Long-term
relationships between rusty crayfish and macrophytes in
lakes
The rusty crayfish (Orconectes
rusticus), a species native to Ohio and Indiana, has been
invading lakes throughout northern Wisconsin for the past
several decades (Hobbs et al. 1989). This exotic species
has the ability to outcompete native crayfish species (Hill
and Lodge 1999) and often replaces native crayfish species in
the lakes it invades (Olsen et al. 1991). In addition,
the rusty crayfish often occurs at higher population densities
than the native species and has been associated with
reductions in macrophyte biomass. Because macrophytes
provide important foraging and reproductive habitat to fish
and other aquatic organisms, the relationship between rusty
crayfish abundance and macrophyte biomass has been of interest
to scientists, lake managers, anglers, and the general
public. Long-term observations of rusty crayfish
abundance and macrophyte biomass in Trout Lake, one of the
North Temperate Lakes LTER program's primary study lakes, have
shown an inverse relationship over the past 18 years
(Figure1). Interestingly, in the first seven years of
record (1983-1989), when rusty crayfish abundance was
increasing rapidly at this site in the lake, there was no
evident decline in macrophyte biomass. The inverse
relationship between rusty crayfish and macrophyte biomass,
which has also been established experimentally (Lodge and
Lorman 1987), was only apparent after 12-15 years of record,
indicating the importance of long-term data in these
lakes.
Literature Cited
Hill, A.M. and D.M. Lodge.
1999. Replacement of resident crayfishes by an exotic
crayfish: The roles of competition and predation.
Ecological Applications 9:678-690.
Hobbs, H.H.I., J.P. Jass and
J.V. Huner. 1989. A review of global crayfish
introductions with particular emphasis on two North American
species (Decapoda, Cambaridae). Crustaceana
56:299-316
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Lodge, D.M. and J.G.
Lorman. 1987. Reductions in submersed macrophyte
biomass and species richness by the crayfish Oronectes
rusticus. Canadian Journal of Fisheries and Aquatic
Sciences 44:591-597.
Olsen, T.M., D.M. Lodge, G.M.
Capelli and R.J. Houlihan. 1991. Mechanisms of
impact of introduced crayfish (Orconectes rusticus) on
littoral congeners, snails, and macrophytes. Canadian
Journal of Fisheries and Aquatic Science 48:1853-1861.