Fishing impact of blue swimming crab (Portunus pelagicus) fishery on target in Lamongan Water, Northern Coast of Eastern Java Province

Abstract

Blue swimming crab (Portunus pelagicus) is a high-value export commodity of fisheries to the international market. Thus, it promotes overfishing, reducing target stocks, and ecological impact on non-target biota. Fishers in Lamongan Regency use traps, trammel nets, and mini trawl (arad) to target the crabs. The fishing gears have different levels of selectivity. This study aims to evaluate the impact of crab fishing on target (P. pelagicus), particularly in the study area. The samples of blue swimming crab (BSC) were collected using the quota sampling method. The parameters of the crab catch (Portunus pelagicus) collected included carapace width, weight, sex, and gonad maturity stage (GMS). 1424 fishing vessels and 3598 fishers targeted the BSC in the Lamongan water. The result of this study showed that 93% of BSC catch was higher than the legal size from traps, 66% (arad), 89 % (trammel nets). The growth parameter of L∞ = 156.95 mm (for female) and L∞ = 182.22 mm (male), while K = 1.4 per year (for female) and K = 1.4 per year (male). The relationship between carapace width and weight of the male and female crabs was positive allometric growth. The LB-SPR parameter value was 23% which indicated that the crab resource stock in Lamongan waters was a ‘fully-moderately’ status, while the selectivity level indicated an ‘over-exploitation’ base on the E value = 0.69 (for female crab) and E = 0.72 (for male). This study proposes urgently reducing the fishing effort targeting BSC, particularly by the mini trawl (arad) and implementing a rebuilding stock program for the BSC.