Trawling ban impact on the stock density of shrimps in the Java Sea, Indonesia

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Tirtadanu, Suprapto. 2017. Trawling ban impact on the stock density of shrimps in the Java Sea, Indonesia. Ocean Life 1: 49- 54. The level of over-exploitation of shrimps and the use of destructive fishing gear in the Java Sea caused the goverment of Indonesia to ban the trawl operation since 2015. Information on the stock density of shrimps in the Java Sea is needed for evaluation of the management regime. The aims of this research was to study the impact of the trawling ban on the density of shrimps in the Java Sea. The research was conducted in October-November 2015 and October-November 2017 using a swept area trawl method. The results showed that the biomass of demersal fish and rays has increased but the biomass of shrimps in the Java Sea has decreased that might be due to the predator-prey relationship.The biomass of some smaller-size shrimps such as Metapenaeopsis palmensis, Trachypenaeus malaiana and Metapenaeopsis stridulans decreased, while the biomass of larger shrimps such as Metapenaeus ensis, Penaeus merguiensis and Penaeus monodon increased. This condition caused the changes of dominant shrimps in Java Sea where the dominant shrimps before the trawling ban were M. palmensis, while the dominant shrimps after two years trawling ban were M. ensis. From the results, there is an assumption that the ecosystem is more stable after two years of the trawling ban. Most of the density of larger-sized shrimp increased only in the middle of Java Sea, while the density in the coastal zone still decreased. We suggest regulations to control the quota of fishing vessels in the coastal waters to ensure the sustainability of shrimp resources.