Tp. Simon et Pm. Stewart, Structure and function of fish communities in the southern Lake Michigan basin with emphasis on restoration of native fish communities, NAT AREA J, 19(2), 1999, pp. 142-154
The southern Lake Michigan basin in northwest Indiana possesses a variety o
f aquatic habitats including riverine, palustrine, and lacustrine systems.
The watershed draining this area is a remnant of glacial Lake Chicago and s
upports fish communities that are typically low in species richness. Compos
ition of the presettlement Lake Michigan fish community near the Indiana Du
nes has been difficult to reconstruct. Existing data indicate that the numb
er of native species in the Lake Michigan watershed, including nearshore La
ke Michigan, has declined by 22% since the onset of European settlement. Fe
w remnants of natural fish communities exist, and those occur principally i
n the ponds of Miller Woods, the Grand Calumet Lagoons, and the Little Calu
met River. These communities have maintained a relatively diverse assemblag
e of fishes despite large-scale anthropogenic disturbances in the area, inc
luding channelization, massive river redirection, fragmentation, habitat al
teration, exotic species invasions, and the introduction of toxic chemicals
. Data that we collected from 1985 to 1996 suggested that the Grand Calumet
River has the highest proportion of exotic fish species of any inland wetl
and in northwest Indiana. Along the Lake Michigan shoreline, another group
of exotics (e.g., round goby, alewife, and sea lamprey) have affected the s
tructure of native fish communities, thereby altering lake ecosystem functi
on. Stocking programs contribute to the impairment of native communities. N
onindigenous species have restructured the function of Lake Michigan tribut
aries, causing disruptions in trophic dynamics, guild structure, and specie
s diversity. Several fish communities have been reduced or eliminated by th
e alteration and destruction of spawning and nursery areas. Degradation of
habitats has caused an increase in numbers and populations of species able
to tolerate and flourish when confronted with hydrologic alteration. Fish c
ommunities found on public lands in northwest Indiana generally are of lowe
r biological integrity, in terms of structure and function, than those on p
rivate lands and are not acting as refugia for native fish populations. Sto
cking of nonindigenous species should be evaluated to enable the restoratio
n of native fish communities on public lands. Habitat quality will need to
be improved and land-use modifications decreased or reversed in order to re
store or slow the decline in native fish communities.