Open AccessFishing, environment, and the erosion of a population portfolio
Author(s) -
Stier Adrian C.,
Olaf Shelton Andrew,
Samhouri Jameal F.,
Feist Blake E.,
Levin Phillip S.
Publication year - 2020
Publication title -
ecosphere
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.255
H-Index - 57
ISSN - 2150-8925
DOI - 10.1002/ecs2.3283
Subject(s) - herring , population , population growth , biological dispersal , geography , ecology , metapopulation , archipelago , fishery , environmental science , biology , demography , sociology , fish <actinopterygii>
Many organisms exhibit tremendous fluctuations in population abundance and experience unexpected collapse. Conservationists seeking to minimize region‐wide variability in resources and reduce extinction risk often seek to preserve a metapopulation portfolio of spatially asynchronous subpopulations connected by dispersal. However, portfolio properties are not necessarily static, and the erosion of a portfolio can fundamentally alter the population dynamics and services a species provides. In the Northeast Pacific, a portfolio of spatially asynchronous herring populations has historically provided regional reliability of herring to mobile predators and commercial fishermen as well as local subsistence and ceremonial harvest. Here, we fit a mechanistic time‐series model to herring spawn and catch records from 1950 to 2015 to quantify how population growth, climate, and fishing have contributed to a major shift in the herring portfolio over time. We document the erosion of the herring portfolio and a severe decline in herring population growth. Commercial harvest historically played a key role in herring dynamics, hovering around typical annual exploitation rates (15%) at the archipelago scale, but local harvest rates were much higher when fishing occurred (as high as 65%). Additionally, the Pacific Decadal Oscillation and population growth had equally strong effects on local and regional herring population dynamics. Our results highlight how spatially structured populations can undergo major shifts following disturbance and emphasize how ecological systems do not always rapidly recover and provide services following disturbance. Developing herring management strategies at a finer scale may ensure greater regional resource reliability by recovering previous levels of spatial population asynchrony. However, doing so may require higher implementation and monitoring costs in order to yield higher ecological, social, and economic benefits. Such place‐based solutions that match the spatial scale of governance to the spatial scale of ecological dynamics have the potential to improve future management and conservation in an increasingly dynamic world.