Document Type : Primary Research paper
Maturity stages of 3,485 individuals of the Indian mackerel Rastrelliger kanagurta (Cuvier, 1817) were measured from a population occurring in Mayalibit bay in Radja Ampat Regency of West Papua during the period of March 2011 through February 2012. Approximately 200-600 individuals were collected each month from the Warsambin and Lopintol villages, respectively,closed to the mouth of Mayalibit Bay. One thousand seven hundred and thirty four out of the 3485 individuals gonads (49.76%)were males and 1751 (50.24%) were females. The estimated length at first maturity values or Lm50 of male and female were at 19.55 cm and 20.71 cm, respectively, this significantly larger than populations examined in the Malacca Strait and Java Sea. In both sexes, individuals in all 5 maturity stages were recorded each month, with the highest cumulative percentage being stage IV (ripe gonads) for both males (50.4%) and females (38.8%). Weights of individual male testes ranged from 0.9 to 20.4 g, while female ovary weights ranged from 3.1 to 28.9 g. The result represents the heaviest ovaries that have not been recorded, yet for an individual of R. kanagurta. Two of the individuals examined showed hermaphroditic development. Forty among female ovaries specimens were at translucent stages which indicated the spawning periods of the species. This finding, along with the overall high percentage of individuals specimens at stage IV and V maturity, contribute a strong support to fisher knowledge and local fisheries office report that Mayalibit Bay may taken into considered as a spawning aggregation area for R. kanagurta.