Hi everybody, I waited as long as possible before I sent out this week’s weekly Chinook update. I was hoping run conditions would improve so I would have better news to report. Unfortunately they haven’t so this is what I have to report.
Shortly after I sent the weekly update last week (4-25-12) flows increased dramatically in the Columbia and a slug of dirty water moved through. Not too surprising the number of Chinook salmon moving over Bonneville Dam dropped off dramatically, as increases in flows - especially when they are coupled with dirty water - have consistently been shown to slow down fish migrations. Some telemetry studies have found that some fish will actually move back downstream in these types of events.
What I was fully expecting after these flows dropped and water clarity improved was the fish counts over Bonneville would rebound. Counts have come back up some, but not to the level I was expecting. This drop in dam counts certainly has influenced our models prediction of what we could expect to come over Bonneville Dam in the future (table below or click 'read more'); however, it is important to realize that these predictions can fluctuate greatly early in the run, which is where we are now.
I fully expect our projected run total to increase, but just how much is hard to tell. Flows are still high on the Columbia. They are at around 400,000 cfs and the average for this time of year is about 250,000, so this could help explain why fish aren’t coming over Bonneville like expected. Some other things that lead me to believe we still have a lot more fish to come are, we have only seen a few jacks destined for Idaho come over Bonneville, which indicates we are still early in the run. Another thing to note is if you look over the timing of runs since the construction of Bonneville Dam (1938), three of the five latest runs on record have occurred in the last 6 years which suggest maybe we are in a new paradigm where late runs are more of the norm.
I still have heard no reports of anybody catching a Chinook in Idaho which is not too surprising since we have had only 129 come over Lower Granite Dam to date. I expect we will have our first Chinook harvested by this time next week. - Joe Dupont, Clearwater Region Fish Manager