Trophic Interactions and Habitat Quality of Invasive Lionfish in the Gulf of Mexico
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Louisiana State University LSU Digital Commons LSU Master's Theses Graduate School July 2020 Trophic Interactions and Habitat Quality of Invasive Lionfish in the Gulf of Mexico Hanna Bauer Follow this and additional works at: https://digitalcommons.lsu.edu/gradschool_theses Recommended Citation Bauer, Hanna, "Trophic Interactions and Habitat Quality of Invasive Lionfish in the Gulf of Mexico" (2020). LSU Master's Theses. 5185. https://digitalcommons.lsu.edu/gradschool_theses/5185 This Thesis is brought to you for free and open access by the Graduate School at LSU Digital Commons. It has been accepted for inclusion in LSU Master's Theses by an authorized graduate school editor of LSU Digital Commons. For more information, please contact [email protected]. TROPHIC INTERACTIONS AND HABITAT QUALITY OF INVASIVE LIONFISH IN THE GULF OF MEXICO A Thesis Submitted to the Graduate Faculty of Louisiana State University and Agricultural and Mechanical College in partial fulfillment of the requirements for the degree of Master of Science in Department of Oceanography and Coastal Science by Hanna Bauer B.S. University of Portland, 2015 August 2020 Acknowledgments I would like to acknowledge my advisor Dr. Cassandra Glaspie, as well as my committee members Dr. Michael Dance, Dr. Dubravko Justic, and Dr. Karen Maruska. Additionally, Dr. Michael Polito, Dr. Hayat Bennadji, Thomas Blanchard, and Dr. Steve Midway provided input and guidance. I sincerely thank my lab members Neal Kolonay, Jill Tupitza, Carolyn Swize, Emily Shallow, and Taylor Clemment for all their help and support with this project. Finally, I would like to thank Louisiana State University for the opportunity to pursue my education. ii TABLE OF CONTENTS Acknowledgments .............................................................................................................. ii List of Tables .................................................................................................................... iv List of Figures .................................................................................................................... v Abstract ............................................................................................................................. vi Chapter 1. Invasive Lionfish Size and Reproductive Capability Across a Depth Gradient in the Florida Keys .............................................................................................................. 7 INTRODUCTION ................................................................................................................. 7 METHODS ....................................................................................................................... 12 RESULTS ......................................................................................................................... 16 DISCUSSION .................................................................................................................... 18 REFERENCES ................................................................................................................... 25 Chapter 2. Trophic Interactions of Invasive Lionfish Across a Depth in the Florida Keys ................................................................................................................................. 31 INTRODUCTION ............................................................................................................... 31 METHODS ....................................................................................................................... 34 RESULTS ......................................................................................................................... 38 DISCUSSION .................................................................................................................... 46 REFERENCES ................................................................................................................... 54 Chapter 3. Habitat Modeling for Invasive Lionfish in the Gulf of Mexico Using a Bioenergetics-Based Growth Model ................................................................................. 59 INTRODUCTION ............................................................................................................... 59 METHODS ....................................................................................................................... 62 RESULTS ......................................................................................................................... 70 DISCUSSION .................................................................................................................... 76 REFERENCES ................................................................................................................... 84 Conclusion ....................................................................................................................... 91 Vita ................................................................................................................................... 93 iii LIST OF TABLES 1.1. Frequency of each lionfish sex by season and depth, including the female to male ratio ............................................................................................................................ 13 2.1. MANOVA results of δ13C and δ15N values as dependent variables, and depth, season, and the depth-season interaction as independent variables. .......................... 42 2.2. Isotopic niche metrics for assessing species isotopic niches by season and depth. ... 44 2.3. Trophic niche overlap estimates for combined and individual ellipse areas for season-depth groupings .............................................................................................. 45 3.1. Bioenergetic parameters and variables used .............................................................. 68 3.2. Gamma regression model output of depth, season, sex, length on lionfish muscle caloric density ............................................................................................................ 71 iv LIST OF FIGURES 1.1. Map of sample collection sites near Marathon Key, Florida ..................................... 13 1.2. Distribution of depths that lionfish sample were collected from in the Florida Keys 14 1.3. Lionfish standard length by sex, where undetermined sex fish are immature, and the depth is indicated by the color. ............................................................................ 16 1.4. Female GSI by season and depth ............................................................................... 17 2.1. Teleost families in stomach contents ......................................................................... 39 2.2. Percent number of each prey category in deep and shallow lionfish stomachs, both fall and spring seasons combined. ............................................................................. 40 2.3. δ13C and δ15N biplot for all lionfish samples and standard ellipse areas ................... 42 2.4. Mean estimates with standard error for isotope values of the total mean, fall samples, and spring samples ...................................................................................... 43 2.5. Bayesian estimates of standard ellipse areas (with 95% confidence intervals shown for season-depth groupings. ............................................................................ 45 3.1. Map of natural and artificial structured habitats off the coast of the United States in the Gulf of Mexico. ................................................................................................ 66 3.2. Gulf of Mexico regions identified for this study with fall bottom temperatures ....... 70 3.3. Correlation between female lionfish GSI values and caloric density with 95% confidence intervals ................................................................................................... 72 3.4. Lionfish GRP value estimated at each identified structured habitat for four seasons 73 3.5. Growth Rate Potentials for lionfish by region in the Gulf of Mexico ....................... 74 3.6. USGS reported lionfish sightings in the Gulf of Mexico and model GRP output values at identified lionfish habitat ............................................................................ 75 v ABSTRACT Lionfish (Pterois volitans and Pterois miles) are one of the most successful marine invaders of all time and pose a threat to native species that inhabit coral reefs, as well as overall reef health. Current management efforts in the invaded Atlantic region revolve around spearfishing to remove lionfish, often limited to 30 m depth. There is evidence that lionfish may seek refuge from fishing pressure in deeper habitat and replenish shallow sites, undermining this management strategy. To investigate the ecological implications of deep lionfish, size, reproductive capability, and diet were examined across a depth gradient for lionfish in the Florida Keys. It was found that size weakly increased with increasing depth and that shallow lionfish had higher reproductive potential. Sex ratios were female-biased in shallow sites. Lionfish are eating a range of teleosts and decapod species, including those of economic importance, and deeper lionfish are eating at a higher trophic level than shallow fish. These results were used to inform the parameters of a bioenergetic-based growth model for lionfish in the Gulf of Mexico. Prey energy density was