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Swarthmore College

Publication Date

Fall 12-1-2014

Program Name

Australia: Rainforest, Reef, and Cultural Ecology

Abstract

Since the world’s coral reefs are currently threatened by a variety of different natural and anthropogenic factors, research on protecting coral reefs is pivotal to protect these diverse ecosystems. However, only Indo-Pacific reefs such as the Great Barrier Reef are dying due to a corallivorous echinoderm threat known as the Crown-of-Thorns Starfish (Acanthaster planci). A. planci is a starfish which feeds on coral tissue and can quickly reduce coral cover on a reef during an outbreak. Although scientists are still unsure as to what causes these outbreaks, one suggestion is the predator-removal theory. The predator removal-theory states that major predators of A. planci are being overfished and are unable to regulate the A. planci population, resulting in outbreaks. This study’s goal was to determine the major predators of A. planci in an attempt to ascertain if predation could be used to control A. planci populations. In situ predation experiments were preformed on reefs off of Lizard Island by staking whole A. planci on the reef with cameras to record any instances of predation. Internal organs were also put out on the reef with the whole A. planci, mimicking the condition of an A. planci after a predation event. The weight of female gonads was collected from select A. planci to determine the percentage of body mass composed of gonad. Overall, nine species of fish were found to consume parts of the A. planci and one of which (Lethinus nebulosus) was found to be commercially exploited. It was also determined that A. planci predators could be divided up into categories of “lethal predation” and “sublethal predation”, with most predators of the internal organs falling under sublethal predation. Since none of the fish species that ate gonads were planktivores, it is improbable that these species are egg predators and regulate A. planci populations during spawning events. Finally, the percentage of mass 4 Chan composed of gonads increased greatly with size, stressing the importance of controlling these highly fecund individuals. Overall, future studies could continue to identify predators of A. planci and rates of predation of fish species on A. planci should be determined in order to estimate whether or not it is enough to regulate A. planci populations.

Disciplines

Animal Sciences | Aquaculture and Fisheries | Life Sciences | Marine Biology | Other International and Area Studies | Zoology

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