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Estimating mortality rates of adult fish from entrainment through the propellers of river towboats

January 1, 2003

We developed a method to estimate mortality rates of adult fish caused by entrainment through the propellers of commercial towboats operating in river channels. The method combines trawling while following towboats (to recover a fraction of the kills) and application of a hydrodynamic model of diffusion (to estimate the fraction of the total kills collected in the trawls). The sampling problem is unusual and required quantifying relatively rare events. We first examined key statistical properties of the entrainment mortality rate estimators using Monte Carlo simulation, which demonstrated that a design-based estimator and a new ad hoc estimator are both unbiased and converge to the true value as the sample size becomes large. Next, we estimated the entrainment mortality rates of adult fishes in Pool 26 of the Mississippi River and the Alton Pool of the Illinois River, where we observed kills that we attributed to entrainment. Our estimates of entrainment mortality rates were 2.52 fish/km of towboat travel (80% confidence interval, 1.00–6.09 fish/km) for gizzard shad Dorosoma cepedianum, 0.13 fish/km (0.00–0.41) for skipjack herring Alosa chrysochloris, and 0.53 fish/km (0.00–1.33) for both shovelnose sturgeon Scaphirhynchus platorynchus and smallmouth buffalo Ictiobus bubalus. Our approach applies more broadly to commercial vessels operating in confined channels, including other large rivers and intracoastal waterways.

Publication Year 2003
Title Estimating mortality rates of adult fish from entrainment through the propellers of river towboats
DOI 10.1577/T01-098
Authors S. Gutreuter, John M. Dettmers, David H. Wahl
Publication Type Article
Publication Subtype Journal Article
Series Title Transactions of the American Fisheries Society
Index ID 1003001
Record Source USGS Publications Warehouse
USGS Organization Upper Midwest Environmental Sciences Center