When anglers head to northeastern Oregon’s Eagle Cap Wilderness, they may soon catch bigger fish.
That is the hoped-for outcome of an Oregon Department of Fish and Wildlife test case in which larger rainbow trout were dropped into the high lakes with the goal of improving survival of the stocked fish.
The smaller stocked trout, usually 2.5 inches long, can succumb to predation, frigid temperatures and injuries caused by the drop.
In the test, ODFW stocked the lakes with 3-inch and 4-inch fish rainbow trout, in addition to the smaller fish. Though space limitations mean ODFW can drop fewer of the larger-size fish, the expectation is that more of the fish will survive to the legal 8-inch size.
“The extreme conditions involved in maintaining healthy fish populations in a landscape above 7,000 feet has its own challenges,” said Jeff Yanke, ODFW district fish biologist in Enterprise, “but anglers have consistently told us that fishing is one of the recreational experiences they expect when they go to the wilderness.”
The 361,000-acre Eagle Cap Wilderness contains more than 40 lakes that are above 7,000 feet, including the state’s highest lake – Legore Lake – located above the Wallowa Valley at an altitude of 8,950 feet.
ODFW stocks the lakes by helicopter every two years, using an aerial stocking device – a “shuttle” – to drop the fish about 70 feet from under the helicopter. The stocking program is paid for with federal Sportfish Restoration Program dollars, funded by a 10 percent excise tax on the sale of fishing equipment. ODFW’s Restoration & Enhancement program paid for the aerial stocking device that makes the trout drops possible. R&E funds also help with monitoring the program.
High lakes rainbow trout face of a variety of challenges. The eastern brook trout, which was stocked in some of the high lakes decades ago, is a voracious predator.
“Our study was initiated to see if we could increase rainbow survival in our lakes enough by raising a larger fish to overcome predation and competition by naturally producing brook trout,” said Kyle Bratcher, ODFW assistant district fish biologist in Enterprise.
The freezing water temperatures also can reduce fish survival rates. And, the drop itself can cause trauma.
Despite concerns that the larger fish might have more severe injuries from the fall because they have more surface area, preliminary results show that all three size groups have high post-drop survival rates, said Bratcher. He noted that samples were sent to ODFW’s fish lab in La Grande where they will be assessed for bruising, injuries and other signs of trauma.
ODFW will sample the stocked lakes in two years, estimating population abundance, growth and condition from collected fish. A determination about whether the larger rainbow trout do have higher survival rates is expected in three to four years.