Title: Evaluation of milkfish (chanos chanos) stock enhancement in the Jatibarang and Sempor Reservoir, Central Java, Indonesia

Author(s): Aisyah Umar
Final project
Year of publication:
Place of publication:
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Supervisors: Pamela Woods , Hlynur Bárðarson , Sandra Rybicki
milkfish; Jatibarang, Sempor, Indonesia; stock enhancement


The main objective of a stock enhancement through fish stocking is to increase fishable stocks. Milkfish (Chanos chanos) is one of the stocked species that have been recommended in a reservoir in Indonesia, because it cannot reproduce in freshwater. Therefore, it has no chance of becoming an invasive species. The objectives of this study were first to gather information about how fishing activitiess in the Jatibarang and Sempor reservoirs related to stock enhancement programs in Indonesia, and second to estimate gear selectivity by using the life history of milkfish and catch data from the Jatibarang and Sempor reservoirs to evaluate the success of fish stock enhancement. This study used catch data including length and weight of milkfish from both the Jatibarang and Sempor reservoirs. This also includes a monthly overview of catch, stocking time, and number of fingerlings. Data were analysed using a simulation of milkfish stocks to estimate expected catch at size compared to the actual catch data. A yield per recruit analysis was then used to estimate the effect of selectivity on yield. The growth and the simulation of expected and observed catch do not seem to describe the real picture of stocked milkfish in Jatibarang. Hence, Sempor data was then used for further analysis. Yet, some mismatches between the simulated expected catch and the actual catch were observed. Fishery dependent data of milkfish in both reservoirs are responsible for the vague results, however, the selectivity in Sempor reservoir shows that gears seem to target a certain fish size. Moreover, yield did not reach the maximum level, which would be an indication of the success of stocking related to the aims of stock enhancement. This study produced valuable information about future evaluation steps of the stock enhancement program. This will increase the quality of the sampled data as well as implement scientific experimental fishing over a longer time-series directly following the stocking events, and the possibility to conduct a tagging program.

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