New Zealand Journal of Marine and Freshwater Research abstracts

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Short communication
Age at first increment formation and validation of daily growth increments in golden perch (Macquaria ambigua: Percichthyidae) otoliths

Paul Brown*
Ian Wooden

Narrandera Fisheries Centre
NSW Department of Primary Industries
P.O. Box 182, Narrandera
NSW 2700, Australia
*Present address: Primary Industries Research Victoria (PIRVic), Department of Primary Industries, Private Bag 20, Alexandra, Victoria, 3714 Australia. email: paul.brown@dpi.vic.gov.au.

Abstract The micro-increments in otoliths from a series of golden perch (Macquaria ambigua) larvae of up to 15 days known age (n = 124, total length (TL) 4.14 to 10.0 mm) were examined and counted to establish the age at formation of the first increment, and periodicity of formation of subsequent increments. The regression of true age on increment count (true age = 3.54 +1.36 × increment count) was significant (r2 = 0.78, P < 0.001) and the slope of the overall regression (1.36 day–1) was not significantly different to 1 (t = 0.09, P = 0.05). First increment formation occurred from day 3 in some larvae, and was completed by day 13 in all larvae. A median estimate for age at first-increment deposition was 6.0 days, when 50% of the daily sample (n = 10 fish) had at least one increment. However, solving the regression for age when increment number equaled 1.0 provided an estimate of mean age at first-increment deposition of 4.9 days. Our study validated daily growth increment deposition for golden perch larvae over the first 15 days of development and cautions that age at first-increment formation varied within a single cohort of larvae by 10 days (i.e., youngest larvae 3 days, oldest larvae 13 days old).

Keywords growth; first increment; otolith; daily growth increment; validation; hatch-date

New Zealand Journal of Marine and Freshwater Research, 2007, Vol. 41: 157–161
0028–8330/07/4102–0157     © The Royal Society of New Zealand 2007
M07002; Online publication date 27 April 2007. Received 9 January 2007; accepted 8 March 2007

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