Big Deep Lake is a 484 acre lake with a maximum depth of 107 feet. It is located six miles east of Hackensack in northern Cass County. The Minnesota Department of Natural Resources (DNR) has classified Minnesota's lakes into 43 different types, based on physical, chemical, and other characteristics. Big Deep Lake is in Lake Class 23. Other area lakes in this same class include Baby (located two miles north of Big Deep Lake), Deep Portage (located six miles northeast of Backus), Hay (located ten miles northeast of Backus), and Stony (located two miles northeast of Hackensack) Lakes. There is no public access on the lake and the only resort is on the north side of lake.An abundant northern pike population exists in Big Deep Lake. The average-size of sampled northern pike was 17.0 inches and weighed 1.3 pounds. Some northern pike larger than 28 inches were sampled. Growth was slow when compared to other area class 23 lakes.Walleye were sampled at a rate typical of other area class 23 lakes. The average-size of sampled walleye was 19 inches and weighed 2.7 pounds. It appears that some portion of the walleye population is immigrating from other lakes by way of the Boy River. Sampled walleye were growing at a good rate when compared to class 23 lakes.The bluegill that were sampled showed good quality with 19% of the sample larger than 7 inches. Quality has declined since 1972 when it was reported that 61% of the sample was larger than 7 inches. The growth rate for bluegill was slow. Six inch bluegill averaged eight years old.As in previous years, low numbers of black crappie and largemouth bass were sampled. Summer netting often does not sample these species relative to their abundance.Other fish sampled include yellow perch, pumpkinseed, rock bass, yellow bullhead, brown bullhead, black bullhead, and white sucker. Muskellunge have also been reported in Big Deep.To help maintain quality fish populations in Big Deep Lake, lake users should safeguard aquatic habitat by preserving or reestablishing aquatic plants and natural shorelines. Aquatic and terrestrial plants provide food and cover for fish and wildlife. They also help protect shorelines from erosion, and absorb nutrients and pollutants. Natural shorelines, shorelines that have not been altered by man, help protect a lake from silt-laden runoff water. They also provide excellent places for wildlife to feed, hide, and raise their young. Protection of the larger watershed that drains into Big Deep Lake is also needed for maintaining water quality.Anglers can help maintain or improve the quality fishing by practicing catch and release of medium to large-sized fish. Releasing these fish will help maintain the quality of the fish population and provide anglers with more opportunities to catch mor large fish in the future.