Predicting New Zealand riverine fish reference assemblages

Adam D Canning

doi:10.7717/peerj.4890

Abstract

Biomonitoring is a common method to monitor environmental change in river ecosystems, a key advantage of biomonitoring over snap-shot physicochemical monitoring is that it provides a more stable, long-term insight into change that is also effects-based. In New Zealand, the main biomonitoring method is a macroinvertebrate sensitivity scoring index, with little established methods available for biomonitoring of fish. This study models the contemporary distribution of common freshwater fish and then uses those models to predict freshwater fish assemblages for each river reach under reference conditions. Comparison of current fish assemblages with those predicted in reference conditions (as observed/expected (O/E) ratios) may provide a suitable option for freshwater fish biomonitoring. Most of the fish communities throughout the central North Island and lower reaches show substantial deviation from the modelled reference community. Most of this deviation is explained by nutrient enrichment, followed by downstream barriers (i.e. dams) and loss of riparian vegetation. The presence of modelled introduced species had relatively little impact on the presence of the modelled native fish. The maps of O/E fish assemblage may provide a rapid way to identify potential restoration sites.

Highlights

Biomonitoring is the use of biota to detect and track change in an environment and underpins much of the environmental management in developed countries (Friberg et al, 2011; Li, Zheng & Liu, 2010)
Fish data Fish and decapod presence absence data were sourced from the New Zealand Freshwater Fish Database (NZFFD) (Richardson, 1989)
Geographic and climatic variables were the primary drivers of New Zealand freshwater fish distribution, this is consistent with the findings of Joy & Death (2002) and Leathwick et al (2005)

Summary

Introduction

Biomonitoring is the use of biota to detect and track change in an environment and underpins much of the environmental management in developed countries (Friberg et al, 2011; Li, Zheng & Liu, 2010). Physicochemical monitoring, such as the measurement of nutrient and sediment concentrations, is popular the world over. Physicochemical monitoring often only provides periodic snapshots of water quality that likely mislead environmental managers on the health of the system (Hazelton, 1998). Whilst dissolved oxygen may be at sufficient levels during the day, at night (when photosynthesis is not occurring) levels may plummet to stressful or even lethal levels, yet these minima are overlooked by seemingly healthy day-time concentrations (Hazelton, 1998). Whereas biological communities are continually exposed to the ranges of

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