Within-stratum catch variance had median shares of 31 percent in Bering and 3 percent in Northeast US trawls in 1982-2019

Within-stratum catch variation had median shares of 30.77 percent of annual latitude variance in the eastern Bering Sea and 2.65 percent in Northeast US fall trawls in 1982-2019. These shares use equal-taxon mean variance for 42 and 44 persistent taxa, with fixed survey strata and area-weighted catches. An exact variance split separates local catch variation from differences between strata. A fixed position per stratum removes the local component. We also tested its link to seasonal sea surface temperature in two regions and two periods. All four corrected slope intervals include zero. The result does not establish that temperature has no effect. Survey geometry, catchability, coarse temperature and short records limit inference. It does not identify a climate cause or pollution effect. Code, catch moments, source hashes, figures and offline checks are included.

species distributions · sea surface temperature · observation bias · variance decomposition · trawl surveys · null result