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The Herring Conundrum:

Does research measure up to theories about the important prey fish?

Posted: Sunday, October 28, 2007

A small, oily fish has been making some big waves in Juneau recently.

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Federal scientists announced in September they are studying Pacific herring stocks in Lynn Canal to see if the fish should be listed as endangered or threatened, a move that could have large implications for proposed developments in Berners Bay, the fish's only remaining spawning ground in the canal.

Herring have become political fodder for debate on certain development projects, including the Kensington Mine and the Juneau access road, but there is no question about how important thay are to Southeast Alaska's ecosystem.

"Herring are a very interesting species to work with," said Scott Kelley, a commercial fisheries supervisor at the Alaska Department of Fish and Game. "Their populations fluctuate dramatically. That's probably because everything eats them. They are a very important prey item for everything from whales to surf scoters, and small creatures swimming around in the kelp (which feed on their eggs)."

The challenge is scientists don't know a whole lot about what affects herring survival. There are limited studies about why they do or don't spawn in certain places anymore, and why their numbers have declined 85 percent in Lynn Canal since the 1970s.

"We know a lot, and yet we don't know enough," said Jeep Rice, one of the lead scientists investigating Lynn Canal herring for the National Marine Fisheries Service, which is expected to make a recommendation on whether to list the fish under the Endangered Species Act by April 2008.

"When we compare herring to salmon, which we've studied for 100 years, we know a lot about salmon. We have 1 to 2 percent the knowledge about herring than salmon," Rice said.

Herring make up more than half the diet of king salmon, halibut and lingcod, and more than one-third of the diet of harbor seals and Pacific cod, according to the Canada Department of Fisheries and Oceans.

Eagles and other birds congregate around spawning grounds in the spring.

"A lot of birds that feed in intertidal zone are getting that huge boost in calories before they then go and lay their eggs," Rice said. "Herring spread a lot of calories throughout a lot of parts of the year to a lot of different species. In general, you could argue that herring are one of the most important prey items that are fish."

Humpback whales are notorious for their habit of conspiring in groups to heard herring, in a method called bubblenet feeding.

Major predators of Pacific herring

Percent of diet comprisedof herring:

• Pacific cod: 42 percent.

• Lingcod: 71 percent.

• Halibut: 53 percent.

• Chinook salmon: 62 percent.

• Harbor seal: 32 percent.

Source: Canada Department of

Fisheries and Oceans via Fish

and Wildlife Science magazine

But scientists aren't clear how much humpbacks affect herring populations, and whether their comeback has had anything to do with declining herring numbers since the 1920s and 1930s.

Herring fishing boomed in the early part of last century, about the same time that humpback whales began to be hunted toward extinction. Humpbacks mainly thrive on krill and other small ocean animals in the summertime, but scientists suspect they rely on herring in the winter, before heading to Hawaii to reproduce.

John Moran, another scientist at the National Marine Fisheries Service, is one year into a study to find out whether whales are having an impact on herring recovery.

He points out that whales and herring clearly can coexist in large numbers.

"In Sitka, you have healthy herring fisheries, lots of whales, and everything seems OK," Moran said.

In Lynn Canal, researchers are seeing fewer herring spawn in the beaches. And there's an unanswered question as to why herring don't spawn in Auke Bay anymore, but Rice suspects development is the culprit.

"In Auke Bay, the habitat is not the same as it was in 1940 or 1960, and no single project is responsible for the herring going, but when you add up all these projects, they add up to less habitat," Rice said.

Rice has done studies that show eggs are very sensitive to chemical contaminants, but he says such toxins are very rare in Southeast waters.

Kelley at Fish and Game believes environmental factors such as salinity and temperature play key roles in herring survival. But he says there's direct evidence herring can coexist with human development for a long time.

"In Sitka, a significant majority of the spawning that takes place in that stock takes place right next to a road, next to a new harbor, and next to houses," Kelley said.

To be listed, scientists must show the Lynn Canal herring are a distinct stock, a factor that has foiled other efforts to list the fish as endangered in parts of Puget Sound. The National Marine Fisheries Service has just begun studies to determine genetics and uniqueness.

Rice emphasized that's only one piece of the puzzle.

"It's certainly an important part of it, but it's not the only part. It's not a yes or no answer. It's a lot more complicated than that," Rice said.

"We don't enter into an issue like this with a predetermined mindset," he said. "We are going to let the chips fall as they may with the science we have. We have some empty pockets of science. We know different factors are operating here, but we don't know the quantitative significance of them."

Facts about herring in Alaska:

• Commercial fishing has been prohibited in Lynn Canal since 1982.

• Range for spawning, feeding, wintering is up to 100 miles.

• Spawn by attaching their eggs to seaweed, especially eel grass.

• Reduction plants that processed herring into meal and oil started in 1882.

• Herring plants in the 1920s and 1930s harvested up to 250 million pounds annually.

• The last reduction plant closed in 1966.

• Harvests now average 75 million pounds annually, valued at $10 million.

• Permits to fish herring have declined from 2,200 average in the 1980s to 632 annually.

• Primarily fished for their eggs, or sac roe, which is in high demand in Japan.

Source: Alaska Department of Fish and Game



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