Assessing stock status of grey sharpnose shark (Rhizoprionodon oligolinx Springer, 1964) in Java Sea

摘要

Increasing demand for shark products leads to over fishing of these species in many areas, damaging their population. Grey sharpnose shark (Rhizoprionodon oligolinx) is caught mostly by gillnet fleet in Java Sea. The objective of the study was to discuss the current stock condition of grey sharpnose shark in Java Sea. Research on shark resources has been conducted by placing enumerators at the main landing base in PPN Pekalongan. Biological parameters of R. oligolinx were estimated based on commercial landings data recorded by enumerators from 2014-2015. The growth parameters of grey sharpnose shark such as L∞, K, t0, values were 96.1 cm, 0.47 year~(-1), and -0.78 year, respectively. Moreover, total mortality rate (Z) were estimated at 1.82 year~(-1) with fishing mortality and natural mortality rates (F and M) were 1.04 year~(-1) and 0.78 year~(-1), respectively. Stock status of grey sharpnose shark in Java sea from view point of gill nets fisheries is still in the sustainable utilization status with biological reference point more than 30% SPR and level of exploitation rate (E) is 0.57.