Stock Availability Potential of Epinephelus fasciatus During the First Transitional Season in the Alas Strait, Indonesia

Abstract

Groupers (Epinephelus spp.) are high-value coral reef fishes that are highly susceptible to overfishing due to their slow growth and complex reproductive strategies. Consequently, biologically based stock assessments are essential for sustainable fisheries management. Epinephelus fasciatus is among the dominant grouper species exploited in the Alas Strait waters, Indonesia. This study aimed to evaluate the stock status and size structure of E. fasciatus during the first transitional season. Data collection was conducted from March to May 2025 at the Tanjung Luar Fish Market, East Lombok, West Nusa Tenggara Province. The collected data consisted of the number of captured individuals and total length measurements. Fish lengths were measured using WCS (Wildlife Conservation Society) Image Tools, followed by length-frequency analysis and stock assessment using the Length-Based Spawning Potential Ratio (LB-SPR) approach. The LB-SPR analysis incorporated biological parameters, including asymptotic length (L∞), growth coefficient (k), natural mortality (M), length at first capture (Lc), length at first maturity (Lm), length at 50% maturity (L50), and length at 95% maturity (L95), obtained from the Scientific Forum for Sustainable Fisheries Management of West Nusa Tenggara Province. Results showed that all sampled individuals (100%) exceeded the length at first maturity (Lm = 16.28 cm), with total lengths ranging from 17.46 to 28.81 cm, indicating that all captured fish had reached sexual maturity prior to capture. The dominant size class ranged from 20–24 cm. Furthermore, the estimated Lc exceeded Lm, suggesting that most individuals had the opportunity to reproduce at least once before capture. The SPR value was estimated at 71%, indicating an under-exploited stock condition. These findings suggest that fishing pressure on E. fasciatus in the Alas Strait during the first transitional season remains relatively low and that the stock retains adequate reproductive capacity to support population sustainability.