Status of the Fishery (as of 07/10/2006)
Blackduck Lake is a 2,596-acre lake with a maximum depth of 28 feet. It is located in east central Beltrami County 1 mile west of the city of Blackduck. There is a public access on the east side of the lake off of county road 30. Blackduck Lake is one of the more popular fishing lakes in the Bemidji Fisheries Management area. Based on winter fish house counts, it is second only to Lake Bemidji in winter fishing activity.
The Minnesota Department of Natural Resources has classified Minnesota's lakes into 43 different lake classes based on physical and chemical characteristics. Blackduck Lake is in lake class 27, along with Big Lake, Clearwater, Big Wolf, Big Turtle, Andrusia, Grace and Kitchi. All of the lakes listed are primarily managed for walleye.
Blackduck Lake is managed intensively for walleye with fry stocking two out of every three years. Angler harvest is high resulting in high mortality rates and rapid turn over of this population. This is most apparent by the age distribution in the 2006 assessment, where 91% of the sample were age 4 and under. This has been a typical pattern in previous assessments as well. With few fish persisting beyond age four most female walleye are harvested before they mature.
Fortunately fry stocking has been a very effective tool for replacing new walleye into the population. Growth rates are very good with walleye averaging 14 inches by age three, and 16 inches at age four. Anglers are generally happy with fairly consistent production of harvestable size walleye. There has been little interest expressed for special regulations to improve the quality component of this fishery. Any special regulation intended to improve spawning stock abundance would need to be very restrictive, sacrificing considerable harvest for some possible improvement in natural reproduction.
Northern pike density tends to be low on Blackduck. The 2006 assessment was no exception, with the lowest catch rate ever recorded. Low density in a pike population is desirable, since it reduces predation effects on walleye and perch. It also reduces competition among pike, improving growth rates. Most anglers prefer fewer nuisance sized northern pike with the opportunity to catch an occasional large one. Pike were sampled in this assessment up to 32 inches in length. Anglers are encouraged to release larger pike and harvest fish under 24 inches to maintain a quality pike fishery.
Centrarchid species (the sunfish family) have been increasing in abundance on Blackduck Lake. Black crappie and bluegill were sampled in record abundance, and largemouth bass were sampled for the first time. Bass were likely present before, but at levels to low to be sampled. These species still occur in relatively low densities compared to the dominant walleye/perch community, but provide some diversity for this fishery. Hopefully the increasing trend in centrarchid species is an indicator of improvements in water quality and aquatic habitat for these species.
While bluegill abundance is increasing, it is still at a level vulnerable to over harvest. The lake has a reputation for producing trophy bluegills in excess of 10 inches. A special five fish daily bag limit regulation was applied in 2006, in anticipation of this emerging fishery. The intent is to protect and maintain this relatively low-density high-quality fishery. Growth is exceptional, with bluegill averaging 7.4 inches by age four. Similar lakes in the Bemidji area average of 6.1 inches at age four.
Yellow perch are important to Blackduck Lake, both as a recreational fish for anglers as well as forage for predator fish. Consistent perch reproduction provides the food base for walleye growth and survival. Perch were sampled in this assessment ranging in length from 4.1 to 12.8 inches. With 18% of the perch longer than nine inches a good portion of this population is of harvestable size.
Another species that was sampled of quality size was the brown bullhead. For those interested in fishing bullheads, these ranged in length from 10.2 to 16.7 inches with an average length and weight of 13.4 inches and 1.4 pounds.
Other species sampled in low numbers include pumpkinseed sunfish, rock bass, white sucker, freshwater drum and lake whitefish. ?