Life history traits and exploitation affect the spatial mean-variance relationship in fish abundance
Journal
Ecology
Journal Volume
97
Journal Issue
5
Pages
1251-1259
Date Issued
2016
Author(s)
Abstract
Fishing is expected to alter the spatial heterogeneity of fishes. As an effective index to quantify spatial heterogeneity, the exponent b in Taylor's power law (V = aMb) measures how spatial variance (V) varies with changes in mean abundance (M) of a population, with larger b indicating higher spatial aggregation potential (i.e., more heterogeneity). Theory predicts b is related with life history traits, but empirical evidence is lacking. Using 50-yr spatiotemporal data from the California Current Ecosystem, we examined fishing and life history effects on Taylor's exponent by comparing spatial distributions of exploited and unexploited fishes living in the same environment. We found that unexploited species with smaller size and generation time exhibit larger b, supporting theoretical prediction. In contrast, this relationship in exploited species is much weaker, as the exponents of large exploited species were higher than unexploited species with similar traits. Our results suggest that fishing may increase spatial aggregation potential of a species, likely through degrading their size/age structure. Results of moving-window cross-correlation analyses on b vs. age structure indices (mean age and age evenness) for some exploited species corroborate our findings. Furthermore, through linking our findings to other fundamental ecological patterns (occupancy-abundance and size-abundance relationships), we provide theoretical arguments for the usefulness of monitoring the exponent b for management purposes. We propose that age/size-truncated species might have lower recovery rate in spatial occupancy, and the spatial variance-mass relationship of a species might be non-linear. Our findings provide theoretical basis explaining why fishery management strategy should be concerned with changes to the age and spatial structure of exploited fishes. © 2016 by the Ecological Society of America.
SDGs
Other Subjects
abundance; age structure; body size; demographic trend; exploitation; fish; fishing; generation time; heterogeneity; life history trait; population ecology; power law; size structure; spatial distribution; spatial variation; spatiotemporal analysis; California Current; Pacific Ocean; Pisces; animal; biological model; classification; ecosystem; fish; fishery; human activities; life cycle stage; physiology; Animals; Ecosystem; Fisheries; Fishes; Human Activities; Life Cycle Stages; Models, Biological
Type
other