For both semi quantitative and quantitative surveys, the length of the site is measured as accurately as possible, and a series of wet and clear width measurements are taken, as well as depth readings. Measurements of temperature, conductivity and dissolved oxygen are recorded at each site. A series of photographs of the survey section, including stop net locations, are also taken and GPS positioned.
Details of surrounding land use, in-stream and bank side habitat, and potential factors affecting the survey results are all recorded at the same time as the raw catch data. This is very important as it impossible to evaluate catch results effectively without accurate records of habitat type, flow conditions, water quality, shading etc.
RAS is qualified in habscore data collection in conjunction with juvenile salmonid surveys. Habscore is a system for measuring and evaluating the quality of salmonid stream habitats. Habscore uses in-stream habitat and catchment features to predict juvenile salmonid populations. Habscore is based on empirical statistical models which were developed using 602 ‘pristine sites’ (where recruitment or water quality were not limiting factors). Habscore predictions reflect the quality of habitat. The method has various applications, including identification of where habitat is constraining fish populations.
The model predicts long-term average density of juvenile salmonids (where water quality and recruitment are not limiting) by referencing field data collected at a site to the original 602 ‘pristine sites’, and the output is called the Habitat Quality Score (HQS). This output can be derived using habitat data alone. It represents at the site level, potential stock status and habitat quality, expressed as fish abundance.
A second output, Habitat Utilization Index (HUI) is obtained by expressing the observed density (from a fish survey) as a proportion of the HQS and is a measure of the extent to which the potential of the site is realized. Both habitat and fish survey data are required to generate HUIs.
