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- Title
Contributions of adult mortality to declines of Puget Sound Pacific herring.
- Authors
Siple, Margaret C.; Shelton, Andrew O.; Francis, Tessa B.; Lowry, Dayv; Lindquist, Adam P.; Essington, Timothy E.
- Abstract
Forage fish undergo dramatic changes in abundance through time. Long-term fluctuations, which have historically been attributed to changes in recruitment, may also be due to changes in adult mortality. Pacific herring, a lightly exploited forage fish in Puget Sound, WA, have exhibited shifts in age structure and decreases in spawning biomass during the past 30 years. Here, we investigate changes in adult mortality as a potential explanation for these shifts. Using a hierarchical, age-structured population model, we indicate that adult natural mortality for Puget Sound Pacific herring has increased since 1973. We find that natural mortality has increased for every age class of adult (age 3+), especially age 4 fish, whose estimated mortality has doubled over the survey time period (from M = 0.84-1.76). We demonstrate that long-term shifts in mortality explain changes in age structure, and may explain biomass declines and failure to reach management thresholds for two spawning sites in Puget Sound (Cherry Point and Squaxin Pass). Temporal shifts in natural adult mortality could have negative implications for herring and herring predators. We demonstrate that adult mortality, in addition to recruitment variation, is an important driver for forage fish, which face exceptionally high natural mortality compared with other fishes.
- Subjects
FISH conservation; PACIFIC herring fisheries; WILDLIFE conservation; WILDLIFE habitat improvement; WILDLIFE rescue
- Publication
ICES Journal of Marine Science / Journal du Conseil, 2018, Vol 75, Issue 1, p319
- ISSN
1054-3139
- Publication type
Article
- DOI
10.1093/icesjms/fsx094