Multispecies spatio-temporal modelling to inform exploratory spatial closures for striped marlin bycatch reduction

This study investigated how the distributions of tuna and billfish species change across space and time in the western and central North Pacific Ocean and assessed alternative time-area closure strategies for conserving striped marlin (Kajikia audax). Researchers compared two hotspot indicators for identifying closure areas, an IMLS indicator, which defined hotspots based on average striped marlin density, and an IR indicator, which defined hotspots using the ratio of striped marlin density relative to six target species. Modeling indicated that using the IR indicator to define time-area closures reduced striped marlin catch while causing smaller reductions in target catch. However, tradeoffs between catch and bycatch avoidance varied seasonally. These results indicate that effective closure design depends on both the level of multispecies overlap as well as seasonal variation.