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Assessment of Potential Effects of Increased Commercial Navigation on the Fishes of the Upper Mississippi River System

Large rivers of the United States are managed by multiple agencies for multiple uses, including commercial navigation (shipping). Commercial vessels, such as towboats, entrain large volumes of water through their propellers. Fish that pass through those propellers may be injured or killed.

This entrainment mortality of fish has not previously been measured, but is well known from descriptive accounts. Commercial shippers have proposed increasing the navigation capacity of the Upper Mississippi River System. Therefore, decision makers, including the U.S. Army Corps of Engineers and the U.S. Fish and Wildlife Service, need estimates of entrainment mortality and the effects of this mortality on fish populations.

Earlier in this study we did the following:

1. Quantified the distribution of larval fish for incorporation into a model of entrainment losses of adult-fish equivalents.
2. Developed new methods to estimate abundance and entrainment mortality of adult fish in navigation channels of large rivers.
3. Estimated abundance of adult fish in the navigation channels.
4. Obtained the first estimates of entrainment mortality of adult fish per mile of towboat travel.

This previous work was conducted in the states of Illinois and Missouri in Pool 26 of the Mississippi River and the lower 20 miles of the Illinois River. Ongoing work will improve the precision of the estimates of entrainment mortality and will identify how those estimates are affected by sample size, estimation method, and the probability of detecting killed fish. We have also proposed expansion of this work throughout the Upper Mississippi River System.

The expanded work would assess fish mortality inside lock chambers and examine operational strategies that would reduce mortality. Additionally, we would assess the sublethal effects of fish entrainment, such as denial of habitat by disturbance and loss of production to avoidance reactions. This project is being funded by the U.S. Army Corps of Engineers. Research on assessment of potential effects of increased commercial navigation on the fish of the Upper Mississippi River System began in 1994 and was completed in December 2001.

Principal Investigator: Steve Gutreuter