Fish fix: Department changes sonar counting procedures

Posted: Tuesday, July 06, 2010

The Department of Fish and Game on Friday announced changes in its sonar counting procedures for Kenai River salmon.

Department commercial fisheries biologist Jeff Fox said that initially, all estimates from a new sonar system were decreased by about 30 percent to fit the current numbers to escapement goals based on an old system that undercounted sockeye.

Fox said that the estimates didn't take into account that the allocation of 150,000 sockeye to sport fishing is based on actual fish taken out of the water, instead of sonar estimates. The department will convert 82.4 percent of the sonar counts from the current DIDSON system's numbers to mirror previous Bendix system estimates, but won't adjust the other 17.6 percent, which is proportional to sport fishing's slice of the escapement goal.

Lowering the numbers, without taking into account the sportfishing allocation, increases the length of time it takes to reach the escapement goal, which was effectively raised by 60,000 fish, the department estimated. Escapement numbers factor in to management decisions made by Fish and Game.

Mark and capture studies showed that the Bendix system undercounted fish by an estimated 40 percent, whereas the current DIDSON estimates "show no consistent bias" high or low, according to the department biologist Mark Willette.

"Some were lower, some were higher," he said.

The timing of the public meeting held to discuss the change -- 6:30 p.m. the Friday before the holiday weekend -- irked many fishermen in attendance.

"It's like a politician holding a press conference on a late night before a holiday weekend," said guide Adam Reid. "You go in expecting bad news."

President of the Kenai River Professional Guides Association, Dave Goggia, thought the public meeting was ill-timed because fishermen are busier once salmon are in the river.

"Sometimes they wake up 4:30 in the morning during the season," said Goggia. "It's tough to wrap their brains around the information when they're tired."

Fox said that the department had known about the conversion process for some time, but that the effects of the sport fishing allocation hadn't come to its attention until recently.

The Bendix displayed data in a wave format, according to a presentation by the department, but the new system shows sonar images of fish swimming in the river. This allows the department to determine which way the fish are swimming, said Fox.

Meeting attendees called for an independent study to check the accuracy of the DIDSON system. A few suggested using fish wheels to verify sonar counts. Fox said that the fish wheels help determine the proportion of fish species swimming in the river, but don't serve as reliable counting devices.

Willette said that the rapid speed of the glacially-fed rivers adds another challenge to counting fish.

"I can't find a system that counts every fish in the river," said Fox. "It doesn't exist."

Tony Cella can be reached at

Subscribe to Peninsula Clarion

Trending this week:


© 2017. All Rights Reserved. | Contact Us