Leave it to the experts to tell your kids where babies come from -- babies with fins and tails, at least.

The Pennsylvania Fish and Boat Commission demonstrates the fish spawning process at its annual open house at the Linesville State Fish Hatchery, in Crawford County near Pymatuning Reservoir from 11 a.m. to 3:30 p.m. April 3. Plenty of activities are planned, including a show-and-tell on how biologists "age" fish, bluegill printing on T-shirts, and casting practice for kids.

But walleye reproduction is the main event, said Larry Hines, the commission's production manager for northern hatcheries.

"Most folks find it pretty fascinating, since they probably don't associate that big fish they catch with what we do here," he said. "But if it weren't for our hatchery, Pymatuning and a lot of other lakes wouldn't have walleyes."

Visitors will see fish culturists boat in from Pymatuning Lake with walleyes collected overnight in trap nets. Inside the hatch-house, they will sort the fish by gender, putting females and males into separate tanks.

"We'll then knock them out with an anesthetic, so we can handle them, otherwise they'd be thrashing around," Hines said. "One culturist will squeeze the eggs of the females into a pail and another culturist will squeeze the male sperm, called milt, into the pail. It takes two males' milt to fertilize the eggs of one female. A female walleye produces thousands of eggs."

The eggs are disinfected with iodine to prevent the possible spread of viral hemorrhagic septicemia (VHS) -- a highly contagious disease so far found only in the Great Lakes -- and then coated with a clay-based mixture to keep them from sticking to one another.

"Walleye eggs are very adhesive, and they'd suffocate if we didn't separate them in the pail," Hines said. "They're poured into jars and incubated at 50 degrees until they hatch into fry, usually 21 days later.

Randy Griffin, a Grove City angler who attended last year's open house at Linesville, found it to be an eye opener.

"A lot of kids were going 'Ewwww ...' when they 'milked' the fish, but it was simply amazing," he said. "I had no idea how they culture fish, so it was an education for me."

Linesville also produces muskellunge, largemouth bass, crappies, perch, channel catfish, paddlefish, bluegills and minnows, plus some of the steelhead stocked annually in Erie streams. Although panfish and bass spawn easily in the wild, they are stocked in some waters to help balance the food chain. Natural reproduction of muskies and steelhead is almost non-existent in Pennsylvania, so stocking them provides recreational angling opportunities that otherwise wouldn't exist, Hines said. Linesville is one of 13 state hatcheries, half of which are dedicated to producing rainbow, brown and brook trout for waters that don't support wild trout.

Linesville is open to the public seven days a week, but spawning is performed only at certain times of year, depending on when the female of a species is "ripe" for reproduction.

"Walleyes will be ready April 3 for sure, and maybe muskies, although it depends on water temperature," said Hines. "Walleyes spawn at 45-50 degrees. For muskies, it needs to be about 55."

While producing walleye fry costs a fraction of a cent, 4-inch to 6-inch fingerlings cost about a dime each. It costs the state $2 to raise a muskie to fingerling size because it grows more slowly in the hatchery, Hines said.

"And $2 is cheap compared to the $10 it would cost on the open market."

The state's fish culturing and stocking program is financed entirely by the anglers who benefit from it. No money comes from the state's general fund.

In addition to raising fish, the hatchery operates an education center with a 10,000-gallon aquarium stocked with many of the species that swim in Pennsylvania rivers and lakes.

"As soon as we open the door people make a bee line for that," said Hines. "You'll see them with their noses pressed against the glass."

Aside from fish culturing, visitors can learn how to fillet and cook walleyes, bluegills and perch. Gem City Fly Tyers, an Erie-based group, will demonstrate fly tying and casting. Boaters can talk boating safety with waterways conservation officers in the boating tent.

Hines said he expects the open house to attract 3,000 to 5,000 visitors.

Jessica Martin and her son Jack, 11, of Linesville enjoyed last year's hatchery open house so much they plan to return this year.

"There's a lot to do and it's all hands-on," she said. "They also have a fish fry and I wouldn't miss an opportunity to eat walleye."

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