Linking the densities o f fish functional groups and developmental
stages to benthic structure
Osuka Kennedy1 2, M elita Samoilys2, David O bura2, Mare Kochzius1 and Ann Vanreusel3
1 Vrije U niversiteit Brussels, Plaine 2, 1050 Brussels
E-mail: Kennedv.Qsuka.Edeve@vub.ac.be or kennvlardv5@ vahoo.com
2 CORDIO East A frica # 9 Kibaki Flats, Kenyatta Beach, Bamburi Beach PO Box 10135 Mombasa
80101, Kenya
3 Marine Biology Section, D epartm ent o f Biology, U niversity o f Gent, Ledeganckstraat 35, B-9000
Gent, Belgium
Identification o f habitats o f sim ilar characteristic is a steppingstone tow ards determ ining
managem ent measures needed to sustain and protect fish stocks. The process plays a crucial part
in designation o f zones m eriting marine protection and restoration. In th is regard studies using
habitat structure to describe regional d is trib u tio n o f fish co m m un ity have revealed substantial
spatial co m p le xity in fish densities (Pitman e t al., 2007). This study builds on th is e xplora tory
habitat approach, in which broad scale coral reef m u lti-h a b ita t types w ill be identified and a link to
associated fish com m unities undertaken. The study purposes to use benthic and fish survey
datasets collected th ro ug h underw ater visual census (UVC) across fo u r geographical countries
w ith in the western Indian Ocean biogeographic province. The benthic dataset consisted o f
percentage cover o f hard corals, soft corals, fle shy algae, tu r f algae and rubble while fish dataset
consisted o f fish densities and size classes o f species representing 12 tro p h ic fu n ctio n a l groups.
C lassification o f surveyed sites based on th e ir m inim um and m axim um depths, w ill provide a
platform to assess the spatial d is trib u tio n o f fish fu nctio na l groups in shallow, deep and whole
range depth zones. Hom ogenous reef habitat types w ill be ascertained in a p rio r i using the
sim ila rity profile routine (SIMPROF) in hierarchical cluster analyses (Clarke et al., 2008) and a
linkage to the densities o ffis h fu n ctio n a l groups evaluated thereafter. C om parison o f species size
classes to size o f m a tu rity m etrics available in FishBase w ill enable resolving o f developm ental
stages (adult and juve nile) o f the censured fish, and th e ir d is trib u tio n w ithin the identified reef
habitat types assessed while m aking inferences to potential causal factors. Prelim inary results o f the
benthic cover shows five sta tistically sim ilar clusters; three dom inated by fleshy algae, tu r f algae
and hard corals and tw o having m ixed habitat types. Linking o ffis h densities to habitat types is on
going.
References
Clarke K.R., P.J. Som erfield and R.N. Gorley. 2008. Testing o f null hypotheses in e xplo ra to ry
co m m un ity analyses: sim ila rity profiles and biota-environm ent linkage. Journal o f Experimental
Marine Biology and Ecology 366(1 ):56-69.
Pittman S..J., C. Caldow, S.D. Hile and M.E. Monaco. 2007. Using seascape types to explain the
spatial patterns o ffis h in the mangroves o f SW Puerto Rico. Marine Ecology Progress Series
348:273-284.
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