Transient inconsistency between population density and fisheries yields without bycatch species extinction

Abstract

Recent studies have demonstrated the great advantages of marine reserves in solving bycatch problems by maintaining the persistence (i.e., avoid extinction) of endangered species without sacrificing the fisheries yields of target species. However, transient phenomena rather than equilibrium states of population dynamics still require further research. Here, with a simple and general model, the transient dynamics of the target fish species are investigated under management which minimizes extinction risk of the bycatch species. An interesting finding is that fisheries yields can strongly fluctuate even if population density both inside and outside marine reserve only slightly varies (or vice versa), leading to transient inconsistency between the population densities and fisheries yields. This finding suggests that population density dynamics of the target fish species cannot be used to predict the transient phenomena of fisheries yields (or vice versa) in fisheries management. However, the unpredictability can be receded as the sensitivity analyses show that a large marine reserve size and low escapement rate can shorten the transient duration.