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Salmon fantasies

scatter plot

Despite a decade-long, average commercial harvest of only about 2.6 million Upper Cook Inlet sockeye salmon, the dream of a scaly silver bounty lives on among the approximately 1,000 Alaskans who own some of the 1,303 permits to fish for profit in the waters that lap at the doorstep of the 49th state’s largest city.

On Saturday they trooped before the Alaska Board of Fisheries to make the case that if only the state let them catch, kill and sell more salmon, there would be more salmon.

“There’s no reason not for 100,000 kings to come back to the Kenai River” every year along with 4 million to 6 million sockeye, Anchorage-educated gillnetter Steve Tvenstrup told the board.

“It isn’t because I’m out there in the center of the Inlet,” said the fisherman who now calls Kenai home.

The Kenai River is the main driver of the sockeye commercial fishermen covet. The last time the Kenai returned 4 million or more sockeye was in 2012, according to Alaska Department of Fish and Game data. It has topped the 4 million mark only five times in the past 20 years and of those five only two years hit the 6 million level.

Tvenstrup’s memories are of the mid to late-80’s, when he first got involved in the fishery, into the early ’90s. From 1987 to 1996, the Kenai River – the Inlet’s biggest sockeye producer – returned an average of more than 5 million sockeye per year.

Cook Inlet today

Those days are history. The decadal average is down to 3.5 million, and if the monster return of 6.3 million in 2011 is treated as the anomaly it appears to be, the average is closer to 3.1 million, according to state data.

Recognizing this shift, Ray Beamesderfer – a widely respected fisheries consult now on contract to the Kenai River Sport Fishing Association – has suggested the state modify its thinking on Kenai management from the simplistic, maximum-sustained-yield (MSY) philosophy of old to a new policy of maximum sustained recruitment (MSR) – recruitment being a fancy management term for the production of little fish.

“MSR is an appropriate standard for a sport fishery,” he told the Board on Saturday. “MSR produces the greatest actual yield in a sport fishery.

“A sport fishery cannot realize theoretical MSY in the real world because it doesn’t have the same fishing power as a commercial fishery. Sport fisheries benefit the most when the run size is great, the catch rates are highest, and the effort is most.”

MSR puts more fish in the river and, from an ecological standpoint, better feeds the environment. Everything from the bears in the woods to the rainbow trout in the river to the forest itself benefits from more fish in the river although all have has historically played second fiddle to the idea of manipulating salmon runs for maximum commercial harvests.

MSY itself has been a much-debated management standard among fishery biologists since the late Canadian biologist Peter Larkin published “An Epitaph for the Concept of Maximum Sustained Yield” in 1977. Larkin described it as a “puritanical approach” to management that ignored the vagaries of the natural world.

Decades later, writing in ICES Journal of Marine Science, scientists Carmel Finley and Naomi Oreskes described it more simply as “a policy disguised as science,” arguing that the entire idea sprang from little more than a desire to expand industrial-scale fishing with little science to back it up.

When it comes to salmon, the theory is inherently flawed at a fundamental level, given that yield is based on the ratio of returns per spawner. Thus, if 100 salmon spawn and 300 come back, the return per spawner of 3-to-1 is much better than if 1,000 salmon spawn and 2,000 come because the bigger return produces a per spawner ratio of only 2 to 1.

Never mind that managing for the spawning goal of 100 fish in this scenario allows for the harvest of only 200 fish year whereas managing for the theoretically less efficient goal of 1,000 spawners allows for the harvest of 1,000 fish.

But salmon MSYs are little more than crap shots anyway in that MSY really doesn’t exist. It’s the point of most likely probability in a scatter plot of data that looks the results of someone testing a poorly patterning shotgun.

Why fewer sockeye?

No one knows why Inlet sockeye returns have fallen the way they have this decade, but fishermen cling to the theory of “over-escapement,” the idea being that the more spawners that escape nets and get into the river the fewer of their offspring survive due to in-lake and in-river competition between the young fish for food.

The theory stems from research done on the Kenai in the wake of the Exxon Valdez oil spill that forced a commercial fishing shutdown allowing more than 2 million salmon to escape into the river at a time when there was no personal-use dipnet fishery at the mouth (that wasn’t adopted until 1990) and the in-river sport fishery for sockeye was relatively small with a harvest under 200,000 fish.

It is likely 1.9 million sockeye or more spawned in the river in ’89. Given a sport fishery that now catches up to 400,000 in a good year and a dipnet fishery that can catch up to a half-million if large numbers of sockeye are allowed to escape commercial fishermen, an “escapement” of 2 million sockeye to the mouth of the Kenai these days would likely result in something more like 1.1 million to 1.2 million spawners.

And that’s just about exactly the average number of spawners Fish and Game calculates made it onto the spawning beds in those banner years of Tvenstrup’s dreams.

It is also a data point largely irrelevant in these times given that studies of over-escapement in both Canada and Alaska since the wreck of the Exxon Valdez have cast serious doubt on the over-escapement theory.

After Fish and Game in 2007 conducted a statewide examination that looked at 40 rivers and found many of them over-escaped, the agency concluded that “as seen in the review of salmon stocks in British Columbia (Canada), we did not observe long-term stock collapse of any of the 40 stocks that could be attributed to over-escapement.”

What the researchers did find was three rivers where returns fell below a one-to-one return per spawner “following consecutive over-escapements that were greater than twice the upper escapement goal range.”

The Kenai’s upper “biological escapement goal” is 1.2 million sockeye.  Twice that would amount to 2.4 million sockeye. The Kenai has never hit that number in any one year let alone in consecutive years.

Other possibilities

Aside from fretting about over-escapement, little attention has been devoted to trying to figure out exactly why returns of both Kenai sockeye and Chinook – the big kings – have dropped in recent years despite adequate numbers of fish reaching the spawning grounds.

But scientists in the Pacific Northwest, where rivers face similar problems, have been taking a serious look at predation, especially in nearshore environments.

In a peer-reviewed study published in the journal Ecosphere in November, scientists studying the Salish Sea noted the vulnerability of young salmon to “opportunistic predators,” notably mergansers and spiny dogfish which “are capable of learned behavior.”

The Salish Sea is the water body that includes Puget Sound, the straits of Juan de Fuca and Georgia, and the waters of British Columbia inside Vancouver Island. The sea is most notably fed by the Fraser River, the largest sockeye producer in the world. 

(Bristol Bay outperforms the Fraser, but the fishery is fed by multiple rivers. No one river can match the 38 million salmon the Fraser produced in 1913.)

Spiny dogfish predation on sockeye has not been specifically studied, but researchers have looked at such predation on other salmon.

“Large numbers of spiny dogfish moved into the area near the mouth of the Big Qualicum River, British Columbia, at the time hatchery-reared smolts of Chinook salmon and coho salmon were leaving the river in 1988 and 1989,” Richard Beamish, one of the world’s foremost salmon scientists, and Gordon McFarlane, reported in a 1992, peer-reviewed study in Transactions of the American Fisheries Society. “A small percentage of the spiny dogfish preyed on the smolts, but the resulting smolt mortality is believed to have been large because of the large numbers of spiny dogfish in this area. Spiny dogfish also fed on adult salmon in the fall. The long-term decline in survival of chinook salmon produced at the Big Qualicum Hatchery was similar to the pattern of survival of other hatchery-produced salmon. We propose that this long-term decline in survival results from predation.”

Federal officials in the 1950s were suggesting predation as a possible limiting factor for some Alaska sockeye runs, but the idea fell largely out of favor because of a focus on consumption by grizzly bears, bald eagles, seals and sea lions – endangered species in most of the country – and Dolly Varden char, rainbow trout, and other salmon species coveted by anglers.

Views on predation have shifted somewhat in the years since. The Pacific States Marine Fisheries Commission is now waging warn on the pikeminnow in the Columbia River drainage with rewards of $5 to $8 per fish for anglers catching pikeminnows of nine inches and larger. Meanwhile, Alaska is the ninth year of an expensive, northern pike control program in the Alexander Creek drainage just across Cook Inlet from Anchorage.

Spiny dogfish predation on sockeye salmon has not been specifically studied anywhere, nor have there been any studies on spiny dogfish predation, or predation by any other species, on salmon in the Inlet.

But what has been reported in the Inlet is a growing population of dogfish.

“They are glutenous, bait pilfering, bantam cousins of their larger equivalents and are also known as piked dogfish, skittledog, spotted dogfish, white-spotted dogfish, codshark, thorndogs and other names only bellowed on Marine Corps drill fields,” Nick Varney wrote in the Fishing Report for the Homer News in 2018.

He compared them to “locusts” and observed that “those annoying a#$%*@$s travel in schools of hundreds to thousands of individuals. They are called dogfish because they move and hunt in packs….

“Not only that, their life span ranges from 25-100 years and it is the most common shark alive. Isn’t that special?

“If you find yourself plagued by a herd of these things, just anchor up and move. Simple as that.”

Halibut anglers being plagued by spiny dogfish is a relatively new phenomenon that would suggest the population has grown significantly.

A 2010 University of Alaska study concluded spiny dogfish numbers had been increasing in the Gulf of Alaska since the 1990s and noted that “the diversity of prey items consumed suggest that increased spiny dogfish biomass and subsequent total consumption by dogfish might impact numerous northeastern Pacific species.”

Inlet setnetters, who have always caught some spiny dogfish, have reported increasing numbers of the nuisance species in their nets in recent years, but there is no data because setnetters are not required to record or report the by-catch of species other than Chinook salmon.

Basically nothing is known about predation on salmon in the Inlet, and the Canadians who have looked at the issue as regards Fraser River fish admit to knowing little more.

“Naming the predators of sockeye salmon should not be a difficult task given that everyone likely loves sockeye, but scientifically supported ecosystem-level information about predator species (numbers, diets, trends, and distributions) is sparse throughout the sockeye salmon range,” scientists involved in the Cohen Commission investigation of Fraser River sockeye declines observed in a 2011 report. “Research in freshwater has largely concentrated on fish species of interest to anglers, and has provided some information on stomach contents, but little to no information about the abundance and trends of potential predators. More information is available from marine systems, but it is again almost exclusively for commercially important fish species, and largely absent for other predator species in the ecosystems.”

No ‘smoking gun’

Those scientists admitted to finding “no smoking gun,” only a list of “usual suspects”  – none of which appeared to be in position to do significant damage to Fraser sockeye.

“…Fish predators (spiny dogfish, and coho and chinook salmon) have all declined in recent decades, and individually seems unlikely to have had any major impacts on sockeye salmon,” they wrote. “Through the Strait of Georgia and Queen Charlotte Sound there are a number of potential predators of which sablefish is one of the more surprising. Sablefish is known as a deepwater species, but the juveniles are more coastal and known to feed on salmon smolts in the early summer months when supply is ample. Arrowtooth flounder is another potential predator, which has increased dramatically in recent decades, and could potentially be a predator on sockeye salmon during their first months at sea.”

Arrowtooth were the Gulf of Alaska species with the highest biomass at the start of the new millennium, but they have since declined significantly, according to National Oceanic and Atmospheric Administration (NOAA) data. 

Sablefish biomass, on the other hand, has been increasing since an all-time low in 2002, according to NOAA data.

Marine ecosystems are inherently complicated, and only get more so the deeper into their examination one delves.

As the Canadians noted, “feeding conditions may have changed for the potential predators of sockeye salmon in the Northeast Pacific Ocean in recent decades. Previously abundant prey species such as walleye pollock and Pacific cod in the Gulf of Alaska…have declined, and could have potentially shortchanged the predators. Such a change could have increased predation pressure on sockeye, but data are unavailable to assess this possibility.”

The November study of the Salish Sea also threw hatchery salmon into the mix as both predator and prey on a couple of levels.

“In the marine environment, hatchery programs may have bottom‐up or top‐down effects on food webs,” the authors of that study observed. “For example, large populations of pink salmon are thought to reduce zooplankton biomass and may affect the success of more economically valuable sockeye salmon. Juvenile or adult hatchery fish may also provide reliable prey subsidies for predators.”

Predator concentrations near hatcheries are well-documented. Whether predator massing occurs in areas where hatchery fish might concentrate along their migration route is an unknown as is the question of whether such predator massing could set up an ambush for wild fish arriving in the feeding area at the tail end of a hatchery fish migration.

Some fisheries scientists say the many unknowns themselves raises serious questions about managing for MSY standards that are more magical than real. The only thing decades of Alaska state fisheries data make clear about the numbers of spawning fish is this:

There is no point at which fisheries managers employing MSY standards can say that “if we put X-number of spawning sockeye in the Kenai, we will get Y-number of fish back in the future.”

At best they can say “X-number of spawning sockeye in the Kenai will give us the best chance of getting Y-number of sockeye back in the future,” but even then the odds of hitting Y are low, and the odds that the return will come back at Y-minus or Y-plus are high.

Nature is quite simply not bound to the mathematical equation “Rt=αSt exp[–βStSt–1] exp(εt).”

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

4 replies »

  1. Craig,

    Thanks for keeping us up to date on these issues and the potential causes for the recent decline in salmon from the record highs. I suspect it is more of a case of a death from 1,000 cuts than it being one specific issue. It really wasn’t all that long ago that the Kenai king was so few in number that they held a lottery for no more than 100 to be caught, back then the cause was a singular issue, that being out of state commercial fish traps that were running roughshod.

    The spiny dogfish makes sense as a contributor to the problems we are seeing, there are anecdotally more now than ever. It’s too bad they can’t be used commercially, I believe in Mexico they use them for fish taco’s. I guess one day when we can no longer catch halibut, or rockfish, or salmon we will find a market and taste for spiny dogfish…they might need to come up with a better more appealing name first though.

    • Stev-o,there used to be a targeted longline fishery for dogfish in and off the straights of jaun de fuca,might still be.This was supposed to be feeding a fish n chips market.
      The area off La Push and into jaun de fuca canyon was covered with immense schools (more like clouds,miles long).
      This was back in the 80’s-90’s.
      From perhaps the early to mid 90’s on into the new millenium they seemed to have gotten worse in the Central gulf(along with arrowtooth flounders,coinciding with slow steady collapse of Black Cod stocks.)
      Ineresting anectode,while i cant cite reference,there is a circular relationship between Black Cod and salmon as far as opportunistic feeding patterns go.
      Adult salmon preying on juvy BC and visa versa.

      • I remember seeing what I figured were juvenile black cod boiling at the surface behind tenders in PWS eating the bits and pieces from the effluent that was pumped out from fishholds, at times you could reach down an grab them with your bare hand. I’m not sure if that still happens or not, that was a couple decades ago.

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