significantly shorter distances when compared to the control, but this was not seen in the individual trials, suggesting that schooling behaviors are an important consideration when analyzing startle responses. By understanding how interactions with fishing gear influence fish behavior and physiology, fisheries managers can learn the true impact that bycatch is having on stocks, facilitating more educated management decisions.



The views expressed in this paper are solely those of the author.