POPULATION DYNAMICS AND MOVEMENT OF OZARK CAVEFISH IN LOGAN CAVE NWR, BENTON COUNTY, ARKANSAS, WITH ADDITIONAL BASELINE WATER QUALITY INFORMAT ION by Myron L . Means Arkansas Cooperative Fish and Wi ldlife Research Unit Department of Biological Sciences University of Arkansas Fayetteville, Arkansas 1993 COOP UNIT PUBLICATION NO. 15 This study was funded by U.S. Fish and Wildlife Contaminant Study Funds &fl-1-f//( Project Code 92-4N07 13 .~~~0 7 30 f 3 POPULATION DYNAMICS AND MOVEMENT OF OZARK CAVEFISH IN LOGAN CAVE NWR, BENTON COUNTY, ARKANSAS WITH ADDITIONAL BASELINE WATER QUALITY INFORMATION iv ACKNOWLEDGEMENTS I would like to thank the U.S. Fish & Wildlife Service: Arkansas Cooperative Fish and Wildlife Research Unit and Logan Cave National Wildlife Refuge, personnel for funding this project and allowing me to work on the Ozark cavefish. I would like to thank the Arka.nsas Game & Fish Commission, especially Rex Roberg, for assisting in several sampling runs and technical advice. I would especially like to thank Mark Clippenger, Arkansas State Parks and Tourism, for spending countless hours of his own time helping me with sampling runs in frigid cave waters. A great deal of thanks goes to my major professor, Dr. James Johnson, who always sacrificed his time unselfishly to assist me in obtaining federal permits and offering valuable advice while formulating and completing my thesis. I would like to thank all the students who assisted with my project, namely: Darrell Bowman, Lowell Aberson, Madeline Lyttle, Gary Seigwarth, Andy Thompson, Jody Walters, and Kristie Hurbert. I also wish to thank my committee, Dr. Charlie Amlaner and Dr. Kenneth Steele, for offering valuable information and technical assistance. Last, but certainly not least, a special thanks goes to my family. My parents for their support of my academic history, and Trish, thank you most of all for making immense sacrifices and offering me invaluable support to further my professional career. Thanks Trish. v TABLE OF CONTENTS page .Abstract.. • . • . • • • • • . • 1 Introduction. • . • . 3 Study Site.............................................. 12 Objectives.............................................. 15 Methods and Materials Cave fish sampling. .................................... 17 Water qu.ali ty. 2 0 Results Cavefish populations. 22 Cavefish movement .......••.• 23 Growth .••••.•••..•••••.••••••• 24 Water qu.ality. 25 Discussion Cavefish movements. • . • • • • • . • • • . • . • . • • • • • • • . • • • • • 27 Cavefish populations •••• 31 Growth and reproduction. 36 Water qu.ality .. 38 Literature Cited ..........••...................•..•... 46 Figures. 51 Tables.................................................. 93 Appendix A. • • • • . • • • . • . • • • • • • • • . • • • • • • • • . • • • • • • • • • • • • • • • • 9 7 Appendix B • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 9 9 Appendix C • • • • • • • • • • • • • • • • • • • • . • • . • . • • • . • . • . • • • • • • • • • • • • l 0 6 Appendix D. • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 12 3 1 ABSTRACT The population dynamics, general biology, and movements of the threatened Ozark cavefish (Amblyopsis rosae) were studied in Logan Cave National Wildlife Refuge, Arkansas. General water quality characteristics for surface recharge streams as well as Logan Cave were monitored from Aug 1992 to Dec 1992 to determine the significance of recharge streams to the Logan Cave stream system. A DataSonde 3 Hydrolab Unit recorded water quality for Logan Cave from Aug 1991 to Jan 1993. Rainfall for the recharge area of Logan Cave was also recorded and plotted against Logan Cave water quality parameters. Logan Cave was mapped and classified into regions to monitor cavefish movements.. Cavefish were tagged using visual implant tags developed by Northwest Marine Technilogical Institute. A mark/recapture sampling effort marked a total of 80 cavefish over a six month period, ranging in size from 8 to 65 mm total length. Schnabel and Peterson population estimates yielded 92 and 72 fish, respectively. Cavefish were captured throughout the entire cave system, and moved throughout the entire system as well. Gross movements of the cavefish ranged from 1 m to 985 m. Net/gross movement ratio was higher in the upper region than the lower regions. Movement was positively correlated with size of the fish, with larger fish moving greater distances. Growth was calculated at a rate of .7 mm/month for nine fish. Two hundred and eighty-nine mean 2 daily readings were recorded for conductivity, dissolved oxygen and temperature from Logan Cave stream, with means of 245.6 uS/em, 6. 95 mg/l, and 14. 48°C, respectivily. Rainfal·l events were closely correlated with fluctuations in the Logan Cave water quality parameters. There was no significant difference (P > .OS) between the water quality! of Logan Cave stream and its surrounding recharge streams • . All heavy metal and pesticide analysis were well below the EPA lower limits. 3 INTRODUCTION At present, there are 40,000 known caves in the United States, with perhaps only 10% of them opening to the outside (Curl 1958). These cave systems are not just limited to passages large enough for a person to pass throug~, but include countless smaller cracks and crevices that have never been explored (Holsinger 1988). Because of ~imited access to such vast underground systems, only a portion of cave dwelling organisms that inhabit them have been observed, identified, or studied. Troglobitic faunas in cracks and intersticial spaces filled with groundwater have been documented for years by sampling of wells, pumping ground water, and collecting in and around .caves, resurgent streams, seeps, and drain tiles (Vandel 1965) . The cave environment is extremely stable (Barr and Keuhne 1971) and such stability is considered a requisite for the troglobitic organisms that inhabit cave systems (Heuts 1951) . Cave aquatic systems are not as stable as their underground terrestrial counterparts because of relationships with surface waters that includes periodic flooding (Poulson 1961). Hawes (1939) stated that flooding was primarily responsible for organic import into cave aquatic ecosystems and is the most important ecological factor benefiting cave environments. Bats, and especially bat guano, are also reported to be important nutrient sources for aquatic ecosystems (Poulson 1972). Barr (1968) 4 and Culver (1982) reported the basic food source in most cave ecosystems was organic matter from external sources, which in turn, when consumed by microorganisms, created a food source for vertebrates. Heuts {1953) described the cave system as an neconomically closed systemn with few species and niches. ~ With few species and niches, ecological diversity in caves is limited. The major reason for low species diversity in caves is the absence of light and thus photosynthesis, causing a reduced energy food base {Poulson 1990) . Underground aquatic systems receive approximately .001% of the energy input of their surface counterparts (Aley and Aley 1979). This low food supply has resulted in cave species becoming generalists and reducing their metabolic rate. Cave dwelling organisms generally tend to be blind, while surface dwelling species rely heavily on sight. To compensate for the blindness, cave dwellers have developed keen and sophisticated sensory systems especially adapted to the cave environment (Culver 1970) . Cave systems are inhospitable to surface dwelling organisms which lack the necessary metabolic and sensory adaptations that are essential to living in cave environments. Conversely, these adaptations make establishment of cave organisms in outside habitats unlikely. This limited ecological diversity in cave communities can lead to rapid extirpation of cave 5 adapted organisms by direct or indirect adverse environmental alterations. Groundwater storage systems (aquifers} usually have hydraulic connections with surface waters. Aquifer volume is the result of topography, geology, temperature, and climate (Dilamarter and Csallany 1977}. Aley and Aley {1987} discussed the dynamic aspects of groundwater systems. The "water table" of an area is an irregular, non­ continuous, non-uniform boundary between saturation zones. Water tables receive water through two types of recharge: discrete and diffuse. Discrete recharge is water that is channelled, usually quite rapidly, into the aquifer at specific localities. Recharge channels usually consist of cracks in the underlying rock formations that open directly into the water table. There are three types of discrete recharges: sinkholes, losing streams, and open underground channels. Diffuse recharge water enters the water table very slowly, over a broad, non-specific area. Aley and Aley (1987} also discussed the amount of time that water is in transit from the surface to the water table as a factor which affects the amount of pollution an aquifer may receive. Soil, rocks, sand, and roots act as filters, trapping particulate matter. Normally, the more time water spends in transit, the less particulate matter it contains. Water that does not spend much time in transit does not receive this natural filtering effect. If surface waters 6 are not filtered extensively during the transit process, many organic and inorganic compounds may enter groundwater systems. Water that spends weeks or years percolating through soil and rocks before entering the water table system is usually well-filtered,