Coarse-scale movement patterns of a small-bodied fish inhabiting a desert stream

Abstract

Located on the floor of Death Valley (CA, USA), Salt Creek harbors a single fish species, the Salt Creek pupfish, Cyprinodon salinus salinus, which has adapted to this extremely harsh environment. Salt Creek is fed by an underground spring and is comprised of numerous pools, runs, and marshes that exhibit substantial variability in temperature, salinity, and dissolved oxygen concentrations. In addition, the wetted area of Salt Creek is reduced throughout the summer months due to high rates of evaporation, with some reaches drying completely. Therefore, it seems logical that short- and long-term movement patterns may play an important role in Salt Creek pupfish population dynamics. The objective of this study was to describe coarse-scale movements of Salt Creek pupfish in Salt Creek during their breeding season from March to May. Sex ratios and length–frequency distributions varied spatially within Salt Creek, suggesting population segregation during the breeding season. Long-distance movements were generally rare, although two fish moved more than 1.2 km. Movement in upstream reaches was rare or absent, in contrast to the greater movement observed in downstream reaches (29% of recaptures). Temporal trends and demographic patterns in movement were not observed. Because the two most downstream habitats dry up in the summer, our results indicate that coarse-scale movements that re-populate downstream reaches likely occur during other times of year. Consequently, the importance of small- and large-scale movements is influenced by season. Further assessment of Salt Creek movement patterns conducted during other times of year may better illuminate long-distance movement patterns and source-sink dynamics.

Keywords:

• movement patterns
• sex ratio
• pupfish
• Death Valley
• desert streams

Acknowledgments

We thank the Death Valley Natural History Association (DVNHA) for helping fund this study. Candace Lieber (DVNHA) and David Blacker (DVNHA) were very helpful with logistics for the study. The study included an educational outreach component, organized by the National Park Service (NPS) and partly funded by DVNHA, which educated 244 elementary and high school students about Salt Creek pupfish ecology in Death Valley National Park. S. Kyriazis (NPS) helped organize educational curriculum for students. In addition, we are grateful for the help of K. Wilson (NPS). We thank numerous volunteers who helped with field sampling, including: D. Wyatt, S. Kyriazis (NPS), J. Snow (NPS), M. Tilman (NPS), J. Tilman (NPS), J. Stoltzfus (NPS), P. Slaton (NPS), V. Schultz, and L. Finn (NPS). Furthermore, J. Stark (NPS) provided help with GIS mapping of Salt Creek. S. Parmenter (California Department of Fish and Game) provided biological insight and helped with permitting. This study was conducted under the California Department of Fish and Game permit number 803089-02, and NPS permit number DEVA-2009-SCI-0038. The Idaho Cooperative Fish and Wildlife Research Unit is jointly sponsored by the University of Idaho, US Geological Survey, Idaho Department of Fish and Game, and Wildlife Management Institute. The use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the US Government.