New Zealand Journal of Marine and Freshwater Research abstracts
Abundance, distribution, and size structure of toheroa (Paphies ventricosa)
at Ripiro Beach, Dargaville, Northland, New Zealand
Jo-Anne M. Akroyd
Kim A. R. Walshe
Akroyd Walshe Ltd
P.O. Box 28 814
Auckland, New Zealand
email: jakroyd@attglobal.net
Russell B. Millar
Department of Statistics
University of Auckland
Private Bag 90 219
Auckland, New Zealand
email: r.millar@auckland.ac.nz
Abstract The distribution of toheroa (Paphies ventricosa
Gray) beds, and the abundance and size structure of toheroa at Ripiro Beach,
Dargaville, New Zealand, were determined by a two-phase stratified sample
survey. The first phase was undertaken in February and March 1999 and the
second phase in June 1999. The first phase located and sized 45 toheroa beds,
and stratified the beds according to the observed density of siphon holes.
A total of 53 transects were sampled. The transects were run perpendicular
to the shoreline and positioned systematically within each stratum. Along
each transect the sampling of beds was done at 5 m intervals using a 1 x
0.5 m quadrat. Outside of the beds, sampling was done at 10 m intervals. The
total number of toheroa ≥75 mm (previous minimum legal size) was estimated
to be 3.3 million with a standard error of 480 000. This abundance of legal-sized
toheroa is roughly comparable with numbers last seen at Ripiro Beach in the
late 1960s. The total abundance of toheroa of all sizes was estimated to be
113.5 million with a standard error of 33 million. It appears that there has
been good recruitment of 0+ toheroa on Ripiro Beach and the abundance of
toheroa of all size ranges has greatly increased since the previous survey
in 1974.
Keywords abundance; Dargaville; Paphies ventricosa;
Ripiro Beach; stratified sampling; toheroa
M01035 Received 7 May 2001; accepted 15 February 2002; published 17 September 2002
New Zealand Journal of Marine and Freshwater Research, 2002, Vol. 36:
547-553
0028-8330/02/3603-0547 $7.00 © The Royal Society of New Zealand
2002
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