Spawning potential ratio (SPR) of Sulphur Goatfish (Upeneus sulphureus): biological basis for demersal fishery management in Java Sea

Goatfish is one of the most dominant demersal-fish species currently caught by local fishermen in North-Coast of East Java and Madura using modified Danish-Seine. This research aimed to investigate species diversity goatfish and spawning potential ratio (SPR) of most representative species, U. suphureus. Identification was completed through morphometric and meristic investigation. A total of 2,550 fish were sub-sampled from catches for length-frequency analysis, length at first maturity (L_m), length-weight relationship and SPR. The results showed that there were five species within catches, being: U. sulphureus, U. moluccensis, U. tragula, U. sundaicus, and P. heptacanthus. Length-weight followed cubic formula with W_t = 0.0159 * Lt^3.124 (p< 0.05; r² = 0.92). Female length-at-first mature was reached at 11.67 cm Fork-Length, with total female biomass in the sample 6.5 kg. Total biomass was 93.1 kg, hence the SPR was < 7%. The minimum value of SPR while maintaining stock at good parent stock was >20%. From these results, it was very clear that demersal fishery in North-Coast of East Java, represented by U. sulphureus is unsustainable. Management measure, either size or effort limitation should be implemented, otherwise, the stock will soon collapse.