Betahwalang has been one of the main contributors to the Blue Swimming Crab (BSC, Portunus pelagicus) fisheries production in Central Java Province. Recruitment of the BSC depends to a large extend on the abundance of crab larvae. However, information on larval distribution of the crab affecting the recruitment to the fishery, fishery management and decision making to support crab conservation in Betahwalang area has been lacking.  The purpose of this study is to describe the spatial and temporal distribution of BSC larvae in the crab conservation area, to identify the larval stage most commonly occurs in the conservation area, and to develop process of decision making to managing conservation areas. This study was conducted in twelve months, starting from January until December 2018. The spatial distribution of the crab larvae was analyzed and mapped by means of SPSS and ArcGIS. The results of this study indicate that the crab larvae occur in the conservation area throughout the year.  The highest larval abundance of the crab occurs in May, September, and November. The most commonly found crab larval stages were megalopa. As megalopa and crablet stages are relatively much more active and closer to the adult form, their occurrence in the conservation area and throughout the year of 2018 suggests the existence of continuous support to the Blue Swimming Crab recruitment for the following year. The spatial and temporal distribution of the larvae were influenced by oceanographic parameters including temperature, nitrate and phosphate, which were associated with monsoonal changes in the Java Sea.

Abstract. Ayodya FP, Wijayanti DP, Sabdono A. 2021. Lunar cycle and reproductive activity of Redbelly yellowtail fusilier, Caesio cuning in Karimunjawa National Park, Indonesia. Biodiversitas 22: 3075-3082. Redbelly yellowtail fusilier (Caesio cuning) is known as fish that has been widely distributed among Southeast Asian countries. Fishers in Indonesia especially target the species, causing the scarcity and depletion of the catch in many fisheries areas each year. One of the priority aspects in improving fisheries management in conservation areas is information regarding reproductive activities. Many reports suggested that the lunar cycle affects the reproductive activity of fishes. However, none of the studies reported on the effect of lunar cycle on the reproductive activity of C. cuning. This study aimed to explain the lunar cycle effect on the reproductive activity of C. cuning through gonadosomatic index (GSI), viscerosomatix index (VSI), and the observation of oocyte conditions. There were 374 individual fishes collected from Nyamuk Island, Karimunjawa from September to November 2020. Samples were taken in each phase and between major phase of the moon (new, first quarter, full, last quarter) during two lunar cycles. The results point out mature gonad (stage IV and V) was present around the new moon. The peak of female GSI occurred around the last quarter moon with figures 6.12 and 5.51% respectively. The condition of the mature oocyte and ovulation were present around the last quarter and the new moon. The condition indicates imminent spawning.