Kochzius, M.

Obura, D.

Osuka, K.

Samoilys, M.

Vanreusel, A.

Open Marine Archive

  
 
 
 
Understanding trophic interaction and the ecological status of 
marine environment requires an assessment of benthic habitat, 
fish abundance and biomass. Indeed there is a relationship 
between benthic habitat and fish community (Pitman et al., 2007). 
 
The taxonomic composition and ecological roles of fish functional 
groups are diverse. A total of 12 coral associated fish functional 
groups have been reported, namely piscivores, omnivores, 
corallivores, invertivores, planktivores, detritivores, large 
excavators, small excavators, scrapers, browsers, grazers and 
grazers-detritivores. This study identifies benthic sub-habitats and 
relate each sub-habitat to the densities of fish functional groups. 
 
Linking the Densities of Coral Associated Fish Functional 
Groups to the Benthic Structure  
Kennedy Osuka1,2*, Marc Kochzius1, Ann Vanreusel3, David Obura2 and Melita Samoilys2  
1Vrije Universiteit Brussels Plaine 2, 1050 Brussels, 2CORDIO East Africa #9 Kibaki Flats, Kenyatta Beach, Bamburi Beach P.O.BOX 10135 Mombasa 80101, Kenya 
 3 Marine Biology Section, Department of Biology, University of Gent, Ledeganckstraat 35, B-9000 Gent, Belgium 
*E-mail: Kennedy.Osuka.Edeye@vub.ac.be or kennylardy5@yahoo.com 
Introduction 
Objective Method Variables Data analysis 
To determine 
the benthic 
sub-habitats 
with similar  
benthic 
structure. 
Visual estimate of 
percent cover of 
benthic variables. 
1-2 estimates per 
site.  
Hard coral, soft 
corals, fleshy 
algae, turf 
algae, crustose 
coralline algae 
(CCA) and 
rubble. 
Hierarchical 
cluster analysis, 
using SIMPROF 
test, of arsine 
square-root 
transformed data 
(Clarke et al. 2008). 
To link 
densities of 
fish functional 
groups to the 
benthic sub-
habitats. 
Underwater 
Visual Census of 
selected fish 
functional species 
using 50 x 5 m 
belt transect. 3 -7 
replicates per site. 
Fish species 
comprising 12 
functional 
groups  
Comparisons of 
relative 
abundance of 
each functional 
groups across 
benthic sub-
habitats. 
Material and methods 
Table 1: Summary of objectives, method of data collection and data 
analysis applied. 
Study area 
This study uses benthic data 
collected by D. Obura and reef fish 
abundance data collected by M. 
Samoilys, from a total 32 sites from  
•  Tanzania,  
•  Northern Mozambique,  
•  Comoros and  
•  Northeast Madagascar.	  
 
Results 
Hierarchical cluster analysis of the benthic variables using SIMPROF 
test revealed 5 distinct cluster groups A-E, henceforth called sub-
habitats (ANOSIM R = 0.769, p<0.001, Fig. 2). The sub-habitats 
were characterized by dominance of different benthic variables: A 
dominated by turf algae at 42.0 ± 6.0 % (mean ± se), B and C by 
hard corals at 51.9 ± 3.3 % and 42.5 ± 3.2 % respectively, D by soft 
corals at 33.3 ± 8.8 %, and E by fleshy algae - 37.5 ± 6.0 % (Fig. 3). 
Figure 2: Cluster analysis of arcsine square-root transformed data of 
benthic variables.  
Figure 3: Mean benthic cover by cluster groups (sub-habitats) 
Variability of the relative abundance of functional groups 
across the sub-habitats was observed, with only the piscivores 
and invertivores, showing significant difference (p<0.05; Fig. 
4). Piscivores were higher in abundance in turf algae 
dominated sites (A) than in soft coral dominated sites (D) 
while invertivores showed higher relative abundance in hard 
coral dominated sites (C) than turf algae dominated sites (A). 
The study shows that on a broad scale, few functional groups 
show preference to particular benthic sub-habitats. It is also 
likely that biomass may show differences across the sub-habitats 
and probably the broad scale visual estimates of the benthic 
habitat structure do not fully explain the fish densities.  
Conclusion      
References 
Clarke K.R., Somerfield P.J. and Gorley R.N. 2008. Testing of null hypotheses in exploratory community 
analyses: similarity profiles and biota-environment linkage. Journal of Experimental Marine Biology and 
Ecology, 366(1), 56-69. 
Pittman S.J., Caldow C., Hile S.D. and Monaco M.E. 2007. Using seascape types to explain the spatial 
patterns of fish in the mangroves of SW Puerto Rico. Marine Ecology Progress Series, 348, 273-284.  
Figure 4: Relative abundance of 12 functional groups by sub-habitats  
©M.Samoilys 
Acknowledgement: Collection of data was supported by the Western Indian Ocean Marine Science Association (WIOMSA) through the Marine Science for Management 
(MASMA) programme.  This study was supported by VLIR-UOS. 
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10.0 
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A B C D E 
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Cluster groups 
Hard coral Soft coral Fleshy algae Turf algae CCA Rubble 
Figure 1: Map of the study area  


Linking the densities of coral associated fish functional groups to the benthic structure

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