O P I N I O N
The End of “Overfishing”?
by Brian Rothschild
Research Interests: Population dynamics, biological oceanography, fisheries management, and natural resources policy. Dr. Rothschild has served on many national and international committees, and has held faculty or other associations with such institutions as Harvard University, Scripps Institution of Oceanography, and the Woods Hole Oceanographic Institution. His research and service have been widely recognized, in 2004 by the Outstanding Achievement Award from the American Institute of Fishery Research Biologists, and most recently with NOAA’s 2007 Sustainability Fisheries Leadership Award. © Photo by Sam Murfitt
January 7, 2013 — The New England Fishery Management Council at its upcoming January meeting is scheduled to consider drastic cuts in groundfish quota for the 2013 fishing year. The cuts will break the economic back of the groundfish industry and have a serious effect on the scallop industry because the scallop fleet catches groundfish stocks incidentally. As the scallop fleet is already scheduled to operate under reduced days at sea next year, reductions affecting scallop bycatch could further reduce scallop fishing.
The necessity of imposing the cuts is not clear. The council’s scientific committee has had difficulties reaching consensus on the management of key stocks. The Council is faced with a dilemma. If the stocks are down and the cuts are necessary, how do we mitigate the impact of the cuts on the people who work in the fishing industry and fishing communities, and then how do we plan for the future? At the same time, if the stocks are not down and the cuts are not necessary, how do we promote stability within the fishing industry and fishing communities, and then how do we plan for the future? To understand the council’s short- and long-range plans on how to deal with its dilemma is crucial, particularly since the condition of the groundfish stocks may not be as bad as it seems.
A good example is the critical case of the Georges Bank yellowtail flounder. Is it really “overfished”? A simple answer to this question is clouded by the fact that there are several definitions of “overfishing.” So by one definition of “overfishing,” the yellowtail flounder might be “overfished.” But by another definition, it might not be “overfished” at all. Interestingly, “overfishing” is a misnomer. The bitter irony of using the prejudicial term when analyzing fish mortality rates is that the fishing industry traditionally only harvests approximately 40 percent of the stock allocated to it by the National Marine Fisheries Service. Thus, in reality, many species are being “underfished” by the fleet, according to the government’s fishery allocations.
It is important to ask whether the council has considered all reasonable definitions of “overfishing.” Let’s consider an example. In the present definition used by the council, someone decided that the “overfishing” definition for yellowtail should be based on keeping yellowtail flounder biomass at 40 percent of its unharvested biomass. Having made this decision, routine calculations are used to determine the fishing mortality rate necessary to maintain the population at 40 percent of its “unfished” biomass. This magnitude of the fishing mortality rate is called a “biological reference point.” If the actual fishing mortality rate is greater than the reference point, the stock is said to be “overfished”; if it is less than the reference point, the stock is said to be “underfished.”
Now suppose another someone decided that the biological reference point should be set at 20 percent rather than 40 percent. In general, this would increase the magnitude of the reference point so that the stock could now be subject to more intense fishing without “overfishing.” Since the stock would be maintained at a lower sustainable level, requirements for rebuilding would be less, and the time for the stock to reach the rebuilt threshold would be shorter. The natural mortality rate also affects the reference point. It is arbitrarily selected. If the natural mortality rate were increased, then the effects of moving from 40 percent to 20 percent biological reference points would be intensified. Even though the calculated natural mortality rate has not been changed, an increased natural mortality rate is plausible because of the substantially increased abundance of predators such as seals and sharks and possible adverse effects of ocean warming.
The council does not have to go with the 40 percent reference point. It is scientifically acceptable for it to have gone with a 35 percent reference point. This is the level used to manage most species on the U.S. West Coast. If 35 percent is OK on the West Coast, why is it not OK on the East Coast? The Council could have also gone with a 20 percent reference point, which is also scientifically acceptable, and this is the level that studies have shown to be sustainable for many species of fish.
A management change from 40 percent to 20 percent can be accomplished by a stroke of the pen. After we make the change, and changing nothing else, an “overfished” stock becomes an “underfished” stock in an instant. But there is more to understand here. Not only is the biological reference point based on an arbitrary foundation, but the actual intensity of the fishing mortality on this economic keystone species is unknown. So in other words, management is based on an arbitrarily selected biological reference point, and we have relatively little idea how close the real fishery is to the arbitrarily selected reference point!
What to do? The council needs to understand its options. Two are critical. First, the council needs to consider alternative reference points to 40 percent - e.g., 35, 30 and 25 percent of “unfished” biomass and various rates of natural mortality. Second, new data is needed. An emergency survey using commercial boats and commercial gear needs to provide fresh data, and the subsequent scientific analysis needs to be a collaborative effort between the government and the educational and research institutions and scientists in our region. The final question is practical and concerns whether anything can be done before the fishing season commences in May. Delaying drastic cuts (possibly on a temporary basis), engaging in an emergency survey and revising the approach to stock assessment and data collection are prudent ways forward. Taking these actions now, supplemented with longer range-planning, is how the council can solve its current “overfishing” dilemma.
Dr. Brian Rothshield
Co-Director of the Massachusetts Fisheries Institute
University of Massachusetts, Dartmouth, MA