Life history traits and abundance trends of emperor fish Lethrinus nebulosus and L. lentjan (Teleostei: Lethrinidae) in the western Arabian Gulf

Abstract

Overexploitation and habitat loss are the two most important threats that cause the losses of marine populations. The understanding of the relationships between life histories and vulnerability to overexploitation could provide the basis for predicting possible trajectories of abundance under increasing levels of fishing pressure. The spangled emperor Lethrinus nebulosus and the pink ear emperor Lethrinus lentjan are the most important species contributing to the landings of the western Arabian Gulf. In this study, we integrated multiple surveys to provide information about life history traits, spatial distributions, and fisheries-dependent and independent abundance indexes from 1997 to 2015 and tested the hypothesis that the species of higher vulnerability more likely exhibited a declining population trend. Both species have experienced an increase of 100 % in fishing exploitation pressure since 1997, and L. nebulosus is expected to exhibit a declining population more likely based on the life history traits and other vulnerability indexes. However, we did not observe declines in fisheries-dependent and -independent population indexes of L. nebulosus, which might be due to its preference of residing in the northern areas where high numbers of oil-gas facility patchworks are installed and fishing activities are much restricted. The fisheries-dependent abundance index of L. lentjan from the large boats significantly correlated with the abundance index from the coral reef monitoring. Information included in this study can be used for fisheries stock assessment models in the future and we recommended that the emperor fisheries could benefit from the conservation of the coral reefs.