Hopf et al. (2022; preprint online at Ecological Applications) investigated the issue of year-to-year variability in the larval recruitment of kelp forest fishes, and how it affects how we assess the effectiveness of marine protected areas for conserving those fishes. Using a 20-year dataset, we found that a common kelp forest fish in southern California has periodic peaks and troughs in recruitment, with a ~6 year cycle. Then, using age-structured population models we found that whether a new marine protected area was put in place during a peak or a trough either enhanced or delayed (respectively) post-protected population increases. That makes it more difficult to determine whether the reserve is successfully enhancing the population. Helpfully we also found that using before-after control-impact designs for monitoring helped mitigate this issue.
This project is a product of the Partnership for the Interdisciplinary Study of Coastal Oceans, and we hope it will inform the assessment of marine protected areas in California and Oregon in 2023.
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