Rainy Lake

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There are specific fishing regulations Rainy Lake that you need to know. For complete fishing regulations visit the Minnesota Department of Natural Resources. To report a violation call (800) 652-9093. Need a Minnesota fishing license?

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Introduction

This investigation was designed to document the population characteristics of Lake Whitefish (Coregonus clupeaformis) in Rainy Lake, Minnesota. Changes in water level management enacted by the International Joint Commission (IJC) in 2000 were expected to be beneficial to Lake Whitefish in the Namakan Reservoir and could impact Rainy Lake whitefish as well. Lake Whitefish spawn in shallow water during October and November with eggs hatching early in the following spring. Whitefish eggs, therefore, are susceptible to desiccation during winters with significant water level drawdown.

This investigation used the Fish Community Index Netting (FCIN) protocol developed by the Province of Ontario (LNFAU 2001) to collect baseline population characteristics of Lake Whitefish in Rainy Lake. FCIN is carried out on a two of four year rotation. The 2023 sampling season represents the first of two surveys in the current four-year rotation on Rainy Lake. There is currently one commercial fishing license issued on the Minnesota side of the lake, however, the fisherman has not harvested Lake Whitefish since 2018.

Methods

Twelve FCIN nets were set from August 14th through August 18th, 2023. Sets were approximately 24-hours in duration. The deeper portions of the lake were broken into four sectors, with each sector having three net stations (Figure 1). Gill nets used were eight feet tall and consisted of nine 50-foot panels of various mesh gill net (1.0, 2.25, 0.75, 1.5, 2.5, 1.75, 0.5, 2.0, and 1.25 inch bar measure). Net locations were selected to sample two depth strata (60'-80' and greater than 80'). Eight nets were set in the shallow-water stratum while the other four were set in the deep-water stratum. Net location and orientation were chosen randomly within strata, however, nets could not be within 330 feet of shore or exposed shoals.

All fish captured in each net were separated by species and capture mesh. Total length, weight, sex, and state of maturity were recorded for all Lake Whitefish captured. Otoliths were collected from Lake Whitefish for aging.

Five metrics were incorporated to track long-term trends in the Lake Whitefish population (LNFAU 2001).
1) Mean age of first maturity
2) Mean age of FCIN catch
3) Relative abundance (Catch per unit effort (CPUE))
4) Recruitment/ juvenile abundance (CPUE of age 3, 4 and 5)
5) Spatial distribution of FCIN catch

Results and Discussion

Nine species totaling 314 individual fish were caught in the 2023 summer FCIN assessment (Table 1). Cisco species were the most common fish, making up 39.5% of the total catch by number while Walleye made up the largest portion by weight at 31.9% of the catch (Table 1). Forty-six Lake Whitefish were sampled for a catch rate of 3.8 per lift. A total of 53 Walleyes (CPUE = 4.4 per net), six Northern Pike (CPUE = 0.5 per net), and 67 Burbot (CPUE = 5.6 per net) were caught during the survey. The Cisco catch rate was 10.3 per net with 124 individuals caught in total.

Lake Whitefish ranged in length from 8.5 to 23.0 inches, with a mean of 17.0 (Table 2). The mean weight was 1.9 pounds. Thirteen age-classes were represented in the 2023 catch with the age-3 year-class composing 23.9 percent of the total catch while the age-2, age-4, age-6 and age-7 year-classes each made up an additional 10.9 percent of the total catch (Table 3).

In addition to overall catch rate, four metrics for evaluating the Lake Whitefish population were calculated. The age of 50% maturity (females) was 7.0 years. The mean age of Lake Whitefish in the FCIN catch was 5.9 years. Recruitment criteria showed that the juvenile abundance (CPUE of age 3, 4, 5) of Lake Whitefish was 1.4 per net. Lake Whitefish were sampled at 12 of 12 stations (Figure 2).

FCIN sampling from recent years suggest the Lake Whitefish population is not being overexploited. Sampling was carried out in a two of four-year rotation resulting in 11 years of sampling between 2003 and 2023. The catch rate of Lake Whitefish has been high and consistent in recent years (Figure 3). However, the 2023 catch rate of 3.8 per net was the lowest overall Lake Whitefish catch rate since sampling began in 2003. The 2023 catch rate was only slightly less than the 2003 catch rate of 3.9 per net. The mean age of the commercial catch (11.6 years) has been consistently higher than the mean age at 50% maturity (7.0 years in 2023) allowing a few years of spawning opportunities before becoming vulnerable to harvest. This is becoming less of a factor as the last commercial fisherman has not harvested Whitefish since 2018. There is no discernible change in the mean age of the FCIN catch over time and there were several age classes of Lake Whitefish present in the 2023 catch with individuals up to 19 years old. Consistent catch rates of juvenile Lake Whitefish suggest good reproduction and recruitment. Monitoring of the Lake Whitefish population and the commercial harvest for signs of overexploitation or stress should continue.

Acknowledgments

Dee Dee Crist (MNDNR), Mike Vaske (MNDNR), and Jake Erickson (MNDNR intern) helped with the field work associated with the 2023 FCIN survey. Phil Talmage and Dave Weitzel (MNDNR) reviewed the document.


References
LNFAU, 1999. Lake Nipigon Fisheries Assessment Unit: Fish Community Index Netting (FCIN). Ontario Ministry of Natural Resources. Ontario, Canada.

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