Evaluation of freshwater invertebrate sampling methods in a shallow aridland river (Rio Grande, New Mexico)

Tf Turner,Js Fencl,As Burdett

doi:10.3354/ab00616

Abstract

Aridland rivers can present several logistical challenges for invertebrate sampling due to shifting substrate and low invertebrate densities. We compared 4 sampling methods for col- lecting both meiofauna and macroinvertebrates in an aridland river (Rio Grande, New Mexico): a water column sampling method, an epibenthic core, a throwtrap, and a stovepipe sampling method. The objective of this study was to find the most efficient combination of sampling meth- ods with which to collect the entire assemblage. Differences were tested among sampling meth- ods in terms of abundance, taxonomic richness, assemblage composition, and invertebrate body size. No single sampling method was able to provide accurate estimates of both abundance and taxonomic richness across the range of body sizes of taxa collected in this study. Invertebrates were concentrated in the epibenthos, and thus using the water column sampling method was not necessary. Samples from the epibenthic core and stovepipe sampling methods contained rela- tively high densities of small-bodied meiofauna, while throwtrap samples included both meio- fauna and macroinvertebrates. Throwtrap and epibenthic core sampling methods together pro- vided the most accurate estimates of taxonomic richness, density, abundance, and invertebrate assemblage composition, and were processed relatively efficiently in the laboratory. Sampling methods that performed well in the Rio Grande are likely to work well in other higher-order (>4) rivers with shifting substrates.

Highlights

Aridland rivers have been poorly surveyed for invertebrate fauna, partly because sand and silt are difficult to sample quantitatively and are thought to be characterized by low densities of macroinvertebrates (Humphries et al 1998)
Taxonomic richness was lowest in water column samples compared to the other sampling methods
Our results indicate that high variation in richness and abundance might be inherent in highly dynamic systems like large aridland rivers, in both spatial and temporal dimensions

Summary

Introduction

Aridland rivers have been poorly surveyed for invertebrate fauna, partly because sand and silt are difficult to sample quantitatively and are thought to be characterized by low densities of macroinvertebrates (Humphries et al 1998). Some parts of aridland rivers can have high densities of invertebrate fauna (Pease et al 2006). Aquat Biol 23: 139–146, 2015 ticular, slow-flowing habitats (such as isolated pools, backwaters and side channels) can have relatively high abundances of potential prey items for small fishes (Thorp et al 1994), including benthic microcrustacea, rotifers, and early instar insect larvae (Humphries et al 1999). Meiofauna often dominate benthic invertebrate assemblages and play important roles in assemblage and ecosystem processes (Palmer et al 2006), such as providing a food source for larval fishes (King 2004a,b). Meiofauna are not sampled effectively using traditional sampling methods that focus on the water column (King 2004b)

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Discussion

Conclusion