Date of Award

1967

Document Type

Thesis

Degree Name

Bachelor of Science (BS)

Department

Geology

Abstract

Mollusks of the Sheyenne River in eastern North Dakota were studied during the summer of 1966. Both living mollusks from the river and fossil forms from the exposed terrace sediments were collected. Nine species of mussels presently occur in the Sheyenne River: Fusconaia flava (Rafinesque), Amblema costata Rafinesque , Lasmigona compressa (Lea), L. complanata (Barnes), Anodonta grandis Say, Anodontoides ferussacianus (Lea), Strophitus rugosus (Swainson), Lampsilis siliquoidea (Barnes), and L. ventricosa (Barnes). Three other species, Quadrula quadrula Rafinesque, Proptera alata (Say) and Ligumia recta latissima (Rafinesque) occur only as fossils in terrace sediments.

Nine genera of gastropods and fingernail clams (sphaeriids) now exist in the river. These same nine genera have also been collected from river terrace sediments.

Long periods of no flow, high alkalinity, high turbidity, unavailability of the proper fish host, and small low-water check dams may be possible factors limiting the mussel distribution in the Sheyenne River. Some of these factors may also limit the gastropod and sphaeriid distribution. Long periods of no flow is perhaps a limiting factor in the upper reaches of the river. High alkalinity may also be another limiting factor in the upper reaches. High turbidity in the lower reaches appears to be a limiting factor here. The absence of particular fish hosts for mussels and small low-water check dams may be significant limiting factors in the upper reaches above Baldhill Dam.

A comparison between the present and fossil gastropods and sphaeriids suggest that no appreciable faunal change has occurred. In comparing the present and fossil mussel fauna, three species, Quadrula quadrula, Proptera alata, and Ligumia recta latissima, were found only as fossils. These three species presently occur in the Red River Valley only in rivers of significantly greater discharge. This suggests that the Sheyenne River had a greater discharge at times in the past.

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