Lake Sullivan is a popular fishing destination in both summer and winter
Near the Crow Wing County border in northeast Morrison County, the lake has a broad connection to Platte Lake via the Platte River. Much of the lakeshore, other than wetland areas, has been developed. Not only does the lake have two boat accesses, shoreline fishing has been provided for from a new bridge on County Road 51 over the channel to Platte Lake. The channel also allows boat traffic between the two lakes. Steep drop-offs, points, vegetation islands, weedlines, flats, and sunken bars provide a variety of fish habitat and angling opportunity. Some of the more common submergent plants include northern watermilfoil, variable- leaf pondweed, white stem pondweed, and coontail. Dense beds of hardstem bulrush are common in the north half of the lake.
Fish species popular with anglers include Walleye, Northern Pike, Black Crappie, Bluegill, and Largemouth Bass. The Walleye population in Sullivan Lake, is sustained through regular stocking and natural reproduction. The gillnet catch continues to be below the management goal for the lake as well as the catch range for similar type lakes, however, spring assessments indicate a healthy adult population. The average size of the Walleye in the summer survey was about 16 inches or 1.6 pounds, but past spring assessments have shown that the lake can produce some trophy size fish over 27 inches. Northern Pike abundance did not appear to change significantly from the last survey and remained within the normal range when compared to similar type lakes. The average Northern Pike in the summer survey was about 21 inches or 2 pounds, but some trophies have been reported by fishermen. While only one Largemouth Bass was caught in the summer survey, previous spring electrofishing surveys have documented bass up to almost 18 inches, with the most common size between 11 and 13 inches in length. Yellow Perch abundance continues to be low, which could affect growth rates in the gamefish as perch can be an important prey species. Sullivan Lake supports a Tullibee population, but the species can be difficult to assess with summer surveys as the nets typically are not set deep enough to sample them. A panfish assessment was conducted in late-June of 2013 to evaluate the Bluegill and Black Crappie populations. The average size for the Bluegill was seven inches, with fish over nine inches measured. Anglers are encouraged not to keep too many larger fish as Bluegill take 7 to 9 years to reach 8 inches in Sullivan Lake. Average length for the crappie caught in the panfish assessment was about 7 inches in length although there were a few fish over 11 inches netted. While only a single Yellow Bullhead was sampled in the summer survey, all three species of bullhead were caught in the spring panfish assessment. Individuals up to 13 inches were caught of all the species. With a majority of the lakeshore’s high ground already developed, the remaining low ground may come under consideration for future residential development. Efforts to develop these low areas should be discouraged as it could negatively impact the lake’s natural characteristics and habitats. The extensive area of emergent vegetation near the inlet from Platte Lake has high value as fish and wildlife habitat. It also provides valuable erosion control and filters pollution. Good land use practices are encouraged in the watershed and by lakeshore owners to protect and maintain the water quality and fish habitat in the lake.