Observed latitude-depth catch correlations fell within haul-shuffle ranges in four US trawl samples in 1982-2019

We tested whether paired survey coordinates can produce observed latitude-depth catch correlations without exact catch-position associations. We used 59 persistent Bering Sea taxa and 62 Northeast US taxa in 1982-2000 and 2001-2019. We shuffled full community catches among haul positions within each fixed stratum and year in 999 draws. Bering reference medians were -0.307 and -0.305, compared with observed values of -0.377 and -0.258. All four observed medians fell within their central 95% shuffle ranges. Four-test adjusted tail values were at least 0.816. Thus, negative correlations alone do not separate a biological trade-off from paired survey geometry. This is a conditional reference test, not proof of a geometry cause or absence of a climate response. Habitat structure can violate exchangeability. Short series, persistent-taxon selection and catchability limit inference. We preserve catch arrays, survey evidence, code, source hashes and checks.

species distributions · observation bias · survey geometry · conditional randomization · latitude · depth · OceanAdapt · null result