New Zealand Journal of Marine and Freshwater Research abstracts
Background and review of ageing orange roughy (Hoplostethus
atlanticus, Trachichthyidae) from New Zealand and elsewhere
D. M. TRACEY
National Institute of Water & Atmospheric
Research Ltd
P. O. Box 14 901, Kilbirnie
Wellington, New Zealand
P. L. HORN
National Institute of Water & Atmospheric
Research Ltd
P. O. Box 893
Nelson, New Zealand
Abstract Studies on New Zealand orange roughy
(
Hoplostethus atlanticus) otoliths, and of orange roughy ageing
conducted in New Zealand and elsewhere are described. Ageing studies have
concentrated on three aspects: the interpretation of daily growth increments,
the interpretation of annual growth increments, and radiometric analyses. All
the methods suffer from problems relating to validation. Daily growth zones
have not been validated, annual zones have been validated for juvenile fish
only, and assumptions necessary for the application of radiometric techniques
may be flawed. However, the weight of current evidence indicates that orange
roughy are a slow-growing, long-lived species. A review of otolith morphology
and microstructure studies, and a summary of the productivity parameters used
in stock assessments of orange roughy, are also presented. Standard protocols
used to prepare and interpret otoliths in current investigations are described.
This review highlights the complexities of ageing long-lived, deepwater fish,
and stresses the importance of obtaining accurate productivity parameters for
stock assessment. The key area for future research is the age validation of
post-juvenile fish, which should lead to the development of an accurate ageing
technique.
Keywords orange roughy; Hoplostethus atlanticus;
review; ageing techniques; growth; otolith; age validation
M98008
Received 24 February 1998; accepted 18 September 1998
PDF file of entire paper: medium quality (2757K); (scanned from paper original: notes about this process)
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