Browsing by Author "Kruitwagen, Guus"
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Item Changes in Morphology and Growth of the Mudskipper (Periophthalmus Argentilineatus) Associated with Coastal Pollution(Springer Link, 2006) Kruitwagen, Guus; Pratap, Harish B.; Hecht, Thomas; Bonga, Sjoerd W.In this paper a comparison is made between the growth and morphology of barred mudskippers (Periophthalmus argentilineatus) from six mangrove forests along the coast of Tanzania. The fish populations from unpolluted sites consisted of different size classes, whereas only small sized fish were present in the polluted Mtoni mangroves. Age estimation based on the examination of otoliths revealed that the mudskippers followed similar growth patterns in all sites with limited pollution. However, the age estimates from the polluted Mtoni site revealed an abnormal growth pattern. The occurrence of unilateral anophthalmia in the Mtoni mudskippers suggested that these fish were affected by pollutants during early development. The study showed that the presence of urban and industrial wastes from Dar es Salaam city, as indicated by isotopic enrichment, correlated with abnormal growth and developmental effects in mudskippers. We hypothesize that pollution might also affect fish species that use the mangroves as a temporary habitat.Item Influence of Morphology and Amphibious Life-Style on the Feeding Ecology of the Mudskipper Periophthalmus Argentilineatus(2007) Kruitwagen, Guus; Nagelkerken, Ivan; Lugendo, Blandina; Pratap, Harish B.; Brown, Sjoerd W.The potential feeding advantages that are offered to the barred mudskipper Periophthalmus argentilineatus by its amphibious life-style were investigated. To this end the feeding ecology of these fish, the position they occupy in the mangrove food web and the importance of different morphological factors for their diet were studied. Analysis of gut contents showed that the major component of the barred mudskipper diet changes during growth from small crustaceans (e.g. copepods and amphipods) to polychaetes to mangrove crabs. This dietary shift was found to be facilitated through enlargement of the mouth, as well as elongation of the gut. The use of stable isotope analysis revealed that barred mudskippers had a similar trophic position as other zoobenthivore fish species, but that their diet did not appear to be affected by competition for food with other zoobenthivores. The amphibious habits of the barred mudskipper provide specific advantages to its feeding ecology, such as access to an abundant food source of mangrove crabs, which are mostly inaccessible for other fish species. # 2007 The Authors Journal compilation # 2007 The Fisheries Society of the British IslesItem Relative Importance of Mangroves as Feeding Habitat for Juvenile Fish: A Comparative Study on Mangrove Habitats with Different Settings(2007-01) Lugendo, Blandina R.; Nagelkerken, Ivan; Kruitwagen, Guus; Van der Velde, Gerard; Mgaya, Yunus D.The importance of mangroves as feeding grounds for fish and other macrozoob-enthos in the Indian Ocean and elsewhere has been a subject of debate. This could partly be due to the fact that studies describing this role have been conducted in mangrove systems that differed in their settings. By using stable isotope analysis of carbon and nitrogen, we investigated two different settings of mangroves along the Tanzanian coast, to establish if mangrove setting influences the extent to which this habitat is utilized as a potential feeding ground by fish. The two mangrove settings were: mangrove-lined creeks which retain water during low tides and fringing mangroves that drain completely during low tides. The δ13C signatures of most fishes from the mangrove-lined creeks were similar to those of food items from the mangrove habitat, which suggests that these fishes feed from the mangrove habitats. In contrast, the overlap in δ13C of some food items from the fringing mangroves with those from adjacent habitats, and the more enriched δ13C signatures of fishes from the fringing mangroves with respect to most typical food items from the mangrove habitat could be an indication that these fishes feed from both habitats but to a lower extent from the fringing mangroves. The results suggest that fishes feed more from the mangrove-lined creeks as compared to fringing mangroves which is probably related to differences in the degree of mangrove inundation. The more or less continuous access provided more time for fishes to stay and feed in the mangrove-lined creeks compared to fishes from the fringing mangroves, which have access to these mangroves only during high tide and have to migrate to adjacent habitats with the ebbing tide.Item Relative Importance of Mangroves as Feeding Habitats for Fishes: A Comparison between Mangrove Habitats with Different Settings(2007) Lugendo, Blandina R.; Nagelkerken, Ivan; Kruitwagen, Guus; Van der Velde, GerardThe importance of mangroves as feeding grounds for fish and other macrozoob-enthos in the Indian Ocean and elsewhere has been a subject of debate. This could partly be due to the fact that studies describing this role have been conducted in mangrove systems that differed in their settings. By using stable isotope analysis of carbon and nitrogen, we investigated two different settings of mangroves along the Tanzanian coast, to establish if mangrove setting influences the extent to which this habitat is utilized as a potential feeding ground by fish. The two mangrove settings were: mangrove-lined creeks which retain water during low tides and fringing mangroves that drain completely during low tides. The δ13C signatures of most fishes from the mangrove-lined creeks were similar to those of food items from the mangrove habitat, which suggests that these fishes feed from the mangrove habitats. In contrast, the overlap in δ13C of some food items from the fringing mangroves with those from adjacent habitats, and the more enriched δ13C signatures of fishes from the fringing mangroves with respect to most typical food items from the mangrove habitat could be an indication that these fishes feed from both habitats but to a lower extent from the fringing mangroves. The results suggest that fishes feed more from the mangrove-lined creeks as compared to fringing mangroves which is probably related to differences in the degree of mangrove inundation. The more or less continuous access provided more time for fishes to stay and feed in the mangrove-lined creeks compared to fishes from the fringing mangroves, which have access to these mangroves only during high tide and have to migrate to adjacent habitats with the ebbing tide.Item Status of Pollution in Mangrove Ecosystems along the Coast of Tanzania(2008) Kruitwagen, Guus; Pratap, Harish B.; Covaci, Adrian; Bonga, Sjoerd W.Worldwide, mangrove forests are under threat of the accumulation of pollutants, which may be imported into mangrove ecosystems through the waters from rivers and streams. The distribution, behaviour, and accumulation of these imported chemicals in the ecosystem are largely defined by the hydrology of the mangroves, the geochemical properties of sediments, and the class of pollutants (e.g. heavy metals, organotins, organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs)). The properties of the mangrove sediments provide good binding opportunities for a number of these pollutants: hydrophobic organic pollutants adsorb to the extensive surfaces that are provided by the fine particulate sediments of estuaries and mangroves. Metals are trapped in mangrove sediments through the formation of complexes with sulphides (Lacerda et al., 1991), particulate organic carbon, or iron oxyhydroxides (Chapman et al., 1998). As a consequence, anthropogenic pollutants are filtered from the water layer and accumulate in the sediments of estuaries and mangroves (Bayen et al., 2005; Bhattacharya et al., 2003; Tam and Wong, 1995; Tam and Yao, 2002). Depending on the speciation of chemicals, the pollutants can accumulate in the tissues of biota