Cisco Lakes in North Dakota

Cisco is a cold-water species, so the lakes where it is documented tend to be the deep, well-oxygenated basins that stay cold through the summer. 5 lakes carry a record. Cisco is narrowly distributed — only 4 lakes in New York and 1 in North Dakota have a documented record. The constraint is usually habitat: cold water, specific depth profile, or river connection.

Trout presence is itself a water-quality signal: a North Dakota lake that supports a Cisco population is almost certainly running cold enough and oxygenated enough to also support healthier overall water quality. Trout-supporting lakes are almost universally A- or B-grade — the cold, deep, well-oxygenated conditions trout need produce the higher grades almost as a side effect.