Spatial distribution of multispecies longline catch per unit effort
Longline catch per unit effort (CPUE) from the ICCAT Task 2 database were analyzed to develop spatial distribution models for six species: bigeye tuna (BET), blue marlin (BUM), blue shark (BSH), shortfin mako shark (SMA), swordfish (SWO), and white marlin (WHM). Historically, longline effort has increased linearly from the 1950s until 2000 followed by a decrease. Spatial distribution of effort expanded from the tropical ecoregion during the 1950s-1960s but has increasingly concentrated back to the tropical ecoregion during the 2000s. Spatial factor analysis is a multivariate ordination technique that can identify common spatial trends among species. CPUE from the Japanese and USA longline fleet were chosen to characterize species distribution based on their spatial coverage for the Eastern and Western Atlantic, respectively. The best model was a six-factor model that primarily modeled the distribution separately for each of the six species, but notable cross-correlations were estimated within taxa for marlin (BUM and WHM) and shark (BSH and SMA) species. The predicted spatial density can be used to inform stock distribution in multispecies spatial operating models.