Uncertainty in daily catch rate in the light fisheries around Ambon and the Lease Islands: characterisation, causes and consequences

Fishermen experience variation in their daily catches that they cannot explain from their knowledge and experience. This uncertainty in daily catch rate is important in the life of fishermen and should be seen as a main characteristic of a fishery. This study tries to decrease the gap in knowledge on this subject by (1) characterising uncertainty in daily catch rate, (2) analysing the sources of this uncertainty and (3) outlining the consequences of uncertainty for the organisation of the fishery and its management. The purse-seine and liftnet fisheries on small pelagic fish in the coastal waters aroundAmbonand theLeaseIslands(Central Moluccas, Indonesia) are used in this study, because they are among the most uncertain fisheries in the world on a daily basis. Daily catches range from 0 to 25 times the average catch (coefficient of variation > 3) and a large proportion of this variability cannot be accounted for.The large uncertainty in catch rates of individual fishing units derives from the relationship between the loosely structured pelagic environment in which the fisheries operateandthe small scale of operation of these fisheries. The multispecies character of the fisheries reduces the uncertainty in total catch relative to that of catches of individual species. However, the developments in the total catch have little indicative value for the catch rates of individual species. The uncertainty in catch rates may be further increased by comparison or combination of catch data from different fishing units with different technical characteristics, if effects of these on the catchability are not accounted for. Therefore, the use of non-standardised catch per unit of effort as an indication of the state of the stocks is questionable. The consequence of this high uncertainty is that individual fishermen are hardly able to perceive spatial and temporal patterns in fish distribution and thus cannot optimise the outcome of their fishery through spatial allocation of effort. This results in risk-aversive behaviour, i.e. concentrated effort near the homeport. These effort concentrations may lead to local overfishing, which, in turn, reduce the accuracy of the perception of the status of the stocks by individual fishermen and local authorities even further. The inaccurate perception limits the role of both groups in fisheries management aiming at sustainable exploitation of the stocks. The high level of uncertainty in combination with the low monetary outcome shapes the livelihood of individual crewmembers, because they need additional income to feed their families. The resulting dependency on other sources of income in combination with the uncertainty has a substantial impact on the organisation of the fishery. Hence we conclude that both the local organisation of the fisheries and the perception of individual fishermen and local authorities should be integrated into fishery management plans in order to be successful.