Against static-distribution replicates, demersal fish in 15 FishGlob trawl survey units experienced 4–10% less year-to-year bottom-temperature change (16–35% on the US Northeast shelf)

Question: do demersal fish experience all of the bottom-temperature change in a survey area, or do they avoid part of it by redistribution? Data: FishGlob_data v2.1. We used 15 survey units with in-situ bottom temperature (10 regions in the NE Pacific, Gulf of Mexico, SE US, NW Atlantic and NE Atlantic; 1967-2023; 86,952 hauls; 748 species-by-unit populations). Method: for each population and year, we compared the catch-weighted haul temperature with a static expectation. The static expectation uses the same hauls and the leave-one-year-out mean catch in each 0.5-degree cell and depth band. Interannual pass-through B is the slope of detrended experienced temperature on detrended static temperature. A simple test against B = 1 is biased: static donor replicates with biomass weights gave B = 0.87-1.02. Thus we report the difference from 20 matched static replicates (dB), with a paired block bootstrap of years and a random-effects mean over regions. Results: the mean dB was -0.044 (95% CI -0.072 to -0.016) with occurrence weights and -0.099 (-0.152 to -0.046) with biomass weights. dB was negative in 14 and 13 of 15 units. The US Northeast shelf had the largest effect (-0.16 to -0.35), then the Scotian Shelf (-0.09 to -0.25). There, populations moved north and changed depth in warm years, and seasonal migrants had the largest effect. The three European units showed no clear effect. The result stayed in 16 analysis variants, when we removed each region, and when we controlled for abundance. In the long term, NEUS-Fall populations avoided 0.18 C per decade of a 0.42 C per decade static-expected warming and moved 15 km per decade farther north. Over all units, long-term and interannual pass-through did not differ (difference -0.003, CI -0.070 to 0.065). Limitations: movement out of the survey footprint is not measured. Catchability that changes with temperature, or survey timing relative to migration, can give the same signal. Long-term estimates have low precision. Only 3 European units had temperature data.

species redistribution · thermal exposure · bottom trawl survey · FishGlob · climate change · demersal fish · null model · static replicates · interannual variability · range shift · bottom temperature · Northeast US shelf