Growth estimates of pelagic thresher shark (Alopias pelagicus Nakamura, 1935) in the Indian Ocean Southern Java waters

Abstract

Alopias pelagicus were highly migratory species, oceanic and almost always found in tropical and temperate seas. This species was particularly vulnerable to exploitation of both targets and side catches. Research was conducted in May 2015 to November 2016 at the landing site of the Cilacap Fishing Port. This research aims was to estimate the growth as the foundation for knowing the stock status utilization rate. The research method was used through observation and data collection by the enumerator. The 1410 individual sharkswere a catch of long line caught in the Indian Ocean Southern Java waters. The results showed that the size structure of the pelagic thresher shark ranged between 60-270 cm FL with a mode ranging between the size of 140 cm FL. The length weight relationship of the male and female shark indicates the growth were allometric positif. A comparison of male and female shark was not balance (1:2.82). Mortality parameters for the covering the total mortality rate (Z), natural mortality rate (M) and the rate of fishing mortality (F), respectively at 0.796/year, 0.295/year and 0.50/year. The rate of exploitation (E) of pelagic thresher shark was 0.73/year. Thus, the utilization rate of pelagic thresher shark was over fishing.