Incubating northern pike eggs
RIVERDALE – This year’s northern pike egg harvest went exceptionally well despite ice covering most of the state’s prime northern pike lakes.
Each year the North Dakota Game and Fish Department determines a quota for the amount of northern pike fry that they would like to stock into North Dakota waters. Biologists in the field are then tasked with gathering the eggs. That requires the setting of capture nets for spawning pike. Sometimes the process takes a week or two of continuous netting from a variety of locations. Not so this year. Fisheries crews gathered all the northern pike eggs they required, and then some, from just two locations. It took only two days.
“They went to Rice Lake in Emmons County, the first open water that we knew of. There were lots and lots of fish down there,” said Jerry Tishmack, Garrison Dam National Fish Hatchery. “The state also went to Beaver Bay on Lake Oahe. It had fewer fish but a lot larger fish. We got about two-thirds of our eggs from Rice Lake and one-third from Beaver Bay.”
Game and Fish collects fish eggs and the Federal hatchery raises them. This year’s pike egg take had a quota of 134 quarts of eggs to be delivered to the hatchery. That actual amount was 215 quarts.
“We got lots of pike, lots of big pike on Oahe,” said Dave Fryda, NDG&F fisheries biologist in Riverdale. “Beaver Bay was open. Just like everywhere there’s lots of pike, nice-sized stuff.”
While a number of the spawning pike at Lake Oahe were estimated to weigh in the teens, the Rice Lake pike were considerably smaller but more abundant.
“We’ve got lots of extra here in the hatchery,” noted Tishmack. “The request was for 134 quarts and we had close to 140 quarts that last day alone. The eggs look like they’ll average about 50 percent hatching success, which is a little below average. Sixty percent is typical.”
The quick success in pike egg taking came as a pleasant surprise to biologists who sometimes have to work longs hours at several locations to fulfill quotas. Randy Hiltner, NDG&F biologist at Devils Lake, has netted spawning pike for many years. However, with Devils Lake covered in ice, he was relieved to learn that enough pike eggs were taken elsewhere and that he could turn his attention to walleyes.
“We’ve set trap nets after late ice out before. I know two years ago we had pike running about May 5-7,” said Hiltner. “You can base some of that on water temperatures, but the photo period is important, too. Each lake is a little different though, and pike can spawn earlier or later. They like that shallow, open water and there is still time for that to occur.”
Walleyes at Devils Lake, says Hiltner, tend to spawn the last week in April. This year could be different. Devils Lake remained encased in thick ice a few days ago.
“Historically this is prime time for their spawning,” explained Hiltner. “Air temps and water temps from 48 to 52 degrees should be pretty good. Not all fish in the population spawn at the same time. There’s no definite answer for that. We don’t have all the answers. Photo period and water temperatures play a role but there is a little slop in those variables.”
One good thing, noted Hiltner, is that he can’t recall a year in which he was not able to net walleyes with viable eggs to send to the hatchery.
“It is not atypically late for walleyes yet,” said Fred Ryckman, NDG&F fisheries biologist. “It’s not that unusual.”
While Devils Lake walleyes are counted on to supply eggs for the hatchery, the middle section of Lake Sakakawea, particularly the Parshall Bay region, remains a key source for walleye eggs. For now, though, fisheries crews are waiting for open water before they can set their nets and begin the process of capturing spawning walleyes. This year’s later than normal ice out is already one for the record books, meaning it may be a few more days before any walleyes can be taken.
“Everything is going to happen at once,” said Ryckman. “We’re way behind schedule. That’s what happens when you get a late spring.”
In the meantime, water temperatures will be adjusted in the jars where northern pike eggs are being incubated at the Garrison Dam Hatchery. Cold water slows development of pike eggs. Warm water speeds it up.
“They’ll be hatching in 12 days at 45 degrees starting this morning,” said Tishmack last Tuesday. “We had them at 39 degrees for a week because it has been so cold outside that we can’t put water in our outdoor ponds.”
The goal is to hatch the northern pike and transfer them to outdoor ponds before the walleye eggs begin to arrive at the hatchery.
“We can cool the walleye eggs down and postpone them,” explained Tishmack. “But we can only wait so long to get the northerns out.”
Once outside, young northern pike fry sit idle in their rearing ponds for a period of 10 days. They’ll be absorbing their yolk sacs and adjusting to their new environment. In the meantime their food source will also be developing.
“It takes 10 days at 52 degrees before they will actually start free swimming and looking for food,” said Tishmack. “It works out good because, typically, you wait 10 days for your zoa plankton to get populated in your pond.”
This year’s northern pike request is for approximately 2 million fish. The number is down from previous years but pike populations are booming throughout most of the state. Of the 2 million, about 800,000 will be raised at the Garrison Hatchery. The remainder are scheduled to be reared at the Valley City Hatchery. The walleye fry quota is again very high.
“They are looking at 10 million again. Nine million here and 1 million at Valley City,” said Tishmack. “There’s no limit to walleyes. They’ll take every one we can make. We’ve had walleyes in every outdoor pond in the last four years straight.”