The words walleye fry — for many — conjures up thoughts of the delicious, mild-tasting meat from this toothy fish. But right now for the Wyoming Game and Fish Department, these words are part of initial work to eventually raise its own cool/warm-water fish species — including walleye. The first year proved it could be done, the second showed more success and the future looks bright for its continuation. “One year tells us we can do it, two years tells us we know we can do it,” said Lars Alsager, hatchery superintendent at the Dan Speas Fish Hatchery in Casper. Just over 54,000 walleye were raised at Speas and released in two Wyoming waters in 2020 — the first year Game and Fish conducted this work. Those walleye were stocked in Hawk Springs Reservoir in Goshen County and Ocean Lake in Fremont County. About 75 percent of the walleye raised at Speas survived to be stocked. “That’s as good as work being conducted in research,” Alsager said. “Anything over 50 percent is hitting a home run, so I guess in a lot of ways we hit a grand slam with it last year.” Thanks to the purchase of a self-cleaning larval tank, Game and Fish increased its production of walleye this year to about 100,000 fish stocked in four waters in the state: Ocean Lake and three waters in the Cody region -- Wardell, Harrington and Deaver reservoirs. Prior to 2020 Wyoming’s 10 hatcheries and rearing stations only raised cold-water fish, which includes trout and kokanee salmon. The only warm/cool-water species raised in the state prior to this work was tiger muskie, however, Game and Fish get the fry from Nebraska and do not spawn them in Wyoming. All other cool/warm-water fish stocked in Wyoming are brought in from other states through trade agreements. Most of the work to raise cool/warm water fish has focused on walleye thus far. Why? Because Game and Fish stocks about 1.2 million walleye annually in Wyoming waters.
Warm water origins
Guy Campbell, fish culture supervisor for Game and Fish, said talks about the possibility of raising cool/warm-water fish began 5 to 10 years ago. Campbell said there are two major factors why raising these fish would be advantageous for Wyoming. The first is to eliminate the potential for aquatic invasive species from entering Wyoming and its waters through interstate transport of fish. Game and Fish does its homework prior to making fish trades with other states, and the states Wyoming works with do an excellent job of providing disease-free fish. However, concerns remain that aquatic vegetation and microscopic organisms could get transported to Wyoming and eventually into its waters. “There’s always a risk and a chance something could get missed,” Campbell said. “Game and Fish puts in a lot of time and effort to protect our waters from AIS. We don’t want to be part of the problem. We want to look for ways to get long-term solutions.” The second is to have a steady and dependable source of cool/warm-water fish which gives Game and Fish stability and flexibility in terms of stocking. While the relationships with out-of-state trade partners are strong, the number of fish Game and Fish gets from those states often varies annually. For example, Game and Fish currently gets walleye from North Dakota. Campbell said North Dakota cut its walleye production this year by 20 percent. That affects the number of fish Wyoming receives. Other benefits for Game and Fish raising its own cool/warm-water fish include: shorter stocking trips, scheduling ideal times for fish releases and raising larger fish — all of which improve fish survival. Since all fish raised in Game and Fish hatcheries are already disease certified and AIS free, the fish will not have to go through the disease testing process which reduces stress on the fish.
How it works
The first step in raising these fish is getting mature male and female walleye. Last year Kris Holmes, Game and Fish spawning coordinator, and his team got eggs from six females and milt from 18 males, all of which were from Buffalo Bill Reservoir near Cody. This year they used nine females crossed with 24 males — also from Buffalo Bill Reservoir. Holmes and his crew spent eight days in April getting the walleye needed for the spawn. Female fish were gill-netted because they prefer deeper water — 20 to 30 feet — but move up to 8 to 15 feet in the evening to spawn. Male fish prefer shallow water, so they were collected at night and captured through electrofishing from a boat. Once the fish were captured Holmes gently squeezed the eggs into a dry bowl. Milt was then added from the males. About 1 to 1 1/2 cups of water was added and stirred with a feather for 15 to 20 seconds. “Walleye milt is only active for about 10 to 15 seconds, so we want to make sure that milt has the best opportunity to fertilize the eggs,” Holmes said. Then, about 1 to 1 1/2 cups of powdered bentonite mud r was added, along with 1 quart of water which was stirred with a feather for about 1 minute. Holmes said walleye eggs are adhesive and the mud prevents the eggs from sticking together during transport. From there the eggs were shipped to Speas where they were incubated in jars for 7 to 14 days before they hatched. The key to that, Alsager said, was keeping the water temperature at 50 degrees. Walleye fry are about 7 millimeters long but can feed on their own. This year Alsager said 160,000 walleye fry — the number of fry in 2020 was just more than 72,000 — were placed into specialized tanks with turbidity injections of clay and specialized spray bars to break the tension of the water. Those things were done because walleye fry must ingest air to fill their air bladders. They need the surface tension of the water broken or they don’t have enough strength to swallow small bubbles of air to fill their air bladders, Alsager said. Walleye fry also react positively to light for the first 21 to 28 days of life. Turbidity is used to refract light evenly throughout the tank as well as prevent light from reflecting off the sides and bottom of the tank. Alsager said that enabled the fry to be evenly distributed in the tank, to start eating food and, in Alsager’s words, “get their grow on.”
Once the rearing portion was complete, walleye were stocked each of the last two years in mid-to-late June and early July. In 2020 the size of the walleye stocked were between 1.3 and 3 inches long. This year the size ranged from 1.3-1.6 inches long. A challenge for Game and Fish with this project was location, not just where but how. Campbell said most cool/warm-water fish rearing units in other states are outside in ponds where natural forage is used to grow the fish. Because of Wyoming’s geographic location and the time of year Game and Fish will rear the fish, weather could make that very difficult. “Some years things may work great, but other years when those late spring weather fronts come in, we could lose all of our walleye production,” Campbell said.
Speas is the largest of Game and Fish’s hatcheries and rearing stations. A new facility wasn’t built for this trial, but modifications to an existing building were done so it could be completed indoors. An isolation facility at Speas that used to be one room was made into two. Some equipment had to be purchased and some things rearranged. This year, the purchase of a self-cleaning larval tank helped double production potential and allowed workers to evaluate the labor portion of the job.
Learning from others
Game and Fish didn’t start raising walleye on a whim, and a big factor for its success the last two years was based on the work and research by two men: Greg Fischer, assistant director and research program manager of the Northern Aquaculture Demonstration Center at the University of Wisconsin-Stevens Point, and Alan Johnson, a fish culture research biologist from the Iowa Department of Natural Resources. “They had 10 to 20 years of groundwork laid ahead of us,” Alsager said.
Johnson met Campbell and Alsager at previous fish culture meetings. At one of those meetings in 2020 Game and Fish was interested in a new recirculating aquaculture system Johnson uses with self-cleaning larval tanks, which Johnson said makes it easier to produce walleye intensively — that means between 50,000 and 75,000 fish per tank. Johnson added he’s seen about a 75 percent survival rate of walleye using this technique, which was what Wyoming recorded in its first trial last year. This year’s survival was 70.5 percent this year with the new larval tank.“The guys in Wyoming saw there was a good set of techniques out there and tried it, and I was glad to see it worked out for them,” Johnson said. Fischer has more than 30 years experience raising walleye and other cool/warm-water fish. He said Game and Fish reached out to him about the hands-on work he’s done. Fischer echoed Johnson’s sentiments that Game and Fish personnel did a good job of taking and using existing work and research. “Those guys have a really good understanding of how to raise fish,” Fischer said. “They also understand the basics and the time that needs to be invested in doing this. I think they are well on their way to doing this. I expect big things from them.”
What’s next
Campbell said he’d like to get preliminary sketches of a new facility completed this fall and possibly get designs started as early as next year. If Campbell got his wish, a new facility could be completed in three to four years. “The two big things are people and facilities,” said Johnson on the next steps for Game and Fish to take raising walleye and other cool/warm-water fish to the next level. Campbell said if Game and Fish moves forward with cool/warm-water fish production, a new indoor facility is needed. He also said Speas may be the best place to have it based on available space and water. He also said there is support from Game and Fish to continue with the trial runs. “The Wyoming Game and Fish culture section is one of the best in the country,” said Alan Osterland, Game and Fish chief of fisheries. “They are extremely proactive and innovative. The section has recognized the increased popularity of these cool/warm-water species in Wyoming and also the continued and increasing threat of AIS introductions into our state. These trials are the first step in a continued effort to provide Wyoming anglers excellent fishing opportunities and protect our state's waters.”
Walleye likely will continue to be the top priority, but other species could be added such as largemouth bass, bluegill, green sunfish, bluegill/green sunfish hybrids, black crappie and catfish. In 2020 some crappie, bluegill and green sunfish hybrids were brought in for a trial and in April of this year about 290 fish were released in the Bryan Stock Trail Pond near Casper. Game and Fish also plans to conduct a trial later this year to see if it can train largemouth bass to feed on food in a hatchery setting at Speas. How much momentum this work gets moving forward remains to be seen, but those involved are eager to keep it going. “The first year is always the greatest because there are no expectations, but now there’s a little bit of a bar and a little bit of an expectation and the pressure that goes with it,” Alsager said. “But it is really fun to get into something that’s a lot different than raising a typical trout.” Added Campbell: “To do things like this that we may not know that much about is kind of cool. We know we may have some failures, but a lot of us are geared to make this work so we can be more efficient and more impactful on the resource.”
— Robert Gagliardi is the associate editor of Wyoming Wildlife.