PARENT SESSION
Oral Session #43: Fish: Ecology and Conservation.
Presiding: B. Harvey
Tuesday, August 6. 1:00 PM to 4:45 PM. Cochise Meeting Room, TCC.

Assessing biological integrity: predicting freshwater fish assemblages using habitat selection functions .

Death, Russell^*,1, Joy, Mike¹, ¹ Institute of Natural Resources - Ecology, Palmerston North, New Zealand

ABSTRACT- Comparison between the number of taxa observed and the number expected in the absence of human impact is an easily understood and ecologically meaningful measure of biological integrity. In this paper, we develop a methodology similar to the RIVPACS process to assess biological integrity at flowing water sites using freshwater fish assemblages. These assemblages were sampled at 118 least impacted (reference) sites in the Auckland region, New Zealand. Individual discriminant models based on the presence or absence of the 12 most common species were developed using environmental measures least likely to be influenced by human impacts recorded at those sites. Using the model, predictions were made at new sites to yield the probability of the capture of each of the species. The output from the model is a ratio of observed to expected taxa number (O/E). Assessment of whether a site is impacted is made under the assumption that human impacts alter the make up of the assemblages that would naturally be found at a site. This model using freshwater fish performed as well as other RIVPACS models but has the added advantage of not having the requirement that distinct assemblages occur at within certain stream types.

KEY WORDS: biomonitoring, freshwater fish, predictive modelling, New Zealand