Date of Award

5-2017

Degree Type

Thesis

Degree Name

Master of Science

Department

Biology

Program

Biology

First Advisor/Chairperson

Jill Leonard

Second Advisor

Edward Baker

Third Advisor

Erich Ottem

Fourth Advisor

John Bruggink

Abstract

Raising lake sturgeon (Acipenser fulvescens) in hatcheries is an important tool for rehabilitation and conservation, but is expensive. When hatchery sturgeon do not grow large enough before stocking, their odds of survival decline significantly and resources are wasted. We investigated the potential limiting effect of large lake sturgeon on the growth rate of smaller conspecifics housed in the same tank, and the possibility of increasing growth rates by separating individuals into different size classes. We also examined plasma cortisol levels of the different size classes over time as an indicator of stress levels, and levels of free plasma thyroid hormones triiodothyronine (T3) and thyroxine (T4). A single family of lake sturgeon (one male/female cross) was raised in the Northern Michigan University Aquatics laboratory for one year. Growth of the sturgeon was determined both as group averages and for individuals. Separating lake sturgeon by size group had no discernable effect on average growth rates in any of the size categories, but individuals within size groups did show increased growth rates. All three categories ended the experiment with broadened size distributions. Cortisol levels showed no consistent differences based on size (Cortisol [pg/mL ± SE] =229.27 ± 11.21). Plasma thyroid hormone levels were also similar between size categories (T3 [pg/mL ± SE] =8.53 ± 0.26; T4=0.86 ± 0.04). Separation of lake sturgeon by size category does not appear to increase their average growth rates in captivity, but all size groups continued to increase in size throughout the experiment.

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