Virginia Institute of Marine Science
MARINE AND COASTAL FISHERIES
Recent advances in methodology allow the history of the total mortality rate experienced by a population to be estimated from periodic (e.g., annual) observations on themean length of the population. This approach is generalized to allow data on several species that are caught together to be analyzed simultaneously based on the theory that changes in fishing effort are likely to affect several species; thus, the estimation of times when the mortality rate changes for one species borrows strength from data on other, concurrently caught species. Information theory can be used to select among models describing the degree of synchrony (if any) in mortality changes for a suite of species. This approach is illustrated using data on Puerto Rican handline fishery catches of three snapper species: Silk Snapper Lutjanus vivanus, Blackfin Snapper L. buccanella, and Vermilion Snapper Rhomboplites aurorubens. We identified the best model as the one that provided for simultaneous decreases in mortality rate around the year 1997 and for separate, species-specific magnitudes of change in total mortality. The simultaneous estimation of parameters for multiple species can provide for more credibility in the inferred mortality trends than is possible with independent estimation for each species.
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We thank Larry Beerkircher and Josh Bennett for assistance with the data. This work was funded in part by the National Oceanic and Atmospheric Administration (Grant Number NA14OAR4170297). Q.C.H. was supported by a National Marine Fisheries Service/Sea Grant Population and Ecosystem Dynamics Fellowship (NA15OAR4170184). This is Contribution Number 3609 of the Virginia Institute of Marine Science, College of William and Mary.
Huynh, Quang C.; Gedamke, Todd; Hoenig, John M.; and Porch, Clay, "Multispecies Extensions to a Nonequilibrium Length-Based Mortality Estimator" (2017). VIMS Articles. 21.