Central catch-latitude width trends were uncertain in four US trawl samples in 1982-2019

We tested whether southern and northern catch latitude quantiles moved at equal rates in two public trawl surveys and two periods. Fixed cohorts contained 59 eastern Bering Sea and 62 Northeast US fall taxa. We held survey strata fixed and used area and haul-effort weights. Central 80 percent width trends were +8.17 and -4.67 km per decade in the Bering Sea, and -5.58 and -6.45 in the Northeast, in 1982-2000 and 2001-2019. All four corrected intervals included zero. No repeated contraction or expansion was established. The late Northeast estimate changed from narrowing to widening without area weights. These are catch quantiles within survey boundaries, not full range edges. Catchability, sample selection, short records and survey changes limit inference. We measured no climate or pollution exposure. The package gives source hashes, code, taxon quantiles, effort weights, uncertainty, independent calculation checks and a figure.

species distributions · catch quantiles · observation bias · survey weighting · marine biodiversity · climate indicators · null result