Date Approved

3-2013

Graduate Degree Type

Thesis

Degree Name

Biology (M.S.)

Degree Program

Biology

Abstract

My study focused on a threatened population of lake sturgeon (Acipenser fulvescens) in the Muskegon River system, Michigan. I assessed the condition, growth and population dynamics of lake sturgeon and compared them to nearby populations using a lengthweight relationship and the von Bertalanffy growth model. I also estimated the abundance of adult lake sturgeon in the Muskegon River system during the spawning run using closed-population models, analyzed movements of adult lake sturgeon during their spawning migrations using ultrasonic telemetry in 2011, and verified reproductive success by capturing larvae with drift nets in 2010 and 2011. The capture of adult lake sturgeon was performed using boat electrofishing and large-mesh gill netting in the spring, and juvenile lake sturgeon were captured using small-mesh gill netting in the fall. From 2008 to 2011, 141 individual lake sturgeon (24.9 – 191.0 cm total length; 0.05- 59.50 kg weight) were captured. Of these, 116 lake sturgeon were aged using pectoral fin rays, representing 24 age cohorts. The weight-length relationship for captured lake sturgeon, where W is weight (kg) and TL is total length (cm), is log10(W) = -6.13 + 3.42•log10(TL) and the von Bertalanffy growth model is TL = 177.62 (1-e-0.0985(t-1.0035)), where t is age. Compared to nearby systems, a 100-cm individual from the Muskegon system tended to weigh less (average: -0.98 kg), and individuals age 23-27 years tended to be longer at age (average: +18.0 cm). Abundances were estimated for the 2009 and 2010 spawning migrations, which were 46 (95% CI: 37-67) and 39 (95% CI: 27-67) individuals, respectively. Successful reproduction in the Muskegon River was confirmed by the capture of 16 larval lake sturgeon in 2010 and 2 individuals in 2011. Consistent with other studies, the onset of larval drift was at a water temperature of 16 °C. The number of larvae drifting downstream appeared to become heavily diluted with increasing distance downstream of a known spawning site. Overall, my results suggest the Muskegon River supports a small (in terms of annual population numbers), healthy (in terms of individual growth rates and proportion of individuals less than age 5), naturally-reproducing population of lake sturgeon. Nevertheless, the small size of the annual spawning run suggests the population should continue to be protected and be the focus of restoration.

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