Increasing the economic value of the eastern Pacific Ocean tropical tuna fishery: Tradeoffs between longline and purse-seine fishing

Abstract

Fisheries harvesting yellowfin and bigeye tuna while targeting skipjack in the Eastern Pacific Ocean (EPO) are not managed optimally with respect to economic value. Bigeye tuna are generally caught at before they reach full size so cannot fetch the higher prices obtained for mature fish which are usually harvested by longline fleets and sold to the sashimi market. This study evaluates the economic and biological trade-offs of managing the fishery to determine how the economic value may increase with different harvest strategies while the spawning biomass of both species is maintained at the optimal sustainable levels. This study uses three analytical models to assess the economic and biological tradeoffs in four possible scenarios with different combinations of purse-seine and longline fishing effort. The first model evaluates the biological tradeoffs under various effort combinations of longline (LL) and purse-seine (PS) that could reach the same optimal biomass level, measured by the spawning biomass ratio (SBR). The second model evaluates the long-term optimal equilibrium economic value under various effort combinations. The third model evaluates the dynamic (short-term) trajectory of recovery path of bigeye tuna under various policy options. The analytical results show that economics and conservation are not incompatible. In one scenario, we show that reducing purse-seine effort by 26.3%, via a per-ton compensation system from longline fleets to the purse-seine, leads to net economic gain of $93 million, annually. The total value of the PS and LL fisheries in EPO increases from $1246 million to $1339 million. The study shows that the economic value of the resource is highly dependent on the allocation of effort between the longline and purse-seine fisheries. Since the longline and purse-seine fisheries in EPO are formed by multiple users in multiple countries/groups, the ideal scenarios would not be feasible without administrative measures and/or economic incentives. This study also discusses three possible ways of implementing a management strategy that would achieve higher economic value while still maintaining tuna conservation goals, such as a tradeable right-based management scheme.