Mortality and Movement of Adult Atlantic Menhaden During 1966-1969 Estimated from Mark-Recapture Models

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Liljestrand, Emily Morgan
Wilberg, Michael J
Atlantic Menhaden Brevoortia tyrannus is an economically and ecologically important forage fish. I built a multi-state mark-recapture model to estimate movement, fishing mortality, and natural mortality rates during 1966-1969. Movement from mid-Atlantic regions to North and South Carolina in the winter was lower than previously described, and natural mortality was approximately three times greater than previously estimated. Fishing mortality was highest in North and South Carolina. We evaluated the model’s performance by generating mark-recapture data sets from known values of mortality and movement then fitting the mark-recapture model to those data. The model estimated movement rates > 0.05 to within 33% of the true value even under different scenarios of spatiotemporally distributed releases and fishing effort. Distributing the fishing effort more evenly across regions substantially improved the estimates of movement and fishing mortality, and increasing the number of marked fish released had a small positive effect on accuracy of estimates.