Collecting cryptobenthic fishes can be delicate. Here, Simon Brandl is transferring an anaesthetized cardinalfish into a collection bag.

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Tiny fish a big lure for life on coral reefs

May 23, 2019
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Researchers from Simon Fraser University have discovered how coral reefs support such an abundance and diversity of life. Banting Postdoctoral Fellow Simon Brandl and a team of international researchers revealed that tiny fish species around the world fuel life on coral reefs.

The research, published in Science, examines how commonly overlooked ‘cryptobenthic’ fishes—tiny, bottom-dwelling creatures—are a bountiful food source for larger fishes.

“These fish are like candy,” says Brandl. “They are tiny, colorful bundles of energy that get eaten almost immediately by any coral reef organism that can bite, grab or slurp them up.

“In fact, the vast majority of tiny fish on reefs are eaten within the first few weeks of their existence.”

The researchers examined the larvae of reef fish, which normally undertake long journeys across the open ocean to find a home. Few of them survive. Tiny fish larvae, however, appear to avoid this migration and stay close to their parents’ reefs.

“Tiny fish larvae absolutely dominate the larval communities near reefs,” says Brandl. “Our data shows that these fish get a lot more bang for their buck with every egg they spawn—probably because they avoid the death trap of the open ocean.”

The behaviour allows adult tiny fish populations to create a steady stream of babies that rapidly replaces each adult tiny fish that is devoured on the reef.

“This conveyor belt supplies almost 60 per cent of all consumed fish flesh on reefs, but we never see it because the fish get eaten much faster than we could ever count them,” says Brandl. “It’s essentially a bag of candy that magically replenishes every morsel eaten.”

The research has important implications for the preservation of coral reefs.

“Coral reefs around the world are undergoing dramatic declines,” says Isabelle Côté, SFU biological sciences professor and co-author of the paper. “With this research, we can help focus conservation efforts on protecting the fuel for the bustling fish communities that underpin reefs and their immense value to people.”