Kroon FJ et al. (2021), Fish predators control outbreaks of Crown-of-Th...

ECB-ART-50642

Nat Commun 2021 Dec 08;121:6986. doi: 10.1038/s41467-021-26786-8.

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Fish predators control outbreaks of Crown-of-Thorns Starfish.

Kroon FJ , Barneche DR , Emslie MJ .

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Outbreaks of corallivorous Crown-of-Thorns Starfish (CoTS, Acanthaster spp.) have caused persistent and widespread loss of coral cover across Indo-Pacific coral reefs. The potential drivers of these outbreaks have been debated for more than 50 years, hindering effective management to limit their destructive impacts. Here, we show that fish biomass removal through commercial and recreational fisheries may be a major driver of CoTS population outbreaks. CoTS densities increase systematically with increasing fish biomass removal, including for known CoTS predators. Moreover, the biomass of fish species and families that influence CoTS densities are 1.4 to 2.1-fold higher on reefs within no-take marine reserves, while CoTS densities are 2.8-fold higher on reefs that are open to fishing, indicating the applicability of fisheries-based management to prevent CoTS outbreaks. Designing targeted fisheries management with consideration of CoTS population dynamics may offer a tangible and promising contribution to effectively reduce the detrimental impacts of CoTS outbreaks across the Indo-Pacific.

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	Fig. 1. Response of Crown-of-Thorns Starfish density to fish biomass removal.Posterior distributions of the biomass-removal scaling exponent of Pacific Crown-of-Thorns Starfish (CoTS, Acanthaster cf. solaris) density. For each target fish group and time lag, the exponent was estimated independently using a hurdle-gamma Bayesian model (see “Methods”; Supplementary Method 2). Exponents are equivalent to the fish biomass-removal slope on the linear scale (log) of the gamma (i.e. non-zero) component of the model. Vertical dashed lines represent zero, and values above this line constitute evidence suggesting that fish biomass removal drives increase in CoTS density over time. Source data are provided as a Source data file. Fish silhouettes for Lethrinidae, Serranidae and L. miniatus from AIMS ©, for P. leopardus from F. Kroon ©, for Lutjanidae from R package fishualize (https://github.com/nschiett/fishualize, License GPL-2) and for Labridae cut and adapted to a silhouette from Fig. 2C (Choerodon anchorago, terminal phase male) in Gomon63.
	Fig. 2. Effects of no-take marine reserves on coral reef fish.Posterior distributions of a biomass, b density and c length, with posterior densities indicating the modelled median differences (middle line) between unfished (U) and fished (F) reefs, with associated 60% (dark blue) and 95% (lighter blue) credible intervals (see “Methods”; Supplementary Method 3). A positive effect indicates higher values on unfished reefs. In each plot, results are presented from top to bottom for (1) Labridae (wrasses), (2) Lutjanidae (tropical snappers), (3) Lethrinidae (emperors), (4) Lethrinus miniatus and L. nebulosus (redthroat and spangled emperors), (5) Serranidae (rockcods) and (6) Plectropomus spp. and Variola spp. (coral trout). Source data are provided as a Source data file. Fish silhouettes for Lethrinidae, Serranidae and L. miniatus from AIMS ©, for P. leopardus from F. Kroon ©, for Lutjanidae from R package fishualize (https://github.com/nschiett/fishualize, License GPL-2) and for Labridae cut and adapted to a silhouette from Fig. 2C (Choerodon anchorago, terminal phase male) in Gomon63.
	Fig. 3. Effects of no-take marine reserves and coral cover on Crown-of-Thorns Starfish density.Marginalised effects of a reef zoning and b coral cover on density of Pacific Crown-of-Thorns Starfish (CoTS, Acanthaster cf. solaris) (see “Methods”; Supplementary Method 4). In a, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\beta }_{o}$$\end{document}βo corresponds to CoTS density on unfished reefs with a hypothetical coral cover = 0; \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\beta }_{1}$$\end{document}β1 constitutes a direct test of whether CoTS densities are higher on fished reefs. In b, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\beta }_{2}$$\end{document}β2 constitutes a direct test of whether CoTS densities decrease with increasing coral cover. Mean posterior predictions presented as points (a) and dashed line (b), and 95% Bayesian credible intervals (calculated from 20,000 posterior draws) as errors bars (a) and grey shaded polygon (b). Source data are provided as a Source data file.

References [+] :

Babcock, Assessing Different Causes of Crown-of-Thorns Starfish Outbreaks and Appropriate Responses for Management on the Great Barrier Reef. 2016, Pubmed, Echinobase