Thursday, September 17, 2015

Our Beloved Salmon

Tuesday, September 15, 2015
2:27 pm

Spawning Coho Salmon on the Sol Duc River. Credit: National Park Service

Things were never looking good for our beloved salmon this year. I've been a fisherman all my life (I actually just got back from catching a bunch of albacore tuna off the Washington Coast), so I care quite a bit about how our salmon are doing. First and foremost, they are some darn tasty creatures, but they are also super fun to catch, and I think there's something special about a fish that leaves a river, travels thousands of miles in a couple years, and then heads right back to that same river. Salmon are one of nature's most fascinating creatures... and for a fish, that's saying something!

The problem, of course, has been our rivers. The journey upstream can be very tough, as salmon often have to navigate strong currents and rapids. Therefore, it is essential that they have water temperatures that are cold enough for them to not get exhausted and water levels that are high enough so that they can migrate upstream in the first place. The two are closely related; when the water is high, it means that there is a lot of cold freshwater input either from remaining snowpack, rainfall, groundwater, melting glaciers, lakes/reservoirs, or other sources. When the water is low, it is more easily warmed by the surrounding atmosphere both because there is less water to warm and the currents are often slower, meaning that the water takes more time to get to the ocean and thus has more time to warm.

Salmon prefer temperatures between 46 and 59 degrees. Once you get above this, they get tired more easily, as warmer water holds less oxygen, resulting in a variety of negative effects.  

Credit: Willamette Riverkeeper Volunteer Monitoring Program

Salmon, like many other of Earth's wonderful creatures, don't want to die. Therefore, if they sense that the river they are about to enter is, according to the Environmental Protection Agency, at least 66.4 degrees, they wait at the mouth of it for it to cool off. This can be great for fishermen at that moment, but it can throw off the salmon's cycle, making it a more difficult experience when they do go up. Think about how you would feel if you had a reservation at your favorite restaurant, but then you found out they COMPLETELY overbooked, and that you had to wait outside... for several weeks.  

I took a look at our current (9/16/2015) streamflows according the United States Geological Survey compared to average for this time of year (see them here), and found that only 29 of 226 stations in Washington had above-average streamflow. When you consider that our August was the 4th wettest on record and September has had near-average rainfall, that's pretty sobering. Ironically, one of the few rivers that is flowing higher than normal in many locations is the Columbia, which happens to be the biggest river flowing from North or South America into the Pacific. This is likely because its headwaters are located in inland British Columbia, which actually accumulated a decent snowpack this past winter. Also, the Columbia River is heavily dammed, so they are able to control how much water flows downriver. Unfortunately, this table did not have average temperatures, but some locations did have temperature measurements for the day. Most of the river temperatures were between 50 and 59 degrees, but many locations in large rivers like the Columbia and Snake were slightly above that 66.4 degree threshold. This is common for these large rivers, but if the temperatures were just a little bit higher, the fish would still be hanging out in the ocean.

So how are the fish going to fare this year as they go up to spawn? It really depends on the river. The Columbia River is forecast to have their third-largest return of Chinook salmon since 1938 and their water levels are near normal, so they should be fine. It's a different story for rivers in the Cascades and Olympics with our record-low snowpack and record-high temperatures. By the way, 6 of our past 11 months have been the warmest on record. And before anybody jumps to conclusions, it's because of our "Blob" and a persistent ridge of high pressure off our coast, not global warming. Global warming has an underlying impact that further raises temperatures, but it was not the principal reason why we broke so many records this year.

But back to our salmon. With the exception of the Skagit (which also has dams), our local rivers are much lower than normal. For example, the Middle Fork of the Snoqualmie River near Tanner was measured today flowing at 120 ft3/sec. There typical flow for this time of year is 549 ft3/sec. The Hoh River, a river on the Olympic Peninsula that gets most of its water from glaciers on the flanks of Mt. Olympus, was flowing at the rate of 519 ft3/sec today near Forks. Average for this time of year? 1,200 ft3/sec. It gets even worse when you go up north by Bellingham, where Anderson Creek's flow is 15 times less than its average.

The Hoh River. Note the blue tint due to the presence of glacial silt. Photo credit: Flickr user "Thomas"

The story is similar everywhere you look. The vast majority of rivers in the Pacific Northwest are much lower than normal and have been for the majority of the summer. 

There's also another factor: the presence of feed in the ocean. I am not a marine biologist, so I have no clue how abundant the feed for salmon has been this year. However, I do know that the amount of feed is directly related to the amount of nutrients in the water, and the amount of nutrients in the water is related to how much upwelling occurs along the coast. El Niño years generally have less upwelling than normal, thus limiting primary productivity and decreasing the amount of animal life that portion of the ocean can support. I don't know if the infamous Blob of warm water in the northeast Pacific affected the salmon, but it probably resulted in less primary productivity way out in the open ocean, as warmer ocean temperatures imply less mixing and therefore imply a more sterile ocean surface.

In conclusion, we've got a number of factors working against salmon this autumn all the way into next spring. This August was a tremendous help, and the additional rain we will see through the end of the month into October will help as well. 

But the tuna fishing's great!

Thanks for reading,

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