Importance of a Kenyan mangrove forest, Mida Creek, for the ichthyofauna in terms of ecological functions as feeding ground and nursery habitat
Gajdzik, L. (2012). Importance of a Kenyan mangrove forest, Mida Creek, for the ichthyofauna in terms of ecological functions as feeding ground and nursery habitat. MSc Thesis. Oceans & Lakes, Interuniversity Master in Marine and Lacustrine Science and Management: Brussel. 63 pp.
Mangrove forests are among the most productive ecosystems, sustaining both terrestrial and aquatic fauna. They are important to coastal fisheries by providing nursery, feeding, foraging and hiding places for fishes of commercial importance. This research investigates the fish assemblage of Mida Creek (Kenya, East Africa) as well as the presumed feeding and nursery functions of the area for the present ichthyofauna. This explorative study contributes to a Kenyan-Flemish project in which scientists aim to identify the impacts of human use and management regimes of mangroves on benthic biodiversity richness and abundance including demersal fish. Since the purpose of this research is to determine the species composition of the ichthyofauna of Mida and their trophic interactions, five representative locations were selected. They are situated at different distances from local villages in order to enlighten the effect of different degrees of human disturbance. Samples were collected during 5-6 consecutive days close to spring tide in mid July 2011. Fishes were caught using several types of passive fishing gears such as large and small fyke nets, gill nets and occasionally beach seine. All fishes were identified to species level, measured and weighed. We performed stomach content analysis to provide information about fish diet. Furthermore, stable isotope analysis was applied on most fishes in order to detect whether the source of primary production for the higher trophic levels is specific of mangroves or not. A total of 29 fish species was found with a catch of 939 teleost specimens. Our analyses showed that a majority of fish belonged to the zoobenthivorous/omnivorous trophic mode since they are feeding on invertebrates. Their diet was quite similar according to locations and life stages. Two species (Sphyraena barracuda and Synodus variegatus) exhibited a mixed diet with a piscivorous preference. Results concerning the population structure revealed that fishes caught in Mida were composed of transient and resident species. Juveniles were, however, numerically more abundant in the whole Creek than adult specimens. In conclusion, our results confirm that Mida Creek mangrove is an important habitat for the ichthyofauna especially for juvenile fishes.
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