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Faculty Sponsor

Dr. Robert Gillespie

Department/Program

Department of Biology

Abstract

Many of the agricultural drainage ditches that border farm fields of the Midwestern United States are channelized headwater streams. Despite their degraded state, these ditches support a surprising variety of fish and macroinvertebrate species including crayfish. Crayfish have long been used as model organisms for laboratory studies of aggression, but little is known about their aggressive interactions in the wild. Even less is known about their behavior in channelized headwater streams. Crayfish need different substrates and habitat types at different life stages, and they can be sensitive to the presence of toxic chemicals in the water. In this study eight sites on channelized headwater streams feeding Cedar Creek in Northeastern Indiana, nine sites feeding Upper Big Walnut Creek in Central Ohio, and one site on the East Branch of the Saint Joseph River in Southeastern Michigan were monitored over two years for evidence of crayfish aggression. Crayfish were collected by a combination of electrofishing and seine netting techniques. Individuals were identified to species, sexed, measured, and any damaged appendages were noted as injuries. Data on instream habitat quality were also collected. Concentrations of nutrients and pesticides at all study sites were provided by scientists at the National Soil Erosion Research Laboratory. The mean count of injuries per individual, proportion of injured individuals, mean number of claw injuries per individual, proportion of individuals with multiple injuries, and crayfish density within the sites were calculated. A habitat diversity index and a water toxicity index were developed to assess site quality. A mixed model multiple regression analysis was used to correlate site quality index values with crayfish injury response variables. We found crayfish density to be the major predictor of all the injury response variables, and that habitat and water quality had no significant correlation with crayfish injury or density. Crayfish may not need high quality habitat as defined for other species, beyond what a typical channelized headwater stream can provide. Also, observed concentrations of agrichemicals in the sites were often well below established chronic effect benchmarks. Crayfish are well adapted to life in ditches due to their flexibility in habitat utilization and tolerance of agrichemicals. However, further research is needed to identify factors that determine crayfish community densities.

Disciplines

Biology

Frequency and Severity of Crayfish Injuries as an Indicator of Quality in Channelized Headwater Streams

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