Canisteo Mine Pit (CMP) is a complex of mine pits abandoned in 1985. Since then ground water has been filling the pit. CMP is located a little north of the cities of Coleraine, Bovey, and Taconite. The complex has as area of 1,425 acres, a maximum depth over 300 feet, a mean depth near 100 feet, and limited littoral area as of 2010. CMP has been managed for lake trout since the initial survey in 1995. Annual stocking of yearling, and occasionally adult, Isle Royale strain lake trout occurred from 1996 to 2005. Biennial stocking of Isle Royale strain yearling lake trout has occurred since 2007. All trout had a distinguishing fin clip to identify stocked fish, except some adults from 1997 to 1999 and 2002. Adult tullibee were introduced twice (2006 and 2008) in an attempt to provide a second, naturally sustaining prey species.
Deepwater gill nets sampled 28 lake trout at a rate of 1.9/net, consistent with catch rates from previous assessments since lake trout had been stocked (1.7-1.9/net), and near the lake management plan goal of 2.0/net. Lengths were from 8.1-22.6 inches with a mean length of 14.3 inches and a mean weight of 1.0 lbs. Field analysis identified two fin clipped marked fish, both from the 2009 stocking and age-2. The remainder of the sample (n=26) had no distinguishing marks and are assumed to be from natural reproduction. Internal examinations of 18 fish identified eight females and 10 males which 75 % of the females and 90% of the males were immature. The 2010 mean length was less than the 2005 (24.1") and 2000 (20.5") assessments. A relatively small mean length, when compared to CMP length frequencies, suggests younger fish comprised the majority of the sample. Interestingly, the 2010 assessment suggests a couple of relatively young, strong natural year classes are present in the system.
Tullibee were the most numerous species sampled in deepwater gill nets at a rate of 2.7/net. Lengths were from 6.9-10.8 inches with a mean length of 8.8 inches. Scale analysis identified ages 1 to 4 present in the sample. It appears tullibee have become established and naturally occurring since adults were last stocked in 2008 and it is clear that at least the 2008 and 2009 year classes were the result of natural reproduction. Tullibee, too small to be sampled in gill nets, were observed in the stomach contents of lake trout and smallmouth bass, and were observed swimming near the surface further suggesting successful natural reproduction.
Bluegill comprised the largest catch in trap nets, 16.5/net, exceeding the expected range for lake of this type. Trap net catches have varied from 2.5/net in 2005 to 17.9/net in 1995. Lengths were from 3.7-7.4 inches with a mean length of 5.3 inches. Ageing structures were not collected during this assessment, but past assessments suggest growth was relatively slow.
Catch rates for other species in deepwater gill nets are typically low and may not be good indicators of relative abundance. Rainbow smelt are occasionally sampled in standard deepwater gill nets, but none were sampled during this assessment. A special assessment for rainbow smelt conducted in 2009 using small mesh gill nets confirmed the occurrence of smelt. Eight smallmouth bass were sampled with lengths from 8.2-19.5 inches and a mean length of 13 inches. Other species sampled in deepwater gill nets include northern pike, rock bass, and white sucker. Other species sampled in trap nets include largemouth bass, northern pike, rock bass, tullibee and yellow perch.