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q-bio.PE · Populations and Evolutionstat.AP · Applications

In 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

Question: does the spatial slope of fish body mass on bottom temperature predict the year-to-year slope in the same populations, as space-for-time substitution and the temperature-size rule (TSR, -2.5 to -5% mass per degC) assume? Data: 13 FishGlob v2.1 bottom-trawl survey units with in-situ bottom temperature (North America and Europe, 1963-2023, 82,994 hauls), 509 species x unit populations (239 species). Method: for each population, log mean individual mass per haul (catch weight/number) was fitted with 0.5-degree cell and year fixed effects plus depth and day of year. Cell effects were regressed on cell temperature climatology (spatial slope, with and without cell depth), and detrended year effects on the annual bottom-temperature anomaly (temporal slope). Units were pooled by random-effects means, with year and cell cluster bootstraps and a permutation test of the anomalies. Results: the pooled spatial slope was -3.6% per degC (95% CI -7.8 to +0.7; 65% of populations negative), but only -1.3% (-4.1 to +1.5) with cell depth held constant. The temporal slope was +1.8% per degC (+0.5 to +3.0); +1.0% (-0.5 to +2.6) with only years of fine weight recording, and +0.7% or +0.8% with lagged anomalies. No unit had a significant negative temporal slope in the main analysis, and no variant included the TSR range. Within units, the slope of temporal on spatial population slopes was 0.10 (0.01 to 0.18) after correction for measurement error (1 if space substitutes for time; upper limit at most 0.41 in all variants). Long-term mass trends did not follow unit warming rates (Spearman rho = -0.35, p = 0.25). Thus the spatial mass-temperature gradients mostly show depth-related size structure and not a thermal effect. Limitations: the response is mean catch mass, not size-at-age; only 13 units; the pooled temporal estimate is significant with random-effects weights (p = 0.001) but not with equal unit weights (p = 0.15); detrending removes slow responses.

temperature-size rule · space-for-time substitution · body size · demersal fish · bottom trawl survey · FishGlob · bottom temperature · climate warming · random-effects meta-analysis · cluster bootstrap · depth

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References

13
  1. usesdoi:10.1038/s41597-023-02866-w

    FishGlob_data: source of the standardized bottom-trawl catch number, weight and bottom temperature.

  2. usesdoi:10.5281/zenodo.19056965

    FishGlob_data v2.1 release (per-survey cleaned files, via SCI shared data).

  3. usesYear-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

    We reuse its prepared haul tables (core cells, cell temperature climatology, annual bottom-temperature anomalies). Its biomass result (year-to-year responses about 3% of spatial slopes) has the same pattern as our body-mass result.

  4. supportsWithin-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 sci:sha256:9fbcc6a31c132aa44d1dd80c36ea666b96cffa65a298e3d4c61b7a6295ea8148

    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.

  5. 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 survey units, experienced bottom temperature.

  6. doi:10.1073/pnas.1220228110

    Space-for-time substitution, the assumption that we tested for fish body mass.

  7. doi:10.1016/S0065-2504(08)60212-3

    Temperature-size rule, about -2.5% mass per degC.

  8. doi:10.1073/pnas.1210460109

    Aquatic temperature-size rule magnitude, about -5% mass per degC.

  9. doi:10.1016/j.tree.2011.03.005

    Declining body size proposed as a universal response to warming.

  10. doi:10.1073/pnas.0902080106

    Warming benefits the small in aquatic ecosystems.

  11. doi:10.1111/gcb.12514

    North Sea fish growth and size decreases with warming.

  12. doi:10.1111/1365-2664.13807

    Bigger juveniles and smaller adults with warming; agrees with our non-negative year-to-year slopes.

  13. supportsdoi:10.1038/s41559-020-1171-0

    Not all fish species shrink with warming; our trawl results agree.

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