New Zealand Journal of Marine and Freshwater Research abstracts
Life history and production of Deleatidium (Ephemeroptera: Leptophlebiidae) in an unstable New Zealand river
GARRY J. SCRIMGEOUR
Department of Zoology
University of Canterbury
Private Bag, Christchurch, New Zealand
Present address: Division of Ecology (Aquatic Ecology Group), Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada
Abstract
Life history and production of a
Deleatidium species (///// group) (Ephemeroptera: Leptophlebiidae) was studied for a 12-month period in a flood-prone river in the South Island, New Zealand in 1985-86. Mean larval density was highest (9170-18 580 nr
2) following a long period (> 5 months) of low stable flow (< 30 m
3 s"
1), but typically ranged from 3550 to 4310 nr
2. The annual cycle
of Deleatidium was difficult to interpret but there appeared to be two overlapping, poorly synchronised generations each year. Production of the winter generation calculated using the Size-frequency method (51.40 g DW nr
2), was five times higher than that of the summer generation (9.17 g DW nr
2) and annual production was 60.57 g DW nr
2 . Mean biomass of the winter generation (7.59 g DW m~
2) was higher than that of the summer generation (0.87 g DW nr
2) but the production to biomass ratio (P/B) of the summer generation (10.54) exceeded that of the winter generation (6.77). The ability to feed on low-biomass epilithic layers, behavioural responses that minimise population losses during floods, and flexible life history patterns enable this species to attain high annual production in a physically harsh environment.
Keywords Deleatidium spp.; Leptophlebiidae; life history; annual production; spates; disturbance; stream
New Zealand Journal of Marine and Freshwater Research, 1991, Vol. 25: 93-99 0028-8330/2501-0093 $2.50/0 © Crown copyright 1991
Received 13 September 1990; accepted 13 December 1990
PDF file of entire paper: medium quality (577K); (scanned from paper original: notes about this process)
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