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Concerns Raised Over Tangle Nets' Impact on Steelhead

by Mike O'Bryant
Columbia Basin Bulletin - May 3, 2002

For the second consecutive year, the spring chinook salmon tangle net fishery on the Columbia and Willamette rivers is showing positive results in immediate survival, according to an interim report by Oregon and Washington fisheries agencies. In addition, a recently completed study on long-term survival is showing that adults caught in the tangle net and released are surviving in high numbers.

While the new commercial fishery is finding success in capturing spring chinook and returning live, unmarked fish back into the river, Northwest conservation groups worry that it may have disastrous effects on steelhead listed under the federal Endangered Species Act.

After successfully testing tangle nets in 2001, Washington and Oregon implemented the tangle net fishery this year from March into May as the only commercial net option on the Columbia and Willamette rivers, according to Bill Tweit of the Washington Department of Fish and Wildlife.

"Although we're still very much in the learning mode, we're trying to improve the selectivity of the non-treaty commercial fishery," Tweit told the multidisciplinary Implementation Team this week. He said tangle nets allow commercial fisherman to target certain stocks and species of fish, while minimizing mortality.

Normal 8-inch gill nets capture salmon by snagging their gills. In the process, the fish drown. With 4-1/2 inch or 5-1/2 inch tangle nets, spring chinook are captured by their jaws in the net and brought to the surface alive. Unmarked fish -- about 50 percent of spring chinook -- are placed in a recovery box on board the fishing vessel and released to the river when fully active. Tweit said when salmon are released as fully alert fish, the chance that sea mammals will prey on them is reduced, as is their overall chances of long-term survival.

In addition, he said the value of the salmon fishermen can keep could also be higher. "When fish come in without net marks, and are often alive or fresher, they get higher prices," Tweit said. He estimated the early season value to be $4 to $5 per pound.

Still, fish caught by any means in a net run the risk of drowning and so the tangle net regulation also includes a maximum "soak time," or time the net is allowed in the water.

"That cuts down on mammal predation, but it also cuts the fishers efficiency," Tweit said. "They aren't catching fish without their nets in the water."

Options for commercial fishers have dwindled in recent years as catches of hatchery fish and unlisted fish have been limited to protect ESA-listed salmon and steelhead that are swimming upstream at the same time. The new fishery allows commercial fishers to catch and keep more fish without increasing their impact on ESA-listed species.

This is where conservation groups disagree. They say the tangle net fishery, especially when using the 5-1/2 inch mesh nets, are trapping and killing more listed steelhead, a by-catch resulting from fishing for chinook salmon.

Washington Trout, the National Audubon Society, the Native Fish Society and Oregon Trout delivered a letter this week to WDFW, the Oregon Department of Fish and Wildlife and the National Marine Fisheries Service to complain about the by-catch issue.

"We appreciate the Compact Managers' attempts to experiment with and embrace terminal, selective-fishery techniques," the letter said. "The difficulties and uncertainties associated with managing the impacts of mixed-stock fisheries will make a conversion to more conservative, selective fishing a necessary component of any successful salmon-recovery effort."

However, the groups are concerned that steelhead mortality -- fish not considered a legal catch in the first place -- is higher than the targeted hatchery spring chinook fish. Mesh size, they said, is the problem. "Some evidence suggests that the 5.5" mesh turned out to be an effective gill-net for the steelhead encountered."

ODFW reported that its observations of spring chinook through March 27 found a mortality rate of 0.7 percent, but a higher mortality (2 percent) in the by-catch of steelhead. It reported a total of 21,600 encounters of steelhead. About 60 percent were unmarked fish.

According to an April 23, 2002 Columbia River Compact fact sheet, 89 percent of returned chinook salmon were returned in a vigorous condition, while only 84 percent of steelhead were released in that best of conditions.

"Overall, we are now concerned that total wild chinook and steelhead encounters and associated mortalities be accurately and conservatively counted and appropriately apportioned across the range of the potentially affected ESUs, so that subsequent fisheries this year will comply with the current Biological Opinion governing the Interim Management Agreement (Mar 2001). We are particularly concerned that the by-catch impacts from this fishery may have already exceeded the allowable steelhead harvest-rates for some ESUs," the letter said.

To an extent, Tweit's information agrees with the conservation groups. He said that steelhead are "going way into the 5-1/2 inch mesh," but on the other hand it appears a 4-1/2 inch mesh is less efficient for catching chinook. "We don't really know what mesh size will be right," he said. "That will take further studies."

Jim Athern, of the U.S. Army Corps of Engineers, said fish counters at Bonneville Dam have been noticing a higher-than-expected level of chinook passing the dam with net marks. "We're concerned about the longer term survival of these fish to spawning," he said.

"Wouldn't you expect that net marks would go up?" asked John Palensky of NMFS. "In the past, when a fish got into a net, it went to the store."

"These observations are useful," Tweit said. "With a 50 percent rate (of fish put back in the river), you would expect a lot more marks on fish."

Tweit also said that WDFW is scratching its head about the high number of steelhead caught during the fishery. "The number of fish caught indicates a phenomenal run," he said. He wondered if that was due to re-catching and counting some steelhead more than once.

"This (the use of tangle nets) is just a tool," Tweit concluded. "It's not the salvation of any fishery. Managers may decide to use a different tool in a different situation. For now, it looks like for the downstream non-treaty fishery, this is a good tool."

Link Information:
Implementation Team
Oregon Trout

Mike O'Bryant
Concerns Raised Over Tangle Nets' Impact on Steelhead
Columbia Basin Bulletin, May 3, 2002

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