Optimal fishing policies that maximize sustainable ecosystem services

Matsuda H, Makino M, Kotani K

World Fisheries Congress, 24 October 2008, Pacifico Yokohama

The classic theory of fisheries management seeks a maximum sustainable yield from a target species. There are several variations that include uncertainty, fluctuation, and species interactions. The knowledge that sustainable fisheries do not always guarantee conservation of a diversity of species is well known. Ecosystems provide several categories of ecosystem services to human well-being: supporting, provisioning, regulating, and cultural services. Fishery yields belong to provisioning services. The existence of living marine resources may maintain these services, and certainly a much larger contribution from regulating services than that from fishery yields. Therefore, we define an optimal fishing strategy that maximizes the total ecosystem service instead of a sustainable fishery yield. We call this the fishing policy for “maximum sustainable ecosystem service” (MSES). The regulating service likely depends on the standing biomass, while the provisioning service from fisheries depends on the catch amount. We obtain fishing policies for MSES in a single species model with and without uncertainties and in multiple species models. In any case, fishing efforts are usually much smaller than those for a maximum sustainable yield (MSY). We also discuss the role of fisheries in sustaining ecosystem services, and the nature of ecosystem comanagement.Keywords: maximum sustainable ecosystem service, MSES, uncertainty, ecosystem comanagement, maximum sustainable yield

Increasing cull limit of Steller sea lions in Japan

Dear all
I heard that the cull limit of Steller sea lions will increase in Japan.
Because the Asian population of Steller sea lions sharply declined until the 1980s, this species is classified as endangered on the IUCN Red List. Fortunately, it has been gradually increasing at a rate of 1.2% per year since the early 1990s (Burkanov and Loughlin, 2005). The entire population size was estimated at 15,676 in 2005. In 2007, the Japan Ministry of Environment ranked the sea lion as vulnerable (the third rank of threatened species).
Despite the threatened status of this species, sea lions are still culled by Japanese fishers because of the extensive damage caused to fishing nets. When an international movement for the conservation of marine mammals began in the 1990s, the Hokkaido Fishing Coordination Commission established a cull limit of 116 sea lions per year. In 2007, the Fisheries Agency of Japan (JFA) recommended a revised cull limit based on the potential biological removal (PBR).
The PBR is used in the management of marine mammal populations and was developed for the conservation of populations suffering from human-related mortality, taking into account the uncertainty of available information (Wade, 1998). The PBR is defined as PBR = Nmin Rmax Fr /2,where Nmin is the minimum population estimate; Rmax is the maximum rate of population increase; Fr is the recovery factor (=0.1, 0.5 and 1 for endangered, vulnerable and common species). Japan Fisheries Agency assumed Fr = 0.75 and set PBR = 227 and the cull limit is 120 (+ by-catch = PBR). There was no official by-catch report of sea lions until 2007.
Now, Japan will revise PBR and cull limit. However, the sea lions is listed as Endangered by IUCN. Increase in cull limit and PBR is far beyond international consensus.