Fish assist management crown-of-thorns starfish numbers on Great Barrier Reef

Reef fish, akin to emperors, tropical snappers and rockcods, assist maintain numbers of crown-of-thorns starfish in test on the Great Barrier Reef, in response to a brand new examine from the Australian Institute of Marine Science.

Published right now in Nature Communications, the examine discovered the abundance of the coral-eating starfish will increase in locations the place fish species that are identified to eat the starfish are eliminated.

Crown-of-thorns starfish (Acanthaster spp.) are native to coral reefs within the Indo-Pacific. They are a significant 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 Sixties—the newest remains to be underway.

“More than 50 years ago concern was raised that removal of predators may contribute to starfish outbreaks. However, at the time only one predator of the starfish was known, the giant triton sea snail,” Dr. Frederieke Kroon, AIMS ecologist and lead writer stated.

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

“Our study is the first to explore how fisheries harvests of these fish species may affect starfish abundance.”

First, the crew 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 instances greater and starfish densities almost 3 times decrease, than these on reefs open to fishing.

“It is well known that no-take marine reserves increase fish biomass and diversity of large fishes. Previous studies have suggested marine reserves could also influence starfish numbers, but our study provides strong evidence there are fewer crown-of-thorns starfish on reefs with more predatory fish,” stated Dr. Kroon.

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

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

“We found crown-of-thorn starfish density increased in areas where more reef fish biomass was harvested,” she stated.

“This relationship was strong for emperors, particularly redthroat and spangled emperors [Lethrinus miniatus and L. nebulosus], both of which are well-known predators of crown-of-thorns starfish.”

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

“Since adult coral trout are not known to eat crown-of-thorns starfish, we are interested in what may explain this relationship. One possibility is that juvenile coral trout may eat small starfish, as part of their invertebrate diet,” Dr. Kroon stated.

“Combined, our results suggest that the removal of emperors, tropical snappers and rockcods contribute to increases in starfish numbers.”

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

“Starfish outbreaks continue to be a major cause of coral loss, but unlike other pressures like climate change, can be managed at local and regional levels,” Dr. Kroon stated.

“Targeted fisheries-based management, in combination with current crown-of-thorns starfish management interventions such as direct manual control, could assist in further controlling outbreaks.”

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

“It is very likely not one, but multiple factors which contribute to the outbreaks,” she stated.

“Large-scale, long-term data such as those used this study, as well as experimental studies are the best scientific tools we have to help understand the complexities of crown-of-thorns starfish outbreaks, and to implement effective and efficient management interventions for their control.”

Provided by
Australian Institute of Marine Science