Effects of Stream Channelization on Fish Populations in the Buena Vista Marsh, Portage County, Wisconsin

[摘要] Fish populations from 6-8 year old ditches and 52-62 yearold ditches within the Portage County Drainage District werecompared with populations in adjacent portions of natural streams.Two study areas were selected, the upstream zone of good brooktrout ( Salvelinus fontinalis) habitat and the other downstreamin marginal trout waters where white sucker ( Catastomuscommersoni) were more numerous. Each area included newditch, old ditch and natural stream , all of similar discharge.Estimates of annual production by brook trout, population andbiomass estimates of brook trout and white sucker, and total catchrecords for other fish species were derived from electrofishingsamples in June, August and September, 1974 and April-May,July and September, 1975. A creel survey was conductedduring the 1975 trout season.Loss of year-round instream cover through channelizationlimited brook trout density, which reduced annual production bybrook trout to 28.8 kg/ stream km in the upstream new ditchstudy area as opposed to 72.2 kg/km in the upstream old ditchand 65.5 kg/km in the upstream natural stream. Angler successwas also reduced, from 1.03 trout/hr in the upstream old ditchand 1.05 trout/hr in the upstream natural stream to 0.26 trout/hrin the upstream new ditch o Approximate equality of these parameters in the upstream old ditch and natural stream indicatedthat recovery of natural channel morphology and trout carryingcapacity was nearly complete after 60 years. Midsummer watertemperatures reached upper lethal levels for brook trout in thedownstream ditches, where current velocity was reduced and whitesucker were abundant. Mottled sculpin (Cottus bairdi} wereconsistently absent from the upstream new ditch and scarce in thedownstream new ditch. Natural stream had the greatest number offish species in both study areas (12 upstream and 18 downstream),and new ditch had the fewest (9 upstream and 11 downstream).

[发布机构] University of Wisconsin-Stevens Point