Gibson, J.

Mumby, P.

Steneck, R.S.

English

Aquatic Commons

 Proceedings of the 64th Gulf and Caribbean Fisheries Institute   October 31 - November 5, 2011  Puerto Morelos, Mexico 
Fishing Down a Caribbean Food Web Relaxes Trophic Cascades 
 
Efecto de la Pesca a traves de la Red Alimenticia en Cadenas Troficas Caribeñas 
 
Impacts Écosystèmiques de la Pêche sur les Réseaux Trophiques Caribéen 
 
PETER MUMBY1*, ROBERT STENECK2, and JANET GIBSON3  
1University of Queensland, St Lucia Brisbane, Qld 4072 Australia. *p.j.mumby@uq.edu.au.  
2School of Marine Sciences, University of Maine, Darling Marine Center, Walpole, Maine 04573 USA. 
3Wildlife Conservation Society, PO Box 768, 1755 Coney Drive, 2nd Floor, Belize City, Belize. 
 
EXTENDED ABSTRACT 
The fishing down of marine food webs has been described in pelagic and demersal systems but rarely documented in 
coral reef environments. We recorded a rapid shift in fish community structure in Belize that accompanied a marked decline 
in grouper and snapper abundance and a switch towards smaller (less desirable), herbivorous parrotfishes. In a six to seven 
(6-7) year period (2002 - 2008/9), observations of large-bodied grouper (Serranidae) declined significantly from an 
encounter probability of 21% per 200 m2 transect to just 2%. The biomass of carnivorous snappers (Lutjanidae) underwent a 
7-fold decline, primarily in the species Ocyurus chrysurus. During this period, the inclusion of parrotfish in fish catches at 
nearby Glovers Atoll increased from a frequency of 6% in 2004 to around 20% of speared individuals by 2008. Parrotfish 
biomass declined by 41% between 2002 and 2008/9, with a major decline in the large and dominant herbivore Sparisoma 
viride. No changes in parrotfish biomass were detectable in nearby marine reserves during this time. Several important 
indirect effects of fishing were observed. The biomass of mesopredators including Cephalopholis fulvus, C. cruentatus, and 
Epinephelus guttatus increased dramatically by 880% of 2002 levels. We putatively attribute this response to a release from 
predation and constraints to foraging behaviour imposed by large serranids. Further, we find that the density of adult 
damselfish of the species Stegastes planifrons and S. partitus decreased by ~45%. We attribute this decline to elevated 
predation by the increased densities of mesopredators, which have been shown to prey upon juvenile damselfish. No change 
in damselfish densities was found at two control locations where fishing was prohibited. The decline of parrotfish in the 
central Mesoameican barrier reef likely accounts for recent anecdotal observations of Halimeda tuna spreading to micro-
habitats that have previously been grazed intensively. While these results imply that the resilience of these reefs may be 
seriously impaired, the Belize Government has recently enacted new legislation to improve the management of grouper and 
outlaw harvesting of most herbivorous fish.  
 
Based on the work published in: Mumby, P.J., R.S. Steneck, A.J. Edwards, R. Ferrari, R. Coleman, A.R. Harborne, and J.P. 
Gibson. 2012. Fishing down a Caribbean food web relaxes trophic cascades. Marine Ecology Progress Series 445:13-24. 
 
KEY WORDS: Fishing, coral reefs, parrotfish, grouper, snapper, damselfish, trophic cascade 


Fishing Down a Caribbean Food Web Relaxes Trophic Cascades

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Fishing Down a Caribbean Food Web Relaxes Trophic Cascades

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