Stock Characteristics of Lake Whitefish in Lake Michigan
File(s)
Date
2014-06Author
Belnap, Matthew J.
Publisher
University of Wisconsin-Stevens Point, College of Natural Resources
Metadata
Show full item recordAbstract
Lake whitefish Coregonus clupeaformis support important recreational,
commercial, and tribal fisheries in the Great Lakes, including Lake Michigan. Genetic
analyses indicate at least six distinct lake whitefish stocks exist in Lake Michigan, and
subsequent analyses show a mixed-stock fishery exists where multiple stocks are often
harvested within a single management zone. Biological characteristics could vary among
genetic stocks, but these differences may not be accounted for in current monitoring
efforts that rely on capture location to assign fish to individual stocks. This could
ultimately affect the utility of statistical catch at age (SCAA) models used to manage the
lake whitefish fishery. The objective of my research was to determine if weight-length
relationships, growth, age structure, and measures of reproductive investment (i.e., gonad
weight-fish weight relationships, fecundity, and egg diameters) differed among genetic
stocks and capture locations for lake whitefish in Lake Michigan collected during
October, the month when the majority of commercial harvest occurs. A total of 1,528
lake whitefish were collected from whitefish management zones (WFM) 08, 07, 05, 03,
01, and WI-2 in Lake Michigan in 2012 (N = 700) and 2013 (N = 828) for genetic and
demographic analyses. Sex, total length, weight, otoliths, gonad weight, ovaries (females
only), and maturity were collected from lake whitefish. Only one genetic stock was
represented in samples obtained from capture locations in four management zones
(WFM-08, WFM-07, WFM-05, and WFM-01), and only two stocks were represented at
capture locations in management zones WFM-03 and WI-2. At the two locations where
more than one genetic stock was represented, stocks were geographically proximal and
biologically similar. Consequently, using October capture location to assign lake
whitefish collected to genetic stock would likely provide fishery managers with realistic
estimates of biological metrics for each genetic stock. Based on similarities in the
biological characteristics I measured, lake whitefish in Lake Michigan could be divided
into four groups. Specifically, the Elk Rapids (ER) and Southern stocks (SOU) appear to
be biologically distinct from all other stocks, the Northeast (NOE) and Northern (NOR)
stocks were biologically similar to one another, but distinct from all other stocks and the
Big Bay de Noc (BBN) and Green Bay (GB) stocks were biologically similar to one
another, but distinct from all other stocks. While stock assignments based on October
capture location appears useful for describing the biological characteristics of specific
genetic stocks, using capture location alone is not sufficient to determine stock-specific
contributions to harvest within each zone throughout the entire year.