FISHER TAKE ALL? A new paper argues that practices emphasizing selectivity in commercial fishing may have undesirable effects on marine ecosystems.
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The oceans are in trouble—overfishing has led to depletion of fish stocks around the world and has driven many species to critically endangered status. But what to do about it?
Officials have responded to the collapse of fishery stocks with a slew of regulations, many of them forcing fishing operators to be more selective in their harvest, whether by targeting certain species and regional populations, by mandating size or gender restrictions on catches, or by defining open and closed seasons for fishing. For instance, U.S. commercial fishing regulations set minimum-size limits on red snapper and many species of Atlantic tuna. But a perspective paper set to be published online this week in the Proceedings of the National Academy of Sciences argues that such "selective fishing" practices can have unintended consequences. By targeting specific segments of the sea for removal, the authors contend, regulations intended to preserve fish populations can instead nudge a delicate ecosystem out of balance.
Lead study author Shijie Zhou of Australia's Commonwealth Scientific and Industrial Research Organization and his colleagues advocate an alternative approach to fisheries management that they call, perhaps somewhat unappealingly, "balanced exploitation." Using their concept, all fish—regardless of species, size or gender—would be fished in proportion to their abundance and replenishment rate, thereby better preserving the makeup of the ecosystem. Less selective fishing practices would remove a representative slice of the ecosystem while keeping populations above a certain threshold.
"Simply speaking, a balanced exploitation aims to maintain, to the extent possible, natural ecosystem structure to support sustainable fisheries and conserve biodiversity," Zhou says. He adds that the concept seeks to balance relationships both among different species and among subpopulations of a given species such as age groups, gender groups or regional schools. Recent research indicates that selectively targeting subsets of a species can drive unwanted population shifts—say, drastically reducing the number of males relative to females—or even genetic and behavioral changes. Setting a minimum catch size, for instance, applies selection pressure that may unnaturally favor smaller individuals, thereby driving down the size of the species over generations. Similarly, the establishment of legal fishing seasons can affect the timing of salmon runs by selectively killing late or early migrants.
A potentially thorny outcome of fishing a broader range of species is that, in addition to catching high-value species such as salmon, fishing operators would also pull up numerous low-value fish, known as bycatch, that would otherwise be avoided or caught inadvertently and tossed back. Not so under balanced exploitation, wherein species would be harvested according to the carrying capacity of their population rather than their value to consumers. "This concept still supports avoiding bycatch of vulnerable or protected species," Zhou says. But avoiding all bycatch is unnecessary, he adds, and may even be counterproductive from a biodiversity standpoint.
The key would be to develop uses for bycatch species so the harvest would not go to waste. Marie-Joëlle Rochet, a fisheries scientist at the French Research Institute for Exploitation of the Sea who did not contribute to the new research, says that incentives might be more effective than regulations in encouraging less selective fishing. "Probably an important part of the approach would be to develop markets for small things and species you would not judge edible nowadays," she says. Zhou adds that fish need not be suitable for sushi or fish sticks to be of value: other uses include fish oil as well as feed for livestock or even for fish farms cultivating more desirable species.
Rochet has run theoretical models on the effects of fishing practices and has indeed found that selective fishing can negatively impact biodiversity and create ripples in the food web as the balance between predator and prey is upset. "However, this is only theory and needs to be substantiated with empirical analyses," she says.
Jim Scott, assistant director of the fish program for the Washington Department of Fish and Wildlife in Olympia, says that the paper by Zhou and his colleagues raises some good points. "It's important for every person with fisheries management responsibility to understand" the potential concerns about selective fishing, Scott says. "It isn't a panacea," he adds. "You have to be really thoughtful about how you approach it." For instance, he says, gender restrictions on Dungeness crab have led to very high harvest rates among males of the species and may need to be rethought.
At the same time, Scott adds, some ecosystems are already so far out of balance that selectivity is necessary just to stave off total collapse of certain species. "In Washington, we have many species that are either listed under the Endangered Species Act or designated as overfished," he says. "So the idea of moving away from less selective fishing strategies in an environment like Washington—it's not readily apparent to me how we would do that."
Even in more stable fishery environments, Zhou acknowledges that it is "very difficult if not impossible" to design and implement a perfectly balanced exploitation strategy. "We suggest balanced exploitation as an ideal," he says, "and a new approach to consider while scientists and managers critically review the current fishing philosophy that points in the opposite direction."
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9 Comments
Add CommentIt�s not just a matter of limits, but a matter of awareness. Here in Brazil the stocks of crabs are in it�s gathering limits, because of the overfishing and habitat degradation. The existing laws are tied but the is no fiscalization. Also, the need of food pushs to its fishing limits.
Reply | Report Abuse | Link to thisNothing any regulatory authority does will have any impact on the degradation of all our environments. The regulatory authorities are a joke, no punishment never ever. Maximum fines are a dime for every 100 million dollars of loot.
Reply | Report Abuse | Link to thisOur species is doomed, get used to it, sadly we are taking along a lot of species with us. If I was still in my youth I would work towards a human-eliminating bacteria or virus, if only to spare the rest of the species on our unique planet.
well I could agree to an extent.But its a natural food chain.The limitataions stated above such as size, gender etc posed by authorities will only cause ecological imbalance.
Reply | Report Abuse | Link to thisHarvesting of commonly edible fish could be a good way out to teh problem
I always love people like you that talk about how bad humanity is and you wish you could get rid of everyone to save the planet. Well everybody but yourself of course. If you are so upset and think there are too many people here why not start with yourself.
Reply | Report Abuse | Link to thisOn to the problem with fishing regulations. They just enforced. I live in Washington dc and you need a permit to fish. All of the immigrants disregard all of the rules and catch and keep EVERYTHING no matter how small or if its off limits. The problem is in the third world countries.
Specific sspecies quotas lead to waste - the bycatch. Fishermen cannot control what fish they catch - they caan only bias it by selection of fishing ground, net type and mesh size or hook size. Undersized pot caught crabs and lobsters can be returned to grow - most other species when hooked or netted do not survive the process - a waste of useful resources. What is needed are financial systems designed and administered to make it worthwhile landing by and over-quota catches yet not providing an incentive to overfishing. The alternative is to completely close fishing grounds which creates major social and economic problems for fisshing communities.
Reply | Report Abuse | Link to thisMany current policies lead to high levels of waste when usable fish is dumped at sea. Fisherman cannot control what fish they catch - they can only boas it by choice of fishing grounds, net type, size of mesh or hook size in line foshing. Underssized pot caught crab and lobsters can be returned to grow to maturity. Netted fish seldom survive and become waste. Ideally all fish should be landed as useful protein - whatr is needed is a financial system which makess it worthwhile to land all the over quota and by catch but low enough to prevent their landing for profit. The only other aalternative is to close whole fishing grounds to rebuild stocks but this creates politicaally unacceptable economic and social problems for fishing communities.
Reply | Report Abuse | Link to this"However, this is only theory and needs to be substantiated with empirical analyses," How can we expect the general public to understand the difference between hypothesis and theory if scientists don't even use the terms correctly? This is not just a technicality, it is the linchpin of many anti-science agendas. Please use your words carefully and professionally.
Reply | Report Abuse | Link to thisto brsecu
Reply | Report Abuse | Link to thisIt's easy blaming foreigners but developed countries are no better at managing their fish resources than undeveloped countries. The United States along with almost every other developed country has a terrible track record when it comes to fisheries management with the best example possibly being the cod fisheries which has completely collapsed almost everywhere. Not only that but along with destroying their own fisheries resources developed countries subsidize their fishing fleets which then go fish off the coasts of Africa and Asia where they destroy the fishing resources of those poor nations. If anything the citizens of those poor countries should be blaming the developed countries for the fishing problems.
Brsecu:
Reply | Report Abuse | Link to thisI follow my ideas. I will not do anything to prolong my life beyond its natural limit. With the world population at close to 7 billion, we don't need to save lives or sustain lives that would naturally end anyway. If every person did this we would have less of an overpopulation problem. I also want the right to end my life with dignity when I believe my life is no longer worth living. Perhaps you can come over and help me end it.
Before you talk of third world countries, think - Japan blatantly violated its fishing quotas for decades. How were they punishes? Their quotas were increased. Australia had her quota reduced. They claim eating whale is part of their culture, read history - whale meat was forced down their throats by the British.
The Japanese humbly apologised for disregarding their quotas, but now chose to disregard their culture and did not commit hara-kiri as required by their culture when humbly apologising.
The human animal stinks, I am ashamed to be part of this ignorant self-indulgent species.