What a tangled web we unravel
True we humans are capable of creating our own brand of complex and sophisticated systems. We use them use them to manage and/or outsmart Nature. We've certainly gotten very clever at tracking and netting increasingly larger catches of fish over the years.
A classic case of the tragedy of the commons? (GW)
By Doug Fraser
Cape Cod Times
February 18, 2008
He said prey species like haddock move into certain areas of Georges Bank when there are large schools of spawning herring.
"I've never gone through a year and seen this few herring," he said. "The amount of haddock we caught in that deep water also dropped. There was no doubt in our minds that there was a correlation between herring and what we catch."
It was a lesson that made a big impression on fishermen: no food, no fish.
"People have been fishing here for hundreds of years and they know that a healthy herring population is key to having other healthy fisheries," said Peter Baker, director of The Herring Alliance, a collaboration of environmental groups dedicated to reforming what they call "industrial" fishing by large herring vessels. The group is concerned the fishing power of these large vessels could bring on a collapse of herring stocks as the foreign factory fleet did back in the 1970s.
Raising the alarm
In December, the Marine Fish Conservation Network, comprising 200 environmental groups, fishing associations, aquariums and marine science organizations, raised the alarm on herring, mackerel, menhaden, squid and other species known collectively as forage fish. They want the National Marine Fisheries Service to give greater protection to forage species that serve as prey for many other fish.
They were especially concerned about the rapidly expanding aquaculture industry's dependence on these fish, an increasing number of which are ground up to produce pellets and fish oil to feed fish raised in aquaculture cages.
"We've created a demand and a need for this ... fishery that I don't think is sustainable," Kenneth Stump, a policy analyst for the Washington, D.C.-based Marine Fish Conservation Network, said of fish food for aquaculture.
A letter signed by 92
Forage species eat plankton and provide a vital link from that food source to the protein required by larger predator species.
Stump said he believes herring's role as prey is too important to allow large
But NMFS scientists counter that well-managed fish stocks would be sustainable no matter what their ultimate use.
"If we're harvesting conservatively, we should be able to avoid the large swings in prey population that could cascade through the ecosystem," said Steven Murawski, NMFS director of scientific programs, and a chief scientific adviser.
No easy answers
Predator-prey relationships are complex, and some changes might not yield expected results, Murawski said. For instance, when the foreign fleet decimated
Stump said it was dangerous to rely on fishing to achieve balance in an ecosystem, and that preserving species that form the base of the ocean food chain was critical.
"We're pretty foolish to presume we have to remove this amount to preserve the balance, given the lack of science," he said.
"We have done a fair bit to understand the role of prey species in the food web," countered Michael Fogarty, an NMFS ecosystem scientist.
NMFS and regional fishery management councils have laid the foundation for ecosystem management by gathering data on fish habitat and by extensive work by regional science centers on predator-prey relationships, Murawski said. Ecosystem management pilot programs are also being drafted. Additionally, fishery management scientists already incorporate natural mortality into their estimates of how much of a species can be caught each year without seriously impacting the population, he said.
"We need to be cautious, but that doesn't mean you don't harvest at all," said
Doug Fraser can be reached at firstname.lastname@example.org.
Forage fish and aquaculture
- Worldwide, wild fish stocks were being caught and fed to caged fish in an aquaculture industry that grew threefold between 1992 and 2003.
- It takes five pounds of fish to produce one pound of fish meal.
- Fish meal supplying aquacultural and agricultural needs accounted for almost 40 percent of the fish landings globally in 2002.
Source: Marine Fish Conservation Network