I know the sockeye run has been quite substantial this year but I couldn't help taking notice of the news the morning when they stated this was the largest in 100 years/ Am I hearing this right or is that just a gross exaggeration?
If all the tall stories are to be believed Salmon were supposed to be so plentiful 100 years ago you could walk over their backs when the run came in. [Obviously very tall stories but you get the gist]. Also heard that people were once able to catch loads of Salmon in English bay as recently as 25 years ago (..not sure if it was sockeye or some other species).
My understanding is Salmon have been in a steady decline due to human pressure/ global warming/deforestation etc. etc. I am assuming this is the case but there are the occasional spikes where returns might actually exceed the Salmon returns as far back as 100 years ago.
Does this actually happen? Opinions/ Thoughts I would be interested to hear because I find some of the statements about Salmon returns confusing. [Last year's pink run in the Campbell was supposed to break certain records too I believe and it was pretty significant in the Fraser as well].
Fishseeker, I met you at Sapperton last year fishing for pinks, nice to hear from you!
The notion of a steady decline in salmon populations doesn't make sense and here is why:
Salmon return in discrete packages each year, all returning in the 2-5 year life span at varying times but nonetheless consistently. As they reach maturity they return to produce a great quantity of eggs relative to their own numbers. This is what is called a K-selected species which are semelparous, meaning their reproductive efforts are focused on one large effort with no parental care. Thousands of juveniles per spawning adult emerge from the gravel the following Spring. The most dangerous part of the salmon life cycle is from egg to smolt, where they are easily eaten by larger fish, and myriad of other predators/disease/parasites. In this manner, the adults are producing far more than replacement numbers of juveniles to compensate for the increased rate of mortality of their offspring as juveniles. As you can imagine, favorable conditions may arise that lower the mortality rate on juveniles to a point where they grow fast enough to a large enough size to avoid most of the predation risk as juveniles. These factors include but are not limited to: coastal upwelling, bloom timing, water temperature, zooplankton abundance, and primary productivity. There are many factors that influence juvenile survivability, and there are models that attempt to quantify these conditions to predict the amount of returning adults. These models consistently fail because they are too simple. The most accurate models are not even remotely dependable, as they have an error range of +/- 60% of their median estimates. The situation could easily arise where a small amount of adults returning produce offspring who in the following Spring are met with very favorable marine conditions that enable them to grow fast enough and large enough to evade the elevated predation risk associated with the egg to smolt life stages. This would mean that relatively few adults returning could potentially restore the stock. What we are seeing this year with Sockeye on the Fraser is a moderate sized escapement (meaning adults on the spawning grounds) met with favorable recruitment (meaning those juveniles that survive to maturity). The juveniles of the 2008 adult return were met with favorable marine conditions such that they grew fast enough that they reached a certain size that yielded them protection.
In terms of how humans interpret this information and attempt to use it is another matter. Our current pre-season forecasting doesn't work and is completely unreliable. Last year the estimates were over by 7 million, this year they are under by 11 million. Another thing you should look at is how reliable our in-season enumeration and our post-season enumeration is and has been for the last 100 years. The test fisheries demonstrate significant error between sampling sites and sampling methods at present. In the past there were fewer and less sophisticated sampling methods. Much of the run estimates were done by calculating the catch per unit effort of fishing vessels, which is a poor indicator as fishing methods vary and over time fishing methods increase in efficiency, which would overestimate numbers in the long run. It is quite likely that this run isn't the biggest we have seen in 100 years as we simply do not have enough information. Frankly, I don't know why people attempt to estimate them at all. The most we can do is alleviate anthropogenic factors that reduce salmon numbers such as deforestation, gravel mining, damming rivers, polluting the environment, open-pen aquaculture. We can't rely on favorable marine conditions to give us these types of returns as the environment is far too tumultuous. We should also manage our fisheries better so that the escapement numbers are high enough each and every year to give their juveniles a fighting chance. Imagine if this huge run we are having was left alone to spawn and next years marine conditions were favorable.. then we would be walking on the backs of the salmon.
Jonathan
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Topic: Curious about Sockey returns. (Read 4889 times)