Economic Evaluation of Implementing Minimum Legal Size on Blue Swimming Crab Fishery in Indonesia

Abstract

The blue swimming crab (BSC) or rajungan is one of the most valuable fish products in Indonesia. It is mostly caught by using bottom gillnets and collapsible traps and by using – to a lesser extent – the now-illegal shallow bottom trawls (baby trawls or mini trawls). Based on recent catch reports, there are indications that the average size of the landed BSC is becoming smaller (as indicated in the increase in catching effort). There are also signs that BSC is no longer producing maximum economic benefits in some regions of Indonesia. In many landing areas, even small crabs (150 crabs/kg) are being caught and harvested. In order to keep its sustainability, it is important to regulate the size of crabs to be caught by fishers. Some management options have already been established, including catch restrictions on the minimum legal size of 8 cm.

This study used a bioeconomic model to assess and compare the consequences of unrestricted fishery (no regulation) and implementation of minimum legal size on the stock condition of BSC. The study determined how much the profit loss would be due to the smaller-sized crab catch and due to the decline in fish catch (overfishing) and how much the implementation of a minimum legal size will change the productivity and income of fishermen over time. The effect of this restriction policy was evaluated using cost-benefit analysis. In the considerably depleted area, the projection showed that implementing a minimum legal size (MLS) policy would increase the stock of BSC in the early years of the projection. The model also showed that for the next 10 years, crab stock with size bigger than 8.5 cm would increase in the early years of the projection and then achieve a stable condition in the following years. Thus, MLS policy can help crab stocks to recover. Meanwhile, in the area where stock condition is considerably good, the crab stock would stay stable in the next 10 years. From the profitability point of view, MLS would benefit those fishermen who catch the mature BSC. Likewise, implementing such policy would also benefit the miniplant industry (BSC-processing business) in the long run (assuming a 10-year period). However, their income would be slightly affected in the short term.