New Zealand Journal of Marine and Freshwater Research abstracts

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Relationships between drifting and benthic invertebratesin three New Zealand rivers: implications for drift-feeding fish

Karen A. Shearer
John D. Stark
John W. Hayes
Roger G. Young

Cawthron Institute
Private Bag 2
Nelson, New Zealand
email: karen.shearer@cawthron.org.nz

Abstract  We assessed whether taxonomic structure and density of aquatic drift could be predicted from the benthos in three New Zealand rivers. The three main orders contributing to both the benthos and drift were Ephemeroptera, Diptera, and Trichoptera. Drift and benthic densities for all taxa and all rivers combined were not significantly correlated (adults inclusive and exclusive). There were significant positive correlations between benthic and drift densities for the three main drifting orders-Ephemeroptera, Diptera, and Trichoptera when data from all rivers were combined. However, these relationships were not always detected in individual rivers. The propensity for Deleatidium to drift was negatively related to chlorophyll a concentration; suggesting density-dependent drift mediated by food limitation. Drift was reduced when periphyton chlorophyll a concentration was high in relation to benthic Deleatidium density. This highlights an unexpected effect of periphyton proliferation on invertebrate drift and drift-feeding fishes. Despite finding some correlations between benthic and drifting communities, defining general relationships between benthic and drifting communities is challenging given the complexity of density-dependent and density-independent mechanisms that influence invertebrate drift.

Keywords  aquatic invertebrate; benthos, density-dependent; drift, drift-feeding; fish; periphyton

M02079 Received 3 October 2002; accepted 15 July 2003; Online publication date 31 October 2003
New Zealand Journal of Marine and Freshwater Research, 2003, Vol. 37: 809-820
0028-8330/03/3704-0809 $7.00 © The Royal Society of New Zealand 2003

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