Influence of mangrove deforestation on trophic organization of fish assemblages in creek systems
(English)Manuscript (Other academic)
The mangrove biotopes in Tanzania are under increasing pressure from domestic uses and changes in land-use for aquaculture and solar salt farms. To investigate the impacts of man-made activities on trophic structure of mangrove-associated fish species, sampling of fish from various trophic groups was performed in mangrove creeks. Trophic organization and stable isotope signatures (δ 13C and δ 15N) of fish in undisturbed areas of mangrove creeks were compared with clear-cut areas of mangrove as well as with reservoirs for saltworks or fish farms constructed after mangrove clearing. Results showed significantly higher densities, species numbers, diversity (H’) and numbers of trophic groups in undisturbed sites compared to both types of disturbed sites. Overall, omnivorous fish comprised the most abundant feeding guild, with the highest number of individuals found in the cleared sites followed in order by the uncleared sites and the reservoirs. The feeding guild zoobenthivores/piscivores was the most diverse group, with the highest species richness in the undisturbed areas. Multivariate analysis showed that assemblage structure of omnivores in the reservoirs was separated from those in the uncleared and cleared sites, while zoobenthivores/piscivores differed between uncleared sites and the disturbed areas (cleared sites and reservoirs). Stable isotope ratios of δ13C and δ15N values in fish tissue muscles indicate significant diet shifts between undisturbed and disturbed mangrove creek systems, although the effects are species-specific. Our findings suggest that mangrove deforestation combined with land-use changes, such as salt- or fish farm constructions, has a greater impact on the trophic structure of fish in mangrove creeks than mangrove deforestation only. Hence, the extent and severity of disturbance seem to be important in predicting fish assemblage composition.
Mangrove, Fish, Functional groups, Anthropogenic disturbance, Tanzania, Western Indian Ocean.
Fish and Aquacultural Science
Research subject Animal Ecology
IdentifiersURN: urn:nbn:se:su:diva-27398OAI: oai:DiVA.org:su-27398DiVA: diva2:214034
ProjectsSida-SAREC Marine Bilateral Programme between Sweden and Tanzania