New Zealand Journal of Marine and Freshwater Research abstracts
Growth and population dynamics of crayfish Paranephrops planifrons in streams within native forest and pastoral land uses
Stephanie M. Parkyn1,2
Kevin J. Collier1
Brendan J. Hicks2
1National Institute of Water and Atmospheric Research Limited
P.O. Box 11 115
Hamilton, New Zealand
email: s.parkyn@niwa.co.nz
2Centre for Biodiversity and Ecology Research
Department of Biological Sciences
University of Waikato
Private Bag 3105
Hamilton, New Zealand
Abstract Population dynamics of crayfish (Paranephrops planifrons
White) in streams draining native forest and pastoral catchments, Waikato,
New Zealand, were investigated from September 1996 to July 1998. Crayfish
densities were generally greater in native forest streams because of high
recruitment over summer, but varied greatly between streams in both land
uses. Peak densities in summer were 9 crayfish m-2 in native forest and 6
crayfish m-2 in pasture streams, but peak biomass in summer was much greater
in pasture streams. Mark-recapture data showed that crayfish, particularly
juveniles, in pasture streams grew faster than in native forest streams,
through both greater moult frequency and larger moult increments. Females
reached reproductive size at c. 20 mm orbit-carapace length (OCL) after their
first year in pasture streams, but after 2 years in native forest streams.
Annual degree days >10°C appeared to explain the differences in the
timing of life cycles. Estimates of annual crayfish production (range = 0.8-3.4
g dry weight m-2 year-1) were similar in both land
uses, and P/B ratios were between 0.95 and 1.2. Despite deforestation and
conversion to pasture, crayfish in these Waikato hill-country streams have
maintained similar levels of annual production to those in native forest
streams, although juvenile growth rates have increased and longevity has
decreased.
Keywords crayfish; density; biomass; secondary production; growth; land use
M02012 Received 14 February 2002; accepted 10 July 2002; Published 14 November
New Zealand Journal of Marine and Freshwater Research, 2002, Vol. 36: 847-861
0028-8330/02/3604-0847 $7.00 © The Royal Society of New Zealand 2002
PDF file of entire paper: Print-quality (536K) | screen-quality (195K)
This year's abstracts |
Journal home page |
All abstracts |
Publishing home page
