In an effort to find juvenile arctic grayling, Montana Fish, Wildlife and Parks has set traps in two streams feeding Ennis Lake.
The traps are set in the Fletcher Channel of the Madison River as well as Meadow Creek, said Pat Clancey, fisheries biologist with FWP.
The traps are called screw traps and consist of a 5-foot diameter rotating drum, two steel pontoons and a capture box. The traps are tethered to large posts in the ground. Both traps are within a short distance of Ennis Lake.
“We’re just looking for young of the year grayling and secondly to get some information on what Meadow Creek and the lower portion of the river may contribute to Ennis Lake,” Clancey said.
Arctic grayling, westslope cutthroat and whitefish are the only trout species native to the Missouri River system in Montana, he said. However, over the years habitat fragmentation and the introduction of non-native fish, like rainbow and brown trout, have nearly eliminated grayling and cutthroat from the Madison River. Still some arctic grayling hold on in Ennis Lake.
Prior to the construction of Madison Dam on Ennis Lake, Clancey suspects the braided sections of the Madison River and Meadow Creek joined where the current reservoir resides could have been prime grayling habitat.
“They seem to really key in on pools in the river,” he said.
Grayling spawn in March and April and the young fish rear in slack water in the river until they are ready to come back to the lake, sometime in mid to late June, Clancey said.
The traps are designed to capture the young fish, which get pushed back to the lake while facing up stream.
Recent efforts to get a sense of how many grayling live in Ennis Lake have been futile, he said.
“There’s so few, that we can’t really derive a population estimate,” Clancy said.
Studies on grayling in the Big Hole River have shown that when their population numbers are equal to those of other trout species, grayling can survive well. However, when they are outnumbered significantly, then their numbers decline, he said.
Clancey and his staff will check the traps at least every other day. Signs warning people of the traps are posted. The traps will likely be in place into early July.