Could we ever reverse the trend of shrinking Chinook salmon?
Much has been said about the decline of Puget Sound Chinook salmon. Often the discussion focuses on how to increase the salmon population, but I believe a good case can be made for increasing the size of these once-mighty “kings.”
There are plenty of reasons why we should strive for larger Chinook, not the least of which is the pure joy of seeing — and perhaps catching — a giant salmon. But I’m also thinking about our endangered Southern Resident killer whales, which don’t seem to find Puget Sound very hospitable anymore. As we know, the whales favor Chinook over any other food.
While it might take more energy for a killer whale to chase down a large Chinook versus a smaller one, the payoff in nutrition and energy far outweighs the expenditure, according to Jacque White of Long Live the Kings, who has been looking into the size issue for some time.
In terms of competition, a giant Chinook might be difficult for a harbor seal to handle, and that could give the orcas a special advantage. Still, we know that harbor seals create problems for the Chinook population by eating thousands of tiny smolts migrating to the ocean before they get a chance to grow up.
Perhaps the major reason that Chinook have declined in size is the troll fishing fleet off the coast of Alaska and Northern Canada, Jacque told me. It is almost simple math. It takes six, seven or eight years to grow the really large Chinook in the ocean. Today’s fishing fleet goes out into the middle of the Chinook-rearing areas up north. The longer the fishing boats stay there, the more likely it is that they will catch a fish that could have grown into a really big one.
Years ago, the fishing boats did not travel so far out to sea, Jacque said. There was no need to travel far when plentiful runs of salmon came right into the shore and swam up the streams.
“In the old days,” he said, “you didn’t have people risking their necks off Alaska trying to catch fish.”
In additional to the trollers, plenty of sport fishermen have taken the opportunity to catch and take home nice trophy fish, putting extra pressure on the big-fish population. Fishing derbies, past and present, challenged people to catch the biggest Chinook.
Long Live the Kings, a conservation group, once held fishing derbies, Jacque noted. But, after giving it some thought, everyone realized that the effort was counterproductive. “Long Live the Kings is now out of the derby business,” he said.
Gillnets, once common in Puget Sound, entrap fish by snagging their gills. Gillnets tend not to catch the truly giant salmon, because of the mesh size, but they do catch the larger salmon. Often only the smaller ones make it through to spawn — and that breeds another generation of small fish.
Fishing is not the only factor that tends to favor the survival of small fish, but it tends to be a big factor, according to Tom Quinn, a University of Washington professor of aquatic and fishery sciences. The issue is complicated, and every salmon run has its own characteristics, he said.
Hatcheries, dams and habitat alterations all tend to favor fish that can compete and survive under new conditions, and often those conditions work better for smaller fish. Changes in the food web may create a nutritional deficit for some salmon stocks, and competition at sea with large numbers of hatchery fish may be a factor. Check out the study in the journal Plos One by researchers for the Alaska Department of Fish and Game.
With the removal of two dams on the Elwha River, I’m hoping that experts can make sure that the conditions will be right for larger fish — if they can survive to make it home.
Quinn, along with doctoral student Michael Tillotson, recently published a paper showing how fishing seasons alone can alter the genetic makeup of a population along with the behavior of individual fish.
Although these characteristics are not necessarily related to the size of fish, it directly affects the fitness of the population. When people are fishing on wild stocks during open season, a fish has the best chance of survival if it shows up before the fishing season begins or after the fishing season is over. But that is not nature’s way.
Through evolution, the greatest number of fish tend to come back when environmental conditions are optimal for migration, spawning and smolt survival. If fishing seasons are timed for the peak of the run, that will reduce the percentage of fish taking advantage of the best conditions. Over time, the population gets skewed, as more fish come back during times when conditions are less than optimal.
The result is likely a lower survival rate for the overall population. The real crunch could come in the future as a result of climate change. If temperatures or streamflows become more severe, the fish may be in a no-win situation: If they show up at most optimal time, they are more likely to get caught. if they come early or late, the environment could kill them or ruin their chances of successful spawning.
“We are reducing the ability of fish to find good environmental conditions,” said Michael Tillotson in a UW news release about the new paper. “We’re perhaps also reducing the ability of fish to adapt to climate change.”
Certain behaviors are bred into wild fish over many generations, and some traits are connected to their timing. Whether they feed aggressively or passively can affect their survival. Some salmon will wait for rain; others will wait for the right streamflow or temperature. Some smolts will stay in freshwater for extended periods; others will move quickly to saltwater. It’s not a great idea when fishing seasons, rather than environmental conditions, dictate fish behavior.
The move to mark-selective fishing — which involves removing the adipose fin of all hatchery fish before they are released — can help solve some problems for wild fish, Tom told me. Under selective fishing rules, fishers are allowed to keep the hatchery fish with a missing fin, but they must release the wild ones that still have all their fins. Some of the wild fish die from injury, but most of them survive, he said.
The key to the problem is a better understanding of the genetic makeup of the individual stocks while increasing the effort to maintain a high-level of genetic diversity. That’s an insurance policy that allows the fish to survive changing conditions.
The genes for giant Chinook have not been lost entirely, as I pointed out in Water Ways on Nov. 25. If we want to have larger Chinook, we must protect the individual Chinook that are larger. That could mean reduced ocean fishing, selective fishing for hatchery populations, and requirements to release fish larger than a certain size. Perhaps it would even be possible to selectively breed larger Chinook in a hatchery for a limited time to increase the size of the fish.
It won’t be easy, because these notions involve messing with billions of dollars in the fishing industry, not to mention complicated international relations. I will save discussions about the Pacific Salmon Treaty for another day. I will just say that this treaty is supposed to be between the U.S. and Canada. But negotiations involve tradeoffs among Washington, Canada and Alaska. Even the Endangered Species Act can’t protect wild Puget Sound Chinook from being caught in Alaska, with the ultimate outcome that fewer fish make it home to spawn.