crown-of-thorns starfish eaten by fish
Dr Frederieke Kroon looking at a crown-of-thorns starfish on the Great Barrier Reef. Photo: D.Westcott/CSIRO

Which fish species eat crown-of-thorns starfish?

Crown-of-thorn spine fragments found in a fish faeces sample. Photo: F.Kroon/AIMS

GREAT Barrier Reef research has found the destructive crown-of-thorns starfish is eaten more often than thought. 

Crown-of-thorns starfish are on the menu for many more fish species than previously suspected, an investigation using fish poo and gut goo reveals. The finding suggests that particular fish including popular eating and aquarium species might have a role to play in keeping the destructive pest population under control. The native starfish acanthaster solaris is responsible for widespread damage to the Great Barrier Reef 

Since 1962, its population has surged to plague proportions on three occasions, each time causing the loss of large amounts of hard coral. A fourth outbreak is currently under way. 

Increasing the amount of predation on starfish has long been touted as a potential solution to preventing outbreaks. Yet aside from a mollusc called the giant triton – charonia tritonis – identifying what eats the starfish has been a challenging task. 

A team of scientists led by Dr Frederieke Kroon from the Australian Institute of Marine Science in Townsville, Australia, has applied a genetic marker unique for crown-of-thorns – and developed at AIMS – to detect the presence of starfish DNA in fish poo and gut contents. 

Over three years, Dr Kroon’s team used the marker on samples taken from 678 fish from 101 species, comprised of 21 families, and gathered from reefs experiencing varying levels of starfish outbreak. 

“Our results strongly indicate that direct fish predation on crown-of-thorns may well be more common than is currently appreciated,” Dr Kroon said. 

The study, published in the journal Scientific Reports, confirms that at least 18 coral reef fish species – including spangled emperorredthroat emperor and blackspotted puffer  – consume young and adult starfish on the reef. 

Among the species were nine that had not been previously reported to feed on crown-of-thorns, including neon damselfish, redspot emperor and blackspot snapper. 

“Our findings might also solve a mystery – why reef areas that are closed to commercial and recreational fishing tend to have fewer starfish than areas where fishing is allowed,” Dr Kroon said. 

She and colleagues from AIMS worked with researchers from CSIRO Land and Water, and managers from the Great Barrier Reef Marine Park Authority to conduct the study. 

The Great Barrier Reef Marine Park Authority director of the COTS control program, and co-author of the paper, Mr Darren Cameron said: “This innovative research sheds new light on the extent that coral reef fish eat crown-of-thorns starfish. A number of the fish species shown to feed on these starfish are caught by commercial and recreational fisheries, highlighting the importance of marine park zoning and effective fisheries management in controlling crown-of-thorns starfish across the Great Barrier Reef.” 

The research was supported by funding from the Ian Potter Foundation 50th Anniversary Commemorative Grants scheme, the Lizard Island Reef Research Foundation and the Australian government’s National Environmental Science Program Tropical Water Quality Hub. 

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