Sockeye egg collection aims to supplement stock, maintain diversity

ANCHORAGE (KTUU) - Each year thousands of sockeye return up the Kenai River to spawn in Hidden Lake. Of those returning fish, several hundred will pass on their genetics with the assistance of the Trail Lakes Hatchery.

"We're looking for about one and one quarter million eggs - roughly 540 females that we need for our brood stock," Trail Lakes Hatchery manager Kristin Bates said.

Each stage of a salmon's life is full of threats to survival. Very few of the over a thousand eggs a female will lay will hatch. Eggs collected and fertilized at the hatchery can make it through the first phase of development with about a 90 percent success rate.

Workers at the Trail Lakes Hatchery remove eggs from female salmon (Sept. 19, 2019)

The eggs taken from the sockeye at Hidden Lake will be released as unfed fry. Last year, Cook Inlet Aquaculture Association, which operates Trail Lakes Hatchery, released 1.2 million unfed fry into Hidden Lake.

Although the the project supplements the wild sockeye stock, there are other factors managers must consider other than the grand total of released fry.

Each year, a team of CIAA employees collect hundreds of carcasses from each region of Hidden Lake. Otoliths, which are small ear bones, are extracted from the fish. Otoliths can tell biologists much about a fish including its age and sex, and those that are developed in hatcheries bear markings that identify which hatchery it came from.

CIAA collects otoliths from carcasses in each region of Hidden Lake and analyzes which area has the greatest proportion of wild fish. Fish in that area are used for the following year's egg take.

Workers remove otoliths from the heads of salmon at the Trail Lakes Hatchery (Sept. 17, 2019)

"We are trying to not get second generation hatchery fish into the hatchery. So if it is a wild otolith it was a progeny that was created here in the lake, and so that parent will contribute to the genetics of the fish that we have at the hatchery, and those that are coming back as well," Bates said.

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