Minnesota DNR Fisheries Management -- Warmwater Hatchery

>>Carl Mills: Okay, now we’re just going to dump the eggs into this tub here and that
will help acclimate them to the temperature of the hatchery. We’re just going to let
them soak here with this water running in. We’ll rinse the rest in and we’ll be ready
to jar them up here pretty quick.
Now we’re just going to grab some jars off the second battery and bring them over and
get them ready to jar up the eggs. What we’re going to do is we have these numbers on them
here and we’re going to wipe off the number. The number is going to be the date in which
we took the eggs. So I’ll wipe off that and today is the twenty-third I believe, yep,
so then we’ll write 23 on here.
So once we have the number 23 on here I’m going to take the hose and put a little water
in the jar that’ll kind of cushion the fall as we’re dumping the eggs in. We’ll get
a few jars ready here so we’ll be ready to go once the eggs are acclimated.
Okay, I’m just going to put two and a half quarts in these jars here and then we’ll
carry them over to the battery and get some water flowing through them. We usually fill
up a few at a time and carry them over there. You have to let them settle down a little
bit. They usually settle down quite a bit once you pour them in. We’re putting two
and a half quarts in each jar and there are about 125,000 eggs in each quart so there
are over a quarter of a million eggs in each jar. Just kind of shake them a little to get
them to settle down a little.
Okay, that’s about good there. Now what I’m going to do is carry these over to the
battery.
So we’ll put this…this is a stand pipe in here, this will help spread the water out.
The water is going to go right down through it. I’m going to open up my nozzle here
and we should see some water start flowing in there pretty soon. There we go. So we’ll
keep the eggs rolling and tumbling like this so they can get plenty of oxygen and each
one has a chance to make it that way. They don’t get piled up and stacked at the bottom
and stick to one another.
We’ll end up filling this whole side up here, we’ve got four jars here right now
with about two and half quarts in each jar and hopefully we’ll fill up this side and
the other side. As you can see, we’ve got this whole side filled up already. We already
have about 380 quarts in the hatchery.
Right here we have our thermometer that tells us what the temp is obviously in the hatchery.
And what I’m trying to do is match the temperature to the lake temperatures in the spring. So
right now we’re running at about 46 degrees and that should be pretty close to what the
lake is at this time. As the spring goes on we’ll heat that up and we’ll end up reaching
55-56 by the time they’re hatching.
How we regulate the temp is we have the cold coming in right here and have the hot water
I can turn on right here. This valve right here, the further I turn it towards the red
it will get warmer and I can tweak the temperature to where ever we want it to be. Right now
we have it running as cold as it can be and that’d be 46. We don’t have chillers here
so that’s whatever the water is coming right out of the city line.
Okay, what we have here is our water gauge right here. It tells you how many gallons
per minute are going in. Water is coming in right here. Right now we’re running just
over 40 gallons per minute and the more eggs we put on a battery, the more we have to turn
it up. Water is coming in the trough and it’s running down each trough and running in and
out of the jars. We have to keep a close eye on this to make sure the water is full the
whole time.
Even though the eggs are treated with formalin to prevent fungus, some eggs will still get
it. Dead and fungus-covered eggs, which become opaque and float to the surface, are siphoned
off and disposed of.
Here is a series of photos showing how the eggs change from day one until hatching. You
will notice the eggs get darker as the walleyes develop inside.
After about three weeks, tails start poking out and they begin to hatch. They are about
the size of a mosquito larva and are called fry. We typically have between a 70-80% hatch
rate.
The fry swim up towards the surface, eventually getting sucked out of the drain at the top
of the jar and ending up in the trough below.
From here they go down the drain to the next trough until they reach the pipe in the floor.
They take a ride through the pipe and finally bubble up into a tank.
This dark cloud is actually several million walleye fry.
A fine mesh seine is used to remove them from the tank.
Water is drained from the seine and the fry are poured into a bucket of water that is
waiting on a scale. One pound of fry is approximately 100,000 fish.
The fry are then transferred to a jug for transport.
The air is pushed out of the jug, a cap is screwed on, and then it is filled with oxygen.
All the fry that are stocked are recorded on this marker board.
Once the jugs are ready, they are loaded into a boat to be taken to the lake. If they are
going to be taken great distances, they are loaded into a tank of water to stay cool.
If a jug has a leak, it is taken back in and the fry are transferred to a new jug.
The fry are either stocked directly into lakes or into ponds to grow throughout the summer.
Even though we may be stocking millions of fry into a lake only a small percentage makes
it back to the angler.