| dc.description.abstract | Blue swimmer crab ( P.pelagicus ) resource have been exploited continuously in Pati regency waters for two decades. The main fishing gear were used by portable traps. It was indicated crab catches decline. It’s caused by decline of crab population that have been fishing continuously. That is a problem to manage the crab resource . This study aims to assess: 1) the distribution and stock abundance of crab and it’s environmental factors, 2) aspects of crab reproduction, 3) the mean width at first capture (Lc) and mean width at the first maturity (Lm), 4) population dynamics such as size distribution, growth, mortality and age, 5) status and exploitation rate of crab resource and 6) management options for sustainable crab resource. Research has been carried out from January 2012 to March 2013. It was divided into three parts, consisting of: observations at the landing base, observations at the sea and observations in the laboratory. Study area were divided into three zones which are crab fishermen fishing ground based in Alasdowo, Pati regency, Central Java. The data consists of environment parameters, biology ( size, weight, sex and TKG ) and the catch ( buku bakul and experimental fishing). Marine environmental conditions were quite optimum for the growth of crab in East and West season, so the distribution of crab catches by season and different substrate are relatively similar (p < 0.05). Crab catch per unit effort ( CPUE ) in fishing zone 1, 2 and 3 are influenced by the lunar cycle (p <0.05). CPUE in zones 1 and 3 was relatively similar (p > 0.05) in the west and east season. While CPUE in West season was higher than east season ( p < 0.05 ). Sex ratio is relatively balanced (p > 0.05) in West season. But sex ratio was not balanced in East season, it’s tendency that females more than males (p<0.05 ). Crab reproduction occured throughout the year in Pati waters. The mean carapace width at first maturity (Lm) of females were 107 mm. The fecundity of crab was ranged between 351 214 to 1 347 029 grains with an average at 957 196 grain. The mean carapace width of the crab caught in zone 2 was smaller (105.2 mm for males and 106.8 mm for females) than the crab caught in the waters of the middle zone 1 and 3 ( p <0.05 ). The average crab in January and February are smaller than in other months due to decreased salinity waters. It made adult crabs which generally maturring were migrated to deeper waters. Crab size between September and November are relatively higher than in other months, alleged that the crabs generally have entered the mature phase and has matured gonad. The mean width at first capture (Lc) of crabs by portable trap was 108 mm . Carapace width and weight relationship of male and female crab were allometric positive (p<0.05). Monthly condition factor of males and females are relatively similar, the females are influenced by gonadal maturation process. The growth rate of males were faster than females, showed by a higher K value. The growth rate of crabs in zone 2 were the most rapidly than in zone 1 and 3. The growth pattern was good enough but exploitation is relatively height and tend to over fishing. Based on the research results were derived management options for crab resources. The options of management are consists of : 1) prohibition of fishing activities in the estuary and coastal area (zone 2), 2) released the female crab that was in egg-bearing condition, 3) establish regulations concerning the minimum legal size that based on the mean width at first maturity and 4) limitation and reduction of fishing effort . | en |
