Habitat Quality and Stream Fishes

Project Title: Refinement and Validation of Habitat Quality Indices (HQI) and Aquatic Life Use (ALU) Indices for Application to Assessment and Monitoring of Texas Surface Waters

Project Summary: The Texas Commission for Environmental Quality (TCEQ) has adopted Aquatic Life Use Standards (ALUS) that rely on indices of biotic integrity (IBIs) and habitat quality indices (HQIs) to support its responsibilities of monitoring and setting standards for surface water quality. These essential tools allow natural resource managers and regulators to assess the status of ecological systems for evaluation of trends and compliance with established water quality standards.

A recent analysis of the correspondence between the fish IBI and the TCEQ’s HQI revealed a very low correlation between these indicators of ecological condition of streams.  A variety of factors could explain this lack of correspondence, including i) errors in one or both of these metrics, ii) poor matching of spatial scales of assessment, and iii) poor correspondence between temporal dynamics of environmental disturbances and habitat or biotic responses, and iv) poor calibration of habitat indices to reflect natural conditions in specific ecoregions.  The issue of scale and resolution, both in terms of space (geography, watershed position, siting within stream reach) and time (seasons, hydroperiod, time elapsed since last major disturbance) must be evaluated quantitatively in order to design and evaluate the validity and reliability of these assessment tools.

In this study, we will sample from a population of streams that have perennial surface water and lie within the Brazos and Trinity River basins within the Texas Blackland Prairies, East Central Texas Plains, and Cross Timbers ecoregions.  Annual surveys will describe and evaluate key metrics of stream habitat in relation to position within stream reach, watershed, and landscape (e.g., geology/soils, topography, land use) as well as fish assemblage structure.  We will determine principal relationships between stream habitat features and sources of landscape variation, as well as composition and structure of fish assemblages for use as biotic indicators of ecological status.  Using quantitative methods, we will identify the most useful (sensitive, reliable) fish community and habitat metrics (individual elements, suites of elements, or aggregate variables derived from multiple elements) for creation of improved HQI and IBI for wadeable streams for these selected ecoregions.