Settlement dynamics of the coral reef fish Stegastes partitus, inferred from otolith shape and microstructure analysis

Abstract

Settlement dynamics of the bicolor damselfish Stegastes partitus (Pomacentridae) were determined by otolith shape and microstructure analysis and compared among different coral reef areas (Windward, Lagoon, and Leeward) of Chinchorro Bank, northern Meso-American Barrier Reef System, eastern Yucatan Peninsula. Estimated age, settlement time, size at settlement, and larval otolith growth rates were compared using a 2-way ANOVA with 2 fixed and orthogonal factors (reef areas and cays) with 3 levels each. Significant differences in planktonic larval duration were found, with (mean) 28.8, 30.3 and 32.7 d spent at Windward, Lagoon and Leeward, respectively. Individuals with shorter larval durations (at Windward) showed faster otolith growth rates and settled at rela- tively smaller sizes than those with longer larval durations (Lagoon and Leeward). However, there was no significant difference in otolith growth rates among reef areas, and there was no clear evi- dence for delay in metamorphosis. Based on both the planktonic larval duration (PLD) and the preva- lent current pattern in the area, it appears that strong northwesterly currents passively transport S. partitus larvae into Chinchorro Bank. Larvae may enter at Windward, pass through the reef Lagoon, and leave by the Leeward. Longer PLD for S. partitus settling at Leeward are not due to differences in larval growth rates, but more likely to a lack of access to suitable settlement habitat by the time the larvae has passed through the reef system. An otolith shape (Fourier) analysis revealed a clear differ- entiation between otoliths from the 3 reef areas, suggesting that the environmental influence on otolith shape of S. partitus is relatively uniform, which means that this fish is affected by similar local environmental conditions within each reef area.