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Differential effects of habitat complexity, predators and competitors on abundance of juvenile and adult coral reef fishes


Greater structural complexity is often associated with greater abundance and diversity, perhaps because high complexity habitats reduce predation and competition. Using 16 spatially isolated live-coral reefs in the Bahamas, I examined how abundance of juvenile (recruit) and adult (non-recruit) fishes was affected by two factors: (1) structural habitat complexity and (2) the presence of predators and interference competitors. Manipulating the abundance of low and high complexity corals created two levels of habitat complexity, which was cross-factored with the presence or absence of resident predators (sea basses and moray eels) plus interference competitors (territorial damselfishes). Over 60 days, predators and competitors greatly reduced recruit abundance regardless of habitat complexity, but did not affect adult abundance. In contrast, increased habitat complexity had a strong positive effect on adult abundance and a weak positive effect on recruit abundance. Differential responses of recruits and adults may be related to the differential effects of habitat complexity on their primary predators. Sedentary recruits are likely most preyed upon by small resident predators that ambush prey, while larger adult fishes that forage widely and use reefs primarily for shelter are likely most preyed upon by large transient predators that chase prey. Increased habitat complexity may have inhibited foraging by transient predators but not resident predators. Results demonstrate the importance of habitat complexity to community dynamics, which is of concern given the accelerated degradation of habitats worldwide.

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I am especially grateful to J. Almany, K. Overholtzer, D. Piechnik, and M. Webster for assistance and advice in the field. Financial support was provided by an NSF Graduate Predoctoral Fellowship and International Research Fellowship, a Fulbright Postgraduate Award, and NSF grants (OCE-96-17483 and OCE-00-93976) and NOAA-NURP grants (CMRC-95-3042 and CMRC-97-3109) to M. Hixon. This manuscript benefited from reviews by my graduate committee: M. Hixon (chair), P. Bayley, M. Carr, B. Menge, and S. Sogard. Additional reviews were provided by M. McCormick, P. Munday, M. Webster and two anonymous reviewers.

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Correspondence to Glenn R. Almany.



Families and species included in each category of fishes

Family and species Recruits Adults
Acanthuridae (surgeonfishes)
 Acanthurus bahianus X X
 A. coeruleus X X
 A. chirurgus   X
Chaetodontidae (butterflyfishes)
 Chaetodon aculeatus X  
 C. ocellatus X X
 C. sedentarius   X
 C. striatus X  
Gobiidae (gobies)
 Coryphopterus dicrus   X
 C. glaucofraenum   X
 Gnatholepis thompsoni   X
Haemulidae (grunts)
 Haemulon album   X
 H. flavolineatum   X
 H. melanurum   X
 H. plumieri   X
Holocentridae (squirrelfishes)
 Holocentrus adscensionis   X
 H. bullisi   X
 H. coruscus   X
Labridae (wrasse)
 Halichoeres garnoti X X
 H. maculipinna X X
 H. pictus   X
 H. radiatus X X
 Thalassoma bifasciatum X X
 Malacoctenus macropus   X
 M. triangulates   X
Mullidae (goatfishes)
 Pseudopeneus maculatus   X
Pomacanthidae (angelfishes)   
 Centropyge argi   X
 Holacanthus ciliaris X X
 H. tricolor X X
 Pomacanthus arcuatus X X
Pomacentridae (damselfishes)
 Chromis cyanea X  
 Stegastes leucostictus X  
 S. partitus X  
 S. variabilis X  
Scaridae (parrotfishes)
 Cryptotomus roseus   X
 Scarus coeruleus   X
 Sparisoma atomarium   X
 S. aurofrenatum   X
 S. chrysopterum   X
 S. viride   X

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Almany, G.R. Differential effects of habitat complexity, predators and competitors on abundance of juvenile and adult coral reef fishes. Oecologia 141, 105–113 (2004).

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  • Competition
  • Habitat shift
  • Marine reserves
  • Predation
  • Recruitment