Varying annual patterns of reproduction in four species of coral reef fish in a monsoonal environment

Peaks in the reproduction of coral reef fish in equatorial regions are hypothesised to usually coincide with periods of the year when winds are weaker, presumably to minimise larval transport and maximise recruitment. The annual patterns of spawning of four species of reef fish in the central Philippines (9.201355A degrees N, 123.327421A degrees E) were investigated over 11-22 months. On an annual basis, the study area experiences two windy monsoon seasons and two monsoon transition periods when winds are weaker. Protracted breeding seasons were evident, but the timing of inferred spawning peaks varied among species. Spawning peaks of Pterocaesio pisang (Caesionidae) coincided with the first monsoon transition period of the year (April-June) and the north-east monsoon (November-March). Caesio caerulaurea (Caesionidae) showed a spawning peak during the south-west monsoon (July-September) extending to the following monsoon transition period (October). In Naso minor (Acanthuridae), an annual pattern was difficult to discern due to insufficient data, but there was some suggestion of higher spawning activity during the north-east monsoon. Spawning in Pomacentrus moluccensis (Pomacentridae) was inferred to occur year-round except during the north-east monsoon. These results suggest that conditions favourable to the survival of pelagic larvae are not restricted to monsoon transition periods. Alternatively, the results indicate direct or indirect effects of temperature, rainfall, wind or wave action on the reproduction of adults. Variable annual patterns of reproduction in reef fish pose a further challenge to fisheries management interventions in the region. This variability is possibly being influenced in complex ways by environmental factors that change with the monsoons.