Impacts of metapopulation dynamics on overfishing risk and vulnerability in multiscale fisheries

• Main Authors: Okamoto, Daniel K, Hessing-Lewis, Margot, Salomon, Anne K
• Format: Text
• Language: English
• Published: Western CEDAR 2017
• Subjects: Fresh Water Studies; Life Sciences; Marine Biology; Natural Resources and Conservation; Pacific; First Nations
• Online Access: https://cedar.wwu.edu/ssec/2016ssec/species_food_webs/87

Fisheries management generally strives to balance tradeoffs between complex economic, social and ecological systems. Yet estimates of overfishing risk under individual harvest guidelines are likely to be biased where the spatial and temporal scales of science and management are improperly aligned with that of either the biology and/or the socioeconomic dynamics of the fishery participants. These biases have the potential to be especially pronounced in the presence of individual sub-stocks (i.e. metapopulation structure). Moreover the consequences of those biases are likely asymmetric when multiple fleets operate at different spatial scales. Specifically fleets targeting the entire metapopulation may be less vulnerable to risky harvest guidelines or naive biological assumptions than those dependent upon a subset of local aggregations. We explore the degree to which bias in overfishing risk and asymmetry in vulnerability among fleets result from the nature of harvest control rules, patterns of synchrony and connectivity among populations, and the scientific uncertainties in spatial and temporal population dynamics using a combination of metapopulation modeling and management strategy evaluation. We first use a basic simulation framework to illustrate how population connectivity, synchrony and harvest guidelines influence both local (single population level) and regional (metapopulation level) overfishing risk and extirpation probabilities. We then apply the models to a case study of Pacific Herring in British Columbia. Here, both transient industrial fishing fleets and local First Nations fleets target a complex suite of herring stocks whose spatial structure is poorly understood at smaller scales. Results are valuable in demonstrating which scenarios may benefit from improved knowledge of the temporal and spatial dynamics of the target species or the risk tolerance of individual fishery fleets.