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Necessity spawns new tools for fisheries management

Posted: July 1, 2011 - 10:22am
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Steelhead salmon
Steelhead salmon

The Kenai Peninsula supports approximately 44 percent of Alaska’s sport anglers but represents less than two percent of the state’s land area. The world famous Kenai River single-handedly has supported over 20 percent of the state’s total anglers between 1995 and 2005. Needless to say, a lot of fishing takes place on the Kenai Peninsula.

The fishing season on the Peninsula typically begins and ends with anglers congregating on the icy river banks between April and November. Chinook, sockeye, and coho are the primary salmon species targeted by anglers between May and November with rainbow trout, Dolly Varden, and steelhead encompass the majority of the catch-and-release fisheries. Several ice fisheries during winter are largely utilized by local residents, in contrast to the heavy tourist use during spring, summer and fall fishing seasons. To top it off, commercial, personal use, and subsistence fisheries add to the mix and coincide with many of the sport fisheries. Obviously, managing fish resources on the Kenai Peninsula is complex due, in part, to the fishing pressure by different user groups competing for the same resources — which is why these stakeholders often demand high levels of accuracy and precision in management decisions made by state, federal and non-government organizations.

Despite the persistent fishing efforts from all users, and extensive management and research studies carried out annually, several fish populations on the peninsula remain poorly understood. This is largely due to the diversity of fish populations that occur throughout the peninsula and the high costs associated with conducting monitoring and assessment studies in complex river systems like the Kenai River. Because of these challenges, fisheries managers are constantly seeking innovative methods to gain new information and build upon prior knowledge to better manage populations. A great example of novel technology is the development of underwater video systems to monitor fish populations on the Kenai Peninsula.

The U.S. Fish and Wildlife Service’s Kenai Fish and Wildlife Field Office (KFWFO) began experimenting with underwater video nearly ten years ago to address fish passage concerns at a remote fish weir located on a tributary of the lower Yukon River. As with many new technologies, there were bumps in the road. Since then, underwater video systems have been refined and are now an important tool for monitoring fish runs. These systems are currently being used by numerous agencies throughout Alaska.

Here on the Kenai, the KFWFO has incorporated video technology into several monitoring and assessment projects, focused primarily on collecting abundance and run-timing data on salmon and steelhead populations. Our underwater video systems operate in conjunction with fish weirs, and the primary reason for using this new technology is to allow our office to carry out more projects with fewer staff and dollars.

Standard components of our system include a sealed box to house the video camera and pond lights, a fish passage chute, a digital video recorder equipped with motion detection software to record video images, and a fish weir. We also incorporate fish traps to collect age, sex, and length information, and use microwave technology to monitor remote sites more effectively. Remote video systems are powered by a combination of solar and thermoelectric energy.

The advantages of underwater video are significant. First and foremost, we save a lot of money over the long-term. It takes fewer people to operate a fish weir equipped with an underwater video system than a traditional weir. The reason is that fish passage recorded as digital video files can be compressed with motion detection software and fast forwarded. For example, 24 hours of fish passage can be reviewed in roughly 2.5 hours from videography, saving 21.5 hours of personnel time! This essentially allows us to do more with less.

Underwater video systems also benefit us in other ways. The systems are easily integrated into new or existing research projects and can be moved with minimal effort. The artificial lighting enables us to record unobstructed fish migrations 24 hours each day, seven days a week. Passage of fish at a traditional weir site can be fragmented because weirs are usually only operated during daylight, preventing fish migration at night.

The system also allows us to record clear images, even through turbid water that typically occurs during spring run-off or rain events. Traditional weirs may be inoperable under these circumstances because fish passage can be either completely blocked or go uncounted, leaving potential gaps in escapement estimates.

The video system virtually eliminates this problem as it continues to record and enumerate fish passage, resulting in more accurate escapement estimates. It also allows us to collect more inclusive biological information such as sex and length compositions for each species, or determine the contributions of hatchery and wild salmon based on the presence or absence of an adipose fin, all without handling the fish.

We have also incorporated microwave transmissions into some of our remote projects. Microwaving video signals from multiple remote locations to one receiving point reduces power requirements at the remote sites and minimizes travel to each location, ultimately reducing personnel needs and our carbon footprint. By doing this, we can receive information in nearly real-time to improve harvest management. Microwave technology has also created valuable opportunities for outreach and education.

Our success using underwater video has created partnerships and collaborations with many agencies and private landowners. It has enabled us to maximize our work force and monitor previously unobserved fish populations with minimal disturbance. With new and improved information, we are able to make better decisions as fisheries managers.

Ken Gates is a U.S. Fish and Wildlife Service fishery biologist at the Kenai Fish and Wildlife Field Office in Soldotna. Visit http://alaska.fws.gov/fisheries/fieldoffice/kenai/index.htm.

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