FAIRFIELD — After two years of spectacular trout fishing at Mormon Reservoir, the trout population has likely returned to what it has traditionally been. Based on sonar data, underwater camera drifts and reports from anglers, it appears that there are now fewer fish in the reservoir.
Anglers who read about the resurgence of the Mormon Reservoir trout fishery might be wondering how the reservoir went from holding big trout — and lots of them — to not holding as many fish.
While winter-kill has been an issue at Mormon in the past, it doesn’t appear that it is responsible for the current decline of trout in the fishery. Idaho Fish and Game biologists have observed very few dead fish around the perimeter of the reservoir. Efforts to document dead trout on the bottom of the reservoir, using video equipment, did not reveal any data to suggest a major winter-kill event occurred.
So if there wasn’t a substantial die-off of fish over the winter, where did those fish go prior to this spring? It’s likely many ended up in anglers’ coolers, which was expected after two years of extraordinary catch rates.
It may be disheartening for those who missed out on the stellar trout fishing in 2017 and 2018, but angler harvest is exactly what the trout in Mormon Reservoir are there for. Basically, as catch rates increased, so did the number of anglers. Many harvested the bounty of big trout that had built up after Fish and Game stocked nearly 35,000 catchable trout in the reservoir in 2015.
There were not enough fish available to continue stocking at that high rate because conditions improved at other reservoirs which had been unsuitable for trout due to drought in 2015.
For more information, go to idfg.idaho.gov/press/fishing-has-slowed-mormon-reservoir-no-signs-winter-kill-found.