By Jenny Neyman
As much as we might wish them to, fish simply don’t talk. Though biologists and fishery managers in Cook Inlet are constantly trying to learn more about king salmon, especially those from the Kenai River, pulling a chinook alongside a boat and asking it, “Where you from?” “Been here long?” or “Where you headed?” does not elicit a response. At least, not in so many words.
But advances in genetic testing make it just about that easy to get much better acquainted with king salmon.
“It’s pretty simple anymore,” said Tim McKinley, research biologist with the Alaska Department of Fish and Game Sport Fish Division. “In this business, when there’s a change in technology there’s rapid learning that goes on about your critter of interest. It’s kind of like when they put the Hubble Telescope up there. It was a whole new leap in technology for the astronomers and physicists and everything else.”
The leap for fishery biologists came with improvements in genetic testing that led to much easier and cheaper ways to derive information from tissue samples. Twenty-five years or so ago, genetic sampling of salmon was a time-intensive, technical, expensive and deadly process.
“If you were going to take genetic samples from fish you had to kill the fish because you were taking all kinds of weird stuff — like heart tissue or kidney or liver and blood. And then, once you took that sample, it had to be preserved using stuff like liquid nitrogen,” McKinley said.
Running the genetic testing lab work could cost a couple hundred dollars per sample.
“If you needed to run dozens or hundreds or thousands of samples, it gets ridiculous,” McKinley said.
Nowadays, sampling is as quick and easy as snipping off the auxiliary — a long, pointed piece of tissue in front of the pelvic fin — putting it in a small vial filled with ethanol, shipping it to the lab in Anchorage, and running a test that costs about $25 a sample.
“Taking this little thing off a fish does not kill them. They do not even wiggle,” McKinley said.
Fish and Game technicians started amassing a repository of genetic samples from Kenai kings in 2002 and have been adding to it ever since. There are two types of sampling — baseline and mixture. For baseline collections, kings are sampled in their spawning locations, whereas mixture sampling involves collecting samples from kings outside their spawning grounds — in the river, in Cook Inlet, or even in the Gulf of Alaska — where they could be headed to any number of spawning locations.
The project began by archiving mixture samples from kings caught in Fish and Game’s test net near its sonar site in the lower river. Mixture sampling expanded to sampling sport-caught kings in the lower river in about 2005, and to sampling sport-caught kings above the Soldotna bridge in 2007.
In 2005, baseline sampling began, with technicians collecting samples from spawning kings in the Kenai River watershed tributaries that support king spawning — Slikok Creek, Funny River, Killey River, Benjamin Creek, Russian River, Juneau Creek, Quartz Creek, Crescent Creek, Dave’s Creek and Grant Creek.
Technicians also have been sampling spawning kings in spawning areas in the main-stem Kenai River, from the outlet of Kenai Lake to Skilak Lake, from the outlet of Skilak Lake to Bing’s Landing, from the confluence of the Moose River to the Soldotna bridge, and from the Soldotna bridge through the lower river.
The baseline sampling from spawning kings creates a genetic map, of sorts. Kings spawning in one location are genetically distinct from those spawning in another. There are some caveats to this, for instance kings spawning in Slikok Creek are genetically somewhat similar to those spawning in Funny River, so those two stocks get lumped together in analysis. But by and large, genetic testing can accurately distinguish between stocks, assigning them to their specific spawning location, about 90 percent of the time, McKinley said.
It takes 100 to 200 samples to establish a reliable genetic profile for each spawning location, and sampling is best done over two to three seasons, McKinley said. Some sites still need more sampling, such as Grant Creek, but most of the Kenai already is mapped.
That’s because genetic testing will assign the kings somewhere, and if baseline profiles from all the stocks represented in the sample aren’t complete, some of those fish will be misidentified. Say, for instance, 100 kings are mixture sampled in the Kenai king test-net site, and 50 of them are from Benjamin Creek, 25 are from Killey River and 25 are from Juneau Creek. If the genetic baseline profile for Juneau Creek hadn’t been established, the 25 kings in that sample would be mistakenly assigned to another baseline profile, such as Russian River or Crescent Creek.
“If you don’t have a baseline in there for an area, the analysis don’t come back saying, ‘20 percent unknown area,’” McKinley said. “It always allocates 100 percent of the sample.”
The genetic information has many uses and can be especially important in determining escapement goals. With a comprehensive map of genetic profiles, biologists can determine where king salmon are coming from.
“We can see, as an example, how many fish coming into the Kenai are from, let’s say, the Killey River, and/or how many of the kings that are harvested in the Kenai are from the Killey River,” McKinley said.
The information can be useful outside the river, as well. For the last two years Fish and Game has been mixture-sampling kings caught in east side set nets, to determine where those fish would be headed. At this point the data can’t be analyzed definitively until all potential stocks those fish could be from in Cook Inlet have baseline profiles established. Because, again, stocks may be misidentified if all the spawning locations represented in a sample aren’t profiled.
Kasilof and Kenai stocks have been profiled and work is ongoing to profile the rest of the stocks in Cook Inlet, such as the Anchor River and west-side stocks. Once that baseline work is done, the information could settle some of the thornier issues of fishery management in Cook Inlet, such as debate over the utility of restricting central district commercial fishermen in order for them to avoid catching kings headed to northern district streams. In the future, testing will be able to show whether kings caught by those commercial nets really are headed to the Susitna River, for example, or whether they’re Kenai kings.
This data could be useful even beyond Cook Inlet, with the issue of by-catch in the Gulf of Alaska. Again, all the potential king stocks of origin would need to be profiled before biologists could determine with certainty what stocks are ending up as by-catch. But that day may soon come.
“The Anchorage lab and other offices are collecting tissue from some of the other king salmon stocks on the peninsula and around the inlet to fill in the holes in the baseline, so the future of it is reaching farther and farther out in the gulf to see if and where our fish show up in other fisheries,” McKinley said.
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