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q-bio.PE · Populations and Evolution

The temperature slope for larval fish composition distance was uncertain in 59 surveys at 12 CalCOFI stations in 1987–2019

We tested if larval fish communities became more alike when water was warmer. We used 59 complete CalCOFI surveys at 12 fixed stations from 1987 to 2019. The panel had 708 bongo-net tows and 38,874 counted larvae in 105 genus groups. The response was mean squared Hellinger distance across six fixed cross-shelf pairs. With survey month and a linear time trend in the model, the temperature slope was +0.0189 distance units per 1 °C. A nominal 95% interval from two-year blocks was −0.0255 to +0.0819. The interval allows both a decrease and an increase. The median resolved catch was 20 larvae per tow. No complete survey had at least 25 larvae at every station, so the planned count-matching check could not use the full panel. An added analysis used 134 individual station pairs with at least 25 larvae per tow. After exact count matching, its slope was +0.0814, with an interval of +0.0150 to +0.1506. This exploratory subset has a different sample and uses local pair temperature. It cannot establish a general effect. The contribution includes the complete panel, an exact expected distance under count reduction, source extracts, provenance, code, all results and figures. A separate calculation reproduced the main values, and an offline repeat matched the result hashes. Limits include small catches, missing surveys, fixed offshore sites, genus groups and no correction for detection. The primary null result does not establish stable spatial structure or a causal temperature effect.

CalCOFI · larval fish · spatial composition · temperature · Hellinger distance · rarefaction · fixed stations · open data

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References

6
  1. usesCalCOFI larval fish community temperature index changed 0.20 °C per °C of year-to-year 10 m temperature in 1951–2021, 59–117% of the spatial relation; a 1951–2013 fit predicted the 2014–2016 heatwave sci:sha256:16e7fa6aa99994401effde45c652662aa580554e63da0947c4b7aae50a0c6c26

    We reuse its retained raw NOAA and Scripps data snapshot, inspect its preparation code, and test a different spatial response.

  2. After the 2014–2016 marine heatwave, the CalCOFI larval fish community temperature index followed local temperature in 2017–2023 at 66 stations; an independent analysis reproduces the 0.2 °C/°C slope sci:sha256:ba9ebf4fff915c3708efe854bfdc664416503ba08b5ce72b6d8d52e1b9e4da04

    This related study reproduced a thermal community index response. We distinguish that response from spatial distance.

  3. doi:10.1038/ncomms9405

    This study of North Atlantic groundfish gives context for changes in spatial similarity in marine communities.

  4. doi:10.1111/gcb.16010

    This study reports unusual CalCOFI larval fish composition and richness during the 2014–2016 marine heatwave.

  5. doi:10.3354/meps14331

    This study reports responses to extreme cold and warm events and spatial barriers in southern California Current larval fish.

  6. usesdoi:10.1007/s004420100716

    This work gives the ecological basis for the Hellinger transformation of community composition.

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