The use of breeding sites of Tilapia congica (Thys & van Audenaerde 1960) to delineate conservation sites in the Lake Tumba, Democratic Republic of Congo: toward the conservation of the lake ecosystem

摘要

To guide the zoning process in Lake Tumba, Democratic Republic of Congo, breeding sites of Tilapia congica were studied. Physical metrics measured were: nest depths, exposure to sun rays, distance from the edges, site spreads, and habitat types. Mean nest depth = 0.23 m +/- 0.08 (SD), range = 0.04-2.2 m (n = 553 nests); 100% (n = 70 sites) sites were exposed to the sun and the polynomial regression analysis showed 90% sites were within the range 51-250 m from the lake shores (y = -1.7143x2 + 10.371x- 1.8; R2 = 0.597, n = 70 sites), with 60% clumped within the range of 51-150 m, indicating a relationship between nesting sites and the distance from edges. The largest group spread group was 300 m, and among the four breeding sites identified, one was similar to 10 km long, meaning a zonal spatial spread p = 300 ha and a core reproduction zone p' = 100 ha. T. congica built 87.30% of their nest in habitats where Hippo grass Vossia cuspidata (48.20%) and Water lily Nympheae stellata (39.10%) dominated. T. congica shared 41.81% of its nesting sites with other fish species, leading to the conclusion that protecting the species habitats would provide the umbrella for the conservation of other species.ResumePour orienter le processus de zonage au lac Tumba, en Republique Democratique du Congo, nous avons etudie les sites de reproduction de Tilapia congica. Les parametres physiques mesures etaient : la profondeur des nids, l'exposition aux rayons du soleil, la distance par rapport a la berge, l'etendue des sites et les types d'habitat. La profondeur moyenne des nids = 0,23 m +/- 0,08 (DS), le domaine vital du nid = 0,04-2,2 m (n = 553 nids); 100% des sites (n = 70) etaient exposes au soleil, et l'analyse de la regression polynomiale a montre que 90% des sites se trouvaient entre 51 et 250 m des berges du lac (y = -1,7143x2 + 10,371x - 1,8; R2 = 0,597; n = 70 sites) et 60% d'entre eux etaient rassembles a une distance comprise entre 51 et 150 m des berges, ce qui indique une relation entre les sites de nidification et la distance par rapport aux berges. Le groupe le plus etendu avait 300 m et, parmi les quatre sites de reproduction identifies, un avait similar to 10 km de long, ce qui signifie une dispersion spatiale zonale Pi = 300 ha et une zone de reproduction centrale Pi' = 100 ha. Les T.congica construisent 87,30% de leurs nids dans des habitats ou dominent l'herbe a hippos Vossia cuspidata (48,20%) et les nenuphars Nymphea stellata (39,10%). Les T. congica partagent 41,81% de leurs sites de nidification avec d'autres especes de poissons, d'ou la conclusion que la protection des habitats de cette espece fournirait aussi une protection a d'autres especes.