Document Type

Dissertation - Open Access

Award Date

2016

Degree Name

Doctor of Philosophy (PhD)

Department / School

Natural Resource Management

First Advisor

Brian Graeb

Keywords

aging reservoir, bioenergetics, climate change, Largemouth Bass

Abstract

There are an estimated 3-9 million small reservoirs and nearly 1,000 large reservoirs in the United States. Most of these reservoirs were built several decades ago and are experiencing symptoms of reservoir aging, including loss of habitat, sedimentation, and decreased fishery production. Furthermore, over the last several decades, there has been an increasing interest among anglers for high quality, trophy fisheries. However, little is known about exactly how the reservoir aging process affects the ecology and especially growth potential of Largemouth Bass, particularly under potential climate change scenarios. Grand Lake in TX is a 45ha ageing reservoir that was built in the 1950s and provides a great laboratory to examine how aging reservoirs affect the ecology and growth potential of Largemouth Bass. We conducted seasonal sampling using boat electrofishing to quantify population genetics, growth, condition, and survival over 3 years. We also assessed movement patterns, habitat use, and seasonal diets. This information was used to model growth potential of Grand Lake Largemouth Bass under predicted future temperatures as a result of climate change as well as different diets. We found that genetics are optimal for Largemouth Bass growth in Grand Lake. The population is composed of primarily Florida parental type Largemouth Bass (28%) and Fx hyrbids (41%), and no differences in growth were detected among the genetic parental types. Survival was also high enough to have trophy sized Largemouth Bass with individuals observed to live to ages 9-10, and survival estimates from PIT tagged Largemouth Bass were approximately 70%. Population growth was slow for all adults ages 5 and older, with observed mean lengths at age at or below the 50th percentile for ecoregion 8 of the United States. Largemouth Bass consumed an even mix of crayfish and fish during spring (May-June) and then switched over to feeding primarily on fish for the rest of the growing season. Under future predicted climate change models, Largemouth Bass will have to increase consumption by 5-20% just to meet baseline energetic demands, and if consumption remains the same as observed in 2013 and 2014, growth will decrease dramatically. Largemouth Bass were able to grow much faster on a diet of 100% shad compared to observed diets or a diet of 100% crayfish. Seasonal use areas were considered large at nearly 5ha during each of the three month summers. Use areas decreased during winter and spring. Largemouth Bass also tended to stay offshore (averaging 30-50m offshore) and use deeper water throughout most of the year, except during spring spawning. Daily movement rates and use areas were also high with mean daily use areas being 2-5ha during the summer months and total daily movement rates averaging 600-1,000m per day. Having more prey fish available in the spring could enhance Largemouth Bass growth if they switch over to feeding on these prey fish rather than crayfish. Bioenergetics simulations also revealed that consumption is going to have to increase substantially to counter the effect of global climate change, although water temperatures will be higher than the thermal optima for Largemouth Bass, limiting their growth and consumption. Systems such as aeration should be considered to reduce water temperatures closer to the thermal optima of Largemouth Bass. The lack of habitat due to reservoir aging has resulted in large daily and seasonal use areas as well as large daily movement rates for Largemouth Bass in Grand Lake. Increased habitat should allow Largemouth Bass, a habitat associate species, to forage more efficiently and thus grow faster.

Library of Congress Subject Headings

Largemouth bass -- Ecology -- Texas

Fish stocking -- Texas

Fisheries -- Texas

Description

Includes bibliographical references

Format

application/pdf

Number of Pages

281

Publisher

South Dakota State University

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Rights Statement

In Copyright