The handwriting might be on the wall for the commercial gillnet fisheries targeting Columbia River salmon in the wake of a new study documenting how almost unbelievably clean it is to fish with traps.
Traps, which steer fish into holding pens where they are kept alive until they can be sorted for harvests or upstream passage, have long been known to be a better means of selective harvest than gillnets, which indiscriminately snag and hold salmon of any species that happen to poke their heads through the mesh or become entangled in it.
But it was not known how much better, with some scientists thinking the stress of the time spent in holding pens might cause the later death of some trapped salmon eventually freed to continue on their way to the spawning grounds.
Now the Wild Fish Conservancy, a conservation group based in the state of Washington, is touting “1`00 percent wild salmon survival” from an experimental trap designed to study how to minimize Chinook salmon by-catch in the Columbia.
Chinook, the big “kings” for which Alaska’s Kenai River is famous, have been in decline Pacific coast-wide for more than a decade, and fishery managers from Alaska south to Oregon have struggled to find ways to harvest more plentiful sockeye, coho and chum salmon in mixed-stock fisheries without capturing kings.
The problem gets especially difficult on the Columbia where struggling wild kings mix with kings returning to hatcheries built to maintain fishing opportunities along the more than 1,200-mile-long river that flows from the Canadian Rockies south through the state of Washington before turning west to form the Washington-Oregon border.
Using data from a genetic testing and tagging program that began in 2019, Fish Conservancy researchers were able to identify and then enumerate the number of Chinook surviving the trap and making it to spawning grounds above the Bonneville Dam more than 100 miles and about a week’s travel time for a salmon upstream from the trap.
“Based upon our tagged sample of fish that had genetically assigned to populations originating above Bonneville Dam,” they reported, every fish tagged in the trap had made it past that obstacle.
“This finding is nothing short of remarkable as no control group was used to account for well-established factors known to bias survival rates low in the absence of a control group (such as tag losses, upriver mammal predation, research handling/tagging effects, etc.),” the Conservancy noted on its website. “In other words, 100 percent survival from this study means that the fish trap not only had a zero mortality effect to Chinook salmon at capture and release over seven days, but not one tagged fish from the sample died from upriver marine mammal predation, not one tag fell off during the 167 kilometer migration, nor did our research team damage a single fish during the rather stressful tag insertion and genetic sampling procedure.”
The study is now in the peer-review process.
Given its small sample size – only 88 fish were identified as spawners headed upstream of Bonneville – it would be a stretch to say that it shows the use of traps could eliminate all bycatch mortality for Chinook in mixed-stock fisheries, but the study makes it clear that if the idea is to harvest salmon cleanly, traps are the way to go.
As the Conservancy put it, “the latest survival analysis provides some of the most irrefutable and persuasive evidence to date that passively operated fish traps may provide sustainable fishing opportunities for hatchery fish (or other healthy and abundant stocks) while eliminating mortality to threatened and endangered wild salmon that co-mingle in the river.”
Traps, however, are controversial.
In Alaska, commercial traps were banned at Statehood. They had been long resented in the territory as the tools of Outside interests that held too much power over salmon harvests.
“The fish trap…is looked upon by most Alaskans as the dipper with which the large absentee owner appeared to skim with relative ease the cream of one of the region’s most valuable natural resources and then carried away to the outside the fullest part of the wealth so guarded,” the late George Rogers, a Juneau economist and a consultant to the Alaska Constitutional Convention once observed.
Even then, however, it was known traps were a scientifically better means of harvest, as Rogers conceded:
“…It was the only way that salmon should have been harvested because the fish worked out to the runs. You could manage. You knew what was coming and going. You could control the escapement of the fish. You could then control the harvest. You didn’t have to chase mobile gear all over the place. And it was just perfect, but the trouble with the fish trap was that it was owned by the processors, the canners, and they were all Outside interests.”
Post Statehood, Alaska took a more democratic view of commercial salmon harvesting and let everyone have at it. By the start of the 1970s, state salmon returns were at record lows in part due to cold water in the North Pacific ocean and in part due to overfishing.
Alaska voters then approved an amendment to the constitution basically undoing the Statehood decision to take the vast majority of the salmon out of the hands of the few and share the catch widely among the many.
As a result, 1.5 percent of Alaska fishermen now catch more than 95 percent of the salmon while the other 95 percent hope to catch a fish, and salmon managers continue to struggle to find ways to get weak returns of some species like Kenai kings, past the gillnets used to catch salmon returning in large numbers, like Kenai sockeye.
And in Alaska, unlike on the Columbia, no one has even dared experiment with a trap to try to determine just how much of a difference technology could make in solving the bycatch problem.