Age Structure and Reproductive Activity of the Blue Sucker in the Milk River, Missouri River Drainage, Montana

Authors

Julie Bednarski, University of IdahoFollow
Dennis L. Scarnecchia, University of Idaho

Date of this Version

9-2006

Document Type

Article

Citation

The Prairie Naturalist (September 2006) 38(3): 167-182

Comments

Copyrigh 2006, Bednarski and Scarnecchia. Used by permission

Abstract

The life history and ecology of the blue sucker (Cycleptus elongatus) in the lower Milk River, Montana were investigated in 2002 and 2003. A total of 253 blue sucker was captured; 248 adult fish, three larval fish, and two age-0 juveniles. The ages (n = 102) of the adult blue sucker ranged from 10 to 37 years; maximum age greatly exceeded ages reported in other studies. Blue sucker in the Milk River population grew slower, matured later, and lived longer than fish at lower latitudes. Adult females of the blue sucker were longer and weighed more than adult males at a given age. The Yon Bertalanffy growth equations for length were expressed as L = 752.9(1-e^-0.1457t) for females and L = 695.1 (1-e^-0.1743t) for males. The Yon Bertalanffy growth equations for weight were expressed as W = 3844.3[(1-e^(-0.1412t))^2.8171] for females and W = 2754.9[(1-e^(-0.16041))^2.8883] for males. In 2002, 189 out of 222 adult fish were determined to be reproductively active: 93 females and 96 males. In 2003, one female fish out of 26 fish caught was determined to be reproductively active. Catches of adult blue sucker were highest during periods of high spring discharge as adults likely migrated into the Milk River from the Missouri River to spawn during May and June.