While the link between global warming, rising sea temperatures and the risk of coral bleaching has received a lot of attention from scientists and the media, a recent study has shown that hot seawater also impacts the health and future prospects of baby fish. Environmental differences experienced early in life not only have immediate consequences for survival, but also profoundly influence the chances of success later in life.

A team from AIMS and the ARC Centre of Excellence for Coral Reef Studies studied hundreds of nests containing spawn from the Ambon damselfish to establish the extent to which parental quality and environmental rearing conditions influence the survival of these fishes. It has been known for some time that maternal condition affects the quality of eggs spawned and that egg quality influences the growth and survival of the hatchlings and juveniles. However the team found that the rearing environment also influences their fitness.

Working from the Lizard Island Research Station on the northern Great Barrier Reef, the team made observations on the egg masses deposited in benthic nests and defended by the male parent. The major result was that survival of the developing embryos was dramatically compromised at 31 °C, which now is not an uncommon temperature at this location during summer and will become increasingly common as the global oceans warm. The hatching cohort of fish was then tracked through to the juvenile stage, which showed that the environment in the nest has long-lasting consequences determining which individuals survive to replenish the next generation.

Future climate change will require the rapid evolution of increased heat tolerance. It is not clear whether species will be able adapt fast enough to cope with warming at the rates that most climate models predict. If species cannot adapt their distribution ranges will shift causing changes in biodiversity.

The Ambon damselfish was used in this study to investigate how the rearing environment influences larval fitness.