Very small fish life on coral reefs

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coral reef swimming

Fish swim along the Great Barrier Reef in Australia. A new study shows that very small fish, which are rarely monitored or studied, provide critical fuel for the coral reef ecosystem. Tane Sinclair-Taylor

Coral reefs generally evoke clear, turquoise waters and an impressive number of colorful fish. But what does such an abundance of life support?

In an article published May 23 in Science, a team of international researchers from Simon Fraser University, the University of Washington and other institutions reveals that the iconic abundance of coral reef fish is fueled by an unlikely source : small reef fish living on the bottom.

Researchers show that these small vertebrates – no more than 2 or 3 centimeters long – play a critical role on coral reefs that allow large reef fish to thrive.

"These fish are like candy," lead author Simon Brandl, a Banting postdoctoral researcher at Simon Fraser University in British Columbia, said. "They are tiny, colorful bundles of energy that are eaten almost immediately by any coral reef organism that can bite, grasp or swallow."


fish sticks out of the hole

Most bottom fishes try to avoid predation by hiding or camouflaging themselves. This colorful bluish blenny fish explores its surroundings with its head sticking out of the hole. Tane Sinclair-Taylor

In fact, the vast majority of small fish on coral reefs will be eaten in the first weeks of their existence.

"We were all really excited to see how entire communities of coral reefs were fed by some of the smallest vertebrates on earth – including some species that live for an average of only 65 days," said co-author Luke Tornabene, an assistant professor at the UW School of Aquatic Sciences and Fisheries and Fish Curator at the Burke Museum of Natural History and Culture.

So why are these fishes not disappearing from coral reefs? The researchers solved this mystery by examining the larvae of coral reef fish, which normally undertake epic journeys through the open ocean to find a home. Few of them survive.

The small fish that lives on the bottom, however, avoids this migration altogether. Most larvae seem to simply stay close to their parents' reefs.


a fish called blenny

Gobies and bubbles, like this red blenny, support coral reef productivity at a high cost: most of these small fish are eaten over several weeks or months, but are almost immediately reintegrated by the next generation. Sinclair-Taylor

"The tiny fish larvae absolutely dominate the larval communities near the coral reefs," said Brandl. "Our data shows that these fish get much more value for their dollar with each egg they generate, probably because they avoid the deadly trap of the open ocean."

This, in turn, supplies very small populations of adult fish with a steady stream of children that quickly replace every adult that is eaten on the coral reef. In total, these fish represent almost 60% of all fish tissue consumed on coral reefs.


the goby fish hovers in small groups above the coral.

The red gobies hover in small groups above the coral heads, which they rely on for shelter. Tane Sinclair-Taylor

Researchers expect this model to occur on coral reefs around the world. Furthermore, as these small fish spend their entire lives short on a specific reef, they are good indicators of how healthy a coral reef environment is, explained Tornabene. If the habitat begins to degrade, even the fish populations will suffer an almost immediate blow.

"In many ways, these miniature fish are more than just a conveyor belt of nutrients," Tornabene said. "If we look at these small communities, they can serve as reef guards, warning us of the imminent great changes in the entire ecosystem."


the small fish faces with caution

A blenny from the Great Barrier Reef faces with caution. It is these small fish that provide over half of the fish flesh eaten on the reef. Tane Sinclair-Taylor

This study was funded by the BNP Paribas Foundation, the National Agency for Research (France), the Smithsonian Institution, the National Science and Engineering Research Council of Canada and the Australian Research Council.

/ Public release. View in full here.

. (tagToTranslate) University of Washington (t) university (t) research (t) Australia (t) Canada (t) Washington (t) Great coral reef (t) research council (t) environment (t) Australian professor (t) (t) migration (t) habitat (t) science (t) Britannica

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