Spring test set for Gulf salmon excluders
A pair of crewmen sort pollock on deck in the Bering Sea. Salmon excluders used to keep chinooks out of the pollock catch are now widely used in that fishery and testing will take place this spring on a device for the smaller Gulf of Alaska pollock fleet.
Photo/Courtesy/Alaska Seafood Marketing Institute
Gulf of Alaska fishermen could receive a new tool to reduce salmon bycatch if gear modification research is successful.
This spring, two trawlers targeting pollock in the Gulf will have an extra piece of gear in the water. The boats will be fitted with the newest version of a salmon excluder, and a recapture net, as part of an effort to adapt the excluders for Gulf use.
John Gauvin from the North Pacific Fisheries Research Foundation, is trying to develop the excluder for Gulf use. Ideally, it will let salmon escape from pollock trawls while keeping the pollock inside.
Currently, salmon and halibut excluders are used in other fisheries.
In the Bering Sea, the excluder is a flapper that is weighted down in the tapered portion of the net, providing a sort of false ceiling.
Craig Rose, from the Alaska Fisheries Science Center, said it works in part because salmon are better swimmers than pollock. AFSC is partnering with Gauvin on some of the science aspects of the research, including sampling design and salmon behavior.
Pollock will swim toward it and get weighed down, while salmon will try to fight it, Gauvin said.
“Think about a salmon stream,” Gauvin said. “Think about a rock in a salmon stream. A salmon noses up behind that and uses it as a way to get out of the flow, this thing has dead water above it and so what a salmon will do is it will rise above that.”
Then the salmon goes above the flapper, where floats pull the top of the net up to create more room, and if they swim forward, they can leave the net.
“Pollock can go up there, some of them will, but they can’t swim forward against the flow,” Gauvin said.
Gulf of Alaska trawlers operate differently than their Bering Sea counterparts, so the device must be adjusted before it is deployed there.
The Gulf boats travel at a different speed, and are generally smaller with a lower horsepower and different size nets.
All of those differences mean that that replicating the Bering Sea excluder exactly wouldn’t leave enough room between the flapper and the end of the net for salmon to fit. So the challenge, Gauvin said, is to find a way to move the flapper forward in the net and find a way to retain the shape that allows salmon to swim, without losing pollock.
Making the excluder work will require testing different flapper locations, different weights and making other adjustments as needed.
During testing, boats will be equipped with recapture nets, to see not only how many chinooks are making it out of the haul, but also to see if any pollock are escaping.
This isn’t Gauvin’s first attempt at helping with bycatch. He’s been trying to keep unwanted fish out of fishermen’s nets for about 15 years.
“It’s an evolution,” he said. “We started doing this work in the Bering Sea.”
The Gulf work comes at a time when there’s an increasing focus on bycatch.
Gulf of Alaska fishermen are now under a hard cap of 25,000 chinooks divided between the western and central Gulf, and between the early and late seasons. Reaching the limit for chinooks, which are a prohibited species catch, closes down the fishery.
In 2012, the Gulf of Alaska pollock fleet caught an estimated 19,119 chinooks and the western Gulf exceeded its limit in the fall season, the first under the new cap.
The North Pacific Fishery Management Council approved Gauvin’s application to test the excluder on Dec. 5, 2012, at the recommendation of both the Scientific and Statistical Commission, and the Advisory Panel.
The council’s motion allows Gauvin to solicit two vessels to conduct the research that will be exempted from the regular pollock fishery and hard cap for prohibited species catch. That is necessary so that the research can fully determine how many salmon are excluded from the tow, how many are caught, and how pollock fare.
Gauvin said testing will likely begin in March. The vessels will be chosen by NOAA after applying, and will be used for two field seasons.
Gauvin said that the vessels will hopefully be different sizes, to ensure that the device would work on various Gulf vessels, which range in size from less than 60 feet to 125 feet.
Onboard, one or two sea samplers will help with the experiment, although the crew operating the vessel will also do much of the work. For each tow, the sampler will record the pollock and chinook portions of the catch. Each vessel will do about 12 tows.
There will also be underwater cameras, to see what’s happening during the tow.
The Alaska Fisheries Science Center helped design the camera portion of the project, as well as working on other components on the science side of the project.
Jeff Hartman, from Sustainable Fisheries division, Alaska Region, had prepared some of the environmental work for the project, and told the council in December that NMFS had acquired documentation for assessing the project.
The council had to be consulted on the application, however, as part of the process, he said. Hartman said that while the project would not count toward regular fishery limits, the amount of prey it took was not a significant amount, and shouldn’t be a problem for protected species, according to assessment work done so far.
Gauvin isn’t alone in his work. He has help from the National Marine Fisheries Service — that’s Rose and his colleagues — and from the fishermen testing the gear.
Rose said that bycatch reduction is the main place where NMFS has worked on developing new technology for the fishery.
“Bycatch reduction’s been the main emphasis, and it’s included halibut excluders as well as salmon excluders,” he said.
Gauvin has worked on other gear modifications.
The halibut excluder essentially sorts the fish, while the salmon excluder relies on behavior. With each device, Gauvin has to find ways to use fish behavior and sizes to accomplish an end goal with regards to what is in the net, and what isn’t.
But he isn’t a net guy, he said. His background is in the experimental design side of the project, and he’s reliant on others to help with the nets and devices.
That sort of partnership is what is ultimately needed to make a device like the excluder possible.
If the excluder works, Gauvin said it could take a couple years to see it used in the fishery. Eventually, he hopes they’ll be a workable option that fishermen want to use, and managers can incentivize. They likely wouldn’t be required, just optional.
“Regulating gear is tough,” Gauvin said. “(Because) the regulators don’t understand the gear and the fishermen do.”
Rose agreed. Even defining an excluder in regulations would be difficult, he said.
“The first time we came up with an excluder, if they put that into regulation, then folks aren’t going to be able to tweak that and adjust it to make it work better,” Rose said.
Ultimately, he said AFSC tries to help develop the technology, and leave it as a tool for fishermen to use.
Molly Dischner can be reached at firstname.lastname@example.org.