Tribal Harvest Management
The primary off-reservation tribal fishery is the ziigwan (spring) spearing and gill-netting of ogaa (walleye). Maashkinoozhe (muskellunge) and other species of fish are also harvested each spring. Harvest occurs in lakes throughout the 1837 and 1842 ceded territories which stretch across portions of Michigan, Wisconsin, and Minnesota.
This fishery is highly regulated with individual lake quotas, a nightly permitting system, and a requirement that only specified boat landings be used. Tribal creel clerks and wardens count all fish harvested each night during the season. Quotas are adjusted daily based on the previous night’s harvest to ensure that they are not exceeded.
With such a system, a wealth of information for describing the tribal fishery and the impact of that fishery on individual walleye populations has been collected. Open water spearing and netting reports for each season are available here.
Over the last twenty-five years, emphasis has been placed on accomplishing the extensive population assessments and harvest monitoring which provide the information critical to a thorough understanding of the fishery. The data collected to date provide a long term portrait of trends in the ceded territory walleye fishery.
In Wisconsin, separate models have been created for walleye lakes based on whether the walleye population is dependent on: 1) natural reproduction with normal year classes produced (NR model); 2) natural reproduction with irregular and weak year classes (NR2 model); or 3) stocking (ST model).
In Minnesota, population models have been developed for walleye and northern pike on Mille Lacs Lake.
Adult Walleye Population Estimates
Fisheries assessment crews conduct mark-recapture spawning adult walleye population estimates in the spring of each year. Soon after the ice goes out, marking surveys are conducted, during which walleye are captured, checked to determine their sex, measured, given a fin clip or tag to identify the fish as being marked, and released back into the lake. Spines are collected from a subsample of fish to determine age.
Between one and three nights after completing the marking surveys, a recapture survey is conducted with electrofishing gear, during which the entire shoreline of the lake is sampled. Walleye captured in the recapture survey are sexed, measured, and examined for the presence of the fin clip or tag given during the marking surveys. The ratio of marked to unmarked walleye in the recapture sample is assumed to be the same as in the entire lake. This information can then be used to estimate the total number of walleye in the lake.
Tribal and state biologists have identified a population density of 3.0 per acre for spawning adult walleye as a benchmark for a healthy, naturally reproducing walleye population. Walleye densities are typically lower in lakes where the population is sustained primarily or entirely by stocking than in lakes where the population is sustained by natural reproduction.
Fall Juvenile Walleye Surveys
Fisheries assessment crews conduct walleye recruitment surveys in the fall of each year. The primary objective of these surveys is to assess year class strength of stocked or naturally reproduced age 0 and age 1 walleye, or those "hatched" in the spring of the year, or in the spring of the previous year.
Data from fall walleye recruitment surveys are used to determine whether the primary source of walleye recruitment in a lake is natural reproduction, stocking, or some combination of the two. These data also provide a picture of trends in natural reproduction on important mixed fishery lakes and regional year-class strength.
Electrofishing begins at dusk and continues until the entire shoreline or a designated portion of the shoreline has been surveyed. Electrofishing temporarily stuns fish so that they can be netted and placed in a recovery tank.
All fish collected are identified to species and their length. Scale samples are collected from a subset of walleye, which are later examined to determine what lengths of walleye are age 0, age 1, or older. After collecting these data, the fish are returned to the lake. Year-class strength is measured in catch per mile of shoreline surveyed for age 0 and age 1 walleye.
On lakes sustained primarily or entirely by natural reproduction, age 0 CPEs typically average between 20 and 30 age 0 walleye per mile, and age 1 CPEs typically average between 6 and 10 per mile. On lakes sustained primarily or entirely by stocking, CPE values are usually lower. Tables and graphs are available showing mean and median CPEs from fall walleye recruitment surveys on lakes sustained primarily or entirely by natural reproduction across the Wisconsin ceded territory, and includedata collected by the Wisconsin Department of Natural Resources.
Liaison with Other Agencies
Effective management of the inland fisheries requires that current population data on hundreds of mixed fishery and naturally-reproducing walleye lakes within the ceded territory be obtained and maintained. Fisheries experts, as well as public leaders, recognize that cooperation between state, federal, tribal, and local organizations is critical in obtaining the information needed to understand the fishery within limited budgets.
In Wisconsin, cooperative fishery assessments through the Joint Assessment Steering Committee provide essential fishery data which is shared by the state, tribal, and federal participants. The Joint Assessment Steering Committee, with representatives from GLIFWC, WDNR, U.S. Fish and Wildlife Service (USFWS), the Wisconsin Chippewa tribes, the Bureau of Indian Affairs (BIA), and the U.S. Forest Service (USFS), manages the appropriation, schedules assessment activities, and shares the data.
GLIFWC biological staff are involved in fishery assessments in numerous lakes throughout treaty ceded territories of Wisconsin, Michigan, and Minnesota. Each spring and fall GLIFWC crews work with USFWS, Bad River, Fond du Lac, Mole Lake, and St. Croix crews to conduct assessment and recruitment walleye surveys. GLIFWC biologists also work cooperatively with DNR biologists in all three states through working groups, where data from assessments are pooled and reviewed.
Accurate age estimation is an important part of sound fisheries management in the ceded territory. Biologists can use age information to estimate growth, mortality, age composition of populations and harvest, and other population parameters. Since fish growth is cyclic with fast growth occurring in the summer and slow growth in the winter, several different bony structures can be used to estimate fish ages by counting annuli like the rings on a tree.
For walleye, scales, spines (from the dorsal fin), and otoliths (inner ear bones) are commonly used to estimate ages. Scales work well for younger fish, but annuli become difficult to distinguish in older fish since scale growth slows considerably. Spines work well for fish up to about age 10, but have the same issues as scales beyond that point. Otoliths are generally considered the best structure for accurate walleye age assessment, but otolith extraction requires killing the fish.
For muskellunge, bones from the pectoral girdle called cleithra provide one of the few reliable ways to estimate age. Unfortunately, removal of cleithra is a lethal procedure. GLIFWC biologists obtain scales from age 0 and age 1 walleye during the fall recruitment surveys, and spines from walleye during the spring adult assessments. Otoliths are collected from the tribal walleye harvest on Mille Lacs Lake, and some cleithra are collected from the Wisconsin muskellunge spear harvest.