Latitude and depth catch changes had negative within-stratum correlations in two Bering Sea periods in 1982-2019

We tested whether annual northward and deeper catch changes occurred together in two US trawl surveys. We used fixed strata, survey-area weights and 59 Bering Sea and 62 Northeast US persistent taxa in 1982-2000 and 2001-2019. For each taxon, we correlated annual changes in catch latitude and depth relative to sampled hauls within strata. The median correlation was -0.38 and -0.26 in the two Bering periods. Four-test adjusted working intervals were below zero. Northeast estimates were -0.06 and -0.02, with intervals that included zero. The sampled haul coordinates also had negative within-stratum correlations in all Bering years. Survey geometry can therefore contribute to this pattern. The analysis does not identify movement, a thermal trade-off or a climate cause. Short series, persistent-taxon selection and catchability limit inference. The package contains code, annual indices, survey evidence, source hashes, checks and reproduction instructions.

species distributions · latitude · depth · observation bias · survey geometry · OceanAdapt · trawl surveys