A Different Kind of Hatchery
Ennis National Fish Hatchery is different from most other hatcheries. Most hatcheries produce fish of various sizes and then stock these fish in public lakes and streams, providing anglers with hours of fishing fun. Ennis Hatchery, however operates as a broodstock hatchery.
Rainbow trout eggs
Photo:USFWS
What is a broodstock hatchery? A broodstock hatchery specializes in rearing fish to adult size, then taking the eggs from those fish, incubating them, and shipping them to production hatcheries where they are hatched and the fish raised to stockable sizes.
Ennis NFH is the largest facility in the Service’s National Broodstock Program, and is one of only two rainbow trout broodstock hatcheries in the nationwide federal hatchery system. The hatchery is currently an integral part of the National Broodstock Program, producing about 20 million rainbow trout eggs annually for research facilities, universities and federal, state and tribal hatcheries in 23 states.To meet the trout production demands, Ennis NFH facilities include 38 hatchery tanks, 48 circular tanks, and 36 raceways.
Blaine Springs - It’s the Water!
Sometime in the geologic past, disturbances in the earth’s crust created an area where pure, disease-free, clean water bubbled from the ground. Today, Blaine Springs flows at a rate of 15,000 gallons per minute. Imagine pouring 240,000 glasses of ice tea every minute. That is the amount of water that comes out of the ground at Blaine Springs 24 hours a day, every day of the year.
Blaine Spring
Photo:USFWS
Blaine Springs is a very dependable water source. Only one decrease in flow was ever recorded, and that was in the spring of 1993 after several years of drought. April and May of that year resulted in abnormally large amounts of rainfall and the Spring resumed its normal flow. The water is a constant 54 degrees F, an ideal temperature to nurture trout.
After passing through Ennis Hatchery, Blaine Springs water is used for irrigation by several ranches.
Broodstock
Rainbow trout fingerlings
Photo: USFWS
Broodstock are adult fish that produce eggs and sperm. Six different strains of rainbow trout broodstock are cultivated at Ennis National Fish Hatchery. The strains are named for the locations from which they came.
- McConaughy (Nebraska)
- Eagle Lake (California)
- Shasta (California)
- Erwin (Tennessee)
- Fish Lake (Utah)
- Arlee (Montana)
Some of the eggs from each strain are hatched and reared at Ennis for future broodstock. They mature at 2 or 3 years of age and are kept for spawning another 2 or 3 years.
Geneticists are hired periodically to monitor the genetic variability of the broodstock using a process called electrophoresis ( identifying amino acids within the fish). When monitoring shows that genetic variability is deteriorating, eggs or sperm will be shipped to the Hatchery from outside sources to restore genetic variability of the stock.
Broodstock at Ennis National Fish Hatchery may grow 32 inches and weight 25 pounds. Once the fish are no longer needed as broodstock, they are transported and released in public waters in Colorado and Montana where anglers test their skill at landing big fish.
Spawning/Fertilizing/Incubating the Eggs
When a female is ready to release her eggs, a hypodermic needle connected to an oxygen bottle is inserted into the body cavity. Air pressure forces the eggs out of the body cavity into a pan. This process does not hurt the fish. Milt (a milky substance containing the sperm) from the male fish is mixed thoroughly with the eggs. Microscopic sperm cells in the milt have a long whip-like tail which propels them rapidly around the eggs. When a sperm cell enters the micropyle (a microscopic hole in the egg) it unites with the nucleus of the egg and fertilization is complete. Fertilization must take place very quickly because the sperm cell only lives about 30 seconds in water!
After fertilization, eggs are put in incubators where they continue to develop until Hatchery personnel can see the eyes of the tiny fish inside the egg. The eggs are then ready to be processed and shipped.
Transporting Fish Eggs
How would you like to be responsible for packing and shipping 20 million fish eggs every year? You would have to be very careful because these eggs are fragile!
First, it is necessary to separate live eggs from dead eggs. To do this, the eggs are poured into a sorting machine that uses optical sensing to separate the orange-colored live eggs from the white dead eggs. Usually about 5% - 8% of the eggs are white.
The live eggs are then packed into specially constructed trays. The trays are stacked in an insulated box topped with a tray containing crushed ice. The ice melts during shipping, keeping the eggs both cool and moist. Packed this way they can stay alive at least two days. Eggs are sent by express carrier and usually arrive at their destination within 36 hours.
