Title: Life history and stock status of scalloped spiny lobster (Panulirus homarus) in Prigi Bay, East Java Province, Indonesia: analysing the potential for stock enhancement.

Author(s): Astri Suryandari
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Scalloped spiny lobster (Panulirus homarus) is one of the dominant lobster species that are captured and traded in Indonesia. Lobster catch in certain fishery areas such as in Southern Java are declining. This can be caused by many factors such as high intensity of fishing or loss of habitat which could limit recruitment. Stock enhancement could be an option to overcome recruitment limitation. Designing effective stock enhancement programmes requires preliminary research into ecological conditions, life history of the species used, status of the wild stock, and the nature and intensity of the fishery. This study attempts to analyse data from a tag-recapture experiment intended to evaluate the potential for lobster stock enhancement in Prigi Bay in southern Java. The objectives of this study were to (1) obtain information about life history and population dynamics of scalloped spiny lobster in Prigi Bay as basic information for potential stock enhancement in the future, (2) gather information about exploitation of the stock and fishing activity and how it may influence a stock enhancement program, and (3) determine how future data collection should be carried out to increase the accuracy of evaluating the potential for lobster stock enhancement. The best-fit Von Bertalanffy growth model of scalloped spiny lobster in Prigi was Lt = 106[1-e0.3(t+0.392)]. The lobster has a long-life span and slow growth. Estimates based on growth parameters (L∞ and k) for lobsters from catch (untagged) was L∞= 106 mm CL and k= 0.3 year-1 while for tagged lobster was L∞= 77 mm CL and k=0.98 year-1. Estimated total mortality (Z) of untagged lobster was 1.74 year-1, natural mortality (M) 0.58 year-1, fishing mortality (F) 1.16 year-1 and exploitation rate (E) 0.67 year-1. Estimated natural mortality of tagged lobsters was 1.4 year-1, which was higher than untagged lobster. Assessment of stock status was based on the spawning potential ratio (SPR). Different scenarios of growth parameters yielded SPR values of 0.04 (4%), 0.2 (20%) and 0.29 (29%), indicating a risk status as heavily exploited. This study provided initial information for potential stock enhancement; however, further study with complete and comprehensive data is urgently needed since there were some weaknesses in this study, such as incomplete time series of catch data, little detailed length at maturity data, and a short monitoring period of released lobster. In the future, it will be essential to record catch data before stock enhancement is conducted, as well as design a comprehensive experimental stock enhancement programme that includes continued monitoring.

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