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Ecology and salmon related articles

Selective Harvest Methods
Still on Trial

by Bill Rudolph
NW Fishletter, July 24, 2014

Washington and Oregon announced in June that 10 permits for selective fish harvesting would be available for the 2014 fall season to continue testing the viability of using beach seines and purse seines to harvest more hatchery salmon while releasing more wild fish safely than by traditional gillnetting. But research over the past several years suggests that far fewer released Chinook are surviving than managers originally thought.

It's part of a new harvest plan that expects the netters to use beach or purse seines in the mainstem to catch more, with less impact to ESA-listed fish, and stay financially whole, if they give up gillnetting Chinook and coho on mainstem waters.

The plan calls for transitioning the fleet to more fishing effort in selective areas, where fish are raised in netpens and salmon production would be boosted to increase off-channel harvest for commercials, by 2017. The recreational sector would also benefit from a larger allocation of impacts to ESA-listed upriver Chinook, and hence a larger share of the non-Indian catch, but the overall share of non-Indian impacts would not change.

The issue went public in March when tribal fisherman Wilbur Slockish, a commissioner with the Columbia River Inter-Tribal Fish Commission, testified at the Mar. 13 meeting of the Pacific Fishery Management Council. Slockish raised questions about the release mortality rates for Chinook and coho that WDFW had estimated in their recent research, and said that the U.S. v. Oregon Technical Advisory Committee had reviewed the work, and had not reached consensus on an appropriate mortality rate. "The results are complex," he said in his written statement. "But the core problem is that in order to accept the stock composition estimates from some radio tag work associated with this study, it suggests that our long set of CWT data for fisheries in the study area are not correct." CRITFC called for the states to keep from implementing the commercial mark-selective seined fisheries until TAC could further consider the results and try to resolve the apparent inconsistencies.

TAC has reviewed those results and has reached consensus on the post-release mortality for seine-caught fish, said TAC chair and CRITFC harvest specialist Stuart Ellis. For Chinook, the adjusted average mortality for fish released from breach seines was nearly 34 percent; for fish released from purse seines, it was more than 22 percent.

The results are considerably higher than earlier research that looked only at immediate survival. In 2010, only 0.1 percent of Chinook released died shortly thereafter.

Earlier research with spring Chinook found about 40-percent post-release mortality from standard gillnets and a 15-percent rate for release from smaller-mesh tangle nets.

The gillnetters say the whole harvest reform effort should be scrapped. "They [the rates] are too high to be workable," said Hobe Kytr, executive director of Salmon For All, representing non-Indian commercial harvesters, "particularly since seine gear catches everything, meaning a huge number of fish would have to be handled."

The TAC review also settled on a 38.4 percent average mortality rate for coho released from beach seines and a 28.9-percent rate for purse seines. This year's research will focus on released coho mortality, said WDFW biologist Ann Stephenson. In 2011 and 2012, PIT tag studies of the releases focused more on Chinook, along with a 2013 radio-tag study that found many of the fish marked for release were evidently bound for destinations below Bonneville Dam.

The PIT tag studies in 2011 and 2012 came up with higher post-release mortalities than a 2013 radio-tag study (the fish were also PIT-tagged) that estimated purse seine probable survival at 89 percent. The 2011 study had estimated survival at 82 percent, and in 2012, it was 79 percent.

The 2013 radio-tag study, which tracked individual fish, picked up on something the earlier research did not. "In this study, 26 percent of the tule Chinook salmon, 21 percent of the bright Chinook salmon, and 14 percent of the coho salmon moved downstream, out of the primary study area, after release," said the report. "This result was unexpected. The telemetry array was developed with the assumption that many fish would pass Bonneville Dam whereas others would remain in the primary study area and likely would return to Bonneville Hatchery, or to tributaries near the Hamilton Island/Pierce Island complex."

The 2013 study said, "The assessment of probable survival in this study suggests that fall Chinook salmon and coho salmon survival rates are high after capture in a beach or purse seine. Behavioral responses by tagged fish following release suggested that 93 percent of the tule Chinook salmon, 87 percent of the bright Chinook salmon, and 84 percent of the coho salmon survived capture in a beach or purse seine. These estimates are conservative because we were unable to assess survival of fish that moved quickly downstream and passed Washougal."

Stephenson said a study plan for 2014 is being finalized, with each fish being tracked individually to determine its fate after it is released from the fishing gear.

The bright spot in all this is the low mortality observed for steelhead releases -- only about 8 percent form beach seines, and 3 percent from purse seines.

Stevenson said by email that one explanation for the differences could be that most of the steelhead were headed above Bonneville and were detected there, but the Chinook and coho may have been more of a combination of fish destined for both above and below Bonneville. Or that Chinook and coho could be more susceptible to harvest by the seines, or were subject to more handling and tagging effects, but other studies have shown these effects to be minimal.

The recreational fishing side, which supported the selective seining effort as part of its campaign to remove gillnetters from the mainstem Columbia, was leery about the post-release mortality results.

Heath Heikkila, fisheries director for Coastal Conservation Association chapters in Oregon and Washington, said his group has real doubts about the studies. He said there were "protocol problems" with the first two years of the studies, and he questioned whether mortality studies associated with gillnets and tangle nets were as rigorous as those done for the test seining.

"There's a bit of a double standard here," Heikkila said, who noted that fishermen who took part in the testing told him they don't believe the post-release mortality is as high as these agency studies have estimated. He said it would be hard to manage the selective fisheries if those mortality rates developed over the past three years are used to calculate impacts, but it does not change anything from a fisheries reform standpoint.

CRITFC's Ellis said the post-release mortality rates may have been higher than what agencies expected, but in August they are likely to be higher than in the spring, when water temperatures are much cooler. He agreed that the big difference observed with steelhead is a bit of a puzzler.

Bill Rudolph
Selective Harvest Methods Still on Trial
NW Fishletter, July 24, 2014

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