Blue Swimming Crab Stock Assessment in the Western Visayan Sea

Sheryll V. Mesa1,*, Drusila Esther E. Bayate2, May R. Guanco1

Abstract

Portunus pelagicus (Linnaeus, 1758) known as the blue swimming crab, ranks 4th major fishery export of the Philippines. The Visayan Sea is considered as the major crab fishing ground of the country to which 25 out of 53 crab picking stations are located in Region 6. The study was conducted in the year 2011 to 2012 in ten crab fishing municipalities of the Western Visayan Sea conducting catch and effort, reproductive biology, and biological sampling. Results showed that a decreasing CPUE is observed compared in 1995 at 0.34 kg/ panel to 0.19 kg/panel in 2011 and 0.26 kg/panel in 2012, with 17 to 20 gillnet-panels per boat per day. Surplus production models showed that MSY at 13,150 MT and fMSY at 19,473 gillnet-panels of the Fox model is achieved prior to the year 1999. In 2011 and 2012, yield decreases as a setback of increasing fishing effort. Population parameters results showed growth overfishing where the L value obtained at 19.10 cm for this study was lower compared to 19.95 to 21.77 cm in previous studies. Computed E value at 0.68year-1 is higher than the threshold at E = 0.5year-1 and at optimum E10 = 0.56year-1. Recruitment overfishing is also apparent from the size catches of major crab fishing gears to length at first maturity of 11.5 cm. Bottomset gillnet catches premature sizes by 57%, crab pot by 62%, and otter trawl by 95%. Seasonality of crab catching peaks in July and January coincides with the peak spawning in August and January, and recruitment in October and January.


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Keywords: Portunus pelagicus, exploitation, length at first maturity, crab pot, crab bottomset gillnet


*Corresponding Author: smyl2428@gmail.com

1Bureau of Fisheries and Aquatic Resources-National Stock Assessment Program, Regional Field Office 6, Iloilo City

2Bureau of Fisheries and Aquatic Resources-Central Office, Diliman Quezon City

https://doi.org/10.31398/tpjf/25.1.2017C0008