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Tuesday, February 7 • 10:40am - 11:00am
Technical Session. Latitudinal Trends in the Age and Growth of Freshwater Drum Along the Mississippi River

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AUTHORS: Joshua Abner, Tyler Ham, Edward Sterling - Southeast Missouri State University; Quinton Phelps, Missouri Department of Conservation

ABSTRACT: Effects of latitude are present in age and growth data for multiple groups of organisms, including fishes.  Widely distributed species are subject to broad environmental gradients with differences in temperature, light, and growing season length, which translate to variations in the dynamic rate functions of populations (i.e., recruitment, growth, mortality).  To persist under broad conditions, populations must exhibit substantial morphological, physiological, and genetic differences.  When evaluating wide geographic distributions of fishes in a large river system, one particular interest is the effect of latitude on growth and body size.  Bergmann’s Rule states that as latitude increases, body size increases.  Equally, the Converse of Bergmann’s Rule states that as latitude increases, body size decreases.  The goal of this study was to investigate effects of latitude on age and growth of Freshwater Drum (Aplodinotus grunniens) in the Mississippi River. 715 specimens were collected from 1992-1996 along a broad latitudinal range of the river at each of the six Long Term Resource Monitoring (LTRM) field stations. From our analyses, we determined that drum from northern locations grow slower, and are consequently smaller at each age class than their southern counterparts.  One potential hypothesis to explain these results relates to colder water temperatures and shorter growing seasons in more northern latitudes. This research has significant implications for understanding Freshwater Drum population dynamics in the Mississippi River.

Tuesday February 7, 2017 10:40am - 11:00am CST
Grand Ballroom C