Collecting 100,00 sturgeon eggs

The call came at 8 a.m. on a Sunday, June 20. I had been waiting all weekend for the phone call, half expecting it to be in the middle of the night. A female sturgeon was ready to spawn. I rushed down to the Kootenai Tribal Hatchery to see the process firsthand.

The female started releasing eggs at 5 a.m. but the fisheries technicians let her ovulate for several hours before they began the egg-collecting process.

Corralling the 170 pound, 7 foot, 10 inch sturgeon into a sling was exciting to watch. Amid some splashing, she was maneuvered into it and quickly transported to the adjacent building. 

Still in the stretcher but partially submerged in a smaller tank of water, the egg collection began. The eggs are stored in the female’s belly, constituting ten to twenty percent of her body weight. As the eggs ripen, they move down the belly and exit through the ovarian duct.

No incisions are made on the female to release the eggs, which is done at some hatcheries. Instead of a caesarean section, the technicians gently push the eggs down the belly. As they squirt out in a steady stream, they are collected. 

Around 100,000 eggs were collected from this female. The number of eggs collected varies depending on the size of the eggs. Her eggs were slightly larger than the average size, so there were fewer. One female that already spawned produced 180,000 eggs.

All the eggs are not collected at once. Since the eggs ripen as they move down the belly, they need time to ripen. The technicians collect eggs about every thirty minutes, so the whole process can take four hours. After egg collection is finished, the female is released back into the river, where she will release any remaining eggs.

Once collected, the eggs are transferred to large metal bowls and gently stirred with a feather. A feather is used to stir the eggs because it is delicate enough not to hurt the fragile eggs. The eggs are then fertilized with milt (sperm) previously collected from males in the river.

The eggs need continuous stirring because each egg is surrounded by an adhesive. Left unstirred, they would become one large mass.

In the river, the adhesive allows the eggs to adhere to the rocky bottom and not be swept downstream. In the hatchery, they cannot be clumped together because the eggs in the middle would not receive the oxygen they need.

Therefore, a solution of Fuller’s earth, a claylike earthy material, is added to the eggs to break down the adhesive. The eggs are stirred for forty-five minutes to two hours and then they are incubated.

The Kootenai Tribe has been doing this every year since 1990. At first, the process was done in a boat on the river according to Jack Siple, a Fisheries Technician who has been there every year. Eggs were collected the first few years just to see if they were viable (fertile).

Biologists have known since the 1960‘s that the sturgeon hasn’t been reproducing successfully. Once it was known that the wild sturgeon were producing fertile eggs but they weren’t surviving, the hatchery was built in 1991. 

Since 1990, the hatchery has collected 8.4 million eggs from 89 females. Milt has been collected from 134 males to create 156 different sturgeon families.

Siple was quick to mention that if it wasn’t for the College of Southern Idaho and UC Davis and their help in the beginning, the process would have been dead in the water. “They showed us how to do this,” said Siple. “There have been lots of contributions to the program.”

Currently, the Steve Patton and Wendy Lawrence from the University of Idaho are helping establish a sperm bank for male white sturgeon. The sperm bank is an “insurance policy” according to Patton in case males are not available when the females are spawning or if the males die before they are sexually mature. The sperm gene bank will help insure genetic diversity from the males.

The process of cryopreserving sperm has been accomplished with trout and salmon but not white sturgeon.  “Nobody has successfully frozen white sturgeon sperm,” says Patton.

White sturgeon sperm is significantly different than trout and salmon sperm. The cell size of sturgeon sperm is 12 times the size of trout sperm. According to Patton, the larger the cell size, the harder it is to freeze successfully.

After the fisheries technicians collected all the eggs they needed, the extra was given to Patton and Lawrence in an adjacent room. A tub of water with rows of petri dishes was set up and ready.

They had previously collected milt from the three male sturgeon in the river and froze it. They used four different freezing techniques because they are still experimenting with the best method.

At first they focused on motility of sperm after being frozen. In trout and salmon, more motility means better fertility. However, Patton and Lawrence discovered that in white sturgeon more motility equals less fertility.

Each year they have a six to eight week window to conduct their experiments based on what worked in prior years. With the petri dishes ready, they carefully mixed 100 eggs with thawed milt and added it to the petri dishes.

Patton said they don’t use a de-adhesive because they have a small quantity of eggs and the adhesive helps the eggs adhere to the petri dish. They will know within 12 to 72 hours if the eggs are fertile.

“We are encouraged now. We had our first hatch this year after six years of trying,” said Patton. 

In nine days, any fertile eggs will hatch and in one-and-half weeks the larvae will be about one-inch long. During the first three weeks of life, they use their remaining yolk sac for nutrition.

Some of the larvae will not stay at the hatchery that long. Only 3,000 of the 100,000 larvae will remain at the hatchery until they are a year-and-a-half-old. The rest will be released back into the river when they are two- to four- days old.

Allowing some of the juvenile sturgeon to be released at a larger size removes the predation factor. The larval sturgeon released do not have a full armor plate and are more susceptible to predation.

There are many unknowns when it comes to the white sturgeon. “We are still learning,” said Eric Wagner, Fisheries Technician. “The sturgeon are all unique, all individuals. This is a unique function of fisheries: having a hatchery for an endangered species. We are ensuring the future of this species.”

Siple echoed in approval, “I enjoy doing this to keep this species going, to keep it from going extinct.”

Tours of the Kootenai Tribal Hatchery are available on Tuesdays and Saturdays at 1:30 p.m.