Date of Award

2021

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Natural Resources

First Advisor

Donna L. Parrish

Abstract

Lake sturgeon (Acipenser fulvescens) in Lake Champlain were listed as endangered in 1972. Significant gaps exist in understanding lake sturgeon in the system as well as the methods needed to properly monitor and assess them. My research had three main goals: (1) investigate movements and habitat use of lake sturgeon in the Lake Champlain basin, (2) develop a method to estimate lake sturgeon abundance using sonar technology, and (3) test an alternative method for aging lake sturgeon.

One of the primary information gaps for lake sturgeon in Lake Champlain is an understanding of the movements and habitat use of multiple life stages. I used acoustic telemetry to describe seasonal movement patterns and distribution of adult and juvenile lake sturgeon and to quantify the spatial overlap between these life stages. We found that juvenile and adult home ranges overlapped in shallow (< 10 m) water in the summer and fall. During the winter, adults remained in shallow water and juveniles moved to deep-water (> 25 m) overwintering sites. These results identified important areas for lake sturgeon and indicated that there are seasonal differences in habitat use between life stages. I also used acoustic telemetry to describe adult lake sturgeon movement patterns during the spawning period and to investigate environmental drivers of these movements in the Winooski River. River discharge, temperature, the magnitude and direction of the change in temperature (3-day lag), and time of day were significant factors in describing upstream movements. Adult lake sturgeon displayed general movement patterns that included a single run upstream, upstream and downstream movements throughout the river, or multiple runs made up the entire length of the spawning tributary to the spawning site. An understanding of the movements during the spawning period was key in the method I developed to estimate lake sturgeon abundance.

To estimate abundance of lake sturgeon spawning in the Winooski River, I used acoustic telemetry data from adult lake sturgeon to estimate observation probability of the sonar and the probability that a lake sturgeon had been seen previously during the season. Using a Bayesian integrated model, I combined these parameters with counts from a dual-frequency identification sonar (DIDSON) to estimate abundances each year: 110 (47 – 229 CI) in 2017, 133 (79 – 242 CI) in 2018, and 99 (51 – 220 CI). The results of this work represent the first estimate of abundance for spawning lake sturgeon in a Lake Champlain tributary, and will be key to tracking progress towards lake sturgeon recovery moving forward.

Age data in long-lived species such as lake sturgeon can point to signs of successful recruitment and recovery. I investigated use of the second marginal pectoral fin ray as an alternative, less invasive method for estimating ages of lake sturgeon. The variability of age estimates among different readers and fin structures indicated that the second fin ray may provide some utility to age juvenile lake sturgeon but is not a viable substitute for estimating ages of adult lake sturgeon. These results provide valuable information to managers looking to gain essential age data while also decreasing the impact of handling endangered lake sturgeon.

Language

en

Number of Pages

174 p.

Available for download on Sunday, April 23, 2023

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