The downsizing of Chinook salmon | Hacker News Reader

The downsizing of Chinook salmon

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42 pointsDoreenMichele12 comments

As someone who has avidly fished for salmon in the NW for the last 30 years (~75 days per year), I can at least give my opinion that this is mostly BS.

Pervasive, non-selective, commercial and tribal gill-netting that is optimized to remove the largest specimens from the gene-pool is a big part of where I point my finger. Throw in the dams and massive increases in non-native, invasive California sea lions in the lower Columbia and you have a mess in the making. Lots of factors but I believe most of the problems are in-river, not in-ocean.

Also disclaimer, my opinions mostly come from experience on the Columbia (The largest Chinook runs in the world), not the Sound or further north.

I wish I could find the selective breeding paper I read years ago. It is as you say. The human practice of keeping the largest fish in both sport and commercial catches is to blame. A 75 year king salmon derby here shows progressively smaller fish winning every year. Its not really hard to reason that if you kill the big fish before they breed the fish are going to get smaller.

We even see short unnaturally fat fish that are just under the minimum length that has been the same for 30+ years. The gene pool is being pressured to shorter fish for survival.

Puget Sound's resident orcas basically refuse to eat anything other than Chinook (King) salmon -- 97% of their diet is salmon, 78% is Chinook salmon. A variety of old dams without salmon runs have been blocking their ideal spawning grounds, but many of them are being demolished or upgraded to let the fish pass.

https://en.wikipedia.org/wiki/Southern_resident_killer_whale...

This is true but doesn't address the why within one human generation the population size change in salmon returning to spawn ( five years in Pacific versus current two-three years in Pacific versus 10000 years prior history at five years). Also I believe the article says that Alaska orcas are now feeding on the salmon before they get to the Puget Sound orcas, and not in the article but linked that marine mammal populations take a larger number of salmon than orcas, so there is pressure on salmon population from all types of natural predation/less habitat.

The resident orcas have declined enough to be endangered, largely tracking the decline in Chinook.

Yeah the Orcas are starving.

http://www.cbc.ca/news/canada/british-columbia/low-orca-birt...

Ship traffic is also likely a factor in that it's likely disruptive to their hunting.

Unfortunately the Canadian government is set on approving the TransMountain diluted bitumen pipeline expansion, which will increase oil tanker traffic through the Haro Strait 7 fold. This will probably be dangerously disruptive to the orcas even if there's never any diluted bitumen spill

The orcas are probably doomed :(

Overfishing?

Hypothesis: Before the latest jumps in industrial fishing in the Pacific, enough salmon could live to five years to dominate the numbers of those returning to spawn. But now, with fishing becoming more "efficient", the probability of a fish living to five years while swimming free in the Pacific has dropped to very close to zero. But some still make it two or three years. Those are all that are left to return to spawn.

On theory I have heard relates to the fishing pressure in the North Pacifci Gyre. From what I understand Chinook and other anadromous species typically make one revolution per year (it's not uncommon for US born fish to be caught off Japan and Kamchatka). With an increase in fishing pressure fish just don't live as long any more without being caught. So the one, two, and three salt fish (two salt being a fish that has spent 2 years in the salt water), are more likely to pass on there genes. Being that how long a fish stays in salt water is largely genetic it would be easy to remove those genes from the gene pool in a relatively short time. I'm sure other factors like dams without fish passage on the Upper Columbia and Elwah (two rivers known for their large salmon) also played a factor.

Additionally fish hatcheries largely select for fish that return at a younger age as they will return in larger numbers, and with such a huge amount of hatchery fish that would further drive down the average size. As would any spawning between wild and hatchery fish (although the reproductive fitness of hatchery fish is particularly bad).

> Fishermen stand next to chinooks almost as tall as they are, sometimes weighing 100 pounds or more.

This is a fish story. 100 pound chinooks have always been INCREDIBLY rare. While there are records of very few fish that size being netted or trapped, the world hook and line record is "only" 97 pounds.

And a salmon of 125 pounds would be about 62-65", certainly not "almost as tall as a fisherman." The writer should learn about the fisherman's trick of forced perspective- i.e. standing behind the fish to make it look bigger.

Hard for me to take a lot of the article seriously when they can't get a pretty simple fact right.

Uh, 62-65" certainly is "almost as tall as a fisherman"!

You think fisherman are all well over six feet tall or something?? Even if that were the case, "almost as tall" qualifies. They didn't say "as tall" without the "almost".

125 is bigger than all but maybe 2 or 3 of the biggest salmon ever caught. A 100 pound fish would be closer to 58”.

Yeah, but I was just using numbers from your post itself, not making a claim about fish sizes in the world, and 58" is still "almost as tall as a fisherman" (the operative word being "almost").

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