Wednesday, January 4, 2012

Steelhead Spawning, Take 1

It is a new year and we are welcoming a new brood of steelhead to Dworshak National Fish Hatchery. Today, January 4th, was our first “take” of the 2012 steelhead spawning season. We successfully paired 66 females with 54 males to fertilize approximately 442,000 eggs! Volunteers, students, and employees from IDF&G pitched in to help Dworshak Fisheries Complex employees work through a total of 438 steelhead.  There is always a lot of fun and enthusiasm on the spawning floor, especially on the first take of the season. Having healthy fish return to the hatchery to spawn affirms all the hard work we do at the Hatchery every day.

A table full of steelhead being checked for ripeness.

The spawning process is somewhat like a balancing act. We have to make sure we spawn an equal, or close to equal, number of males to female so no fish goes to waste. Typically we start by spawning males as a very ripe male can be used to fertilize the eggs from two females. A problem we sometimes encounter is males and females ripening at different rates. Female steelhead often ripen before males, and if there is no milt to fertilize the eggs we lose progeny. As an insurance policy we inject some of the males with a hormone to help them mature. This is done by staff from the Idaho Fish Health Center about two weeks prior to the first spawning.

USFWS employee, Clarice Holt, returns a "green" steelhead to the holding ponds.

Once we spawn our males we begin collecting eggs from female steelhead. Like the males, if a female is not ripe she is put back into our holding ponds and will be spawned in a few weeks. As soon as eggs are taken from a female both eggs and milt are carried to the incubation room where the eggs from one female are paired with the milt from one male. A saline solution is added to the eggs and sperm to activate the sperm and aide in fertilization of the eggs. The mixture is swirled around, and fertilization takes place in less than one minute.  After fertilization the eggs are rinsed to remove excess milt and any blood or egg shells, and then the eggs are placed in their own individually numbered tray for incubation. The eggs that were fertilized today are already beginning to develop and will be at the eyed stage in 3 to 4 weeks. They will hatch in about 6 weeks and will begin to feed in about 10 weeks. By early May the eggs we fertilized today will be about 3 inches long and will see their first sunlight as they are ponded into our outdoor burrows ponds. By May 2013 these fish will be experiencing their first taste of freedom as they make their way down the Clearwater River, into the Snake, and ultimately to the Pacific Ocean where they will spend 1-4 years before returning to the Hatchery.
Mixing milt into eggs

Brood year 2012 is off to a great start! We will continue spawning steelhead on a weekly or bi weekly schedule until we reach our egg take goal of 2.5 million eggs. A new year is a time to look forward and we are certainly looking forward to welcoming a new brood of healthy fish to the Hatchery!

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