Tuesday, February 7th, 2023
Tuesday, February 7th, 2023

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Wisconsin Lake Profile – Diamond Lake, Bayfield County

Diamond’s walleyes doing OK, largemouths exploding 


DNR Report


The local DNR fisheries team surveyed Diamond Lake in Bayfield County in 2018 and 2019, with objectives to obtain a population estimate of walleye and assess the other game fish and panfish populations. Sampling included spring fyke netting, spring and fall electrofishing, and a creel survey.


The team found that adult walleye abundance (15 inches or longer and sexable fish) was 1.3 adults per acre, slightly below the average of stocked ceded territory lakes. The walleye size structure has consistently included high average lengths. Stocking has driven Diamond walleye populations since 1986, however very low levels of natural reproduction may be present.


Diamond has supported a diverse fish community and popular sport fishery. Natural reproduction supports all species, except for walleye which is supported by stocking. Harvest regulations aimed at protecting adult walleyes have been successful. Northern pike harvest management has shown mixed results. The recent changes in harvest regulations for bass are too recent to show any major results.


Results from the 2018-19 survey suggest that the regulation change for walleye (size limit of 15 inches, protected slot of 20 to 24 inches and a bag limit of three with only one over 24 inches) has been successful in protecting adult walleyes. Average length of adult walleye in 2018 was 22.5 inches, showing the regulations can maintain the excellent size structure.


The harvest of walleye by anglers was down in 2018, most likely due to the lowest fishing pressure for walleye in the eight survey years. The decrease in harvest also may show that the new walleye regulations implemented in 2016 still protect the adult walleye stock. Walleye densities fell significantly from 1990 to 2012 and have increased from 2012 to 2018 but not by much (1.3 adult walleyes per acre). Walleye recruitment has also changed dramatically during the survey years. The success of stocking small fingerlings also decreased during the survey years. Large walleye fingerlings have been stocked since 2007 and have shown stronger recruitment.


The success of the northern pike regulation (size limit of 26 inches and a bag limit of two fish) is hard to evaluate. Fishing pressure for northern pike was the lowest it has ever been and the lowest for all game fish species. Estimated catch and harvest of pike was also down. Northern pike sampled in 2018 had an average length of 23.2 inches.


The more restrictive regulation (size limit of 32 inches and a bag limit of one fish) showed no signs of improving northern pike size and relative abundance fluctuated. Spring fyke netting in 2018 sampled six pike over 26 inches.


Largemouth bass abundance increased significantly from 1996 to 2009 and decreased a tad from 2009 to 2018. Overall largemouth bass abundance increased by 306% from 1996 to 2018. The average length was 13.1 inches, the highest for all survey years. Smallmouth bass abundance decreased from 1996 to 2009 and fluctuated from 2009 to 2018 with an overall significant decline. Historical surveys on Diamond indicated smallmouths outnumbering largemouth bass. However, surveys in 2009 and 2018 showed largemouths outnumbering smallies at ratios of 28:1 and 8:1, respectively.


Regulation change in 2018 implemented a no size limit for largemouth bass and an 18-inch limit for smallmouth bass, with a release season for smallmouths and a combined bag of five bass, of which only one may be a smallmouth.


Bluegills were the most abundant and most popular panfish species among anglers. Length at age data from previous panfish surveys indicate slow growth. Diamond has historically had high abundances of small bluegills, but recent surveys show decreasing bluegill abundances. Angler catch rates of bluegills are also on a downward trend. The decreasing bluegill abundance in Diamond Lake could be leading to faster growth. 


Diamond lake is slightly oligotrophic with a maximum depth of 83 feet, which could be associated with the slow bluegill growth. Diamond Lake’s bluegill population could also be influenced by angler exploitation. In 2018, creel surveys estimated that 2,330 bluegills were caught and 603 were harvested Anglers in 2018 tended to harvest larger bluegills; the average length of harvested fish was 7.5 inches. Harvesting larger bluegills forces smaller bluegills to reproduce, slowing their growth, and ultimately shrinking the size structure of the population. Removal of the larger breeder bluegills could be what is stunting the bluegill population. Rebuilding quality size structure is a long-term process and can take years to reach desired results. Decreasing harvest of large bluegills may be a useful tool for increasing their size. Increasing the predator base could also be a solution to reducing density and improving growth.

Diamond Lake

Nearest town: Cable

Surface area: 322 acres

Max. depth: 83 feet

Water clarity: N/A


Fish species present: black crappies, bluegills, pumpkinseeds, rock bass, yellow perch, white suckers, trout, smallmouth  bass, largemouth bass, northern pike, and walleyes.


For information: DNR regional fisheries office (715) 685-2900, the DNR web site http://www.dnr.state.wi.us/org/water/fhp/fish, or call Clam Lake Junction, (715) 794-2781.

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