New Zealand Journal of Marine and Freshwater Research abstracts

---

Diel changes in the abundance and size composition of invertebrate drift in five rivers in South Island, New Zealand

P. M. SAGAR G.J.GLOVA

Freshwater Fisheries Centre Ministry of Agriculture and Fisheries P. O. Box 8324, Riccarton Christchurch, New Zealand

Abstract Drift was collected over 24-h periods in five rivers in South Island, New Zealand, to determine whether diel periodicity was; consistent across a range of river types, and whether the pattern was similar for different life stages/sizes of selected taxa. Total drift density (numbers per 100 m³) of aquatic invertebrates was greater at night than during the day in all rivers; peak abundance occurred shortly after sunset in clear water rivers and shortly before sunrise in a turbid, glacier-fed river. Densities of drifting Deleatidium spp., Nesameletus spp. (both Ephemeroptera), Aoteapsyche spp., and Hydrobiosidae (both Trichoptera), were generally greater at night than during the day. However, the timing of peak abundance in the drift for other common taxa varied between rivers. Larger Deleatidium spp. larvae (> 1.00 mm head width) were more common in the drift at night than during the day in all rivers. However, this was not apparent for Aoteapsyche spp. and Hydrobiosidae, for which diel differences in the size of drifting animals were not consistent even within the same river. The propensity for some aquatic invertebrates to drift at night may influence fish feeding behaviour, particularly with respect to the timing of feeding and the species or life history stages of their prey.

Keywords aquatic invertebrates; diel periodicity; Deleatidium spp.; drift density; life stages; drift-feeding fish M91077 Received 4 November 1991; accepted 14 January 1992

New Zealand Journal of Marine and Freshwater Research, 1992, Vol. 26:The Royal Society of New Zealand 1992
Received 4 November 1991; accepted 14 January 1992

PDF file of entire paper: medium quality (811K); (scanned from paper original: notes about this process)

---

This year's abstracts | Journal home page | All abstracts | Publishing home page