A Review of the Research on the Benthos of Lake Winnipeg
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Date
1994
Authors
Flannagan, J.F.
Cobb, D.G.
Flannagan, P.M.
Journal Title
Journal ISSN
Volume Title
Publisher
Department of Fisheries and Oceans, Winnipeg, MB
Abstract
Lake Winnipeg, a remnant of Glacial Lake
Agassiz, is the eleventh largest (by area) freshwater
lake in the world and the seventh largest in
North America. Bordered on the north and east by
the Precambrian Shield, and on the south and west
by the Central Plains, the lake is the focal point of
rivers draining its 953,250 km2 watershed. It is
extremely shallow relative to its area and does not
stratify thermally during the open water season.
This, together with the high nutrient load entering
from the watershed, especially the south and western
parts, have resulted in the lake being highly
productive and supporting a very large commercial
fishery. Compared to other Canadian Great Lakes,
with the possible exception of Lake Erie, the offshore
benthos of Lake Winnipeg are relatively well
known. This knowledge results from three main
sources: 1) a survey of the benthos of several
large Manitoban lakes related to their capacity to
support fish, carried out by Ferris Neave and
Alexander Bajkov in the late 1920's and early
1930's (Bajkov 1930; Neave 1932, 1933, 1934); 2) .
a "baseline survey" of the physical, chemical and
biological condition in the lake carried out by staff
of the Freshwater Institute (FWI) in 1969, when it
was thought that some major changes in the lake's
drainage basin may have been influencing the lake
(benthos papers include: Flannagan 1979;
Flannagan and Cobb 1981, 1984, 1991, 1994;
Chang et al. 1992, 1993, 1994); and 3) the
continuing program on the lake carried out by
biologists from the Fisheries Branch of the
Manitoba Provincial government (many manuscript
reports including Rybicki 1963, 1966; Stone and
Cober 1965; Crowe 1969, 1972a, b, 1973a, b;
Slack 1973; Kristofferson et al. 1975). These latter
publications are unrefereed internal Departmental
reports not generally available to the scientific
community, thus reference will only be made to
them when it is considered that the information
they contain is not available elsewhere.
Ekman grabs of various sizes, and mesh
sieves of 0.2-1.27 mm opening were used in all
surveys, except for some Provincial government
studies, where Ponar and Peterson grabs were
used (Table 1). Comparisons using the latter two
grabs or widely different mesh sizes must be
carefully made, since the use of different grabs
(Flannagan 1970) or different mesh sizes (Reish
1959) can affect species counts and abundance
estimates. This report attempts to collate the existing
knowledge of the species composition, distribution,
life history, production and changes in the benthos
of Lake Winnipeg. As a result, it will be possible to
better understand changes to the lake ecosystem.
Potential threats to the presentlake biota include:
1) direct introduction of undesirable species (e.g.
zebra mussels) via inter-basin transfer of boats; 2)
diversion of water originating in the
Mississippi/Missouri watershed into the Lake
Winnipeg watershed (e.g. Garrison Dam and diversion
in the north-central United States) perhaps
providing the necessary water routes required for
the introduction of exotic species (Flannagan and
Flannagan 1982); and 3) predictions of climate
warming, and its effect on water temperature and
water supply.
Description
Keywords
Benthos, Lake Winnipeg, Oligochaeta, Hirudinea, Crustacea, Ephemeroptera, Plecoptera, Trichoptera, Chironomidae, Mollusca
Citation
Flannagan, J.F., D.G. Cobb, and P.M. Flannagan. 1994. A review of the research on the benthos of Lake Winnipeg. Can. Manuscr. Rep. Fish. Aquat. Sci. 2261: iv + 17 p.