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Biological reference points for fishery management depend on estimates of current stock status relative to unfished biomass (depletion). The ratio of fish density outside to inside a marine reserve, the density ratio, could serve as a proxy for depletion for data-poor management. However, transient dynamics associated with time lags in returning to the unfished state following reserve implementation make that proxy inaccurate on short time scales. We assessed density ratio management rules using an age-structured, spatially explicit model of four US west coast nearshore fishes following reserve implementation, with scenarios encompassing sampling error, recruitment variability, and uncertainty in natural mortality. In deterministic simulations, management incorporating time lags generally resulted in a higher mean and lower variability in biomass over 20 years, but lower mean yield compared to management that did not. However, when stochastic recruitment was included, differences among simulations due to stochasticity were much greater than any difference in performance between management strategies. Nonetheless, in certain cases, accounting for time lags could help avoid unwarranted increases in harvest effort after reserve implementation.
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Projecting the timescale of initial increase in fishery yield after implementation of marine protected areas
Abstract Adaptive management of marine protected areas (MPAs) to determine whether they are meeting their intended goals requires predicting how soon those goals will be realized. Such predictions have been made for increases in fish abundance and biomass inside MPAs. However, projecting increases in fishery yield (“fishery spillover”) is more complex because it involves both how the fishery is managed and uncertainty in larval connectivity. We developed a two-patch, age-structured population model, based on a renewal equation approach, to project the initial timing of increase in fishery yield from larvae exported from a no-take MPA. Our results link our understanding of the predicted timing of increases in biomass (and thus reproduction) in MPAs with the time-lags associated with new recruits entering the fishery. We show that the time-lag between biomass peaking within the MPA and the increased fishery yield outside the MPA reaching its maximum depends, in a predictable way, on the age-dependent patterns of growth, natural mortality, and fishing mortality. We apply this analysis to 16 fishery species from the US Pacific coast; this difference ranged from 7 to 18 years. This model provides broadly applicable guidance for this important emerging aspect of fisheries management.
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- Award ID(s):
- 1734999
- PAR ID:
- 10346806
- Editor(s):
- Anderson, Emory
- Date Published:
- Journal Name:
- ICES Journal of Marine Science
- Volume:
- 78
- Issue:
- 5
- ISSN:
- 1054-3139
- Page Range / eLocation ID:
- 1860 to 1871
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1093/icesjms/fsaa233
