Evaluating the levels of capture-related stress and physical injury in métiers that use gillnets and trammel nets

Abstract

Captured fish are subjected to a variety of stressors, but exhaustion and injury stand out as the most harmful and common. While hanging nets like gillnets and trammel nets may have fewer overall environmental effects than towed gear, they are commonly associated with high rates of incidental mortality among discarded fish, posing the highest stressor exposure risk and the least opportunity for practical mitigation measures. The present study sought to determine and compare the amount of physical damage and stress (plasma cortisol and malondialdehyde (MDA) levels) caused by trammel nets and gillnets to fish in a small-scale fishery in the North Aegean Sea (E. Mediterranean). We focused on four fish species with minor commercial importance and high discarding potential to examine whether captured related stressors are not only gear-specific but also species-specific. We found that trammel net deployments are associated with higher levels of physical injury and physiological stress than gillnets which were attributed to different soak-times but also to differences in the mechanics of capture between the two gears and among the four species.