James Cook University researchers have found brightly coloured fish are becoming increasingly rare as coral declines, with the phenomenon likely to get worse in the future.

Christopher Hemingson, a recent PhD graduate at JCU’s Centre of Excellence for Coral Reef Studies, led the research. He said over the past 30 years, human-induced stressors have caused profound changes to reefs – typically from the loss of corals.

“Reefs these days are becoming increasingly defined by non-coral substrates, especially turf algae. We wanted to investigate what effect this had on the kind of brightly-coloured fish people like and that attract tourists and visitors,” said Dr Hemingson.

The scientists used a new community-level measure of fish colouration and then explored the links between fish community colouration and the environment.

“We found that as the cover of structurally complex corals increases on a reef, so does the diversity and range of colours present on fishes living in and around them. But, as the cover of turf algae and dead coral rubble increases, the diversity of colours declines to a more generalised, uniform appearance,” said Dr Hemingson.

He said it was notable that fish community colouration declined significantly in the years following the 1998 global coral bleaching event – likely driven by the loss of branching corals.

“We found the structure of the sea floor appears to be very important in shaping fish colouration; more so than its composition (that is, its live coral cover). Having places to hide from predators may have allowed reef fishes to evolve unique colourations due to a reduced reliance on camouflage to avoid being eaten.

“Unfortunately, the types of corals most capable of surviving the immediate impacts of climate change (massive and boulder corals) are unlikely to provide these refuges. Fish communities on future reefs may very well be a duller version of their previous configurations, even if coral cover remains high,” said Dr Hemingson.

He said the loss of colourful fishes may not have a huge impact if assessing reefs through a strictly functional or ecological lens.

“But in a human context, loss of these colourful species may trigger a broad range of human responses, including grief.”

VIDEO ABSTRACT

PAPER

Hemingson CR, Mihalitsis M, Bellwood DR 2022. ‘Are fish communities on coral reefs becoming less colourful?’. Global Change Biology. DOI: 10.1111/gcb.16095

IMAGES

A selection of images can be used for media stories with credit to the photographer as stated in the file name. Please note these are for single use with this story only, not for any other story. No archival permissions are granted.

CONTACT

Dr. Christopher Hemingson (Townsville, AEST)
P: +61 (0) 450 848 901
E: christopher.hemingson@my.jcu.edu.au

Scientists at the ARC Centre of Excellence for Coral Reef Studies at James Cook University say more needs to be done to protect vulnerable table corals on the Great Barrier Reef.

Researchers studying the role of table corals have found that they provide vital sun protection for large fish in shallow reef areas.

They found that the corals are so important that if lost, the fish that depend on them will leave the reef.

“The loss of table corals denies fishes important habitat, which they use to shelter from the sun, avoiding harmful UV-radiation, just as we might sit under an umbrella at the beach,” says study lead author James Kerry.

“Large fishes maintain balanced coral reef ecosystems, they’re the predators that help control fish populations,” says study co-author Professor David Bellwood.

Table corals are particularly vulnerable – and are the preferred meal of the Crown of Thorns Starfish. Credits: James Kerry

“These fish are important for reefs and people; lose your table corals and you lose your coral trout,” Professor Bellwood explains.

The scientists say this is particularly concerning as table corals are especially vulnerable to the pressures currently facing the Great Barrier Reef.

The corals are highly susceptible to ocean acidification and bleaching, and are the preferred meal of the destructive crown of thorns starfish.

Given their shape, table corals are also easily toppled and are often destroyed in cyclones.

“Ultimately we need to conserve table corals because they are the primary structure on the Reef that provides shelter from the sun’s harmful rays. However, because they are so vulnerable to climate change and other growing threats, this is going to be a major challenge,” James Kerry says.

“The research suggests that we need to do everything we can to promote the health of the Great Barrier Reef, and in doing so, reduce the multiple threats facing these valuable corals.”

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Papers:
The functional role of tabular structures for large reef fishes: avoiding predators or solar irradiance? By J.T. Kerry and D.R. Bellwood is published in the journal Coral Reefs.
DOI 10.1007/s00338-015-1275-1
http://link.springer.com/article/10.1007/s00338-015-1275-1#page-1

Do Tabular corals constitute keystone structures for fishes on coral reefs? By J.T Kerry and D.R. Bellwood is published in the journal Coral Reefs
DOI 10.1007/s00338-014-1232-4
http://link.springer.com/article/10.1007%2Fs00338-014-1232-4

Images and video:
Image credit – James Kerry
https://www.dropbox.com/sh/3p6m9fzudy3whpq/AAB-XHZBhb_U1acvU5bGJfEOa?dl=0

Contacts:
James Kerry – mr.james.kerry@gmail.com +61 (0) 407475576
Prof David Bellwood – david.bellwood@jcu.edu.au +61 (0) 47814447
Eleanor Gregory – eleanor.gregory@jcu.edu.au +61 (0) 428 785 895