Distant reef fish populations respond to climate in synchrony


AIMS fish ecologist, Alistair Cheal says these patterns were all strongly associated with a global climatic phenomenon, the El Niño- Southern Oscillation (ENSO), which refers to changes in the ocean and atmosphere that result in a body of unusually warm water building up in the Eastern Pacific Ocean. Photo: AIMS

 21 June 2007

Fish populations on reefs separated by hundreds of kilometres show synchronised population changes, they can boom or bust simultaneously due to effects of climate fluctuations.

Research along the length of the Great Barrier Reef over 1 years by ecologists at the Australian Institute of Marine Science (AIMS) has shown the synchronizing effects of climate on coral reef fish populations for the first time.

This study, recently published in the journal Ecology , demonstrates consistent synchronized changes in the size of damselfish populations on reefs separated by tens of kilometres and up to 800 km for some species.

The El Niño also affects water temperature, currents, wind and rainfall patterns on the east coast of Australia . One year after El Niño events, damselfish populations increased on many GBR reefs.

"El Niño events cause changes in water temperatures, wind speeds and patterns of water circulation, all of which can affect the breeding success of reef fishes and survival of their larvae.

"Conditions during ENSO events in 15 and 18 were good for small reef fishes… many other reef organisms have similar life cycles and may well have been affected similarly," he adds.

Why is this important knowledge? "First it shows that reef fish populations are affected by climate. Also any changes in the nature of ENSO regimes due to global climate change will affect coral reef fishes" Mr Cheal explains "According to some climate models, ENSO like conditions will become more common"

"The finding that distant populations change in synchrony means that while conditions are favourable, fish do well across large parts of the GBR, but when conditions are unfavourable for recruitment in one region, populations in other areas will be similarly effected.

"In such circumstances, localized extinctions will be more likely, particularly for small populations of short lived species," Mr Cheal explains.

The synchronizing effects of climate on population dynamics are well documented for a range of land animals but such patterns had not previously been documented in coral reef systems because of a lack of long term and broad scale data.

Media contacts:

Alistair Cheal, AIMS Fish Ecologist
Telephone: 07 4753 4474
Email: a.cheal@aims.gov.au

Wendy Ellery , AIMS Media Liaison
Telephone : 07 4753 4409
Mobile : 0418 729 265
Email : w.ellery@aims.gov.au