Thrasher

Thrasher is a designated stream trout lake that has been managed for trout since 1972. Rainbow and Brook Trout have been stocked in this lake in the past, but Splake stocking began in 1982, and since 1995 2,500 Splake fingerlings have been been stocked annually. The goal established for Splake in the latest (2013) lake management plan (LMP) was to maintain a catch in 0.75-in-mesh trap nets of at least 2.5 fish/net, with three catchable-sized (over 10 inch) year classes present, including some fish larger than 18 inches. The equivalent catch goal in terms of gill net catch would be a catch of about 10 fish/net. This was the second of two standard surveys scheduled in the 2013 plan to determine whether temperature-oxygen conditions continued to be suitable for stream trout and to determine whether long range goals for Splake were met by the current splake stocking regime. The first survey was completed as planned in 2016. Splake appeared to have been abundant in Thrasher Lake in 2021, and the population included fair numbers of larger fish (over 18 inches). The 2021 Splake gill net catch was the highest ever seen in this lake. It exceeded the normal range for catches in stream trout lakes in this area (5.8-12.0 fish/net), indicating the long range catch goal would have been met in 2021. The catch included four catchable-sized Splake year classes, and several fish over 18 inches in length were taken. Splake as old as six years were present in relatively high numbers, indicating long term survival had been excellent. Splake growth appeared to have been slow; fish reached a mean length of just 10.3 inches at the end of their third year, compared to an area average of 12.6 inches. Slow Splake growth may have been due, at least in part, to the sheer numbers of Splake present and competing for forage in this small lake. No undesirable or competing fish species were sampled in 2021. The only non-trout fish species ever collected in Thrasher Lake have been Fathead Minnow, Finescale Dace, and Pearl Dace. Temperature-oxygen measurements made in mid August as part of this survey suggested that, in 2021 at least, slow growth of Splake was probably not related to stress caused by a lack of cold-water habitat. Splake are believed to have temperature and oxygen requirements similar to those for Brook Trout. Optimal conditions for Brook Trout are water temperatures of 68 F or less, with at least 5.0 ppm dissolved oxygen. On 16 August 2021 those conditions were found at depths of 8.3 to about 15 feet in Thrasher Lake. Even in shallower waters conditions were tolerable, if less than ideal, for Splake. High numbers of Splake taken in our 2016 and 2021 surveys, and the slow growth experienced by those fish, suggested that a reduction in stocking numbers or frequency should be considered in this lake. The current long range goal is at the upper edge of the normal range for stream trout lakes in this area, and is probably higher than necessary. A minimum catch goal closer to average, if consistently met, would mean the lake usually provided above-average numbers of Splake that could still drive very good fishing success. A stocking reduction might result in an improvement in growth due to reduced competition, and that could improve the quality of the fishery.

Thrasher is a designated stream trout lake that has been managed for trout since 1972. Rainbow and Brook Trout have been stocked in this lake in the past, but Splake stocking began in 1982, and since 1995 2,500 Splake fingerlings have been been stocked annually. The goal established for Splake in the latest (2013) lake management plan was to maintain a catch in 0.75-in-mesh trap nets of at least 2.5 fish/net, with three catchable-sized (over 10 inch) year classes present, including some fish larger than 18 inches. An equivalent goal for gill net catches would be to maintain a catch exceeding about 10.0 fish/net. Both goals describe above-average Splake numbers. This was the first of two standard surveys scheduled in the 2013 plan to determine whether temperature-oxygen conditions continued to be suitable for Splake and to determine whether long range goals would continue to be met by the current Splake stocking regime. Splake were abundant in 2016, and their average size was good, although few large (over 18 inch) fish seemed to have been present. The 2016 Splake gill net catch was one of the highest ever seen in this lake. It was above the normal range (5.0-12.0 fish/net) for spring catches in stream trout lakes in this area, indicating the long range catch goal would have been met in 2016. The catch included four catchable-sized Splake year classes, although no fish over 18 inches were taken. Splake as old as five years were present in relatively high numbers, indicating long term survival had been excellent. Splake growth appeared to have been slow; fish reached a mean length of 13.4 inches at the end of their fourth year, compared to an area average of 15.1 inches. Slow Splake growth may have been due, at least in part, to the sheer numbers of Splake present and competing for forage in this small lake. Splake over 18 inches in length have often been sampled in this lake, but to reach that size, with growth rates observed in 2016, would require survival of some fish to six or seven years of age - rare, but not impossible in lakes like this. No undesirable or competing fish species were sampled in 2016. The only non-trout fish species ever collected in Thrasher Lake have been Fathead Minnow, Finescale Dace, and Pearl Dace. Temperature-oxygen measurements made in late August as part of this survey suggest slow growth of Splake could also have been related to stress caused by a lack of suitable cold-water habitat. Splake are believed to have habitat requirements similar to those for Brook Trout. Brook Trout thrive at water temperatures of 68 F or less, with at least 5.0 ppm dissolved oxygen. Water temperatures over 68 F are stressful, and prolonged exposure to those higher temperatures can result in slower growth, particularly among larger fish. Exposure to water temperatures over 77 F can be lethal. Measurements in Thrasher Lake on August 17 2016 found cold-water habitat prefered by Splake, if any existed, was limited to a very narrow band at depths between 10 and 11 ft. Deep waters that might have provided cool enough water lacked sufficient dissolved oxygen, while shallower waters were too warm. While not lethal, warm surface water temperatures observed in 2016 (up to 72.0 F) could have resulted in stress responses, including slower growth, among Splake.

This was the second of two assessments scheduled in the 2005 lake management plan to measure attainment of long term goals for this lake. Goals in the 2005 plan were to maintain a splake population with a minimum trap net catch of 2.5 fish/set in spring assessments, with some fish over 18 inches present, and with three catchable-sized (over 10 inch) year classes present. Results of assessment activity in Thrasher Lake in 2011 were inconsistent. The splake trap net catch in this assessment failed to meet the long range goal from the 2005 plan, and fell below the median (1.80 fish/set) for spring assessments of stream trout lakes in this area. However, the gill net catch was relatively high, above the normal range (5.25-12.00 fish/set) for stream trout lakes in this area, and exceeded catches seen in recent assessments of this lake. No splake over 18 inches in length were captured in gill nets or trap nets in this assessment, but two fish of that size were taken in an earlier special assessment. The goal of providing three catchable-size year classes was apparently met by fish taken in gill nets and in the special assessment, but was not met by the trap net catch in this assessment. Marking of splake collected in the earlier special assessment allowed us to estimate that in late May 2011, Thrasher Lake supported about 250 splake, of which about 105 were 12 inches or more in length. That estimate was similar to past estimates obtained for this lake, and it was typical of estimates made for other stream trout lakes in this area. Four year classes contributed to the splake catch in this assessment, which included fish as old as four years. A few older fish may also have been present, as indicated by the catch of a couple larger fish (up to 21 inches in length) in the earlier special assessment. Splake growth had apparently been somewhat slow; fish reached an average length of 12.0 inches by the end of their third year, compared to an average of 13.0 inches for splake lakes in this area. No exotic or undesirable fish species were collected in this assessment. Thrasher Lake has generally been free of species that would compete with stocked trout for forage.

Based on Minnesota DNR survey data, anglers target Splake and Lake Trout in Thrasher. See the full species list above for catch rates, size structure, and quality scores.

Minnesota DNR records list public access for Thrasher. Check the DNR LakeFinder page for the launch type and directions before you go.

Thrasher has a maximum depth of 27 feet, per Minnesota DNR data.

The most recent Minnesota DNR survey data for the main sport fish in Thrasher is from 2021.

No invasive species are on record for Thrasher in Minnesota DNR data. Always clean, drain, and dry your equipment to help keep it that way.