Sustainable Harvesting Alone Cannot Prevent Decline of the Green Crab Fishery in Portugal

Abstract

Estuarine fisheries are of high regional socio-economic importance worldwide, by providing an important livelihood for many families. The Portuguese green crab (Carcinus maenas) fishery was assessed using a socio-economic assessment to understand the importance of the fishery and a stock assessment analysis to determine the exploitation status of the fishery during 1960–2020. Fisher knowledge revealed that crab fishing was a family affair that provided a livelihood for hundreds of families directly targeting crabs, with catches exported to Spain during 1960–1990s, and in later years, crab demand increased as bait for octopus fishing. Despite its socio-economic importance, the fishery was regulated without a scientific basis and economic value of crabs remained similar through time. Annual landings never exceeded sustainable catch rates, but engagement in the crab fishery declined due to low economic value of crabs compared to other fisheries and regulatory hurdles. Consequently, the number of fishermen declined to 20–30 elderly men fishing on the largest estuaries, with the fishery currently on the verge of extinction. Fishers pointed to a reduction in the minimum landing size and enforcement of crab-specific trap regulations as ways to avert fishery decline. Such changes would stimulate recruitment of new crab fishers, while reducing fishing pressure on other estuarine resources through fisheries diversification.