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

Transactions of the American Fisheries Society

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Abstract

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.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Estimating mortality rates of adult fish from entrainment through the propellers of river towboats
Series title:
Transactions of the American Fisheries Society
Volume
132
Issue:
4
Year Published:
2003
Language:
English
Contributing office(s):
Upper Midwest Environmental Sciences Center
Description:
pp. 646-661
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
First page:
646
Last page:
661
Number of Pages:
16