What happened to our Columbia River steelhead?
By now, you have probably heard steelhead returns to the Columbia are well below the most recent ten-year average. As a result, places like the Methow River will not be open to steelhead angling this fall.
In short, that is a bummer.
There has been much speculation about the causes for the decline and potential fear that changes in the Columbia may be signs of larger problems in the region. We too are concerned about the declines in Columbia steelhead. We also agree with other scientists that a combination of poor ocean conditions and poor river conditions for smolts are major contributing factors.
Without question, looking across the Pacific Rim, it is clear that ocean conditions are one of the most important factors influencing run sizes of salmon and steelhead. What are poor ocean conditions? For salmon and steelhead it is when there are warmer than normal water temperatures in the ocean during the time of year — spring — when steelhead are outmigrating as smolts.
Conditions are better for salmon and steelhead when there is strong upwelling of cold water during the spring. The food salmon and steelhead feed on as smolts is less abundant when ocean temperatures are warmer and more abundant when the temperatures are cooler. Accordingly, we tend to see better smolt survival during those “good” ocean periods.
At the same time, freshwater conditions in the Columbia and Snake Rivers play an important role in steelhead smolt survival. For example, research by Petrosky and Schaller (2010: Influence of river conditions during seaward migration and ocean conditions on survival rates of Snake River Chinook salmon and steelhead) found that steelhead smolt survival was reduced when river temperatures were warmer and river velocities were slower.
Basically, steelhead did not do as well when stream flows were low and temperatures were warm.
This makes sense when we consider that the 2015 spring and summer was one of the worst on record from the perspective of a steelhead. It was warm and stream flows were low. Slower velocities make it more difficult to swim through the reservoirs in the Columbia and Snake Rivers. Further, the smolting process in steelhead is strongly affected by water temperature. If temperatures are too warm, the process may be interrupted or abbreviated and consequently, smolts may not be physiologically prepared for ocean entry.
Although there is value in trying to identify the cause of the decline, there are a couple things to remember. First, the run is not over yet and so we don’t have all of the information on both fish abundance and the survival of different age classes. To fully understand the problem, we will also need to look to next year’s two-salt steelhead to see if they show the same relatively poor survival as this year’s one-salt fish.
Second, we also need to consider the context of the current run size. For instance, this year’s steelhead run size is well below the most recent ten-year average, but to date it is larger than all but one year during the five year period from 1994 (the first year hatchery and wild steelhead were differentiated in Columbia dam counts) to 1998. The mid 90’s was our most recent period of low abundance resulting in the listing of steelhead as threatened in the Columbia Basin, so this year’s run is not as bad as things could be.
Last, at Bonneville Dam wild steelhead are 164 percent of the 5-year average from 1994-1998, while hatchery steelhead are only 92 percent of the average for the same period — though hatchery plants have been reduced by about 10 percent since the mid-90s’. This suggests that wild steelhead are benefitting from the habitat improvements in the basin, changes in dam operations, and differences in fish management. It also suggests that while hatchery and wild steelhead tend to do well when ocean conditions are good, wild steelhead are more resilient when freshwater and ocean conditions are poor.
Fortunately, the run sizes in the Columbia are not indicative of a region-wide decline in steelhead. Last year wild winter steelhead returned to Puget Sound in numbers not seen in 15-25 years, depending on the river. The Nisqually escaped more than 2,000 steelhead and so did the Puyallup, which is remarkable considering both populations were down to a few hundred fish for much of the past 15 years.
The sharp reduction in the Columbia and increase in Puget Sound may reflect an emerging pattern in shifting ocean conditions. We can’t say for certain, but there is enough data to make us wonder. Figure 1 shows annual run sizes for steelhead in the Columbia River and the Skagit River, which is pretty representative of Puget Sound and is the best long-term data set for the region. We can see that both areas did pretty well in the 80’s and dipped in the 90’s. But in the early 2000’s steelhead run sizes dramatically increased in the Columbia and sharply declined in Puget Sound. The pattern reversed beginning around 2009-2010.
It is not uncommon to see geographic shifts in ocean conditions and related changes in steelhead survival. Whatever the cause, it is clear that ocean conditions can be quite variable for different stocks of fish and that ocean conditions are rarely equally productive along the Pacific Coast. This can result in fish from more northerly areas doing better than fish in more southerly areas, and vice-versa. It can also produce long-term patterns. The Columbia and Skagit River steelhead data suggest that patterns of survival may be shifting, which would bode well for anglers in Puget Sound.
Ultimately, the changes in steelhead abundance are a reminder that nature is challenging to predict and that the amazing conditions in the Columbia during the early- and mid-2000’s are, as with all great angling experiences, often fleeting. Of course, we can only speculate what the future holds. Perhaps the pattern will once again reverse. Regardless, the variation underscores that we can’t take a break from working hard to restore steelhead habitat and improve management of their fisheries. The greater buffer we provide to make it through these tough times the greater our fish and fisheries will be.