Subproject W07

Prof. Dr. K. Eduard Linsenmair, Universität Würzburg, Lehrstuhl für Tierökologie und Tropenbiologie, Zoologie III, Am Hubland, 97074 Würzburg

Fish communities in the ephemeral savanna waters of the Comoé Nationalpark, Ivory Coast, West Africa

Introduction
Tropical freshwaters are currently subject to massive changes. In many places water quality deteriorates due to increasing amounts of erosion borne sediments and sewage. Draining as well as dam building change the hydrology radically, leading to the elimination of broad spectra of habitats. Climate change influences the amount and temporal pattern of rainfall causing profound alterations in the basic hydrological conditions of certain regions. These abiotic changes might lead to shifts in species abundance if not to their extinction. Consequently, functional relationships in the species-rich tropical fish communities are expected to change.

Objectives
In our project we investigate fish communities that use, for part of their lives, ephemeral savanna waters temporarily connected to the Comoé river. Up to date already 66 fish species have been caught in these ephemeral waters, among them some new to the hitherto known fish community of the Comoé. We are interested in the benefits (possibly better feeding or spawning conditions and possibly also a reduced predation pressure on certain developmental stages) and on the costs (e.g. high risk of too early a drying up) associated with the use of these types of transient waters to understand what these species gain by leaving the permanent water bodies. It has to be expected -and is already evident- that different species differ considerably in their temporal, spatial, behavioural etc. modes of using the ephemeral waters. We are furthermore especially interested in those factors steering the temporal use patterns, e.g. those releasing migrations out of the main river during the first half of the rainy season and back to it towards the end and finally we want to understand the overall importance of the temporal waters for the species composition and productivity of the entire fish community.
During the first three years of BIOTA we want to learn as much as possible about the mode of use by the different species, examine the community structure of different ephemeral water bodies and the annual variability in dependence upon climatic differences (e.g. temporal patterns of rainfall and amounts of rain are highly variable between years). During the main phase of BIOTA antropogenically altered habitats shall be included, the effects of disturbances influencing the fish community investigated and their socio-economic consequences illuminated and quantified. Due to direct as well as indirect anthropogenic changes, ephemeral waters are reduced in numbers and quality. So far, the resulting impact of these changes on the fish communities and the productivity of river systems is mostly unknown. Based on a better knowledge of the fish communities and the factors influencing them it will be possible to design scientifically based management plans for these water bodies. By this means, we hope to be able to contribute to the protection of Africa´s ecologically and socio-economically highly important freshwater habitats by providing sound guidance to the preservation of their biodiversity and to the maintenance of their productivity.

Cooperation within BIOTA:

The research team:

Prof. K. E. Linsenmair, Projektleiter, Zoologie III, Am Hubland, 97074 Würzburg
Dipl. Biol. Timo Moritz, Doktorand, Zoologie III, Am Hubland, 97074 Würzburg
Exam. Biol. Minnattallah Boutros, Zoologie III, Am Hubland, 97074 Würzburg

External partners of cooperation:

Dr. G. G. Teugels, Labo Ichtyologie, Musée Royal de l`Afrique Central, Tervuren, Belgien
CRE, Centre de Recherche en Ecologie, Université d'Abobo-Adjamé, Côte d' Ivoire