Fish assemblages in Tanzanian mangrove creek systems influenced by solar salt farm constructions.
Loading...
Date
2009
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Deforestation of mangrove forests is common occurrence worldwide. We examined fish assemblage
composition in three mangrove creek systems in Tanzania (East Africa), including two creeks where the
upper parts were partly clear-cut of mangrove forest due to the construction of solar salt farms, and one
creek with undisturbed mangrove forest. Fish were caught monthly for one year using a seine net (each
haul covering 170 m2) within three locations in each creek, i.e. at the upper, intermediate and lower
reaches. Density, biomass and species number of fish were lower in the upper deforested sites compared
to the mangrove-fringed sites at the intermediate and lower parts in the two creeks affected by deforestation,
whereas there were no differences among the three sites in the undisturbed mangrove creek
system. In addition, multivariate analyses showed that the structure of fish assemblages varied between
forested and clear-cut sites within the two disturbed creeks, but not within the undisturbed creek. Across
the season, we found no significant differences except for a tendency of a minor increase in fish densities
during the rainy season. At least 75% of the fishes were juveniles and of commercial interest for coastal
fisheries and/or aquaculture. Mugil cephalus, Gerres oyena and Chanos chanos were the most abundant
species in the forested sites. The dominant species in the clear-cut areas were M. cephalus and Elops
machnata, which were both found in relatively low abundances compared to the undisturbed areas. The
conversion of mangrove forests into solar salt farms not only altered fish assemblage composition, but
also water and sediment conditions. In comparison with undisturbed areas, the clear-cut sites showed
higher salinity, water temperature as well as organic matter and chlorophyll a in the sediments. Our
results suggest that mangrove habitat loss and changes in environmental conditions caused by salt farm
developments will decrease fish densities, biomass and species numbers as well as alter the overall fish
assemblage composition in the salt farm area but not downstream in the creek.
Description
Keywords
Fish, salt, constructions
Citation
Mwandya, A.W., Gullström, M., Öhman, M.C., Andersson, M.H. and Mgaya, Y.D., 2009. Fish assemblages in Tanzanian mangrove creek systems influenced by solar salt farm constructions. Estuarine, Coastal and Shelf Science 82: 193-200.