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Egg take: How salmon hatcheries harvest eggs

During egg take season, Trail Lakes Hatchery collects eggs and milt from a selection of fish to help produce the next generation of salmon.

by | August 11, 2023

Sockeye for egg take
Staff show off some good looking sockeye salmon. From left: Bear Creek Weir Technician Colton Isenhart, Trail Lakes Hatchery Manager Aly Crocker, Trail Lakes Hatchery Assistant Manager Troy Pierce, Bear Creek Weir Technician Hillary-Faye Hobbs. Trenton Schipper, CIAA

Late summer and early fall marks a big change at CIAA hatcheries. A new production year is beginning! In July, Trail Lakes Hatchery began conducting its sockeye egg take at Bear Lake in Seward.

This summer, staff at Bear Creek Weir allowed over 10,000 returning adult sockeye into Bear Lake. Half of these fish were female and the other half were male. These fish are known as broodstock, which we use to produce fish raised at Trail Lakes Hatchery and released into Resurrection Bay. With a successful egg take, CIAA hopes to continue providing commercial fishermen as well as the general public with this fishery.

The egg take at Bear Lake is an example of how salmon hatchery programs like those operated by CIAA get the eggs used to enhance the next generation of salmon.

It all starts early in the summer

Sockeye seen moving through the Bear Creek Weir in June and early July are not yet ready to spawn. The eggs in a female are still tightly wrapped in a membranous sac called a skein, and the milt of males is not yet free flowing. Fish in the lake have plenty of time to become “ripe,” or ready to spawn. A ripe female’s eggs will be loose in her body cavity and ready to be released.

Once we see that the fish in the lake are ripe, the excitement of egg take begins. We first collect the fish which, at Bear Lake, is done with a beach seine net. Each year, we’ve released fry in an area of the lake in hopes that they imprint and return to a fishable beach. Once we catch salmon in the beach seine that are ready to spawn, we transfer them to submerged holding pens overnight to be used the next day. 

Removing the eggs and milt

A female Sockeye gets spawned during egg take.
A female Sockeye gets spawned during egg take. Trenton Schipper, CIAA

When we remove eggs and milt from sockeye, we pay close attention to disinfection. Our staff take special precautions to disinfect all equipment used, the fish, and themselves often. Viral infections are enemy number one of hatchery operations. 

Starting with females, we euthanize the fish and dunk them in a disinfecting iodophor solution. We wipe down the bellies of females to avoid any foreign material getting in the eggs. Then, we cut open up the belly, starting at the vent. Clean Ziploc bags are used to transport fish eggs for the egg take site to the hatchery. A ripe female’s eggs will be loose in her belly and should essentially pour out of her body cavity. Sometimes staff need to give the eggs a little extra persuasion with their fingers. 

Then on to the males.

Milt is collected from as many males as females. We place the milt in small plastic portion cups. It only takes a few drops for fertilization. To get the milt out, we squeeze the base of the belly toward the anal vent. Both eggs and milt go into chilled coolers bound for Trail Lakes Hatchery to continue the fertilization process. 

Fertilizing and storing the eggs

Disinfecting salmon eggs in individual cups.
Fertilized eggs from 50 Sockeye get disinfected and water harden in iodophor solution. Trenton Schipper, CIAA

At the hatchery, we disinfect our equipment to prevent the spread of viruses to different stocks of fish. Eggs are first placed in disposable paper cups. While in the cups, the milt is poured in at a ratio of one female to one male.

A saline solution, a mixture of low amounts of salt dissolved in water, is also poured into the cups, the eggs and milt are then mixed for 30 seconds. This mixture is set aside for at least one minute. The eggs are now fertilized!

From here the eggs get rinsed and are placed in an iodophor solution to disinfect for an hour. During this hour the eggs also become “water hardened.”

Eggs will absorb the water they are in and become slightly more full in size and shape. Once the hour is up, eggs get weighed and sampled so that a total number of eggs can be determined. All that’s left to do is place the eggs in an incubator and let time work its magic.

CIAA hopes to collect enough eggs this year to continue supporting the Resurrection Bay sockeye fishery. The Bear Lake egg take goal is to collect 3.5 million eggs to raise and release back into the ocean. 

Tour Trail Lakes Hatchery

Schedule a tour of our Trail Lakes Hatchery to get an inside look at the work hatchery staff conduct raising juvenile salmon.

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