Comparing Habitat Suitability Indices (HSIs) Based on Abundance and Occurrence Data

Abstract

Suitability-based physical habitat modeling is sensitive to the choice of habitat suitability index. We compared the effects of using abundance versus occurrence data on suitability indices along environmental gradients for four fish species collected by means of prepositioned electrofishing in a mountain stream in southern Taiwan. The results indicate that abundance data provide more sensitive outcomes than occurrence data in terms of both mean values and habitat suitability. The mean values of flow velocity and water depth from the abundance data separated the four fish species into four distinct flow groups and two depth groups; the occurrence data did not produce similar groupings. Habitat suitability curves from the abundance data provided clearer outcomes than those from the occurrence data. The differences were greater for species with differential densities along environmental gradients that were related to species characteristics. Advancements in point abundance sampling methodology, such as the development of prepositioned electrofishing, provide novel opportunities to collect abundance data that can enhance suitability results.Received April 15, 2012; accepted October 17, 2012