Report: TR 2007/23
Author: Mike Joy, Institute of Natural Resources, Massey University
Software by Ian Henderson,
Centre for Freshwater Ecosystem Modeling and Management, Massey University
The index of biotic integrity (IBI) was originally developed using fish in the USA by James Karr during the early 1980s. The original version had 12 metrics that reflected fish species richness and composition, number and abundance of indicator species, trophic organization and function, reproductive behaviour, fish abundance, and condition of individual fish. This process has been repeated and IBIs developed on many continents. The fish fauna of New Zealand is radically different from the continental faunas the IBI was originally developed on. To apply the IBI here a number of changes have been made. The basic concept has been retained; applying metrics to fish assemblages and the use of a large number of sites to give a background level of biological condition and then comparing a site of interest with that dataset to assess the status of the test site. Details on metrics and calculations are given below, for more details see: Joy, M.K. & Death, R.G. (2004) Application of the index of biotic integrity methodology to New Zealand freshwater fish communities. Environmental Management, 34, 415-428.
New Zealand’s freshwater fish fauna has only a single trophic level and disease in wild fish populations is virtually absent, thus, those metrics could not be used here. The six metrics decided on measure taxonomic richness over a number of habitat types. Some indicator species are used by measuring the number of species showing tolerance to degraded conditions and finally the ratio of native to exotic species. Many studies have shown that New Zealand’s fish fauna is largely structured by elevation and distance from the coast and this is obvious in the Waikato region (Fig. 1).
Because elevation and distance from the coast are the overriding controllers of species distribution they were used to structure expectations of fish assemblages. The six metrics were assessed for both elevation and distance from the coast to give 12 metrics overall and these were summed to give the final score.
Since the development of the first New Zealand IBI1 and the Waikato IBI2 there have been developments in the statistical tools available to get an accurate measure of regressions. This new approach - quantile regression enables a more accurate allocation of IBI scores from the data used in this approach and is described later in this report.
Available as download: A New Fish Index of Biotic Integrity using Quantile Regressions: the Fish QIBI for the Waikato Region.
Report, calculator and usage instructions
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|1||The conventional IBI scoring approach||1|
|2||The QIBI Quantile Regression approach||4|
|3||Waikato Fish QIBI metrics||4|
|4||Calculation of total QIBI score||7|
|5||Interpretation of results||7|
|6||Comparison between the conventional IBI and the Quantile IBI mapped over the Waikato Region||8|
|Instructions for using Waikato fish QIBI software||10|