Density-dependent changes in effective area occupied for sea-bottom-associated marine fishes

James T. Thorson, Anna Rindorf, Jin Gao, Dana H. Hanselman, Henning Winker

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The spatial distribution of marine fishes can change for many reasons, including
density-dependent distributional shifts. Previous studies show mixed
support for either the proportional-density model (PDM; no relationship
between abundance and area occupied, supported by ideal-free distribution
theory) or the basin model (BM; positive abundance–area relationship,
supported by density-dependent habitat selection theory). The BM implies
that fishes move towards preferred habitat as the population declines. We
estimate the average relationship using bottom trawl data for 92 fish species
from six marine regions, to determine whether the BM or PDM provides a
better description for sea-bottom-associated fishes. We fit a spatio-temporal
model and estimate changes in effective area occupied and abundance, and
combine results to estimate the average abundance–area relationship as well
as variability among taxa and regions. The average relationship is weak but
significant (0.6% increase in area for a 10% increase in abundance), whereas
only a small proportion of species–region combinations show a negative
relationship (i.e. shrinking area when abundance increases). Approximately
one-third of combinations (34.6%) are predicted to increase in area more
than 1% for every 10% increase in abundance. We therefore infer that population
density generally changes faster than effective area occupied during
abundance changes. Gadiformes have the strongest estimated relationship
(average 1.0% area increase for every 10% abundance increase) followed by
Pleuronectiformes and Scorpaeniformes, and the Eastern Bering Sea shows a
strong relationship between abundance and area occupied relative to other
regions. We conclude that the BM explains a small but important portion of
spatial dynamics for sea-bottom-associated fishes, and that many individual
populations merit cautious management during population declines, because
a compressed range may increase the efficiency of harvest.
Original languageEnglish
Article number20161853
JournalProceedings of the Royal Society B: Biological Sciences
Issue number1840
Publication statusPublished - 2016

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