Length-based stock assessment for Malabar blood snapper in Makassar Strait-Indonesia: Status and recommendation for sustainability

Abstract

Snapper is one of the important groups of fish in demersal-reef fisheries in Indonesia. Malabar blood snapper Lutjanus malabaricus is the main and dominant species in snapper fisheries, making it the major target of fishing activities in Indonesia, including in Makassar Strait. Current management is still limited based on aggregate stocks (i.e., TAC for demersal-reef fish, snapper is included in this group), to reduce uncertainty, focused management is needed on specific fish stocks. The length-based approach for stock assessment was conducted under a data-limited situation. This study revealed the character of L.malabaricus in the Makassar Strait based on life history parameters as the categories of slow growth, late maturity and long-lived species. The condition of L.malabaricus has indicated a decrease in stocks based on several length models (LBSPR, LBB and LBI). A simulation of determining reference points for setting length size as a management intervention has been carried out with the scenarios: BaU (Lc=33.5 cm), Limit (Lc=Lm50=47.2 cm), and Target (Lc=Lc-opt =57 cm), but F is constant (F=0.5, as the current F). The BaU scenario performed it is difficult for L.malabaricus to achieve sustainability. In the limit scenario, MSY could be achieved by maintaining F=0.5 and SPR at 30% with Lc=Lm50. In the target scenario, there is no sustainability risk with FFSPR40%=0.5 and Lc=Lc-opt. It can be said that the limit reference point is determined at SPR 30% with Lc=Lm50, while the target reference point is at SPR 40% with Lc=Lc-opt.