Fish Community Structure of a Mangrove Creek, Tudor, Kenya

Abstract

Tudor Creek is one of the largest mangrove tidal creeks in coastal Kenya that supports important artisanal fisheries. Despite the importance of estuarine habitats like creeks in the life cycle of fishes, there is little information on the ichthyofauna of mangrove tidal creeks in most of the Western Indian Ocean (WIO) region. This study therefore aimed at describing the fish assemblage structure within the Tudor Creek in coastal Kenya. The fish were sampled at four stations ranging from the mouth of the creek upto approximately 10 km inside the creek using a beach seine. Sampling was carried out for 10 months between October 2007 and July 2008 during the northeast (NEM) and southeast (SEM) monsoon season. In total, 92 species belonging to 45 families were sampled within the creek. There was seasonal within-creek variability in fish species abundance and diversity. Overall, the mean catch rates (individuals m-2) was highest during the SEM season (0.336 ± 0.084) compared to NEM season (0.229 ± 0.044). The NEM season had significantly more species than the SEM season (82 and 54 species, respectively) (2=317.760, P<0.0001). Fish community structure estimated by the ecological diversity indices showed variations between stations and seasons. The famil y Gobiidae contributed the highest to the total catch and species abundance in the creek (18.9%, 12 species, respectively). The transient (e.g. Carangidae, Fistularidae and Leiognathidae) and estuarine dependent fish (e.g. Lutjanidae, Gerreidae and Teraponidae) formed the main bio-ecological groups in the creek. The feeding groups in the creek were dominated by zoobenthivores (32.66%) while, herbivores had the lowest numerical abundance (<6%). The dominance of immature fishes in the samples indicated that Tudor Creek is an important nursery ground for many species. Fish assemblages in the creek formed a distinct seasonal structure that varied between stations suggesting the influence of habitat on fish distribution within the creek. The results of this study will contribute to scientific management of fisheries within the creek in the face of human pressure and climate change effects and will also add to the database on estuarine fishes from the WIO.