Before statehood, federal fisheries officials were assigned as "stream guards" to protect and monitor commercially important salmon-producing rivers throughout Alaska. These hardy individuals would set up camp at river mouths and spend the summer attempting to visually estimate the number of salmon "escaping" upriver to spawn.
Since statehood, the Alaska Department of Fish and Game has employed a variety of more sophisticated methods to count fish, such as the weir and sonar on the Anchor River. Aerial survey is another method that's long been popular in Alaska because a single observer can monitor escapements for a number of remote streams during a single flight, making it very cost effective. Unfortunately, the accuracy of aerial survey counts can be affected by the weather, stream cover, water conditions, and pilot and observer experience. Therefore, the Homer office of Fish and Game sought to develop a reliable, cost-effective technique to improve escapement estimates where aerial surveys are currently conducted.
In 1997, Fish and Game began experimenting with video technology to see if it was possible to monitor salmon escapement at remote, clear water streams. We envisioned a system that could be easily set up, visited infrequently for maintenance and video retrieval and would reliably collect more accurate escapement data than aerial surveys. Borrowing from existing designs and making necessary additions and modifications to suit our needs, we developed a Remote Video Escapement Recorder, which we call RiVER.
The system operates under its own solar, wind or hydro-generated power, depending on each site's individual characteristics. RiVER is designed to capture time-lapse images of adult salmon as they swim over a high-contrast substrate panel fixed to the stream bottom below an overhead camera. The entire system is self-contained on an aluminum stand that can be easily assembled on the stream bank. Because the camera operates continuously during daylight hours, it is potentially capable of providing near-census quality escapement data. RiVER is also capable of providing a visual record of an area's environmental conditions (e.g., stream discharge and water clarity), along with the timing and abundance of the stream's salmon returns.
In 2002, we converted our original analog system to digital and began experimenting with satellite transmission and custom image processing software to help streamline the video review process. What we hope to end up with is a modern-day, technological version of the original human stream-guard — always on duty and never missing a fish.
For more information on this project, or salmon management, visit your local Fish and Game office at 3298 Douglas Place in Homer (behind Alyeska Tire) or call 235-8191. To learn more about the Kachemak Bay Research Reserve, please visit www.kbayrr.org.
Ted Otis is a research biologist with the Alaska Department of Fish and Game's Division of Commercial Fisheries in Homer. Mark Dickson is a fish and wildlife technician IV who works with salmon research and management.
The Alaska Department of Fish and Game's Remote Video Escapement Recorder (RiVER) in operation at Delight Creek in East Nuka Bay, 2002.
Along with protecting spawning and rearing habitats, the most important ingredient to the long-term sustainability of Alaska's salmon fisheries is ensuring that enough adult salmon "escape" upriver to spawn. We learned in the last Bay Science article how fishery managers use "emergency order" announcements to open or close fishing areas in-season according to how well salmon runs are progressing toward their individual escapement goals. But how do fishery managers know how many salmon are making it upriver to spawn?
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