Science & Technology

Fish Predators Help Control Coral-Eating Crown-of-Thorns Starfish on Great Barrier Reef

A pink throat emperor (Lethrinus nebulosus) checks out the digicam in entrance of an aggregation of crown-of-thorns starfish on the Great Barrier Reef. Credit score: Australian Institute of Marine Science

Reef fish, comparable to emperors, tropical snappers, and rockcods, assist hold numbers of coral-eating crown-of-thorns starfish in examine on the Great Barrier Reef.

Reef fish, comparable to emperors, tropical snappers, and rockcods, assist hold numbers of crown-of-thorns starfish in examine on the Great Barrier Reef, in line with a brand new examine from the Australian Institute of Marine Science.

Revealed at present (December 8, 2021) in Nature Communications, the examine discovered the abundance of the coral-eating starfish will increase in locations the place fish species which might be identified to eat the starfish are eliminated.

Crown-of-thorns starfish (Acanthaster spp.) are native to coral reefs within the Indo-Pacific. They’re a serious contributor to coral loss when present in giant numbers, as they feed on the dwelling tissue of many onerous coral species. On the Great Barrier Reef, 4 outbreaks have occurred for the reason that Nineteen Sixties – the newest remains to be underway.

“Greater than 50 years in the past concern was raised that removing of predators might contribute to starfish outbreaks. Nonetheless, on the time just one predator of the starfish was identified, the enormous triton sea snail,” Dr. Frederieke Kroon, AIMS ecologist and lead writer stated.

“Current research have revealed almost 100 species of coral reef organisms feed on totally different life phases of the starfish. Eighty of those are fish, together with fashionable seafood species comparable to emperors, tropical snappers, and rockcods.

“Our examine is the primary to discover how fisheries harvests of those fish species might have an effect on starfish abundance.”

An aggregation of crown-of-thorns starfish feeding on a plate coral on the Great Barrier Reef. Credit score: Australian Institute of Marine Science

First, the workforce in contrast AIMS’ long-term coral reef fish and starfish abundance information collected at reefs open and closed to fishing. On reefs closed to fishing, biomass of emperors, snappers, and rock cods was 1.4 to 2.1 occasions increased, and starfish densities almost thrice decrease, than these on reefs open to fishing.

“It’s well-known that no-take marine reserves improve fish biomass and variety of huge fishes. Earlier research have recommended marine reserves might additionally affect starfish numbers, however our examine offers sturdy proof there are fewer crown-of-thorns starfish on reefs with extra predatory fish,” stated Dr Kroon.

The scientists additionally in contrast 30 years of reef fish harvest information from the Queensland Division of Agriculture and Fisheries with crown-of-thorns starfish abundance information from AIMS’ long-term reef monitoring over the identical interval.

A college of stripey snapper, Lutjanus carpotonatus, on the Great Barrier Reef. This species is thought to eat crown-of-thorns starfish. Credit score: Australian Institute of Marine Science

Dr. Kroon stated the connection between the fisheries’ harvests and the numbers of starfish was putting.

“We discovered crown-of-thorn starfish density elevated in areas the place extra reef fish biomass was harvested,” she stated.

“This relationship was sturdy for emperors, significantly redthroat and spangled emperors [Lethrinus miniatus and L. nebulosus], each of that are well-known predators of crown-of-thorns starfish.”

The connection was additionally sturdy for tropical snappers and rockcods, together with coral trout (Plectropomus spp. and Variola spp.)

“Since grownup coral trout usually are not identified to eat crown-of-thorns starfish, we’re thinking about what might clarify this relationship. One chance is that juvenile coral trout might eat small starfish, as a part of their invertebrate eating regimen,” Dr Kroon stated.

“Mixed, our outcomes recommend that the removing of emperors, tropical snappers and rockcods contribute to will increase in starfish numbers.”

A crown-of-thorns starfish feeding on a plate coral on the Great Barrier Reef. Credit score: Australian Institute of Marine Science

The findings have offered a possibility to research new instruments for controlling outbreaks on the Great Barrier Reef and maybe throughout the Indo-Pacific, comparable to focused fisheries-based administration.

“Starfish outbreaks proceed to be a serious explanation for coral loss, however not like different pressures like local weather change, may be managed at native and regional ranges,” Dr. Kroon stated.

“Focused fisheries-based administration, together with present crown-of-thorns starfish administration interventions comparable to direct handbook management, might help in additional controlling outbreaks.”

Dr. Kroon stated the findings make a big contribution to understanding potential drivers of starfish outbreaks, such because the pure tendency of the starfish to breed in excessive numbers and the position of water high quality, as they aren’t mutually unique.

“It is rather possible not one, however a number of components which contribute to the outbreaks,” she stated.

“Giant-scale, long-term information comparable to these used this examine, in addition to experimental research are the most effective scientific instruments we’ve got to assist perceive the complexities of crown-of-thorns starfish outbreaks, and to implement efficient and environment friendly administration interventions for his or her management.”

Reference: “Fish predators management outbreaks of Crown-of-Thorns Starfish” by Frederieke J. Kroon, Diego R. Barneche and Michael J. Emslie, 8 December 2021, Nature Communications.
DOI: 10.1038/s41467-021-26786-8

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