Patterns of settlement and growth of juvenile flounder Rhombosolea tapirina determined from otolith microstructure

• Published in: Marine ecology. Progress series (Halstenbek) 1992-01, Vol.79 (3), p.203-214
• Main Authors: May, Helen M. A., Jenkins, Greg P.
• Format: Article
• Language: English
• Subjects: Fish larvae; Larval development; Marine; Marine fishes; Metamorphosis; Mortality; Otolith organs; Rhombosolea tapirina; Settlement patterns; Water temperature; Winter; Young animals
• ISSN: 0171-8630; 1616-1599
• DOI: 10.3354/meps079203

Otolith microstructure was used to examine settlement and growth of juvenile Rhombosolea tapirina Günther from a site within Swan Bay, Victoria, Australia. A distinct transition zone on sagittae coincides with settlement from the pelagic larval phase to the benthic juvenile habitat. The daily settlement pattern was reconstructed using otolith increments from fish collected during and at the end of the settlement season. Settlement was continuous from July to October. However, most individuals had apparently immigrated from other settlement areas or were inaccessible to sampling for a brief period after settlement. The settlement pattern persisted over time, however, peaks were no longer evident at the end of the settlement season. The population growth rate of juvenile flounder was found to be approximately linear over the size range sampled, averaging 0.29 mm d⁻¹. A significant linear relationship between standard length and otolith radius allowed back-calculation of individual growth trajectories for a 'winter' and a 'spring' cohort. Significant differences were found in growth trajectories for each cohort; growth rate over the first 20 d post settlement for the winter cohort averaged approximately 0.17 mm d⁻¹ compared to 0.23 mm d⁻¹ for the spring cohort. The relationship between daily growth and air temperature was compared using cross correlation. Cross correlation functions showed a significant positive correlation at lags of 2 to 5 d for the winter cohort and a significant negative correlation at a lag of 1 d for the spring cohort. This suggests that early in the settlement season, temperature had a positive influence on metabolism, which in turn affected somatic and otolith growth rates. However, temperature apparently reached a critical level later in the season, which resulted in high temperature having a deleterious effect on metabolism, leading to a negative correlation between temperature and growth.