The importance of mangroves, mud and sand flats, and seagrass beds as feeding areas for juvenile fishes in Chwaka Bay, Zanzibar: gut content and stable isotope analyses

Abstract

The relative importance of bay habitats, consisting of mangrove creeks and channel, seagrass beds, and mud and sand flats, as feeding grounds for a number of fish species was studied in Chwaka Bay, Zanzibar, Tanzania, using gut content analysis and stable isotope analysis of carbon and nitrogen. Gut content analysis revealed that within fish species almost the same food items were consumed regardless of the different habitats in which they were caught. Crustaceans (mainly copepods, crabs and shrimps) were the preferred food for most zoobenthivores and omnivores, while fishes and algae were the preferred food for piscivores and herbivores, respectively. The mean d 13 C values of fishes and food items from the mangrove habitats were significantly depleted to those from the seagrass habitats by 6Á9 and 9Á7% for fishes and food items, respectively, and to those from the mud and sand flats by 3Á5 and 5Á8%, respectively. Fishes and food items from the mud and sand flats were significantly depleted as compared to those of the seagrass habitats by 3Á4 and 3Á9%, for fishes and food, respectively. Similar to other studies done in different geographical locations, the importance of mangrove and seagrass themselves as a primary source of carbon to higher trophic levels is limited. The different bay habitats were all used as feeding grounds by different fish species. Individuals of the species Gerres filamentosus, Gerres oyena, Lethrinus lentjan, Lutjanus fulviflamma, Pelates quadrilineatus and Siganus sutor appeared to show a connectivity with respect to feeding between different habitats by having d 13 C values which were in-between those of food items from two neighbouring habitats. This connectivity could be a result of either daily tidal migrations or recent ontogenetic migration.

The mangrove forests as nursery habitats for the ichthyofauna of Mida Creek (Kenya, East Africa)

“…The connectivity between mangrove forests and the adjacent ecosystems for the ichthyofauna has already been elucidated by several studies and evidence from the overlaps in carbon and nitrogen signatures of fish collected in these different environments (Nagelkerken et al, 2012;Igulu et al, 2013;Kimirei et al, 2013). These isotopic signatures suggest that juvenile and/or adult fish probably choose more than one habitat to feed, find shelter or both (Lugendo et al, 2006(Lugendo et al, , 2007. Their movements may be triggered by several factors: tides, food availability, variation in salinity and/or ontogeny (Cocheret de la Morinière et al, 2003;Lugendo et al, 2005Lugendo et al, , 2006Nakamura et al, 2008;Kimirei et al, 2013).…”

“…These isotopic signatures suggest that juvenile and/or adult fish probably choose more than one habitat to feed, find shelter or both (Lugendo et al, 2006(Lugendo et al, , 2007. Their movements may be triggered by several factors: tides, food availability, variation in salinity and/or ontogeny (Cocheret de la Morinière et al, 2003;Lugendo et al, 2005Lugendo et al, , 2006Nakamura et al, 2008;Kimirei et al, 2013). Mangroves may, therefore, be designated as potential nurseries for pelagic and demersal coral reef fish and crustaceans (Laegdsgaard & Johnson, 2001;Nagelkerken et al, 2002;Nagelkerken, 2009).…”

Orientation from open water to settlement habitats by coral reef fish: behavioral flexibility in the use of multiple reliable cues

“…This largely zoobenthivorous fish species typically occurs as juveniles in seagrass beds and mangroves, which provide shelter (Igulu et al 2011) and feeding areas (Lugendo et al 2006), whereas the adults are predominantly found on coral reefs (Kimirei et al 2011). Experimental fish were caught daily in a tidal pool at an average depth of 0.4 m (Fig.…”

Trophic relationships among fish assemblages on a mudflat within a Brazilian Marine protected area

“…Estuaries are recognised for encompassing a variety of habitats, including mangrove swamps, algal banks, and mudflats (TSE et al, 2008), with vegetated habitats exhibiting greater fish abundance and species richness than non-vegetated habitats (LUGENDO et al, 2006). This pattern is the result of the greater structural complexities and resources that develop on a vegetated substrate, providing greater protection from predators and increased food availability (WANG et al, 2009).…”