Glacier Bay National Park Ponders High-Tech Method for Important Salmon Study

Fishing in the Bartlett River at Glacier Bay NP. NPS photo.

How's the salmon population doing in Glacier Bay National Park? With increasing fishing pressure, it's an important question, so the park is proposing a high-tech, low-impact method to gather some key information from the Bartlett River. It involves a location in designated wilderness, and the park is inviting public input on the idea.

The Bartlett River is a popular recreational fishing destination in Glacier Bay National Park, and based on two-fold increase in angling effort over the past decade, it's likely that the harvest of sockeye and coho salmon has also increased.

That fishing pressure is expected to grow even further when the Alaska Marine Highway System begins regular weekly ferry service to nearby Gustavus next summer, and there could be additional impacts on angling from new regulatory changes to the charter halibut fishery.

How much additional harvest can the Bartlett River sockeye and coho populations sustain?

That's an important question for the long-term health of the salmon population, the larger ecosystem and for anglers, and the park is candid about the answer: "We don't know, but we need to find out."

The NPS has been studying Bartlett River salmon for several years, attempting to estimate salmon escapement (the number of adult salmon that manage to reach their spawning grounds).

This isn't a case of frivolous research, but important data which can be used to make decisions about managing an important park resource. Because the number of sockeye and coho salmon spawning each year within this river system is not well known, this information would provide a baseline against which future changes in fish abundance can be compared and overharvest avoided.

Gathering the information is a challenging task. Turbid water quality and poor visibility, especially during fall rains, make visual fish counts very difficult. Furthermore, in these days of tight funding, conducting fish counts the old-fashioned way by stationing a human observer at a remote location day after day isn't a very efficient solution.

Better methods to gather the necessary information are available, so the park is proposing a high-tech and low impact solution: a portable DIDSON (Dual frequency IDentification SONar) unit installed directly in the stream. According to the park, "DIDSON sonar, in contrast with other methods, is the best alternative to estimate escapement because it works in poor visibility, doesn’t delay fish migration or aggregate fish (enabling excessive predation), and minimizes impacts in park designated wilderness."

The equipment records “near video” quality images that can be accurately recorded as fish pass by the sonar "camera." A laptop stores all data until biologists can review the images and fish can be identified and counted. Power for the equipment is provided by "a clean, quiet, 65 watt EFOY fuel cell." http://www.efoy.com/en/fuel-cells-technology.html

The park is proposing a four year study (2011-2014); the equipment would be put in place from June through October and removed the rest of the year. The sonar device would be installed about two miles upstream from the locations where most angling activity occurs, so few visitors would be aware of the equipment's presence.

This seems to be a pretty straightforward idea, but the site for the proposed study is located in designated wilderness. As a result, the park will complete an Environmental Assessment (EA) analyzing potential effects of the installation, and the staff is currently inviting public comments.

A park spokesperson noted, "Potential issues to be discussed include wilderness quality and character, impacts to Coho and sockeye salmon, impacts to visitor use and quality of experience, concerns over equipment maintenance and operation, and protection from wildlife." The EA will also analyze other alternatives to use of the sonar equipment.

The staff will be preparing the EA over the next several months, and a 30-day public review of the environmental assessment could take place by March, 2011. However, before they begin work on the EA, the staff is "asking for your comments and ideas on this proposal so they can be considered early in the effects analysis process" for the EA. Your comments will be most useful if they are received by January 15, 2011."

Whether you choose to comment or you're simply curious about the idea, you'll find a photo of a similar DIDSON device, a map of the proposed location, and a few more details about the proposal on this NPS website.

You can submit comments on-line via this link, via e-mail to or by mail to Glacier Bay National Park and Preserve, P.O. Box 140, Gustavus, AK 99826.