New Zealand Journal of Marine and Freshwater Research abstracts
Age determination, validation, and growth of blue cod Parapercis colias,
in Foveaux Strait, New Zealand
Glen Carbines
National Institute of Water and Atmospheric
Research Limited
P.O. Box 6414
Dunedin, New Zealand
email: g.carbines@niwa.co.nz
Abstract Blue cod (Parapercis colias) is an important
inshore commercial and recreational fish species in the southern islands
of New Zealand, and estimates of their growth rate, age at maturity, and
longevity are required for fisheries management. This study provides validation
and comparisons of ageing methodologies for blue cod in Foveaux Strait, Southland.
Sectioned otoliths showed a consistent banding pattern, and counts of these
had good consistency between readers. Scales, broken and burnt, and whole
otoliths gave lower band counts than equivalent sectioned otoliths counts.
Blue cod otoliths were small, and otolith weights and lengths showed no relationship
with sectioned otolith band counts. Marginal increment analysis provided
a partial validation of ages estimated from sectioned otoliths, and oxytetracycline
marking completed the validation for blue cod over 300 mm total length. Fin
spines also showed promise as an excellent and non-lethal ageing tissue.
Blue cod growth in Foveaux Strait was then described and compared to previous
studies, which are likely to have underestimated ages because of the use
of broken and burnt and whole otoliths.
Keywords Parapercis colias; blue cod; otolith;
validation; scales; fin rays; fin spines; ageing; growth
M03035; Received 4 July 2003; accepted 5 November 2003; Online publication
date 8 June 2004
New Zealand Journal of Marine and Freshwater Research, 2004, Vol. 38:
201-214
0028-8330/04/3802-0201 © The Royal Society of New Zealand 2004
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