Evaluating the impact of variable en route mortality on spatially varying harvest strategies for Fraser River sockeye (Oncorhynchus nerka)

Single stock terminal fisheries for Fraser River sockeye salmon (Oncorhynchus nerka) have been proposed as an alternative to lower-river mixed-stock fisheries to avoid weak stocks and support terminal allocation objectives. However, increasing natural mortality rates during the upriver migration (en route mortality) have been overlooked when evaluating alternative harvest strategies. I used a spatially explicit, individual based model of sockeye migration and fisheries to examine how fishery location options affect management performance under variable en route mortality scenarios and a fixed total catch objective. Under all scenarios tested, re-distributing a fixed total harvest from lower-river mixed-stock to multiple upper-river single stock terminal fisheries resulted in increased en route mortality, decreased spawner abundance, and, in most cases, reduced total catch. While lower-river mixed-stock fisheries performed better at meeting a fixed catch objective under the scenarios in my analysis, single stock terminal fisheries may be preferable for meeting other objectives.