The Ecology of Invertebrate Drift and Feeding Chronology of the Striped Shiner, Notropis chrysocephalus (Rafinesque) in Polecat Creek, Illinois

The downstream drift of macroinvertebrates and the daily feeding cycle of the striped shiner, Notropis chrysocephalus (Rafinesque), were studied during the spring and summer of 1978 in Polecat Creek, Illinois. The purpose of the study was to: investigate the drift phenomenon of an entire lotic community, determine the pattern of diel periodicity for several important benthic populations, make qualitative and quantitative assessments of the relation of drift to benthos, and examine drift in relation to the daily feeding ecology of a cyprinid carnivore. Polecat Creek at the sampling site was a relatively fast-flowing third-order stream, with frequent riffles. Drift sampling was conducted at the downstream end of a single riffle over four 24-hour periods; April 28-29, May 19-20, August 10-11, and September 1-2. Current velocity was measured at the mouth of the net and the number or weight of aquatic invertebrates collected was standardized according to volume of water, defined as drift density. The standing crop of invertebrates in the riffle benthos was estimated from four Surber foot square samples taken in the riffle area upstream of the drift net after drift sampling was concluded. Fish were collected, by seining, at six-hour intervals on May 19-20 and four-hour intervals on August 10-11. The fish were measured and weighed, stomach contents were removed from the digestive tract beginning at the esophagus and extending to the first 180 degree turn, the contents were identified, counted and wet weighed. Invertebrates other than insects comprised only 0.3 per cent of the total numbers of aquatic drift. Chironomidae larvae and pupae dominated drift collections in April and May. The mayflies, Baetis and Caenis, the adult elmid, Dubiraphia vittata and the caddisfly, Cheumatopsyche, were the predominant taxa in the August and September drift samples. Several insects collected during this study had not previously been reported as part of the drift or as drifting within a pattern of diel periodicity in warm water streams these included: Isonychia, Pseudocloeon dubium, Stenacron interpunctatum, Dubiraphia vittata, Macronychus glabratus, Stenelmis crenata, and Simulium. Benthic samples contained fewer taxa than drift samples and some invertebrates which were common in the drift were not present in bottom samples. Terrestrial invertebrates contributed nearly one-third of the drifting biomass over the entire study period and adult chironomids were the predominant taxonomic group. Adults from aquatic immature stages (Chironomidae, Hydropsychidae, Ephemeroptera) drifted within a pattern of diel periodicity, however adults from terrestrial origins exhibited no consistent patterns of drift. Peaks in feeding activity of the striped shiner occurred prior to sunset and after sunrise, therefore, it was not feeding most actively when drift densities were highest. Chironomid larvae were the principal food item of the striped shiner, even though other aquatic insects were common in the drift. Diurnal drift densities of chironomid larvae were higher than other prey organisms and therefore they were more available as a food item when fish were feeding most actively