Temporal patterns of spawning and hatching in a spawning aggregation of the temperate reef fish Chromis hypsilepis (Pomacentridae)

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Journal Article
Marine Biology, 2007, 151 (3), pp. 1143 - 1152
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Descriptions of temporal patterns in the reproduction of damselfishes (family Pomacentridae) and adaptive hypotheses for these patterns are derived mostly from studies of coral reef species. It is unclear whether the types of temporal patterns and the explanatory power of the adaptive hypotheses are applicable to damselfishes of temperate rocky reefs. This study tested hypotheses about the existence of lunar spawning cycles, the diel timing of hatching, and the synchronization of temporal patterns in hatching and tides in the schooling planktivorous damselfish Chromis hypsilepis on a rocky reef in New South Wales, Australia. Reproductive behaviour was observed daily for 223 days between August 2004 and March 2005. C. hypsilepis formed large spawning aggregations of 3,57533,075 individuals. Spawning occurred at a uniform rate throughout the day on a semi-lunar cycle. The greatest number of spawnings occurred 1 day after the new moon and 1 day before the full moon. The cost to males from brood care was an 85% reduction in their feeding rate. The semi-lunar spawning cycle may be an outcome of the use of the lunar cue to synchronize the aggregation for spawning of widely dispersed individuals and the need for males to recuperate after brooding. Eggs hatched 37 h after sunset following a 4.5-day incubation period. This study provides no support for hypotheses that link temporal patterns in hatching with particular tidal regimes believed to facilitate early survival of larvae and their dispersal. The result that hatching occurred over the tidal cycle was due to the rapid off-reef dispersal of larvae from the spawning ground at all stages of the tide. C. hypsilepis is similar to other planktivorous damselfishes in its semi-lunar spawning cycle, cost of brood care, and protracted diel spawning regime. It differs in its lengthy period of hatching and its breeding in spawning aggregations, believed to be rare among demersally spawning fishes.
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