Fish Community Structure and Water Quality Assessment (Index of Biotic Integrity) of the San Marcos River, Texas
A study was conducted on the San Marcos River to examine fish community structure by surveying fishes and to assess water quality and impacts from point and nonpoint sources using the Index of Biotic Integrity (181). The stable water temperature, flow and clarity found in the headwaters of the San Marcos River has allowed the development of a refugia for endemic and introduced aquatic plants and animals. Over the entire length of the river, fifty-three species of fishes were collected. Due to the unique characteristics of the San Marcos River's headwaters, eight species were collected only in the headwaters of the river, while 14 species were collected only downstream of the headwaters. Six 181 stations were established along the San Marcos River to examine potential effects from point and nonpoint source inputs. Sites I and II were chosen to examine effects from a wastewater treatment facility discharge and fish hatchery outflow into the headwaters. Site 111 was chosen to examine effects from the confluence of the Blanco River. Sites IV and V were chosen to examine effects of oil field activity on the river. Site VI was chosen to give reference data for future use. 181 integrity classes for the sites were as follows: site I - good; site II - good; site Ill - good to excellent; site IV - fair; site V - fair; site VI - poor. Although 181 results varied little among sites, examination of individual aspects of the 181 showed variation in certain aspects of fish community structure between sites.
fishes, fish populations, water quality, ecological integrity, San Marcos River
Kelsey, T. (1997). Fish community structure and water quality assessment (Index of Biotic Integrity) of the San Marcos River, Texas (Unpublished thesis). Southwest Texas State University, San Marcos, Texas.