Uncertainty on king salmon counts; Didson offers promise

As many as 51,900 late-run Kenai River king salmon may have made it to the spawning grounds in 2011. Or it could have been as few as 16,100.

That’s the range of escapement estimates provided by the Alaska Department of Fish and Game to the state Board of Fisheries at its Oct. 5 work session, underscoring the high degree of uncertainty for measuring abundance of Kenai River kings.

Conservation concerns from Kenai River Sportfishing Association in the form of an agenda change request, or ACR, to the board were the impetus for the discussion about whether escapement goals for late-run king salmon have been met in the past three years.

The next Upper Cook Inlet board meeting isn’t until 2014, so KRSA asked the board to take up Kenai River king salmon management outside of the normal three-year cycle in response to below average returns in 2009, 2010 and 2011.

The board unanimously rejected the KRSA request, 7-0, but not before a nearly two-hour discussion with Fish and Game staff in which several members pressed the department on how it is counting king salmon and the process behind a late-season decision to open up 56 hours of fishing for sockeye salmon over the Aug. 5 weekend when it appeared the low end of king salmon escapement would not be met.

That Aug. 5 announcement sparked an outcry from KRSA, which went on a public relations push over that weekend blasting the Fish and Game decision and Commissioner Cora Campbell as putting “greed over conservation” by risking king salmon goals to mop up what had already been a top five all-time sockeye harvest.

Sunday, Aug. 7, the department closed the sockeye fishery on the east side of Cook Inlet citing the 1 percent rule — which closes the sockeye season if less than 1 percent of the total season harvest is taken in consecutive fishing periods — and concern over meeting king salmon escapement.

But in response to the ACR, staff with Fish and Game produced estimates for escapement in 2010 and 2011 that were 26,600 and 29,800, respectively, well above the lower end of the goal for Kenai River kings. The escapement goal range for late-run Kenai River kings is between 17,800 and 35,700.

Fish and Game staff used a combination of five indices to estimate the escapement, and reported to the board there was a 4 percent chance the goal was not attained in 2011 and a 12 percent chance it was not met in 2010. Kenai River kings failed to meet the escapement goal in 2009.

A major component of the uncertainty for department staff in measuring king salmon abundance — already a difficult task in counting hundreds of kings among tens of thousands of sockeye — is the lack of confidence in two sonar systems previously used.

Both target-strength (amplitude of signal) and echo-length (duration of signal) sonar counters used to distinguish between larger kings and smaller sockeyes have proven unreliable with a high bias in the last two years.

The target-strength counter — the basis for escapement goals — was biased so high in 2010 that it was not used in 2011. The echo-length counter also began showing high bias in 2010, a trend that continued in 2011 even during the early run of king salmon when sockeye aren’t as abundant.

One reason for the sudden high bias showing up in the sonar counters may be declining size of king salmon (becoming closer in size to sockeye and throwing off the counters), or a greater proportion of smaller 4-year-old fish in the run compared to larger 6-year-old fish.

The shifting numbers on escapement produced confusion among the board, but based on the information provided there was little grounds to establish a conservation concern to support taking up king salmon management out of cycle.

“We’re not sure exactly about this new model they came up with,” said new board chairman Karl Johnstone said Oct. 18. “It has not had any peer review, or review by the board. With an ACR, we have to depend on the best information available. With that new information we were given, we almost had to come to the conclusion that we didn’t have enough evidence to say they had not met escapement goals, and the only way to have an ACR out of cycle would be to show it’s a conservation concern.

“With these new numbers there is no conservation concern. They’ve met their numbers, apparently. We’ll hope they’re right about the model and we’ll have some empirical data to look at (at the next Upper Cook Inlet meeting) rather than anecdotal information.”

Didson technology shows promise

Department staff told the board they will continue to use a combination of the five indices to estimate run strength as the transition continues to Didson, or dual-frequency identification sonar, a promising sonar technology that could offer much better in-season data.

Didson was developed for the military to detect enemy divers and underwater mines, and it has now become the tool of choice for in-season fisheries management. Unlike previous sonar tools that use a single or a split beam, Didson uses 48 or 96 beams to produce acoustic images that resemble an ultrasound.

Fish are clearly pictured swimming by the counters, and Didson also can differentiate between the unique “tailbeat” frequency of sockeye and king salmon.

(Go to alaskafisheriessonar.org/DIDSON.html to watch video of the sonar images. One shows the difference between king and sockeye; another video shows a seal lurking, then snatching a sockeye as it swims by.)

After a few seasons spent ironing out bugs and calibrating the Didson units, the 2011 season was the first with the Didson sonar on both banks of the Kenai River.

Staff told the board they hope to gather enough data on how the Didson counts king salmon over the next two seasons to bring revised escapement goals to the next Upper Cook Inlet meeting in 2014.

A key component of the effort is converting the old target-strength data used since the 1980s into “Didson units” so historical information that cost millions of dollars to collect can still be useful.

Some additional budget funding could also help speed the process along. ADFG needs a backup Didson, and also would like to scout for a new location to set up the Didson counters. The current location at mile 8.6 on the Kenai is subject to greater tidal influence that brings more debris and silt.

A location farther upriver would remove those issues, and because Didson is not influenced by the shape of river bottoms — unlike single or split beams that require more of a uniform surface — its performance would not change at a new site.

Ideally, ADFG needs funds for staff to scout for a better location while the current site operates, and to purchase the latest Didson equipment, which are sealed and self-contained to keep out silt and debris. The Didson transducers cost about $100,000 each.

Setnet decisions

In the interim, Fish and Game staff are now acutely aware at the public attention over how it makes decisions regarding sockeye salmon harvests that can impact king salmon. Until the Aug. 5 opener, KRSA had generally expressed support for department management decisions that included the preservation of Tuesday closures for setnetters when the management plan would have allowed for openers based on the large run of sockeye.

ADFG Commercial Fishing Director Jeff Regnart acknowledged the department could have done a better job with public relations during the discussion with the board Oct. 5. Rather than announcing 56 hours of fishing over three days, Regnart said staff should have taken it one day at a time.

“In hindsight, I think we would have conducted ourselves in a little different manner, being perfectly frank,” Regnart said. “We probably would have done it like we’d been doing it with daily periods being announced, in part because of the perception that can be given with the information at the time.”

The information at the time in early August was that sockeye escapement was not in danger of going over the upper range of the goal, while king salmon escapement was on track to miss its lower end.

At an Aug. 8 emergency board meeting conducted by teleconference, Sport Fishing Director Charles Swanton said, “it doesn’t look good,” for meeting king salmon escapement. About six weeks later, the department estimated escapement was well above the lower end of the goal.

“Those quick changes, which some board members may consider reactionary, are confusing to a lot of people,” Johnstone said Oct. 18. “It’s confusing to the board. It’s confusing to setnetters that were permitted to fish only to be told to stop. It’s confusing to in-river users. I know their challenge in counting king salmon. I’m hoping what they came up with is accurate and we do have a healthy run. I do think their heart is in the right place.”

Andrew Jensen can be reached at [email protected].

10/27/2011 - 10:12am