Catch and Deceased: Study of Different Catch Methods on Salmon

Whole in the Water

Well-Known Member
Interesting article on the impacts of different catch methods.

Catch and Deceased
When caught as untargeted by-catch, salmon snagged by gill nets suffer higher rates of injury and death than those caught in seine nets.
Authored by
by Christopher Pollon

British Columbia’s Fraser River is one of the world’s last great sockeye strongholds. Every year, millions of salmon run a deadly gauntlet of hooks and nets as they migrate from the ocean to spawn in their natal streams.

But with poor rates of survival at sea and climate change pushing summer river temperatures ever higher, the future of the Fraser River sockeye is under threat. Ensuring salmon fisheries are putting as little pressure on the remaining fish as possible has never been more important. Enter Arthur Bass, a doctoral candidate at the University of British Columbia.

In 2014, Bass embarked on an unusual sockeye fishing expedition. He targeted an autumn sockeye run, setting up fishing stations at three points along the Fraser: near the mouth, close to the spawning grounds, and one in between. From these points, he caught and released sockeye using two commercial fishing methods: gill nets and beach seines.

Gill nets have mesh large enough to trap salmon by the head. These nets usually ensnare the fish just behind the hard plate that covers the gills, though sometimes by the mouth or fins. Gill nets are anchored to the river bottom or set to drift in the river. Beach seines, nets used primarily by First Nations, have much smaller mesh. Fishers will anchor one end of the net while a small boat pulls the other into a semicircle, corralling fish as the two ends are pulled together.

Bass wanted to know if the catch method affected the salmon’s likelihood of survival if they escaped or were released. Such survival is important because at a given time there can be multiple salmon species and stocks migrating simultaneously on the Fraser, necessitating the release of non-targeted fish.

Bass and his collaborators, including First Nations fishermen, found that gill nets on the lower river cause more injuries and deaths than beach seines, but the disparity closes as the salmon move upriver.

Gill net fishing is rougher on fish, Bass says, and often results in wounds to the body and gills. This is especially so earlier on in the salmons’ migration. This is explained in part by the physical and chemical changes the fish undergo as they migrate. When sockeye enter fresh water, for instance, stress hormones naturally increase. As their migration progresses, this makes them increasingly resistant to any wounds they sustain. By the end of their migration, “they are already so jacked up on stress hormones that it’s hard to really disturb them,” Bass says.

The corollary of this is that fish caught early in the migration fare much worse than those caught later on. Fish caught earlier are also stronger, and will typically fight to exhaustion if caught in a net. The fish that survive this encounter can be so worn out they must delay their migration to recover—which is dangerous if the river temperature is higher than normal.

Fisheries and Oceans Canada (DFO) salmon research biologist David Patterson, who worked on the study, says the research is important because it demonstrates the real-world consequences of different fishing methods, unlike most studies that simulate the impact of a single type of gear in a lab.

Bass’s findings have already been added to a DFO internal review of the subject, Patterson says, meaning the research will now be taken into consideration when deciding how the fishery will be managed—decisions that would affect the fates of the sockeye that will soon be running the deadly gauntlet.
 
I am a big fan of reef net fisheries

Fisherman still stand on towers, waiting to spot a school of Sockeye, Chinook, Pink, Coho or Chum salmon swimming along the reef and over the small net suspended between two boats. This process is incredibly selective, as spotters can identify the exact type of fish swimming below. When a school of salmon is observed, the net is quickly pulled up and the fish are gently spilled into a netted live well to relax after a brief struggle. This process is not only humane but allows for the dissipation of bitter lactic acid built up in the salmon flesh, which results in a sweeter flavor.

The fish are then sorted and any unwanted species that may have been caught (called “by-catch”) are harmlessly diverted back into the water. The remaining salmon are bled by cutting a gill and placing them in another live well to swim until dead. This fishing method not only treats the salmon with the utmost reverence and respect but also the other fish caught inadvertently.

Reefnetting can only be done in a flood tide, because the boats (called “gear”) are set up to face the flood current when salmon are moving northward toward the Fraser River. By utilizing this flood tide, the fishery can use stationary gear and wait for the tide to bring the harvests instead of chasing the salmon. The days and times of day that fishing occurs are determined by a combination of nature and fisheries management with the State and tribal interest. The amount of fish taken each year is a natural percentage of the ebbs and flows in annual returns to the Fraser River. The catch season typically extends from mid July to mid October.

https://www.slowfoodusa.org/ark-item/reefnet-salmon-fishing-method-of-the-northern-puget-sound

 
Who wooda thunked. So how much did the study cost to confirm what is already known ?

Every time a new group of biologist come into DFO they repeat that same stupid studies. Why? because when faced with closures/reductions guess what all the groups say at the table? they all say, show me the evidence and when its old they all say that evidence is old and does not apply. Their is nothing that has come out of the DFO biologist division in the last 20 years that was not already know 20 years before that.

It's all about giving the new political masters some more tools/excuses, When we cry for more science, what our true goal is is just delay to keep our fisheries open.
 
Wildmanyeah...you should see how the beach seining goes every year on the Fraser. Seabird island and below the Harrison are awesome examples of how selective this fishery is.
 
Seining is lower mortality than gill net, but I believe seining mortality is around 50%, which I personally found shockingly high, but it is what it is. Just because they APPEAR to swim away unharmed doesn't mean they won't die from stress/scale loss/predation before spawning.
 
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