William Fletcher | Geology Reports

USGS2001

Continuous automated sensing of streamflow density as a surrogate for suspended-sediment concentration sampling

A newly refined technique for continuously and automatically sensing the density of a water-sediment mixture is being tested at a U.S. Geological Survey streamflow-gaging station in Puerto Rico. Originally developed to measure crude oil density, the double bubbler instrument measures fluid density by means of pressure transducers at two elevations in a vertical water column. By subtracting the density of water from the value measured for the density of the water-sediment mixture, the concentration of suspended sediment can be estimated. Preliminary tests of the double bubbler instrument show promise but are not yet conclusive.

Conference Paper↗

USGS1998

Evaluation of two oral baiting systems for wild rodents

Tetracycline hydrochloride (TC)-treated peanut butter or rodent chow baits were distributed during March 1990, on separate 0.53 ha sites in Oglethorpe County, Georgia (USA). Rodents were trapped on a control site prior to bait distribution and on two baited sites 6 days post-distribution. Cleaned skulls from euthanized mammals were grossly examined for TC florescence using an ultraviolet (UV) light. Mandibles were sectioned and examined for TC fluorescence using an ultraviolet light microscope. All 21 cotton rats ( Sigmodon hispidus ), four eastern harvest mice ( Rithrodontomys humulis ), and two golden mice ( Ochrotomys nuttalli ) captured on the control site were negative for TC fluorescence. On the peanut butter bait site, mandible sections from 29 of 32 (91%) cotton rats, three of three (100%) eastern harvest mice, two of three (66%) golden mice, zero of five (0%) white-footed mice ( Peromyscus leucopus ), one of three (33%) short-tailed shrews ( Blarina brevicauda ), and zero of two (0%) least shrews ( Cryptotis parva ) were positive for TC. Results from the rodent chow bait site indicated that 18 of 25 (72%) cotton rats, zero of three (0%) eastern harvest mice, two of seven (29%) golden mice, zero of four (0%) white-footed mice, and zero of four (0%) least shrews were positive for TC fluorescence in mandible sections. These results suggest that a large portion of a free-ranging small rodent population can be administered biological markers or vaccines using baits.

Georgia↗