Browsing by Author "Lugendo, Blandina R."
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Item Different Fish Composition in Seagrass Beds Adjacent to Extensive Mangrove Areas as Opposed to Coral Reefs(2007) Dorenbosch, Martijn; Grol, Monique G. G.; Nagelkerken, Ivan; Lugendo, Blandina R.; Van der Velde, GerardLittle is known about fish assemblages on seagrass beds located adjacent to different habitats. Visual census surveys were used to study the fish composition of two types of seagrass habitats in Zanzibar (Tanzania): seagrass beds adjacent to extensive mangrove areas in an embayment (bay seagrasses) and seagrass beds situated on the continental shelf adjacent to coral reefs (reef seagrasses). At species level, 39 fish species were common in the seagrass habitats, of which nine showed significantly higher densities in bay seagrasses, and four species were exclusively observed in bay seagrasses. Seine net data supported these data a the connectivity with mangroves.Item Fish Community Composition of a Tropical Nonestuarine Embayment in Zanzibar, Tanzania(Wiley, 2007) Lugendo, Blandina R.; Nagelkerken, Ivan; Jiddawi, Narriman S.; Mgaya, Yunus D.; Van der Velde, GerardBy using a seine net, fish samples were taken from the nonestuarine Chwaka Bay (Zanzibar, Tanzania) from the mangroves, mud/sand flats and seagrass beds. Sampling was done twice per month between November 2001 and October 2002. In total, 150 fish species belonging to 55 families were identified. Diversity (H′) ranged from 1.9 in mud/sand flats to 3.4 within the Chwaka seagrass beds. Mean density of fishes was significantly higher in the mangrove creeks than in any other habitat (mean = 238.7 ind./1000 m2). Highest, but non-significantly different mean biomasses were recorded in the mangrove creeks (1.7 kg/1000 m2) and in the Marumbi seagrass beds (1.6 kg/1000 m2). The mangrove channel had the lowest biomass (0.6 kg/1000 m2). A high overlap in species composition (as high as 93.4% similarity) was found for adjoining habitats (i.e. mangrove creeks and mangrove channel), while habitats that were far apart showed low overlap (6.6% similarity for the Marumbi seagrass beds and mangrove creeks). On average, 58.4 and 63.2% in terms of abundance and biomass, respectively, of the fish assemblage of Chwaka Bay were of commercial fishery importance. Thus, Chwaka Bay appears to be an important juvenile habitat for various commercially important fish species.Item Habitat Utilization by Juvenile of Commercially Important Fish Species in a Marine Embayment in Zanzibar, Tanzania(2005) Lugendo, Blandina R.; Pronker, Anna E.; Cornelissen, Ilse; De Groene, Arjan; Nagelkerken, Ivan; Dorenbosch, Martijn; Van der Velde, Gerard; Mgaya, Yunus D.Habitat utilisation by juveniles of 13 commercially important fish species was studied in five habitats located in Chwaka Bay, Zanzibar: mangrove creeks, mangrove channel, sand/mud flats, a seagrass area close to mangroves, and a seagrass area far from mangroves. Fish samples were collected from each habitat using a seine net, and fish abundance and size were measured to determine habitat utilisation. The seagrass beds near to mangroves showed the most diverse fish assemblage of all habitats, possibly because it functions as a corridor between the mangroves and deeper parts of the embayment. Juveniles of Cheilio inermis, Hipposcarus harid, Leptoscarus vaigiensis, and Scolopsis ghanam inhabited seagrass beds only. Juveniles of Gerres filamentosus and Monodactylus argenteus were mainly found in the mangrove habitats. Lethrinus variegatus, Pelates quadrilineatus and Siganus sutor were found in more than two habitats, with highest abundances in seagrass beds. Juveniles of Gerres oyena, Lethrinus lentjan, Lutjanus fulviflamma and Sphyraena barracuda were the most generalist species and were found in all studied embayment habitats. Visual census surveys supported the seine net data showing that most fishes in the embayment habitats were juveniles or sub-adults. In terms of habitat utilisation by different size classes, five of the 13 species (Lethrinus lentjan, L. variegatus, P. quadrilineatus, Siganus sutor and Sphyraena barracuda) were found as small-sized individuals in shallow and turbid mangrove areas, whereas large-sized individuals were observed in deeper and less turbid seagrass beds. A possible explanation for this pattern could be an ontogenetic shift in habitat utilisation, although this could not be proven. The patterns observed in the present study show a high similarity to those observed in marine embayments in the Caribbean, indicating that similar mechanisms are at work which make these systems attractive juvenile habitats.Item 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(Wiley, 2006) Lugendo, Blandina R.; Nagelkerken, Ivan; Van der Velde, Gerard; Mgaya, Yunus D.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 d13C values of fishes and food items from the mangrove habitats were significantly depleted to those from the seagrass habitats by 6 9 and 9 7% for fishes and food items, respectively, and to those from the mud and sand flats by 3 5 and 5 8%, respectively. Fishes and food items from the mud and sand flats were significantly depleted as compared to those of the seagrass habitats by 3 4 and 3 9%, 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 d13C 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. # 2006 The Authors Journal compilation # 2006 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 The Seagrass and Associated Macroalgae at Selected Beaches along Dar Es Salaam Coast(2001) Lugendo, Blandina R.; Mgaya, Yunus D.; Semesi, A. K.Intertidal seagrasses and macroalgae were studied at a sewage-polluted beach (Ocean Road) and a control site at Kunduchi beach, with a view to assessing the effect of sewage discharge on macrophyte species composition, abundance and above-ground biomass. A total of six species of seagrasses were recorded at Ocean Road of which two, Thalassia hemprichii and Cymodocea rotundata were the most abundant. Eight species of seagrasses were recorded at Kunduchi. Two species, Syringodium isoetifolium and Thalassodendron ciliatum were dominant in areas with strong oceanic influence. Halodule wrightii and Halophila ovalis were widely distributed in the two study areas. The mean biomass of seagrasses between Ocean Road and Kunduchi beaches was not significantly different (z = 4.053; p = 0.001; d.f. = 54). A total of 25 and 24 macroalgae species were recorded at Ocean Road and Kunduchi beaches, respectively. The total biomass of macroalgae was higher at Ocean Road than at Kunduchi (t = 4.838; p>0.001). While the biomass of brown macroalgae was higher at Kunduchi (t = 2.115; p = 0.039), that of red algae was similar at both sites (t = 1.986; p = 0.052). Of the 11 epiphytic species of macroalgae recorded on T. ciliatum at Kunduchi area, 73% were red algae, 18% green algae and 9% brown algae. The dominant species on this beach was the brown alga Cystoseira myrica. It was concluded that elevated levels of ammonium at Ocean Road is a likely cause of the observed higher biomass of green macroalgae at this site.Item Small Estuarine and Non-Estuarine Mangrove Ecosystems of Tanzania: Overlooked Coastal Habitats?(Springer Link, 2016) Kimirei, Ismael; Igulu, Mathias M.; Semba, Masumbuko; Lugendo, Blandina R.Small estuaries and non-estuarine habitats harboring mangroves are very important ecosystems which provide important ecosystem goods and services; such as provision of ecological niches for juvenile fishes and invertebrates, enhances fisheries, and in biodiversity conservation. Similar to large estuaries, they are highly perturbed which threatens their existence. This chapter uses beach seine, underwater visual census, and stable isotope data to discuss the importance of and threats to small estuaries and non-estuarine mangroves found in Dar es Salaam, Bagamoyo and Zanzibar, Tanzania. For example, mangroves of Kunduchi (Dar es Salaam) and Mbegani (Bagamoyo) which harbour predominantly higher densities of juveniles (≤10 cm) of two economically important species—Lutjanus fulviflamma and Lethrinus harak—than adjacent coral reefs. Evidence suggests further that the Kunduchi mangroves replenish fish populations on adjacent coral reefs; where over 90% and 29% of adult L. fulviflamma and L. harak individuals, respectively, have been identified to have lived in the mangroves as juveniles. In terms of habitat utilization by different size classes of fish, five of the 13 species (Lethrinus lentjan, L. variegatus, Pelates quadrilineatus, Siganus sutor and Sphyraena barracuda) found in Chwaka Bay (Zanzibar) were found as small-sized individuals in shallow and turbid mangrove areas with large juveniles and sub-adults in adjacent seagrass beds. The non-estuarine mangroves of Kunduchi and those of Mtoni estuary (Dar es Salaam) are subjected to pollution from urban activities. For example, stable isotope data of fishes indicate elevated levels of nitrogen in these mangroves with highest levels (δ15N = 15.2 ± 0.2) recorded in Mtoni estuary. In view of their importance and threats they face, these ecosystems require attention similar to large estuaries. If the current degradation rate of these ‘overlooked’ but equally important ecosystems continues, they may be declared ‘functionally disappeared’ in a few decades.Item Utilisation by Fishes of Shallow-Water Habitats Including Mangroves and Seagrass Beds along the Tanzanian Coast(2007) Lugendo, Blandina R.Proefschrift Radboud Universiteit Nijmegen. Met lit.opg. - Samenvatting in het Nederlands.