Effect of Hydroperiod on the Growth of the Crayfish Species Procambarus Alieni and Procambarus Fall Ax: Two Keystone Species in the Florida Everglades
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THE EFFECT OF HYDRO PERIOD ON THE GROWTH OF THE CRAYFISH SPECIES PROCAMBARUS ALLEN! AND PROCAMBARUS FALLAX: TWO KEYSTONE SPECIES IN THE FLORIDA EVERGLADES by Matthew D. Gardner A Thesis Submitted to the Faculty of The Charles E. Schmidt College of Science in Partial Fulfillment of the Requirements for the Degree of Master of Science Florida Atlantic University Boca Raton, Florida August 2006 © Copyright by Matthew D. Gardner 2006 11 THE EFFECT OF HYDROPERIOD ON THE GROWTH OF THE CRAYFISH SPECIES PROCAMBAR US ALLEN! AND P. F ALLAX: TWO KEYSTONE SPECIES IN THE FLORIDA EVERGLADES by Matthew D. Gardner This thesis was prepared under the direction of the candidate's thesis advisor, Dr. John C. Volin, Department of Environmental Science, and has been approved by the members of his supervisory committee. It was submitted to the faculty of The Charles E. Schmidt College of Science and was accepted in partial fulfillment of the requirements for the degree of Master of Science. SUPERVISORY COMMITTEE: Dr. Ja . Stauffer, Jr. Date lll ACKNOWLEDGEMENTS I would like to thank the members of my advisory committee, Dr. John C. Volin, Dr. John D. Baldwin, and Dr. Jay R. Stauffer, Jr. for their helpful comments. I would especially like to thank Dr. Volin for extending the opportunity to perform this project and for helping me see it to completion. I also extend my thanks and appreciation to Michael S. Lott for his endless support and assistance at every stage of this study. I thank Dr. Dianne Owen for her helpful comments regarding statistical analysis. Finally, I thank all ofthe individuals who helped me complete the field and laboratory work associated with this project. Funding for this project was provided by the South Florida Water Management District through the Recover program (CP040132). lV ABSTRACT Author: Matthew D. Gardner Title: The effect of hydroperiod on the growth of the crayfish species Procambarus alieni and Procambarus fall ax: two keystone species in the Florida Everglades Institution: Florida Atlantic University Thesis Advisor: Dr. John C. Volin Degree: Master of Science Year: 2006 The Everglades ecosystem is home to two species of freshwater crayfish: the Everglades crayfish Procambarus alieni and the slough crayfish Procambarus fallax. These species play a key ecological role by transporting energy from primary producers to higher trophic levels. Understanding the factors that regulate crayfish growth is an essential step in restoring their productivity in the Everglades ecosystem. In order to determine the effect ofhydroperiod on crayfish growth, I collected crayfish from the Florida Everglades and subjected them to one of three hydroperiod treatments. The growth of both crayfish species in reduced hydroperiod treatments was significantly less than those in long hydroperiod treatments. Procambarus alieni had a significantly faster initial growth rate than P. fallax, which may give it a competitive advantage in shorter hydroperiod marshes and help explain the distributions of these two species. The results of this study indicate that lengthening hydroperiods in the Everglades ecosystem may have a positive effect on crayfish productivity. v TABLE OF CONTENTS LIST OF FIGURES .... .. ............................... ........... ... ... .. ........................ vii LIST OF TABLES ................... ................................................ .... .......... viii INTRODUCTION ....................................... .. .................... ....................... 1 METHODS ............................................ ... ... ... ... ... .. .... ........................... 8 Experimental Design ... ... ................ .... ...... ... ...................... ................ ..... 8 Statistical Analysis .... .... .... .. ..... .................................. .. ........... ............ 13 RESULTS .................................................... ........................................ 15 DISCUSSION ............................ ........................................................... 26 LITERATURE CITED ..................................... ................ ...................... 35 Vl LIST OF FIGURES Figure 1. Collection sites of Procambarus alieni and Procambarus faliax in Water Conservation Area 3A and southwestern Shark River Slough, Everglades National Park .................................... 9 Figure 2. Example of one of six 6.1 m x 3.0 m concrete block mesocosms used to study crayfish growth ..... ................................... 10 Figure 3. Mean(± S.E.) dry mass and fresh mass measurements for Procambarus alieni and Procambarus fallax through time ........................................................ ; ............................ 18 Figure 4. Mean(± S.E.) final relative growth rate for Procambarus alieni and Procambarus faliax in short, medium, and long hydroperiod treatments where relative growth rate is based on dry mass and fresh mass ....................................... ......... 21 Figure 5. Mean(± S.E.) relative growth rates based on dry mass for Procambarus alieni and Procambarus fall ax treatments through time ............................................................... 23 Vll LIST OF TABLES Table 1. Comparison of male and female fresh mass and dry mass at time for Procambarus alieni and Procambarus fallax .. ... ....................................... ..... ............. .................... 16 Table 2. Linear regression equations used to estimate dry mass for Procambarus alieni and Procambarus fall ax ... ... .................. 17 Table 3. Mean (±S.E.) total length (mm) for Procambarus alieni and Procambarus fall ax at time ................................................... 24 Vlll INTRODUCTION The Everglades ecosystem has undergone a variety of changes resulting from anthropogenic influences; including the alteration of historical hydropattems, water quality changes, fragmentation, and compartmentalization (Light and Dineen 1994). Wide scale changes in the Everglades first began in the late 1880's with the construction of canals leading from Lake Okeechobee to the Gulf of Mexico. By 1929, there were five major canals leading from Lake Okeechobee to the Atlantic Ocean (DeGrove 1974). In 1928 and 194 7, South Florida experienced two major hurricanes that resulted in widespread flooding and economic damage (Light and Dineen 1994). These events provided the impetus that was needed to begin larger water management projects throughout southern Florida. Today, the region has 1,600 km of levees, 1,160 km of canals and nearly 200 water control structures (USACE 2005) that provide flood protection, irrigation for agricultural needs, retention areas for drinking water and control inputs to Everglades National Park (Hendrix 2000). The hydropattem, water quality, and landscape changes have altered the Everglades ecosystem in a number of ways. For example, researchers have observed shifts in the composition of plant communities (Davis et al. 1994; Davis et al. 2005; Ogden 2005), decreases in marsh fish abundance (Loftus et al. 1990; Loftus and Eklund 1994), severe reductions in wading bird populations (Ogden 1994), decreased production among the Everglades crayfish (Procambarus alieni) (Faxon) (Acosta and Perry 2001; Acosta and Perry 2002a), etc. The Everglades ecosystem is comprised of a variety of 1 plant communities that are determined by and respond to a variety of fluctuating environmental variables (Gunderson 1994). Davis et al. (1994) and Ogden (2005) discuss the disturbance and alteration of marsh plant communities that most likely result from altered hydrology. Changes to hydrology patterns are most often expressed as decreased water levels and/or hydroperiods, although in some areas, the contrast is found where water levels and/or hydroperiods are greater than historical conditions. Changes to fire management practices in the Everglades have also contributed to shifts in vegetative communities (Ogden et al. 2005). Freshwater fishes are affected by shifts in vegetative communities and they represent an important component of the Everglades ecosystem; they are found throughout the trophic scale ranging from primary consumers of vegetation and detritus to top-level predators (Loftus and Eklund 1994). Loftus et al. (1990) and Loftus and Eklund (1994) discuss the reduction in small fish abundance due to repeated annual dry-downs in Northeast Shark River Slough. They speculate that historical fish biomass across the Everglades was many times greater than it currently is and that complete dry-downs were probably much more infrequent. One of the most dramatic reductions of a functional group has been among the wading birds. Ogden (1994) indicates that wading bird populations have experienced a 90% reduction from historical levels. Some authors have speculated that the reduction in wading bird populations may have resulted from a disturbance of their prey base within the Everglades ecosystem (Gunderson and Loftus 1993; Ogden 1994; Frederick and Spalding I. 1994; Gawlik 2002). Crayfish (Procambarus spp.) are an important prey item for many species and provide a direct link between primary producers and higher trophic levels (Acosta and 2 Perry 2001). Everglades crayfish are preyed upon by large fish, bull frogs (Rana grylio), American bitterns (Botaurus lentiginosus), pied-billed grebes (Podilymbus podiceps), white ibis (Eudocimus albus), raccoons (Procyon lotor), river otters (Lutra canadensis), and alligators (Alligator mississipiensis) (Kushlan and Kushlan 1979). Kushlan and Kushlan