Length-based stock assessment of the blue swimming crab Portunus pelagicus (Linnaeus, 1758) in the northern coast of Java, Indonesia

Abstract

The blue swimming crab Portunus pelagicus is heavily exploited in the northern coast of Java (NCJ), due to its high economic value as an export commodity. Without any management measures, the continued fishing efforts could lead to the depletion of the blue swimming crab (BSC) stock, threatening the economy of fishing communities. Stock assessment is crucial to evaluate stock status and to develop management recommendations. Length frequency and some biological data for 2019 was used to perform a length-based assessment of BSC fisheries in the NCJ. This study revealed that a high fishing mortality and a low selectivity of gillnet fishery had resulted in recruitment overfishing of BSC, with a spawning potential ratio of 0.20±0.05. The current fishing mortality has exceeded 37% of the optimum level and the current selectivity is below the optimal value of a 12 mm carapace width. A combination of management measures including 37%  reduction in fishing effort, gear modification to attain 12 mm selectivity, closure of the spawning area in August and habitat restoration, could be implemented to ensure the sustainability of blue swimming crabs in the northern coast of Java Keywords: Gillnet, Management recommendation, Spawning potential ratio, Stock status