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Abstract

Climate change and fisheries exploitation are dramatically changing the abundances,species composition, and size spectra of fish communities. We explore whether variationin ‘abundance size spectra’, a widely studied ecosystem feature, is influenced bya parameter theorized to govern the shape of size-structuredecosystems—therelationshipbetween the sizes of predators and their prey (predator–preymass ratios, orPPMRs). PPMR estimates are lacking for a vast number of fish species, including at thescale of trophic guilds. Using measurements of 8128 prey items in gut contents of 97reef fish species, we established predator–preymass ratios (PPMRs) for four majortrophic guilds (piscivores, invertivores, planktivores, and herbivores) using linearmixed effects models. To assess the theoretical predictions that higher community-levelPPMRs leads to shallower size spectrum slopes, we compared observations ofboth ecosystem metrics for ~15,000 coastal reef sites distributed around Australia.PPMRs of individual fishes were remarkably high (median ~71,000), with significantvariation between different trophic guilds (~890 for piscivores; ~83,000 for planktivores),and ~8700 for whole communities. Community-levelPPMRs were positivelyrelated to size spectrum slopes, broadly consistent with theory, however, this patternwas also influenced by the latitudinal temperature gradient. Tropical reefs showed astronger relationship between community-levelPPMRs and community size spectrumslopes than temperate reefs. The extent that these patterns apply outside Australiaand consequences for community structure and dynamics are key areas for futureinvestigation.

Item Type:	Article
Authors/Creators:	Coghlan, AR and Blanchard, JL and Heather, FJ and Stuart-Smith, RD and Edgar, GJ and Audzijonyte, A
Keywords:	coastal ecosystems, community composition, habitat complexity, predation, predator-prey mass ratio, size spectrum
Journal or Publication Title:	Ecology and Evolution
Publisher:	John Wiley & Sons Ltd
ISSN:	2045-7758
DOI / ID Number:	10.1002/ece3.8789
Copyright Information:	© 2021. The Authors. This is an open access article under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0) License, (https://creativecommons.org/licenses/by/4.0/), which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Related URLs:	Google Scholar: Blanchard, JL UTAS Profile: Blanchard, JL Google Scholar: Stuart-Smith, RD UTAS Profile: Stuart-Smith, RD Google Scholar: Edgar, GJ UTAS Profile: Edgar, GJ Google Scholar: Audzijonyte, A
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