According to the authors' analysis, Alaska and New Zealand have led the world in terms of management success by not waiting until drastic measures are needed to conserve, restore and rebuild marine resources.
Some other regions are currently recovering from overfishing: fish abundance has recently been increasing above the long-term average in Iceland, the Northeast U.S. Shelf and the California Current.
This new study is a follow-up to a 2006 paper in Science by Worm and others that highlighted a widespread global trend toward fisheries collapse. The results of that paper led to a public disagreement between Worm and Hilborn. Through their subsequent discussions, however, the two scientists recognized a shared sense of purpose.
They decided to collaborate on a more detailed assessment of the world's fisheries, and brought together many of the world's fisheries scientists and ecologists for a two-year series of working groups at NCEAS.
The current paper is the result of those meetings.
"Prior to this study, evaluations of the status of world fish stocks and communities were based on catch records for lack of a better alternative," explains Ana Parma of Centro Nacional Patagónico in Argentina. "Results were controversial because catch trends may not give an accurate picture of the trends in fish abundance.
"This is the first exhaustive attempt to assemble the best-available data on the status of marine fisheries and trends in exploitation rates, a major breakthrough that has allowed scientists from different backgrounds to reach a consensus about the status of fisheries and actions needed."
The analysis includes catch data, stock assessments, scientific trawl surveys, small-scale fishery data and modeling results.
The authors liken their strategy to constructing a "Russian doll," with each nested layer of data adding to the strength and value of the whole.
In looking at the tools that have been used to reduce exploitation rate, the authors note that "some of the most spectacular rebuilding efforts have involved bold experimentation with closed areas, gear and effort restrictions and new approaches to catch allocations and enforcement."
Laws that explicitly forbid overexploitation and specify clear rules and targets for rebuilding were seen as an important prerequisite, for example in the U.S.
While the study suggests that these tools have long-term benefits, they also come with short-term costs to fishers. "Some places have chosen to end overfishing," says Trevor Branch, a co-author from the University of Washington. "That choice can be painful for fishermen in the short-term, but in the long-term it benefits fish, fishermen, and our ocean ecosystems as a whole."
Key among the group's recommendations is to fish at rates lower than those producing maximum sustainable yield (MSY), a long-standing and internationally accepted benchmark for total catch. They call for MSY to be reinterpreted as an absolute upper limit rather than a target, in line with U.N. recommendations.
The authors used ecosystem models to calculate a multi-species MSY (or MMSY) that adds up yield across all species, taking account of their interrelations. That analysis suggests that fishing below MMSY yields just as much fish as exceeding that benchmark, but has many ecological benefits including fewer species collapses, an increase in fish size and fish abundance.
"Below MMSY there is a fishing-conservation 'sweet spot,'" says co-author Steven Palumbi of Stanford University, "where economic and ecosystem benefits converge."
The team also notes that in addition to reducing exploitation rates below MMSY, there are several other measures that can reduce fishing impacts on ecosystems. "Fishing at maximum yield comes at a significant cost of species collapses," explains Heike Lotze, a co-author from Dalhousie University.