Within-species mean fish mass in 31 trawl survey segments (1980–2026) changed +0.3% per °C of yearly bottom-temperature anomaly (95% CI −0.7 to +1.3), not the −2.5 to −5% of the temperature–size rule
Question: does the mean individual mass of demersal fish in scientific bottom-trawl catches decrease with time and with warmer bottom water, as the temperature-size rule (TSR, -2.5 to -5% body mass per degC) predicts? Approach: we used FishGlob v2.1 survey units with catch numbers and weights, plus NOAA AFSC FOSS data for the eastern Bering Sea, Gulf of Alaska and Aleutian Islands. We kept a constant spatial footprint, split documented gear eras into separate segments, and used only unit-years with fine weight recording. For 1,674 species x segment series (545 species, 31 segments, 138,003 hauls), the annual index was the year effect of log(catch weight/number) with 0.5-degree cell fixed effects. For 20 segments, in-situ haul temperatures gave annual bottom-temperature anomalies. Inference used the yearly mean index of each segment (so shared year shocks count once) and a random-effects meta-analysis. Results: mass trends were heterogeneous: pooled -0.6% per decade (95% CI -2.7 to +1.7), 10 segments with significant decreases and 7 with significant increases. With the trend removed, mass changed +0.3% per degC of same-year anomaly (95% CI -0.7 to +1.3; minimum detectable effect 1.4% per degC). This excludes the TSR range. The result was the same with an abundance covariate, a catch-weighted index, Newey-West errors, 3-year or lag-1 anomalies, body-mass classes, all years or only catches of 1 kg or more, and leave-one-region-out. Segments that warmed faster did not have more negative mass trends. The index detected recruitment signals: mass was lower in high-abundance years in 17% of series and higher in 3.5%. In NEUS 1967-2008, coarse weight recording before 2001 caused about one third of an apparent -18.5% per decade decrease. Limitations: the index is the mean catch mass, not size-at-age. DATRAS weights come partly from length-weight conversions. The test applies to year-to-year variation and lags of 1-2 years, not to slow responses over generations.
temperature-size rule · body size · demersal fish · bottom trawl survey · FishGlob · climate warming · meta-analysis · shrinking · NOAA AFSC · DATRAS · measurement artefact · weight resolution
References
13- usesdoi:10.1038/s41597-023-02866-w
FishGlob_data: source of the standardized bottom-trawl survey data for all non-AFSC survey units.
- usesdoi:10.5281/zenodo.19056965
FishGlob_data v2.1 release used (via the SCI shared parquet conversion).
- Year-to-year biomass responses of demersal fish to bottom temperature were about 3% of their spatial temperature slopes in 13 trawl survey units (1963–2023) sci:sha256:73ec8e55114714e88c3a1d65b19dc7fbadba02fb93318f40a435610325a52c6a
Same FishGlob surveys, year-to-year biomass responses to bottom temperature; body mass not examined.
- 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) sci:sha256:64e9211e9d66f96b3c901393f2eddaa2e16985901d0046a2ef094b470aff3b9e
Same FishGlob surveys, experienced bottom temperature.
- Early-half shift rates of 1,404 fish populations do not predict their late-half rates of latitude or depth change in 25 bottom-trawl survey units (1967–2021) sci:sha256:440f3c8b47c8a5ab03f5738ceeee021cc15fd66ba491c22caf206c3966b8dac8
Same FishGlob surveys, persistence of distribution shifts.
- In 1982–2026 NOAA trawl surveys, eastern Bering Sea fish moved north 7.7 km per decade more than bottom temperature predicts, and a 1982–2006 trend fit predicted 2007–2026 sci:sha256:4e3b4bd22dc60b2863c99153690bb156083d235ef3fafabc229d05bf8d99db1b
NOAA eastern Bering Sea trawl survey data, distribution shifts.
- doi:10.1016/S0065-2504(08)60212-3
Temperature-size rule, about -2.5% mass per degC.
- doi:10.1073/pnas.1210460109
Aquatic TSR magnitude, about -5% mass per degC; the prediction that we tested.
- doi:10.1016/j.tree.2011.03.005
Declining body size proposed as a universal response to warming.
- doi:10.1073/pnas.0902080106
Warming benefits the small in aquatic ecosystems; community size shifts.
- doi:10.1111/gcb.12514
North Sea fish growth and body size decreases with warming.
- doi:10.1111/1365-2664.13807
Bigger juveniles and smaller adults with warming; agrees with our positive lag-1 estimate.
- supportsdoi:10.1038/s41559-020-1171-0
Reef fish: not all species shrink with warming; our trawl results agree.
Cited by
3 publicationsPublic catalog entries on Sciscape.
- supportsFish mean body mass did not decrease in warmer years in 13 trawl survey units, spatial slopes were weak, and steps at 1985 and 2009 gear changes made most of the US Northeast shelf decrease
Parallel study of the same question. With a different design (13 units, cell-year ratio index, spline detrending, year permutation, harmonized weights) we get almost the same year-to-year response (+0.4 vs +0.3% per degC). We add spatial slopes and a transfer test. We also find a shared step at the 1985 NEUS door change, inside its 1963/1982-2008 NEUS gear era; with that break the NEUS trend is -5 to -6% per decade, not about -13 to -18%.
- Mean length changes were uncertain for six fish taxa in matched catches at 168 English sites, 2000–2009 versus 2016–2025
Related fish-size work uses mean mass in trawl surveys and temperature anomalies. The current study uses individual freshwater lengths.
- supportsIn 13 trawl survey units (1963–2023), fish mass was lower in warmer cells (−3.6%/°C, mostly a depth effect) but not in warmer years (+1.8%/°C); spatial slopes did not predict temporal slopes
Our temporal mass-temperature slope agrees with its +0.3% per degC with a different design; we reuse its weight-resolution rule for a sensitivity analysis.