A Washington Department of Fish and Wildlife test this late summer and fall of “selective” commercial gear produced “very positive results” in catching salmon and steelhead efficiently and benignly.
Thirteen fishers – six using beach seine nets, five fishing purse seines and two employing trap nets – caught a total of 21,000 salmon and steelhead this late summer and fall in the lower Columbia River.
The research effort involved the catch and release of the fish. Fewer than 25 of the fish suffered direct mortality, which would be about one-tenth of a percent of the catch.
“That is very acceptable to us right now,” the WDFW’s Eric Kinne said. One of the main goals of the study is to find commercial gear that allows fishers to release wild fish unharmed.
The catch included 10,800 chinook, 8,100 coho and 2,100 steelhead. Both purse and beach seines proved to be effective capture methods, with purse seines being the most effective of the two gear types, according to an agency “green sheet” describing the project. Agency officials previewed the 2010 data Friday for the Washington Fish and Wildlife Commission.
A total of 13,100 salmon and steelhead were caught with purse seines and 7,900 with beach seines. The trap nets were generally ineffective with a total of 39 fish captured for the season, including 10 chinook, 26 coho and three steelhead.
All three gear types allow the fish to be encircled while leaving them free-swimming. Fish can be identified and released by type or species with a minimum amount of handling.
This year’s venture was the first full scale test following a pilot project undertaken in 2009. The tests were carried out with the help of a $1.975 million Mitchell Act award allocated to the WDFW.
The overall goal of the research is to identify alternatives to the gill nets now used by commercial fishers in the lower river. The idea is to maximize catch of hatchery-origin fish that are produced to feed sport and commercial fisheries with minimum mortality to native salmon and steelhead.
Such gear could be used to help reduce the number of hatchery fish that stray onto the spawning grounds and compete with wild fish and, many scientists believe, reduce the fitness of native fish and pose disease risk. A recent review, called for by Congress, by the Hatchery Scientific Review Group identified the need to increase the harvest of hatchery produced salmon in order to reduce their interaction with wild fish. The WFWC endorsed that strategy in is Hatchery and Fishery Reform policy.
Laws require that impacts be limited on wild portions of 13 Columbia-Snake river basin salmon and steelhead stocks that are listed under the Endangered Species Act.
To limit those impacts, there are three available management tools: increasing the harvest of hatchery fish; installing tributary weirs to remove hatchery fish, and/or decreasing hatchery production,
“In order to implement alternative fishing gears and methods in lower Columbia River commercial fisheries it will be important to identify those gears that are most effective in capturing fish in a live condition,” according to the green sheet. “It will also be important that catch rates are adequate to support an economically viable commercial fishery. Additionally, it will be necessary to determine post-release survival rates for these gears prior to implementation in a full-fleet commercial fishery.”
Due to low funding levels the 2009 effort was implemented as a pilot study to help guide future efforts. It aimed to begin learning that seines and traps effectively, evaluate and refine tagging protocols for use in future post release mortality studies and assess relative species-specific catch per effort for each gear type. All gears were initially fished for 11 days with additional operations of a purse seine and trap net occurring for an additional six and four days respectively.
The purse seine had the highest catch rate and the trap net had the lowest catch rate.
Fish captured were in excellent condition, regardless of gear type, with no immediate mortalities being observed. Modifications were noted for all three gears that would improve effectiveness in future tests.
For 2010, WDFW expanded the test to include multiple fishers in multiple locations in the Columbia River downstream of Bonneville Dam. The 2010 study was also expanded to estimate species-specific short-term mortality rates by gear type.
The study focused on capture of fall chinook and coho from August through October.
The objectives for the 2010 feasibility study were to:
-- test deployment and operation of three different gear types (Purse Seine, Beach Seine and Trap Net);
-- directly estimate short-term (24-48 hours) species-specific mortality rates resulting from capture for each gear type, and
-- directly estimate and compare species-specific catch per unit effort for each gear type.
Researchers failed to accomplish the short-term mortality assessment goal because of the intervention of otters, sea lions and seals. Some of the captured fish were to be kept in in-stream net pens for 24 to 48 hours to see how they fared after their netting. But the pens were regularly plundered by the predators.
“We really don’t have enough data to make an estimate” of short-term mortality, Kinne said.
Participants in the 2010 feasibility test were selected through a competitive bid process.
In the fall they were distributed geographically throughout the lower Columbia River with the beach seines operated between river miles 3-118, purse seines operated between river miles 23-131 and trap nets operated at river miles 3 and 30. All gears were fished during a 2½-month time frame from mid-August through late October. All 13 participants fished a total of 30 days.