SALMON DECLINE NOT A SIMPLE CLIMATE CHANGE SOLUTION

SALMON DECLINE AND CLIMATE CHANGE

A MORE COMPLICATED STORY THAN WHAT IT FIRST SEEMS

I read today (10/3/21) in the AP News (See:  “Dwindling Alaska salmon leave Yukon River  tribes in crisis” by N Howard and G. Flaccus) that the  state of Alaska Fish and Game has closed subsistence fishing for chum salmon in the Yukon River and elsewhere.  Salmon is  an anadromous  fish that spawn in rivers, then as fingerlings swim out to sea where they mature.  As adults they return to the same river to mate and lay eggs in the very gravel beds where they hatched.  (Only one in one-hundred live long enough to return to lay their eggs.). Chum salmon are a  mainstay species which Native American fishermen have been harvesting and surviving on for years.  The more commercially valuable King and Chinook salmon have been in decline for many years, due to overfishing,  but the chum salmon have been  a staple and standby fish.  Many upriver natives who depend upon the summer run of this species will have no food in their freezers this winter. 

What is the cause?  If you accept stories in the press….it is of course— the catch-all  cause… ”climate warming”. Yes indeed the climate is warming.  The last glacial epoch  ended about 20 thousand years ago.  Glaciers have been retreating and the Earth and its oceans have been warming ever  since.  

No doubt, humans  have intensified and  sped up the natural end of the glacial epoch and warming process by cutting down vast global forests, plowing up the earth, denuding vegetation, and digging up carbon sources which had been long ago removed from the atmosphere by green plants and buried in rocks  for millions of years.  These fossil sources of carbon were mined by humans to generate energy by burning in the air.  In the process, ancient carbon in the form of CO2, a gas which tends to heat the atmosphere,  was added back into the atmosphere, from whence it had been removed eons ago during a much warmer period of earth history. 

But by focusing only on one cause—-“warming”  we tend to ignore the real culprits.  And many powerful forces with financial or political interests would like to keep it that way.  

In regard to the decline in the salmon fishery in both the Atlantic and Pacific,  there are many culprits other than the overused bugaboo of  “ climate warming”.   No one can prove that the tiny fractional heating of the oceans and the atmosphere, as a result of natural earth heating and human-induced warming in the last century can have as much detrimental affect on fish stocks as:  drastic overfishing, offshore trawl netting of salmon, fish lice parasites, pesticide pollution, and physical barriers such as dams and weirs.

In the best on times a salmon’s life is a hazardous one in which only 1% ever get back to spawn in the river where they were raised.  Only a small change in the perilous journey of a salmon can cause great changes in population.  These human caused and environmental effects  perhaps  minor when examined individually, combine in nature as “additive effects” to have a great impact on populations. 

What are the additive effects? Commercial fishing of salmon has grown exponentially in the last decades .  Netting  salmon before they spawn simply reduces the breeding stock.  Offshore ocean trawlers net  thousands of tons of fish as they seek cod, pollock haddock and halibut and other fish. Salmon are taken in the nets as  “ by catch” that  can not be harvested and are dumped overboard.  This clearly  reduces adult salmon that will spawn. . Sea lice infect “farmed salmon” kept in pens in near-shore or estuarine settings.  These farmed fish are vectors for fish parasites such as fish lice and other disease. Wild salmon are often found infested with sea lice which weaken, reduce vitality or breeding success,  or even kill fish.  

There is no need to explain or elaborate on the effects of dams  weirs , or other barriers that make it often impossible for salmon species to complete their life cycle. All of these above effects combine as additive effects  in nature to reduce the success of salmon breeding.  

Salmon decline does not have one cause—-climate warming.  Even if it did, we can not do much to alter the natural process of a closing and warming glacial epoch.  But humans have imposed their own “additive effects” which we can address to modulate the warming.  The Earth will become a warmer planet whatever we do.  It is a natural outcome of our geology, our drifting continents, and other natural earth cycles.   But we can begin a process of global reforestation, probably the most effective method of climate amelioration. We can begin realistically and reasonably reduce the use of carbon fossil fuels. It is also obvious that we must begin to stabilize and reduce our own burgeoning human populations. 

But as for the salmon,  we can help the salmon most by reducing those impacts to its survival which affect it most directly.  We can address the problems of commercial overfishing, of offshore trawlers and by catch, of fish disease, pesticides, pollution and dams, weirs and other fish barriers erected on spawning rivers. 

But that is the more complex answer.