Evaluating data-limited fisheries for grouper (Serranidae) and snapper (Lutjanidae) in the Coral Triangle, eastern Indonesia

Abstract

Small-scale fisheries (SSF) in southeast Asia contribute more food fish for human consumption than industrial fisheries and in Indonesia, employ almost 85% of the total fisheries employees. Grouper and snapper are commercially important species highly targeted, including by small-scale fishers. We estimate the spawning potential ratios (SPRs) of high-value species in a small-scale fishery in Saleh Bay (Plectropomus leopardus, Variola albimarginata and P. maculatus) and in the Timor Sea (Lutjanus gibbus, L. boutton and Epinephelus areolatus) from a larger scale fishery (Kupang) and a SSF (Rote), using length-frequency data, biological parameters and empirical equations and the length-based SPR methodology. Measuring programs collected 10,621 lengths frequency samples from six species over 12 months, with ¿ 800 recorded lengths for each species. The SPRs for all species were very low (0.02–0.12), except for E. areolatus (0.49) and ratios of fishing to natural mortalities (F/M) were high (1.8 – 9.3). The results from the length-based SPR model indicate that the fish are harvested below the size of maturity, except for E. areolatus. Further analysis indicated that the smaller E. areolatus landed in Rote is likely under-represented compared to that of E. areolatus landed in Kupang. The expanding landings of grouper and snapper on a broad-scale and low SPRs highlight the importance of seeking measures to rebuild these stocks. These estimates of SPR would be enhanced by detailed biological studies of these species to obtain local estimates of growth parameters and size at maturity, as well as the size-at-selectivity for different fishing gears.