Part 4 Life of a Rainbow Trout
In Part 3 of Life of a Rainbow Trout you learned about operations at Sterling Springs Hatchery where the fish are raised from egg to fingerling. We then transfer the trout to Page Springs Hatchery where they are grown to a catchable size of 9 to 10 inches. This is Part 4: Life of a Rainbow Trout.
We transfer trout to Page Springs Hatchery when they are approximately 3 inches or 4 to 5 months old. The hatchery trucks have transport tanks that hold 500 to 1,000 gallons of water each. We keep the water oxygenated using oxygen “stones” installed on the bottom of the tanks. These stones feed pure oxygen from high pressure bottles held in racks attached to the bed of each truck.
Once the trout reach Page Springs Hatchery we divide the fish out equally among the available empty raceways on A-bank. Page Springs Hatchery consists of three banks of raceways and is a three pass system. A-bank is supplied with only fresh spring water. B-bank is supplied with both fresh spring water and the “reuse” water from A-bank. And finally, C-bank receives only the “reuse” water from B-bank. We place most incoming fish in the raceways on A-bank so that they have the best water quality possible.
Loading fish to stock
Typically we will stock each raceway with 25,000 to 30,000 3-inch trout. The fish move from Sterling Springs where water temps range from 48 to 52 degrees Fahrenheit to Page Springs where the water is a constant 68 degrees is quite a shock for the fish. At first we feed the trout at similar growth rates to Sterling Springs (0.7 inch/month) so as not to stress them too much. Over a period of six weeks we increase feed amounts until they are being fed at a 1.0 inch/month growth rate.
During the first month after fish arrive at Page Springs, the trout will experience fish health problems. Typically we see a build-up of mucus on the gills and this is often followed by bacterial and/or parasite infections. The first line of defense includes salt baths which aids in removing the mucus allowing the fish to take up oxygen more effectively.
Stocking Rainbow Trout
Once the fish in A-bank reach certain densities we move them to the larger raceways in B or C-banks. The trout have become better equipped to deal with the poorer water quality on B and C-banks after acclimating to the warmer water and developing a stronger immune system on A-bank.
The trout remain at Page Springs Hatchery from nine months to a year. We typically move fish twice while at Page Springs. This lets us keep fish densities low and make room for the next lot of fish from Sterling Springs. Sterling receives four lots of rainbow trout eggs per year. Each lot corresponds to the months of the year that the fish will be stocked out from Page Springs. For example, the 2016 December lot of eggs will go out in January through March of 2018. This means even within one lot of fish, we use different growth rates to have fish at the size requested for each month. The current target sizes for Rainbow Trout from Page Springs are 9.3 and 9.55 inches.
Stocking Rainbow Trout
We stock fish from Page Springs every week. Each month we sample every raceway to see which fish to hold back and which fish to grow faster. When the time comes to stock out a raceway we crowd the fish to count them. We can then determine the weight that we need to load the fish onto the truck. We cool the water in the trucks with ice so the fish will be calmer during transport.
There are two different ways we load fish. One way is to load fish by hand with nets. The second way is to use a hydraulic fish loader. The hydraulic fish loader sucks fish and water up, but separates out the water prior to dropping the fish into the tanks. We use a water displacement method to calculate the weight of each load of fish using a sight gauge on each tank. Once again we diffuse oxygen into the water via stones. We also use aerators to break up the surface of the water. This releases carbon dioxide, which can escape through the vents on the tank.
Catching stocked Rainbow Trout
We then deliver rainbow trout to waters throughout the entire state from the Verde Valley to Yuma to Riggs Flat up on Mt. Graham. It makes all the hard work worthwhile when we hatchery folks see the happy expressions on the angler’s faces. We then drive back to the hatchery with the satisfaction of knowing we’ve provided fishing opportunities throughout our great state!
If you missed it, you can catch up on the the first stages of a Rainbow Trout’s life at Sterling Springs Hatchery at Part 1 of Life of a Rainbow Trout, Part 2 Life of a Rainbow Trout, and Part 3 Life of a Rainbow Trout.
