Five-haul standardization gave uncertain changes in northern catch-limit trends in two US trawl surveys in 1982-2019

We tested northern catch-limit trends in 56 eastern Bering Sea taxa and 45 Northeast US fall taxa in 1982-2019. We compared the largest observed latitude with the exact expected maximum of five positive hauls. Separate tests used 1982-1999 and 2000-2019. Median paired slope changes were -1.62 and +2.45 km per decade in the Bering Sea, and +6.67 and +1.05 in the Northeast. All four adjusted block bootstrap intervals included zero. Block-length and secondary measure checks gave the same broad result. This does not show that sample count has no effect. The five-haul measure has a different target and is not the true range boundary. Persistent-taxon selection, detection, survey boundaries, spatial effort and short records limit inference. We did not test climate or pollution causes. The package gives exact code, positive-haul evidence, source hashes, all results and independent checks.

species distributions · northern catch limit · rarefaction · observation bias · OceanAdapt · null result