Here’s some salmon video footage superior to what was posted a few months ago. These clips were shot in the last few weeks.
First, some adult Chinook resting on their way up the North Fork of the Chena:
Juvenile Chinook feeding:
Juvenile Chinook versus the shockwave from an airboat:
All the videos are much lower-quality than the originals due to YouTube’s high file compression. To get a sense of the original HD video, here are some full-resolution stills captured from the HD video. Click a picture to see it full-sized.
Adult Chinook in the North Fork of the Chena, with a grayling and a whitefish in the foreground.
Juveniles foraging in the North Fork:
And in the main stem Chena:
Each of these videos and stills comes from a pair of side-by-side Sony HDR-SR12 video cameras in underwater housings with special wide-angle ports. Using two fixed cameras and some calibration equipment allows us to analyze the positions of these fish in 3D on the computer. That enables us to precisely measure their lengths, feeding positions, spacing, and many other scientifically interesting attributes.
Three to six inches of rain fell in the Fairbanks area last week, the highest amount many places have received since the great flood of 1967 (which was much more severe). It came with little warning, and we suffered some equipment losses, but we also decided to take advantage of the opportunity to see how the flood affects the condition of juvenile Chinook salmon. With parts of Fairbanks about to be declared a disaster area, three of us drove up the Chena to see what our study area looks like when it’s roaring at 8,000 cubic feet per second — enough flow to cover a football field with eight feet of water in less than a minute. It’s bank-full on the high, cut-bank side in most places, and the gravel bars are all covered up.
First, here’s what one of our pools looked like in May during the peak of the spring snowmelt runoff:
And here’s the same spot during this flood:
Despite the high water, we managed to catch a few juvenile Chinook at the site above and gather information about their condition. At least some of them have weathered the storm pretty well. Some of our equipment (in this case, an insect trap tied to a log “above” the river) did not fare so well:
The water was beginning to creep out of its banks in places where the banks are a bit low:
Here’s the view downstream from the first bridge over the Chena on Chena Hot Springs Road, at what’s usually a popular gravel bar for camping and launching boats:
Even the eagles look bedraggled.
The North Fork is falling and clearing much faster than the main stem. The high-water mark was about a foot higher than the level in the picture below. The tree is new.
It’s been a while since the last update, because we’re all out on the river all the time, or in lab processing samples and tinkering with equipment. We’ve all had our setbacks but the project is generally going well.
From July 24th to the 27th, I floated 50 miles of the Chena in a cataraft. I stopped in prime locations to shoot stereoscopic, high-definition digital video of foraging juvenile Chinook salmon, which I’ll use to analyze the ways that habitat and competition affect their foraging success. It took months of trial-and-error customization of the video equipment, but I finally got many hours of ideal footage for my analysis. This post simply chronicles the trip, and the fish footage will take a while longer to process, but you can expect to see it on the website soon.
The raft fit all my gear… barely.
Much of it gets unloaded at every data stop:
I spent a lot of time at huge logjams, which seem to be the most important Chinook habitat on the upper Chena. At this one, the fish live deep in the back of the logjam:
Here’s more Chinook habitat. The orange flag marks the top of the handle pole on my camera mount.
Spending 72 hours on the river allowed me to both better absorb the “big picture” and pick up on some little details I might otherwise have missed. For example, I learned that many juvenile Chinook are now venturing far from cover to feed late in the evening, either because they’re safer from predators or because there’s enough food to justify the risk (or both). This isn’t completely unexpected, but such behavior was seemingly absent early in the summer when the fish were smaller, and the timing of its development may be worth further study. Here’s a photo from one such site, where the fish were surface-feeding on tiny midges:
It’s hard to spend so much time on the Chena without some golden photo opportunities, and I didn’t pass them up. Enjoy the moose, eagles, baby mink, and scenery:
Here’s a sample of the data being used to guide the selection of study reaches. These ArcGIS maps show the distribution of juvenile Chinook salmon in the Chena River in the spring (mid-June) and early fall (late August) of 2007. Each dot on the map represents fish counts in a 50-meter stretch of river. Big dots mean more fish, but dot size is not directly proportional to the fish count (or else some of the dots would have been huge). Counts were spaced at 5-km intervals.
Baited minnow traps and unbaited snorkelers were used to count fish. Interestingly, the snorkelers were far more successful in the spring than the minnow traps, and were almost useless in the fall. They were cold both times, and whined occasionally throughout.
Because these different counting methods are not equally effective, it’s more useful to compare the patterns of distribution between spring and fall than the actual number of fish found at each site. Remember, these are raw counts, not estimates of the total fish population at the site.
Spring (trap + snorkel counts):
Fall (traps only; snorkel counts were negligible):
In the lab, these data are being cross-referenced with other relevant numbers, like aerial redd counts. Those maps will get posted later. The most evident pattern is a downstream shift in distribution in the fall. A few of the several hypotheses to explain this pattern include:
The slightly warmer temperature downstream is more favorable for growth.
The lower water clarity downstream offers more protection from predators.
A major mid-summer flood carried most surviving fish downstream.
The study will hopefully reveal which of these (if any) explains the downstream shift.
Update August 1, 2008. New observations suggest there may not actually be a downstream shift. We used the same methods and sampled similar habitat in the upper and lower river in 2007, but lower-river fish may be more inclined to utilize that habitat than upper-river fish. We don’t have conclusive proof either way, but this possibility is noteworthy.
Underwater video is going to play a huge role in Megan’s and my projects. Last fall we went out and tested the first and simplest of several video cameras we’ll be using, an Aqua-Vu DVR made for ice fishing, which I’ll be setting up with auxiliary batteries to do lengthy surveillance of juvenile Chinook schools. We found some salmon in a very large, dense logjam and shot these videos:
This year we’ll be using higher-quality cameras in stereoscopic setups to do 3D analysis of fish lengths and positions, utilizing and advancing the methods described in these two papers:
Hughes, N. F., Hayes, J. W., Shearer, K. A., & Young, R. G. (2003). Testing a model of drift-feeding using three-dimensional videography of wild brown trout, Salmo trutta, in a New Zealand river. Canadian Journal of Fisheries and Aquatic Science, 60(12), 1462-1476.
Hughes, N. F. & Kelly, L. H. (1996). New techniques for 3-D video tracking of fish swimming movements in still or flowing water. Canadian Journal of Fisheries and Aquatic Science, 53(11), 2473-2483.
Back on August 2nd, Sam Decker did a helicopter flyover on the Chena to count and map adult Chinook salmon redds. I rode along to take photos of the spawning sites (and other interesting features) from the air. Because I synced the camera’s clock with the clock on my GPS, a little post-processing enabled me to place all the pictures precisely on a map. You can browse the interactive map at Flickr.
Here are some highlights. Notice the spawning Chinook on their redds in the top/middle picture, and the large woody debris piles in the pictures on the right, which seem to be especially important habitat for juvenile Chinook.
We’re using these photos right now, along with plentiful GIS data about fish abundance, to narrow down our potential study reaches for this summer.
This is a project blog for a new (started in 2007), comprehensive study of the ecology of chinook salmon in the Chena River, a major spawning tributary in the Yukon drainage in interior Alaska. We’re trying to better understand and quantify how factors like water level, invertebrates, and woody debris influence the salmon population. The study is mostly being undertaken by several graduate students at the University of Alaska - Fairbanks under the supervision of Dr. Mark Wipfli, Dr. Nick Hughes, and Matt Evenson of the Alaska Department of Fish & Game. We are funded by the Arctic-Yukon-Kuskokwim Sustainable Salmon Initiative. There are many other significant contributors and collaborators.
This summer we’re testing methods and refining logistics for next summer’s rigorous data collection. We’ll be using this blog to share our activities with the public and fellow scientists.
