Application Of Population Dynamics Models To The Conservation Of Imperiled Stream Fishes
Bart W. Durham, Wildlife and Fisheries Management Institute, Texas Tech University, Box 2125, Lubbock, TX 79409-2125; (806) 742-1983; FAX (806) 742-2280; bart.durham@ttu.edu
Gene R. Wilde, Wildlife and Fisheries Management Institute, Texas Tech University, Box 2125, Lubbock, TX 79409- 2125
The Arkansas River shiner Notropis girardi is a small minnow endemic to the Arkansas River drainage basin. Arkansas River shiner has drastically declined during the past three decades. This led to its being formally listed as threatened by the U. S. Fish and Wildlife Service in 1998. The Canadian River in New Mexico, Texas, and Oklahoma support the last viable populations of Arkansas River shiner. Arkansas River shiner population data collected between 1977-1995 from the Canadian River, Oklahoma documents continuing declines for these remaining populations. Using this long-term data set and published life-history information, we developed an age-structured population dynamics model for the Arkansas River shiner. Because reproductive success of the Arkansas River shiner, is closely associated with stream-discharge patterns, we parameterized the model to relate population dynamics to stream discharge. Specifically, we modeled survival of age-0 individuals as a function of stream discharge and used maximum likelihood to determine the optimum relationship between observed and predicted abundance. The final model was evaluated using Akaike's Information Criterion. The results of this analysis indicate that population dynamics of Arkansas River shiner are related to patterns in stream-discharge. The predicted abundance from the discharge-based model suggests that multiple years characterized by high, or low, discharge have a greater effect than single high or low discharge years. The specific mathematical parameterization of the discharge-based model also provides an objective method to determine the minimum average annual discharge necessary for population increase. The flexibility and utility of the model developed here has the potential to become an important tool for managers charged with conservation of imperiled stream-fish species.