New Zealand Journal of Marine and Freshwater Research abstracts
Ovarian development and the potential annual fecundity
of western stock hoki (Macruronus novaezelandiae)
KATHY A. SCHOFIELD
MARY E. LIVINGSTON
National Institute of Water & Atmospheric
Research Ltd
P. O. Box 14 901, Kilbirnie
Wellington, New Zealand
Abstract Hoki (Macruronus novaezelandiae) form two of
New Zealand's largest spawning fisheries, one centred off the west coast of the
South Island (WCSI), the other in Cook Strait. Research data collected during
surveys 1983-96 show that ovarian development begins on the feeding grounds
between March and April, whereas spawning occurs mainly in July and August.
Research has also shown that a significant proportion of adult hoki do not
develop to spawn in a given year. Plans to estimate the absolute abundance of
the western spawning stock off the WCSI using an egg production method require
estimates of total annual fecundity and proportion spawning. Although
determinate spawners, hoki are capable of multiple spawning in one season, and
it is difficult to differentiate between fish about to spawn and fish that have
already begun to spawn on the WCSI. In this study, we applied a modified
stereological technique to samples of western stock hoki obtained from the
feeding grounds south of New Zealand in May to determine the feasibility of
estimating fecundity, at the same time as estimating the annual proportion
developing to spawn. Mean fecundity estimates ranged from 0.4 million to 3.0
million oocytes and compare favourably with previous unpublished estimates of
fecundity in early spawners on the west coast. We concluded that samples
collected from the Southern Plateau during surveys of pre-spawning hoki in May
could provide useful estimates of fecundity.
Keywords hoki; spawning cycle; fecundity; ovarian
development
New Zealand Journal of Marine and Freshwater Research, 1998, Vol. 32:
147-157
0028-8330/98/3201-0147 $7.00/0 (c) The Royal Society of New Zealand
1998
PDF file of entire paper: medium quality (671K); (scanned from paper original: notes about this process)
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