By Micah True

Biologists are at work on a two-year, $200,000 radio-tagging study of Chilkat sockeye that could shed light on the mystery of precisely where the fish spawn and what they do while en route.

Although red salmon most often spawn in lakes, some Chilkat fish lay their eggs in faster moving tributaries.

"We’re trying to find in more detail where they go," said state biologist Ben Kirkpatrick. Biologists believe about 80 percent of Chilkat reds swim upstream as far as Chilkat Lake. But exactly where the others go is something the state Department of Fish and Game wants to learn.

Biologists have long known that some fish spawn in the main channel of the Chilkat River. But how many is currently unknown, and recent restrictions on commercial jet boat operations in the river have been criticized because of the lack of data.

"We really have no idea if it’s just a couple fish or if it was anything substantial," Kirkpatrick said. "We were criticized because we didn’t have any hard data. We really need to find out if this is a concern there."

Approximately 20 fish have been tagged so far this year, and about 100 will be by summer’s end, said University of Alaska Fairbanks grad student Brian Elliot, who’s working on the project.

The study has already yielded some interesting information about where fish go to spawn, if not the lake. Three of the first 12 fish tagged ended up in Little Salmon River, Elliot said.

"We knew sockeye went up there, but that’s a pretty high percentage," Kirkpatrick said. Biologists also suspect some sockeye spawn at bear flats, just upstream of the Kelsall Confluence, in Mosquito Lake and in the Tahini, Kelsall and Klehini rivers, Elliot said.

Biologists track the movements of the fish using four receiving towers stationed along the river system, aerial surveys and surveys in boats. Flying over the fish allows Fish and Game workers to pinpoint their location within about half a mile, Elliot said. Surveys from boats allow biologists to establish a tagged fish’s location within about 50 feet.

"Between those three methods, we’re getting pretty good location data," Elliot said. Receivers used to determine a fish’s location read data from a transmitter lodged in the fish’s stomach.

The method allows biologists to gather data that would otherwise be impossible to get. "It gives you abilities you’d never usually have in a turbid river," Elliot said.

Fish and Game workers at the department’s fish wheels are charged with inserting the transmitters into fishes’ mouths and sliding them down the gullet. A wire antenna protrudes several inches from the mouths of the tagged fish, Elliot said.

That method has been used in radio-tagging studies for years, Kirkpatrick said. Since the fish have stopped eating by the time they reach the river to spawn, the transmitter doesn’t interfere with their ability to survive.

"Occasionally, they do spit them out, although that hasn’t happened (in this study) yet," Kirkpatrick said. All fish tagged have continued their journeys up the river, confirming the harmlessness of the method, he said.

Another objective of the study is to see if sockeye are somehow making it to Chilkat Lake without being counted by technicians at the weir there, as biologists have long suspected, Kirkpatrick said.

"The numbers just didn’t seem to match up with what we had in the fishery and what we had in the spawning grounds," he said.

So far, at least one fish has made it to the lake without being counted by weir workers. An orange tag on the fish’s dorsal tag would’ve alerted weir workers to its transmitter, and they would’ve alerted Fish and Game, he said.

It’s unclear how fish might be bypassing the weir. Some may slip through the weir when the boat gate is lowered to allow human traffic to pass. Gaps under or at the sides of the weir also could allow fish to sneak past, or an alternate route unknown to biologists could be the cause.

"It’s entirely possible that there’s some place in there that fish can get through to the lake without going through the main channel," Kirkpatrick said. "We’ve looked for a place like that, but the salmon are better than us at finding them."

Monitoring the sockeye will give biologists information about how fish travel en route to the spawning grounds. Specifically, Elliot says the study should shed light on whether they tend to stop to rest at certain points, or if their movements in the river are less predictable.

"We’re going to see if there’s any correlation of if they just go up the river randomly," he said.

The study also will allow Fish and Game to verify the accuracy of a technique long used to determine where a fish spawns, analyzing fish scales.

Comparing historic data to information collected in this study should determine for certain whether fish-scale analysis is accurate, Elliot said.

"We can either verify or dispute what’s been practiced by Fish and Game for a long time," he said. So far, comparison of the data shows the method is accurate. "It really verifies some of what’s been done for a long time."

Another goal of the study is to gather data on fish mortality from radio-tagging. So far, none have died, Kirkpatrick said.

Next summer, Elliot said the study aims to tag about 250 fish. "We’re taking it a little conservative this year while we figure out how to use the equipment and how to run the project," he said.

Anglers catching radio-tagged fish are asked to return the tagging equipment to Fish and Game. "It’s very sophisticated electronics," Kirkpatrick said. "We’re wanting to get those tags back."

Elliot said the transmitters cost about $160 each.

So far, three tagged fish have been caught, and the tags were returned to biologists. The department is having hats made to reward those turning in transmitters from fish they’ve caught, Kirkpatrick said.

The study is funded by federal money from the sustainable salmon fund, Elliot said.