8092

• UCREFRP Catalog Number: 8092
• Author: U.S. Department of the Interior.
• Title: Proceedings of the Symposium on Restoration Planning for the Rivers of the Mississippi River Ecosystem.
• USFW Year: 1993.
• USFW - Doc Type: Washington, D.C.
• Copyright Material: NO

DoNFAGOANDJAvHATCH 23

Aquatic Resources of the St. Croix River Basin

by

Don Fago

Wisconsin Department Natural Resources
1350 Femrite Drive
Monana, Wisconsin 53716

and

Jay Hatch

Bell Museum \General College-University of Minnesota
128 Pleasant Street S.E.
Minneapolis, Minnesota 55455

Abstract. The St. Croix River is a sixth-order stream draining a 20,OI8-km2 area in
east-central Minnesota and northwestern Wisconsin. The 276-km mainstem (average
gradient = 0.46 m/km) includes a 1,889-ha natural lake at its mouth and two small
reservoirs created by the 3.7-km-high Gordon Dam and the 18-km-high St. Croix Falls
Dam. The latter dam, which has a discharge area of 16,162 km2 and an annual mean
discharge of120 m3/s (water years 1902-91), is a barrier to upstream fIsh migration. The
basin has a total of 134 dams on 1,770 tributary streams (9,004 km total length) and has
628 open lakes that are greater than or equal to 0.4 ha (41,012 ha total surface area).
Historically, 110 species of fish representing 24 families have been identified from the
St. Croix River basin. Six species have been introduced, while seven other native species
have not been collected since 1974. One species (Ammocrypta asprella) is on Wisconsin's
endangered species list, and eight species are on its threatened list. With a minimal
conunercial fishery, the sport fishery for walleye, sauger, smallmouth bass, brown trout,
and lake sturgeon constitutes almost all of the economic value of the fishery. There are
39 freshwater mussel species in the basin. Two species (Lampsilis higginsi and Quadrula
fragosa) are on the federal endangered species list. Nine species are considered
endangered and three threatened in Wisconsin. Aquatic insect surveys on the St. Croix
River and a few tributaries identified invertebrates representing 332 taxa, 235 genera,
and 100 families. In 1968, with the enacbnent of the National Wild and Scenic Rivers
Act, 165 km of the St. Croix River and 157 km of the Namekagon River became one of
the first eight rivers to become part of the National Wild and Scenic Riverway system.
In 1972, 87 km of the lower St. Croix River were added to the system. The water quality
of this scenic riverway is generally good and is one of the outstanding recreational
resources in the Midwest.

ffistorically, Native Americans used the St.
Croix River to travel between Lake Superior and
the Mississippi River basin. During the eight-
eenth century, the river became a major route for
French and English fur traders. In the nineteenth
century, the St. Croix River became one of the
most heavily used logging rivers in the central

United States (Dunn 1979). Early in this century,
an 18-m-high hydroelectric dam was built on the
mainstem at St. Croix Falls, Wisconsin, which in
Minnesota is known as Taylors Falls (Fig. 1), and
numerous smaller hydroelectric dams (most of
which have been removed) were constructed along
many of the tributaries. In 1880, the U.S. Army