Work

Accounting for Salmon Body Size Declines in Fishery Management Can Reduce Conservation Risks

Year: 2024

Type: article

Abstract: ABSTRACT Changes in population demographic structure can have tangible but unknown effects on management effectiveness. Fishery management of Pacific salmon is often informed by estimates of the number of spawners expected to produce maximum sustainable yield (S MSY ), which implicitly assumes that reproductive output per spawner does not change over time. However, many salmon populations have experienced long-term trends in age, sex, and length-at-age compositions that have resulted in smaller body sizes of mature fish. We present an empirically-based simulation approach for evaluating management implications of declining reproductive output that results from shifting demographics. We simulated populations with or without demographic trends, selective or unselective harvests, and harvest policies based on assessment methods that did or did not account for demographic trends when estimating S MSY . A management strategy evaluation showed that expected mean harvests and run sizes were reduced when populations exhibited negative demographic trends. Reduced abundances and increased conservation risks could be partially mitigated by using a stock-recruit analysis based on egg mass instead of spawner abundance, or by using a precautionary management strategy where target escapements were higher than the estimated S MSY , especially in fisheries that selectively removed large fish. Accounting for demographic trends in stock-recruit analyses resulted in up to 25% higher run sizes and up to 20% lower conservation risks compared to traditional methods when trends toward smaller, younger, and male-biased runs were present in the population. Conservation of population demographic structure may be critical for sustaining productive fish populations and their benefits to ecosystems and people.

Source: Fish and Fisheries

DOI: 10.1111/faf.12869

Authors: Jan Ohlberger, Daniel E. Schindler, Benjamin A. Staton

Institutions: University of Washington, Washington Department of Fish and Wildlife, Columbia River Inter-Tribal Fish Commission

Language: English

Topic: Marine and fisheries research

Subfield: Global and Planetary Change

Field: Environmental Science

Domain: Physical Sciences

SDG: Life below water

Open Access status: green

Funder: North Pacific Research Board