A Talk on the Wild Side.
A researcher displays juvenile freshwater fat mucket mussels that will be used as stand-ins for rarer species in studies on water temperature tolerance. Study data will help researchers assess how vulnerable rare Oklahoma aquatic species will be to potential warming tied to climate change. Photo: David Martinez, USFWS. Download.
Several rare and distinctively-named creatures depend for survival on the cool, mountain-fed Little and Kiamichi River Basins in southeastern Oklahoma and southwestern Arkansas. At Little River National Wildlife Refuge and surrounding areas, the Ouachita rock pocketbook — a freshwater mussel — filters the water alongside two other endangered mussels, the scaleshell and winged mapleleaf. A small federally threatened fish called the leopard darter also hides in these upland streams.
Because streams in these river basins originate in the Ouachita Mountains, their water is relatively cool compared to streams in other ecosystems such as the Great Plains. High temperatures range from about 64 degrees Fahrenheit in winter to 84 degrees in summer — a range that suits popular game fish such as smallmouth bass.
But threats abound. Water pollution, agriculture runoff and the construction of dams and reservoirs have already shrunken habitat for these rare aquatic species. A historic drought is compounding the problem. And now, biologists speculate the fish and mussels could face another potential stressor: rising stream temperatures resulting from climate change, if projections by an intergovernmental panel prove accurate.
The naturally cool waters of the Little River Basin in southeastern Oklahoma and southwestern Arkansas provide essential habitat for several rare aquatic species. Scientists worry that warming caused by climate change may add to stresses on threatened and endangered fish and mussels. Photo: Daniel Fenner, USFWS. Download.
Research has shown that higher stream temperatures impair species’ feeding, growth and reproduction. Biologists worry that changes to these important biological processes may lead to a general decline in the condition of these rare species, leaving them more vulnerable to competition from other creatures that share their food, habitat and spawning areas.
U.S. Fish and Wildlife Service biologists are conducting research to measure how the rare species will likely respond, and what scientists and resource managers can do to protect them.
Working with other state and federal agencies at the Tishomingo National Fish Hatchery and Ecological Services Field Office in Oklahoma, the Service is nearing completion of the first phase of a three-part study. Lab scientists have measured the tolerance of common Oklahoma mussel and fish species to changes in water temperature. Once data analysis is complete, they will prepare a preliminary report to guide the next study phases.
Phase two will study the temperature tolerance of species similar to the federally listed species in their distribution and use of resources. Studying more-abundant “surrogate” species ensures that enough live specimens can be captured without harming the rare species.
Biologists in the Little River Basin don snorkeling masks and fins to look for leopard darters — tiny, federally threatened fish found only in southeast Oklahoma and southwest Arkansas. Photo: Daniel Fenner, USFWS.
The last phase of the study will involve leopard darters only. Leopard darter populations fluctuate considerably from year to year. During a year when population numbers are well above average, researchers will collect a small sample for thermal tolerance research. The collected fish will then be used for further research or educational purposes.
This phase of the study will let researchers compare the thermal tolerance of leopard darters to that of species that share their resources (determined in phase two) to determine if competition for shared resources could be a future threat. Once the potential effects of higher stream temperatures on these rare species are better understood, scientists will be better equipped to gear recovery actions to projected climate change impacts.
Climate Change Focus: Engagement
Authors: Daniel Fenner, USFWS; David Martinez, USFWS