Climate Change Effects on Salmon

This summer and early fall are the driest and warmest we have had, and recent summers have been much the same. Those of us who fish are justifiably concerned with wild salmon numbers, particularly in rivers where climate changes will make great difference to salmon.

Here is a summary document that, at four pages, is short and worthwhile reading for all anglers:  https://cmsdata.iucn.org/downloads/fact_sheet_red_list_salmon.pdf. 

And for ocean effects, and there are many, this 2009 review document by Dick Beamish, Brian Riddell (who we know as CEO of the PSF) and others, covers all the countries rimming the Pacific Ocean that have wild Pacific salmon, in 11 pages: http://www.npafc.org/new/publications/Special%20Publications/LRMP_Synthesis.pdf. 

Sockeye are the most heat sensitive of the five species, and over 20 Degrees C is lethal to them. If you follow DFO’s sockeye panel stats, you will know that Qualark Creek temps moved into the lethal range at times this summer. And note that coho, in saltwater are almost as temperature sensitive as sockeye.

But there is more to higher temperatures than simply death. Higher temperature, has been accompanied by lower precipitation in summer, monsoon rains in the fall, and lower snowpack in winter, setting up lower flow, of higher temperature, and lower oxygen all summer long.

Lower oxygen is the result of fewer riffles that mix air and water together. And as chinook are mainstem residers for more than a year, they suffer the oxygen effects the most. And lower clearer rivers make fry more visible to predators, thus reducing their numbers. 

Pink and chum hatch in March/April and migrate to sea almost immediately, a period of high flow. The down side for them is that greater precipitation in winter smothers or washes out egg bearing redds – of all species really. 

But low flow in late summer, can eliminate most water for pink spawning. They mate in very shallow water, particularly riffles hardly six inches deep. If those prime spots are only a couple of inches, in addition to low oxygen, they don’t give the pinks enough depth to spawn, and thus they move to other water with small pebbles.

Low, warm flow has effects on all species. Chum return in huge numbers on Van Isle and tend to spawn on greatest flow; this results, when the water recedes, in huge areas of dead redds. A gravel bar on one river I fish, is 400 yards wide, and 600 yards long. When the flood subsides, the entire area looks like it has been bombed with very small munitions. All chum, and all dead. Chum waste as high a percentage as 90% even in the best conditions. 

I started wading through a pool of dead chum, washed behind a new log – and log movement changes river bed, both scouring out bottoms and burying bottoms. I calculated 10,000 carcasses and began walking through. Soon I was up to my thighs, then waist, then chest and rather than go down with the chum, I slowly backed out of them, and smelled like death all day.

But there are other effects. If spawning channels have no water to enter, those fish may not be able to spawn or may move to areas of lower success, or higher use by other species. If river flow is very low, it affects chinook the greatest, as they need almost a foot for a 20- to 30-pounder to torpedo through.

I have watched chinook that can hardly move beyond the tidal reaches of rivers, reluctantly spawn in the highest water, with the largest gravel. One pair would spawn and go, and the next day, another pair would dig up the previous redd and also spawn and go. This went on for a full month, ie. 30 days of repeat spawning and waste of virtually all chinook eggs.

It may be that the sudden rise in merganser numbers about a decade ago represents another climate change effect. If prey is easier to see, water is shallower, and slower, fry are easier to catch and eat, so add predation to climate change effect.

While sockeye have temperature difficulties, and pre-spawn mortality rises, as shown in Dr. Miller’s work, on Fraser subcomponents to as high as 90% (also a disease effect, PRV for example), they get an easier pass by residing in lakes. The downside is that, like Lake Erie that has algal effects this year on news video, lakes can acidify and become more lethal, in some cases changing the plankton (a bigger problem in the open ocean) the base of the food chain.

One effect of lesser obviousness is that lower, smaller rivers have less spawning space than when at normal levels. That means there is less main-stem place to spawn, and thus, the respawning phenomenon I have mentioned, and by more than one species. And the last to spawn would be the fry of greater numbers, usually chum. However, as chinook are the largest, can move the largest gravel, chum effect would be greatest on pink salmon and secondarily chinook, and sockeye.

Coho are a special case. They tend to spawn in side channels, and seasonal streams. In my winter fishing, I check on several such creeks to monitor the spawn. As coho can spend an entire summer in seasonal streams, they are most susceptible to low precipitation – even though coho hold on in freshwater the longest, in some rivers into January, waiting for highest water. 

These days, several streams, don’t get filled up enough to offer a good spawning chance. Some don’t fill at all anymore and from being ones where I have watched coho spawn for a decade, have not had water for the last five, meaning none of those coho survived (unless they spawned in other water, crowding other coho, too).

And those seasonal creeks usually shrink in low water, so potholes around root balls, provide the only habitat for coho through one summer and back into the next high-water event – that means not being able to migrate out in the first summer.

But in the past few years, I have watched those small pans of water disappear completely. It is hard to watch water that will support coho disappear with fry in them. Just so that you know, coho fry have orange tails, so they are the easiest to identify. As pink and chum migrate out immediately, chinook are mainstem spawners, and sockeye are associated with lakes, chances are those fry cutoff from river flow are likely coho. 

And when river flow goes down in summer, those small pools cut off from flow, are likely to kill all fry when/if that happens, it is coho that are most affected.

There is much more to say, but I will cut to the chase and end. For several reasons it makes sense for anglers to get involved with chinook netpens – along with all the other restoration and recovery projects. 

Chinook are around 12 months of the year and are our species of interest. But chinook and coho numbers (particularly in the Salish Sea for coho since the mid-nineties) have fallen over the years, so that, in Victoria, we now catch more US chinook in winter, because there are not enough Canadian chinook.

When you add to this that our orcas are in deep trouble, and reputed to eat mostly chinook (I’d say this is more because chinook are around all year, rather than the two months of other species, and the largest, rather than a dietary preference), it makes great sense to do what the South Vancouver Island Anglers Coalition has done and put in a netpen in Sooke Basin to raise and release chinook – for orcas and us.

The argument that that changes things for wild fish because there is more competition for food resources, I think unlikely, because there are far fewer wild fish around these days. Other types of competition can be solved by using diploided chinook that are sterile and thus cannot breed. Netpen fish also return to the netpen site and can be recaptured by anglers.

When you consider that the CBC – a Toronto-centred network – has done the Right Whale deaths in the St. Lawrence almost weekly this past summer, and there are 500 of them, rather than talk loudly about the 78 orcas left, it means we on the BC coast need to be stepping up to fund, or operate netpens for chinook as much as we can.

I am in contact with a dozen environmental NGOs, and they repeatedly call for ending the sport fishery to save orcas. I point out politely that the issue isn’t sport fishing, it is lack of fish, and that the real key here is to quickly increase chinook numbers. That means a greater willingness by DFO to authorize netpens, and sport anglers to step up. The other thing I say is that the people who man such operations are sport fishermen, and thus that the ENGOs should look upon sporties as allies on behalf of orcas, rather than enemies. I’d say it will take several years of polite suggestion for this to sink in.

Sorry to go on so long. There is far more to say, (for example, there is great need for DFO stats on 50% of stocks), but do read the documents above, and if you want to read more, Google climate change effects on salmon: https://www.google.ca/search?q=climate+effect+changes+on+salmon&ie=utf-8&oe=utf-8&gws_rd=cr&dcr=0&ei=YRjZWdTiH4K6jwP8lq2ICQ.