Mosquito Flat Reservoir Fishing in Custer County, Idaho

• Overview

  Mosquito Flat Reservoir is one of the Custer County waters in Idaho. The surface lies 6,926 feet up. Surface area is around 49 acres, which gives you real water without needing a boat. With about 1.3 miles of edge, you can try several depths in one session. On our Custer County list it sits near the top for size. Challis sits 10 miles from the bank. Boise is the closest city, 107 miles away. It lies deep inside the county rather than near an edge.

• Where to Fish on Mosquito Flat Reservoir

  Depth is not on record here, which means reading the ground instead. A reservoir gives you a hard edge, a shelf, and not much else. Draw-down through summer strips the margins, so follow the water out. County-wide records name rainbow trout, cutthroat trout and Chinook salmon. At least one recorded species is protected in parts of its range; read the local rules before targeting anything. Mosquito Flat Reservoir fishes better once you know its edges.

• Seasonal Patterns

  Temperature averages peak at 54°F in July and bottom out at 18°F in December. The year runs cold to warm and back, with clear transitions. The lid arrives early and lasts until roughly mid May. From about mid May to around mid November, expect open water on the long-run figures. May into June fishes hardest, and September gives a second good stretch before the lid returns. Mosquito Flat Reservoir runs to that rhythm year in and year out.

• Tackle & Baits

  Public data does not answer the access question here. Formal access is not mapped, so the last stretch is likely on foot. Trout here take small spinners, spoons and, where fly water allows, a nymph or dry. Take the rules with you rather than trusting memory. Some stretches are reserved and marked as such on the ground. Buster Lake, 5.5 miles away, makes the obvious fallback. Nothing here settles the position at Mosquito Flat Reservoir for certain.