'Twilight zone' fish swim silently with forked tails

January 19, 2016
Tail shape can help predict if a fish will be found at a greater range of depths. Credit: Tom Bridge

An international team of researchers has identified a way to predict which reef fish can live across a greater range of depths, increasing their chances of surviving natural disasters such as cyclones and coral bleaching.

Study lead author, Dr Tom Bridge from the ARC Centre of Excellence for Coral Reef Studies at James Cook University, says the research, published in the journal Proceedings of the Royal Society B, found that tail shape can help predict if a fish is likely to exist across a range of water depths.

"We found that the 'caudal fin aspect ratio', which measures the shape of the fishes tail, is the best predictor of which fish can live in a range of deep and shallow reefs." Dr Bridge says.

"In other words, fishes with more forked tails are significantly more likely to be found in both shallow and deep habitats than species with more rounded tails."

Dr Bridge says it's not known exactly why this is the case, though it's suspected that the forked tail allows fish to swim more 'silently'.

"The capacity for 'stealth swimming' is particularly important in deeper habitats, where light irradiance and wave energy are low and species rely on sensing changes in water pressure to capture prey and avoid predators."

Coral reefs are typically thought to occur in shallow, sun-lit waters, but new technology is revealing that reefs in the ocean's 'twilight zone', 50-150 m deep, support diverse and unique communities

Reef fish are swimming in "twilight zone" deep reefs. Credit: Tom Bridge

However conditions on these deep reefs can be challenging for coral reef fishes, with low light, high pressure, and low temperatures.

Study co-author Dr Osmar Luiz from Macquarie University says species that can survive in the twilight zone may be less susceptible to population declines and extinction.

"Identifying which species can occur over a broad depth range is important for understanding which are more vulnerable to local population declines and extinction, particularly from disturbances such as cyclones and events."

The researchers say the next step is to understand exactly what it is about the forked tails that provides fishes such an advantage in deeper water.

Explore further: Tough times for the tree of life on coral reefs

More information: Ecological and morphological traits predict depth-generalist fishes on coral reefs by Tom C. L. Bridge, Osmar J. Luiz, Richard R. Coleman, Corinne N. Kane and Randall K. Kosaki is published in the journal, Proceedings of the Royal Society B, dx.doi.org/10.1098/rspb.2015.2332

Related Stories

Tough times for the tree of life on coral reefs

January 12, 2016

Marine scientists are calling for a re-think of how marine protected areas (MPAs) are planned and coordinated, following a global assessment of the conservation of tropical corals and fishes.

Deep refuges 'can help save our reefs'

May 30, 2013

(Phys.org) —Marine scientists from Australia and the USA today called for global efforts to protect deeper coral reefs as insurance against the widespread destruction of shallow reefs and their fish stocks now taking place ...

Researchers study sediment record in deep coral reefs

December 2, 2015

A University of Miami (UM) Rosenstiel School of Marine and Atmospheric Science-led research team analyzed the sediments of mesophotic coral reefs, deep reef communities living 30-150 meters below sea level, to understand ...

Fish go deep to beat the heat

August 7, 2015

A James Cook University study shows fish retreating to deeper water to escape the heat, a finding that throws light on what to expect if predictions of ocean warming come to pass.

A fish too deep for science

July 17, 2015

Drs. Carole Baldwin and Ross Robertson from the Smithsonian Institution discovered a new small goby fish that differs from its relatives not only in its size and colors, but also in the depth of its habitat (70-80 m) in the ...

Recommended for you

Cow gene study shows why most clones fail

December 9, 2016

It has been 20 years since Dolly the sheep was successfully cloned in Scotland, but cloning mammals remains a challenge. A new study by researchers from the U.S. and France of gene expression in developing clones now shows ...

Blueprint for shape in ancient land plants

December 9, 2016

Scientists from the Universities of Bristol and Cambridge have unlocked the secrets of shape in the most ancient of land plants using time-lapse imaging, growth analysis and computer modelling.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.