The Richardson Clearwater, our grayling study stream, is difficult to access. Its much better-known big brother, the Delta Clearwater, holds as many or more big grayling and there’s a boat launch right on the river. My main reason for choosing the smaller, more remote stream is that I thought the Delta might be a little bit too big, too swift, and too deep for us to place our cameras near the fish to record their feeding behavior.
However, I hadn’t actually seen the whole river myself. So I was pleased when the ADF&G biologist in Delta Junction invited me to visit the Delta Clearwater with her on August 1, 2014, and see if it might be a better fit for our study.
We navigated the river as far upstream as we could, up two different forks.
Ultimately, I realized that my initial reasons for choosing the other river were correct. The Delta Clearwater was very much like our study stream, except that it was very difficult to find any place to set cameras on grayling without the cameras (or me) getting swept away in the icy current. But it was very good to gain this confidence that we left no stone unturned in choosing the ideal sites for our study.
On July 30, 2014, I accompanied some scientists from Mark Wipfli’s lab at UAF on some of their fieldwork on the Chena River, where they are also studying Chinook salmon ecology. I hoped to learn something from what they’ve found, and vice versa.
We floated a section of the upper river setting minnow traps and gathering diet samples. We particularly focused on off-channel habitats, which may be important to the fish, especially in high-flow years.
These habitats aren’t a focus of our study because the fish in them have to cruise feed (swim around searching for food) instead of drift feeding. But it’s important to know what else is going on in our study system. And not just fish activity…
Working along the Chena for years during my Ph.D. research, I never once encountered bear or wolf tracks, although both species live in the area. It was a treat to find the well-preserved tracks of a bear and a wolf just a few feet from each other on sandbars just a short distance up one of the Chena’s pretty little tributaries.
An eagle watched over us, too.
There was also, at one point, a thick emergence of midges. The larvae and pupae of these insects are a major food source for juvenile Chinook salmon in the river.
It was a beautiful day to be out on the water in Alaska and a benefit to both our projects.
On July 26th, 2014, Gary and I took a short visit to the upper Chena River. We were checking on a study site I used during my Ph.D. research to make sure it’s still ideal for the kinds of observations we’re doing on juvenile Chinook salmon.
We only saw a few adult salmon, including this one that was well on its way to fertilizing the ecosystem for next year.
We found some juvenile Chinook salmon in the big logjam as expected. However, they were few and far between compared to past years. The river had been flowing extremely high for most of the year, and the relative lack of fish anecdotally agreed with one of the hypotheses proposed in my Ph.D. dissertation — that the juvenile salmon don’t do very well during high-flow years.
One of the ultimate aims of our project is to help figure out what it is about these mainstem Chena habitats that allows them to support so many fish in low-flow years, and why the fish do so poorly by comparison in high-flow years.
On July 25, 2014, Gary and I took our first trip to our grayling study stream along with our collaborator at ADF&G. Our goals were 1) to figure out which stretches of the river will be most suitable for our study, 2) to test our methods for pumping the stomach contents of grayling, and 3) get to know the boat we were borrowing.
We were able to catch enough fish to get some diet samples, which we will be sent back to the lab in Georgia to test and practice processing methods.
The extraction of diet samples, technically called “gastric lavage” and less technically called “puking” the fish, went fairly well. We did identify some possible improvements in our methods.
The scenery was outstanding, a reminder of how lucky we are to do part of our jobs outdoors in Alaska.
We accomplished all our objectives for the day.
Testing a new understanding of drift-feeding fish behavior.