Winged mapleleaf -
Quadrula fragosa (Conrad 1835)

General Introduction

The winged maple leaf mussel is a federally endangered species whose only known remaining population lives in a 20-kilometer stretch of the lower St. Croix River between Minnesota and Wisconsin.  Surveys of this stretch of river taken between 1988 and 1992 found just 77 individuals.  Recruitment in recent years has been low, with the last large cohort recruited to the population in 1984.  The specific habitat requirements of Q. fragosa are not known; the St. Croix River has generally high water quality and is a moderately to minimally disturbed watershed.  The river is a National Wild and Scenic River, which confers some protection from human disturbances to the population.  Major concerns for the population include:

• low reproduction
• low stream flow episodes
• high variation in stream flow caused by hydroelectric dam peaking operation during certain seasons
• toxic spills
• potential zebra mussel colonization of the St. Croix River
• habitat disturbance or alteration by recreational or commericial activities
• human and non-human predation and disturbance
• water quality deterioration
• land-use changes in the watershed
• lack of knowledge of the mussel's life history, especially its glochidial host.

Information for this page was paraphrased from "Winged Mapleleaf Mussel Recovery Plan (Quadrula fragosa)",written by Peter W. Vaughan, PhD. and published by the Department of the Interior United States Fish and Wildlife Service on June 25, 1997.