Strawberry Gets Sterile Bows

A half-million sterile rainbows were released into Strawberry Reservoir in late June. The fish were between 4 and 5 inches long and were carefully placed in strategic locations around the reservoir to insure the highest possible survival rate. It took biologists five days to complete the job, which is intended to give fishing at Strawberry a boost for years to come.

The loss of a year-class at Strawberry prompted the change in stocking methods. Few fish survived from the class of '95, and the result is fewer large fish in the reservoir now. Stocking methods were modified in '96 and '97, and fish from those year-classes are showing up well in gillnet studies, said Strawberry biologist Bob Spateholts.

In past years fish were stocked in the early spring or fall, and most were pumped into the reservoir near boat ramps or other places, which are easily accessible. But beginning in '96 fish have been loaded into barges and transported to strategic places around the reservoir.

Strawberry was treated in 1990 - all of the fish were killed - because the reservoir had become over-run by chubs and other "rough" fish. An aggressive management plan was launched in an attempt to provide biological controls to keep chub numbers in check. The plan called for Bear Lake cutthroats (good sport fish which prey on chubs), kokanee salmon and sterile rainbows. It is important for rainbows stocked in Strawberry to be sterile so they do not cross with the cutts and destroy the cutts to thrive and reproduce in natural waters like Strawberry.

The plan worked well for several years and produced very good fishing at the reservoir. But three years ago the federal government ruled against the method the DWR was using to sterilize the rainbows. The method worked well and was not associated with any known problems, but had not been clinically proven to be completely safe. Because of the ruling Utah had no reliable source for sterile rainbows and had to discontinue stocking the fish.

Now a California company has won approval to produce sterile rainbows using a method that also produces fish that are all female. DWR studies have shown the process is reliable and so the DWR bought a half-million fish. The agency hopes to purchase another 500,000 this fall for planting next summer.

Sterile rainbows grow quickly - the fish stocked in late June should be 10-14 inches long and some will reach 18 inches by the fall of '99.

Some 500,000 cutthroats were also stocked in the reservoir, and another 2 million are scheduled for this fall. Natural reproduction by the cutts supplements the stocked fish.

Kokanee reproduce well at Strawberry, but their population is also supplemented by stocking.