Life history and production of Coloburiscus humeralis (Ephemeroptera: Oligoneuriidae) in two South Island high-country streams, New Zealand

Abstract

The life history and production of Coloburiscus humeralis (Walker) were investigated over 12 months in a lake outlet, and a forested stream near Cass in the South Island high country. Length of larval life cycle wasabout 18 months in the lake outlet and 27 months in the forested stream. Small larvae appeared in late autumn and early winter (April-June) in both streams, and the main period of emergence began in late winter (August-September) and spring (October-November) in the forested and lake outlet streams, respectively. Production estimatedby the size-frequency method was 3.62 g DW m−2 yr−1 in the lake outlet and 2.42 g DW m−2 yr−1 in the forested stream. Mean annual biomass was slightly higher in the forested stream (1.43 cf. 1.0 g DW m−2 yr−1). The higher production in the lake outlet was primarily a consequence of the faster growth rate of individuals. This in turn reflected the higher water temperature of the lake outlet (approximately 3050 cf. 2610 degree days above 0°C), particularly in spring. © The Royal Society of New Zealand 1993.