Assessing the performance and capture efficiency of the Fukui trap as a removal tool for the invasive European green crab (Carcinus maenas) in Newfoundland, Canada

Invasive species are recognized as a serious threat to biodiversity, ecosystem functions, plant and animal health, and economic activities. Habitats around the world have been transformed through the negative ecological impacts of invasive species, such as the displacement of native species and changes to community structure. The European green crab (Carcinus maenas) is a destructive marine invasive species that can cause widespread damage to invaded ecosystems, and is renowned for its aggression, broad environmental tolerances, and voracious diet. Discovered in Newfoundland waters in 2007, the green crab has since become established in nearshore ecosystems on the south and west coast of the island. Targeted fishing efforts aimed at removing green crabs commonly use Fukui multi-species marine traps, but prior to this thesis the direct interactions between green crabs and these traps had not been formally assessed. In this study, underwater cameras were used to directly observe Fukui traps as they fished for green crabs. Analysis of these videos revealed that only 16% of green crabs that attempted to enter the Fukui trap were successfully captured. Based on these findings, four distinct trap modifications were designed to increase the number of green crabs caught in Fukui traps per deployment. In situ testing of these modifications revealed increased green crab catch-per-unit-effort (CPUE) by as much as 81%, without increasing the impact on non-target species. This thesis demonstrates that modifications to Fukui traps can increase CPUE, thereby making them more effective tools for removing green crabs from invaded ecosystems