LAUSR

We develop a length-disaggregated spatio-temporal delta-generalized linear mixed model (GLMM) and apply the method to fishery-dependent catch rates of shortfin mako sharks in the North Pacific. The spatio-temporal model may provide an improvement over conventional time-series and spatially stratified models by yielding more precise and biologically interpretable estimates of abundance. Including length data may provide additional information to better understand life history and habitat partitioning for marine species. Nominal catch rates were standardized using a GLMM framework with spatio-temporal and length composition data. The best fitting model showed that most hotspots for “Immature” shortfin mako occurred in the coastal waters of Japan, while hotspots for “Subadult and adult” occurred in the offshore or coastal waters of Japan. We also found that size specific catch rates provide an indication that there has been a recent increasing trend in stock abundance since 2008.