This is the third of four posts on the nuts and bolts of estimating wild steelhead populations, spawning success, and other key management variables. First, we covered the concepts of carrying capacity and density dependence and how habitat can be used to estimate carrying capacity. Last week’s post shifted gears to review studies that found the spatial distribution …
Science Friday: Juvenile Density, Distribution and Habitat Capacity
By John McMillan New Year, new Science Friday! Last week we looked at the concept of carrying capacity, how it is estimated, and the most important habitat factors used to come up with those estimations. This week we shift gears a bit and review studies that illuminate how patterns in fish distribution can affect assumptions about carrying capacity. Recall …
Science Friday: The habitat that steelhead prefer, and how we use it to estimate capacity of rivers
By John McMillan How many steelhead can you fit into a given watershed? Put another way, what is the carrying capacity of a given watershed for steelhead? This question, and its answer, are important for steelhead fishery managers, and anglers, as we collectively try to rebuild wild fish runs up and down the West Coast. To be clear, we …
Science Friday: The fate of stranded post-spawn adult steelhead
By John McMillan One significant way in which steelhead differ from salmon is that O. mykiss have the ability to survive spawning and try to make the journey again. This behavior is referred to as repeat spawning. Repeat spawner rates are highly variable among populations of steelhead, with rates being higher in coastal streams than among inland populations …
Science Friday: Who’s who in the Elwha after dam removal
By John McMillan We should not be surprised by steelhead and salmon rushing upstream to pass former dams. That is their nature — to push boundaries, access new habitat. Unbuild it, and they will come. And come they have in Washington’s Elwha River, where in 2014 two old dams were taken down. Not only have we observed hundreds …
Science Friday: Why are half pounders declining in the Trinity River?
When anglers dream of steelhead, they mostly fantasize about fish that have spent 2-4 years in the ocean and return to freshwater to spawn as full adults, packing four or more pounds and brutish power into their physique. However, one of the most common forms of returning steelhead in some rivers is not the adult, but the so-called half-pounder. …
Science Friday: Behavioral Thermoregulation
Most steelhead anglers know that the family of fishes called salmonidae (trout, char, salmon and whitefish) are highly sensitive to water temperature and quality. These fishes require cold, clean water to thrive. But what happens to them when water temps become unfavorable? As you might expect, they seek out places in the river that regain cool water — now often …
2017 – a Bad Year or Part of a Trend?
Ocean conditions are vitally important for wild steelhead runs — probably every steelhead angler knows this. But what does that phrase really mean? The ocean is a massive and incredibly complex system, and there are many factors out in the big blue that can influence steelhead in any given year. That is why it is so difficult to parse out …
Science Friday: More on summer and winter steelhead genetics
By John McMillan Two weeks ago we reviewed a study by Prince et al. that discovered a single gene differentiated steelhead which return immature (referred to as pre-mature in the study) to freshwater (i.e., summer steelhead) and those that return in a mature or relatively mature state (i.e., winter steelhead). Anglers have long known there is something inherently different about …
Rise of the Phoenix: wild summer steelhead in the Elwha River
By John McMillan, science director, Trout Unlimited Wild Steelhead Initiative A few years back, while working on the Elwha dam removal project, I donned a wetsuit for one of many snorkel surveys I conducted that summer. I had been snorkeling the main-stem Elwha, but that day – a crisp cool day in mid-October – I found myself drawn to …