Ecological analyses to inform management targets for the culling of crown-of-thorns starfish to prevent coral decline
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Ecological analyses to inform management targets for the culling of crown-of-thorns starfish to prevent coral decline E´va E. Plaga´nyi1 E. Bee Morello1,3
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Russell C. Babcock1 • Jacob Rogers1 • Mary Bonin2
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Received: 8 February 2020 / Accepted: 15 July 2020 Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The crown-of-thorns starfish (COTS), Acanthaster cf. solaris, is one of the main contributors to declines in coral cover on the Great Barrier Reef (GBR) and remains one of the major acute disturbances on coral reefs throughout much of the Indo-Pacific. Extensive control programs on the GBR involve manual culling of COTS in the field, and research is needed to inform these management efforts. Data from the Great Barrier Reef Marine Park Authority’s (GBRMPA) COTS control program provide near-real-time CPUE (Catch-Per-Unit-Effort, COTS culled per minute) data ideal for operational decisionmaking but these must be converted to density estimates before they can be related to ecological status of reefs or incorporated into ecological models. We developed conversions between common COTS field survey methods (i.e. manta tow, SCUBA transect searches) and COTS control program CPUE data using estimates of sightability and detectability. We used a population model and COTS sizestructure data from COTS control program culling efforts to estimate that, on average, only 19% of 1-yr-old COTS
(1–15 cm) are available to be culled. Finally, we developed a CPUE-COTS density relationship to estimate the threshold levels of COTS that prevent net growth of hard corals. Culling programs should therefore aim to achieve CPUEs below these ecological thresholds in order to effectively promote coral growth and recovery. These ecologically sustainable thresholds of COTS density varied depending on hard coral cover. For example, for 35% fastgrowing coral cover, COTS culling needs to continue until CPUE decreases to below 0.05 COTS/min (1 COTS per 20 min) in order to prevent coral decline, whereas if coral cover is higher (80%), then a higher target threshold CPUE of ca. 0.08 COTS/min (ca. 3 COTS per 40 min) may be ecologically sustainable. These estimates underpin the current pest management rules being implemented by the GBRMPA in its COTS control program. Keywords Acanthaster cf. solaris Great Barrier Reef Ecological threshold Pest management COTS Culling Coral reef
Topic Editor Morgan S. Pratchett
Introduction Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00338-020-01981-z) contains supplementary material, which is available to authorized users. & E´va E. Plaga´nyi [email protected] 1
CSIRO Oceans and Atmosphere, PO Box 2538, Brisbane, QLD 4001, Australia
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Great Barrier Reef Marine Park Authority, PO Box 1379, Townsville, QLD 4810, Australia
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Present Address: General Fisheries Commission for the Mediterranean (FAO), Food and Agriculture Organization of the United Nations (FAO), Rome, Italy
The crown-of-thorns starfish (COTS),
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