Research Repository :: Browsing by Author "Ndaro, Simon G. M."

Browsing by Author "Ndaro, Simon G. M."

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Community Structure and Microhabitat Preferences of Harpacticoid Copepods in a Tropical Reef Lagoon (Zanzibar Island, Tanzania)
(2008) Gheerardyn, Hendrik; De Troch, Marleen; Ndaro, Simon G. M.; Raes, Maarten; Vincx, Magda; Vanreusel, Ann
Three microhabitat types (dead coral fragments, coral gravel and coral sand) were distinguished and sampled at two locations (Matemwe and Makunduchi) in a tropical lagoon (Zanzibar Island, Tanzania), and the community structure, habitat preferences and biodiversity of the associated harpacticoid copepod fauna was investigated. The harpacticoid fauna is affected by sediment granulometry and by the structural differences between coral and both gravel and sediment. The coral fragments contained a specific assemblage composed of typical ‘phytal’ taxa (Tisbe, Paradactylopodia and Dactylopusia) along with other eurytopic and sediment-dwelling forms (Ameira, Ectinosoma and Amphiascus), which may be attracted by the sediment retained between the coral branches. The assemblages of coral gravel and upper sediment layer did not differ signifi- cantly from each other and had mostly the same dominant genera. The sediment from Matemwe was dominated by the interstitial Paramesochridae and the sediment from Makunduchi by Tetragonicipitidae. The coral fragments from Makunduchi sustained a more diverse assemblage than gravel and the different sediment layers. It was assumed that coral form and complexity, with implications for habitable space, nutritional resources and level of predation, are important in structuring diversity of the associated assemblage.
Ecological Aspects of Soft Bottom Meiofauna in Eastern Africa
(1998) Ndaro, Simon G. M.
Effects of Intensive Seaweed Farming on the Meiobenthos in a Tropical Lagoon
(Elsevier, 1995) Olafsson, Emil; Johnstone, Ron W.; Ndaro, Simon G. M.
Open water aquaculture of the seaweed Eucheuma spinosum, imported to Zanzibar from the Philippines in 1989, is presently a large scale operation on the island, with algal farms covering around a 1000 ha of the intertidal area. To assess the effects of the farming on benthic communities both field and laboratory studies were conducted. Two field studies conducted at different times showed that all major meiofaunal taxa were found in significantly lower numbers within the farm area compared with control areas. Multidimensional scaling ordination of nematode species, genera and family abundance data separated samples from farmed and control areas. There was a significant difference in the nematode assemblage structure among areas in pairwise comparisons using ANOSIM. The trophic structure of the nematode assemblage was characterised by a high number of epistrate feeders in all areas ranging from 73 to 96% of total numbers in the samples. To test the hypothesis that toxic substances excreted by the seaweed were responsible for lower abundance inside the farm area, a laboratory experiment was conducted. Eucheuma plants were added to several microcosms and allowed to grow there for 40 days. The results indicated no effects of the seaweed on the density of the major infauna taxa as no significant difference was found among the treatments. It is concluded that other factors such as increased predation by benthic feeding fish and the mechanical disturbance of the sediments may better explain the observed differences in infauna abundance inside and outside the algal culture farms.
Feeding Ecology of the Indo-Pacific Bottlenose Dolphin (Tursiops Aduncus) Incidentally Caught in the Gillnet Fisheries Off Zanzibar, Tanzania
(Elsevier, 2005) Amir, Omar A.; Berggren, Per; Ndaro, Simon G. M.; Jiddawi, Narriman S.
The stomach contents of 26 Indo-Pacific bottlenose dolphins (Tursiops aduncus) incidentally caught in gillnet fisheries around Unguja Island (Zanzibar) between February 2000 and August 2002 were examined. The relative importance of each prey species was assessed through indices of relative importance. In total, 1403 prey items comprising 50 species of bony fish and three species of squid were identified from food remains. Five species of fish, Uroconger lepturus, Synaphobranchus kaupii, Apogon apogonides, Lethrinus crocineus, Lutjanus fulvus, and three species of squid, Sepioteuthis lessoniana, Sepia latimanus and Loligo duvauceli, were the most important prey species. Based on an index that included frequency of occurrence, percentage by number and by weight, Uroconger lepturus proved to be the most important prey species of mature dolphins whereas Apogon apogonides was the preferred prey of immature dolphins. These results indicate that Indo-Pacific bottlenose dolphins off the coast of Zanzibar forage on a relatively large number of prey species, but that only a few small- and medium-sized neritic fish and cephalopods contribute substantially to the diet. Further, the ecology and behavior of the preferred fish prey species indicate that the dolphins forage over reef or soft bottom substrata and near the shore.
The Fishes and Fisheries of two Lakes, Sagara and Nyamagoma in the Malagarasi Wetland Ecosystem, Tanzania
(Dar es Salaam University Press, 2004) Ndaro, Simon G. M.; Chitamweba, D.
Harpacticoid copepod colonization of coral fragments in a tropical reef lagoon (Zanzibar, Tanzania)
(2012) Callens, Martijn; Gheerardyn, Hendrik; Ndaro, Simon G. M.; De Troch, Marleen; Vanreusel, Ann
Colonization experiments were conducted in a tropical lagoon (Zanzibar Island, off the coast of Tanzania) to investigate thetemporal dynamics and mode of colonization of the harpacticoid copepods community on dead coral fragments. There wasfast colonization of the coral fragments attaining a substantial diversity after only two days. The ability to colonize dead coralfragments is thought to be related to the morphology and life style of different harpacticoid species. Phytal taxa (e.g. Tisbidae)were fast colonizers, reaching high abundances during the initial colonization phase. Sediment-associated and eurytopic taxa(e.g. Ameiridae, Miraciidae and Ectinosomatidae) showed lower colonization rates and became the dominant group duringthe later colonization phase. Most species are able to colonize the coral fragments through the water column. However,colonization along the substrate surface is also considered to be an important colonization mode, especially forsediment-associated taxa, which showed lower colonization rates when migration through the sediment was hindered.
The Impact of the Mangrove Crabs Uca Annulipes and Dotilla Fenestrata on Meiobenthos
(1997) Olafsson, Emil; Ndaro, Simon G. M.
To assess the effects of 2 mangrove crabs on benthic meiofauna a laboratory experiment was performed in Zanzibar, eastern Africa. The 2 ocypodidae crab species Uca annulipes and Dotilla fenestrata are commonly found at mid to high water levels among Avicennia marina trees. Both genera are borrowers in soft sediments and feed upon drained surface deposits by forming pseudofaecal pellets. They are efficient bioturbers of the uppermost few mm of the sediment and some Uca species may prey directly on meiobenthos. The 2 species were added to microcosms containing sediment with natural meiofauna populations. After 10 d of enclosure, numbers of harpacticoid copepods in the top 1 cm layer were significantly lower in microcosms containing U. annulipes than in control microcosms. Two nematode assemblages were found in the microcosms, one in the surface layer and one deeper down. The crabs did not alter the structure of these assemblages. It appears that the nematodes are quite resilient to the reworking of the sediment surface. We conclude that the ocypodid crabs do not regulate resident nematode assemblages, but may inhibit settlement of colonisers that have not adapted to the intense surface disturbance created by these crabs. Such biological control is most likely to be in those areas where tidal water contains relatively high numbers of migrating meiofauna.
The Malagarasi Wetland Ecosystem: An Integratesd study
(Dar es Salaam University Press, 2004) Nkotagu, Hudson H.; Ndaro, Simon G. M.
Meiobenthos of Hypersaline Tropical Mangrove Sediment in Relation to Spring Tide Inundation
(2000) Olafsson, Emil; Carlström, Susanna; Ndaro, Simon G. M.
Tropical intertidal sediments often contain porewater of relatively high salinity, especially in areas exposed to longer periods without seawater inundation and high evaporation. Such an area exists on the west coast of Zanzibar: a high intertidal mangrove plateau, flooded only during spring high tides, with sediment porewater salinities commonly exceeding 100 ppt. A field survey was conducted in this area to examine variations in population density of major meiofaunal taxa and the assemblage structure of free-living marine nematodes during spring-neap tidal cycles. Samples were taken on seven occasions for two months, starting from the end of the rainy season. Porewater salinity remained high throughout the sampling period, ranging from 89 to 160 ppt. Neither spring tide inundation nor heavy rains lowered the salinity markedly. The meiofauna consisted only of four taxa, present on all sampling occasions: nematodes, harpacticoid copepods, plathyhelminthes and chironomids. Densities in surface sediments (0–5 cm) were low compared to other mangrove areas, ranging from 271 to 656 animals 10 cm−2 with nematodes dominant on all sampling occasions (58–87%). Density fluctuations could not be explained by the effects of spring tide inundation, but the meiofauna showed significant correlations with grain size and organic material. Despite the wide range of salinity, only the numbers of chironomids were negatively correlated with increased salinity. Nematode species diversity was low in all samples, although altogether 28 species were recorded in the samples. Four species occurred in more than 50% of the samples (Microlaimus sp. (100%), Metalinhomoeus sp. (76%), Daptonema sp.l (56%), Chromadorina sp. (56%)) while 12 species were found only in one or two samples. Multidimensional scaling ordination (MDS) of the nematode species abundance data indicated little effects of spring tide inundation on the assemblage structure, but rather a successive change from wet to dry season with a reduction in species diversity and increased numbers of the dominant nematode species Microlaimus sp.
Nearshore Fish Resources and Fisheries around Kigoma, Eastern Coast of Lake Tanganyika
(1992) Ndaro, Simon G. M.
The fish habitats along an inshore water stretch along the eastern/central coast of Lake Tanganyika are discussed and a quantitative analysis of the species composition, distribution and abundance of the littoral fishes within the area of study is presented. Seventy-one species of fish belonging to 48 genera and to 15 fish families were collected and identified during the study. The majority of species belonged to the Cichlidae family. Intensive beach seining for clupeids is suggested as one of the causes of low fish biomass in the area surveyed. The areas south of Kigoma appeared to contain more fish, with average catch rates of 11.7 kg/haul than those north of Kigoma where average catch rates of 7.6 kg/haul were recorded. Some suggestions for improved management of these resources are given.
A Note on the Selection of Meiobenthic Prey by Gerres Oyena in a Tropical Lagoon in Eastern Africa
(1995) Ndaro, Simon G. M.; Olafsson, Emil
Reproductive Biology of Gerres oyena (Pisces: Gerreidae) Along the Bagamoyo Coast, Tanzania
(2008) Lamtane, H. A.; Pratap, Harish B.; Ndaro, Simon G. M.
The reproductive biology of Gerres oyena (Forskal, 1775) (Gerreidae) along the Bagamoyo coast was studied from January to December 1999 using samples from monthly commercial catches. Size at first maturity was 12.8 and 13.9 cm TL for males and females respectively. The sex ratio was found to be 0.98:1 (m:f) and was not significantly different from 1:1. G. oyena spawns throughout the year with two peaks: one in March and the other between October and December, which coincide with the northeast monsoon. Ova-diameter frequency distributions indicated that G. oyena is a multiple spawner. They may spawn in three successive batches within the same prolonged spawning season. On an average, the numbers of mature ova produced were 148,138 per fish. For management purposes, a focus should be on the size of maturation relative to length-body depth or capture size. This would reduce harvesting of prereproductive individuals.
Small-Scale Variation in Major Meiofaunal Taxa and Sediment Chemistry in Tropical Sediments
(1995) Ndaro, Simon G. M.; Sjoling, S.; Olafsson, Emil
Variations in sediment biochemistry and abundance of meiofauna were investigated in three tropical habitats: mangrove forest, intertidal lagoon, and subtidal reef area in eastern Africa. Both the biochemical components of the pore water and the meiofauna varied substantially over small distances in all three habitats. In the mangrove area, the color of the pore water was found to be positively correlated with the major meiofaunal taxa, especially the nematodes. In the coastal lagoon, polychaetes showed negative correlation with particulate organic matter while other groups showed no correlation with any of the chemical components analyzed. In the subtidal reef area no chemical components were found to correlate with the meiofauna. When data from the three habitats are taken together two clear associations emerge. First, grain size shows a highly significant relationship with both total fauna and nematode numbers. Second, there is clear association between the amount of particulate organic carbon and particulate organic nitrogen in the pore water.
Soft-Bottom Fauna with Emphasis on Nematode Assemblage Structure in a Tropical Lagoon in Zanzibar, Eastern Africa: I. Spatial Variability
(Kluwer Academic, 1999) Ndaro, Simon G. M.; Olafsson, Emil
Twenty stations were sampled in a reef-protected lagoon on the east coast of Zanzibar from a variety of habitats: seagrass beds, fine sand, bare medium sand and coarse sand. Total meiofauna densities ranged from 219 to 3422 ind./10 cm2. Stations in the upper lagoon (< 400 m from shore) had relatively higher densities of meiofauna than those of other habitats, apart from seagrass beds. Of the 12 major taxa recorded, Nematoda normally was the most abundant taxon, contributing between 13% and 97% of total fauna, followed by Harpacticoida, Polychaeta and Turbellaria. Nematodes were dominated by epistrate feeders in all habitat-types and altogether 100 nematode genera were found within the lagoon. Clear nematode assemblage structures were depicted by non-metric multidimensional scaling ordination in seagrass bed, fine sand and coarse sand habitats. On a larger scale, sediment characteristics seem to determine the gross assemblage structure. Samples from the same station were more similar in terms of generic occurrence and population structure than samples from different stations in similar habitats. This indicates that there are localised factors influencing the nematode populations on a small scale in each habitat-type.
Some Aspects of Ecology and the Distribution of Infauna in Lakes Sagara and Nyamagoma in the Malagarasi Wetland Ecosystem
(2004) Ndaro, Simon G. M.
Some Aspects of Sea Cucumber, Holothuria Scabra (Jaeger, 1935), Along the Coast of Dar Es Salaam
(2002) Kithakeni, Twalibu M.; Ndaro, Simon G. M.
Some aspects of the biology of the sea cucumber Holothuria scabra Jaeger, 1935 were studied along the coast of Dar es Salaam. Samples of H. scabra were collected from Kunduchi and Buyuni between January and December 1999. The abundance of Holothuria scabra was higher in Buyuni (3951) than in Kunduchi (1176). However, the level of exploitation per year from far reefs was higher in Kunduchi than in Buyuni. Sea cucumber harvesting by villagers is done monthly on intertidal areas and from reef flats near to the villages. Higher catches from Buyuni were recorded during August and November (perhaps due to light winds such that trips could be made to far-off reefs), while the catch from Kunduchi was relatively low throughout a year. The length-frequency distribution of H. scabra was found to be unimodal, with most individuals ranging between 8.5 cm and 26.5 cm. The species showed continuous breeding with peaks between May and September and December. The average size at first maturity in H. scabra was 16.8 cm.
Some Aspects of Sea Cucumber, Holothuria Scabra (Jaeger, 1935), Along the Coast of Dar Es Salaam
(2002) Kithakeni, Twalibu M.; Ndaro, Simon G. M.
Some aspects of the biology of the sea cucumber Holothuria scabra Jaeger, 1935 were studied along the coast of Dar es Salaam. Samples of H. scabra were collected from Kunduchi and Buyuni between January and December 1999. The abundance of Holothuria scabra was higher in Buyuni (3951) than in Kunduchi (1176). However, the level of exploitation per year from far reefs was higher in Kunduchi than in Buyuni. Sea cucumber harvesting by villagers is done monthly on intertidal areas and from reef flats near to the villages. Higher catches from Buyuni were recorded during August and November (perhaps due to light winds such that trips could be made to far-off reefs), while the catch from Kunduchi was relatively low throughout a year. The length-frequency distribution of H. scabra was found to be unimodal, with most individuals ranging between 8.5 cm and 26.5 cm. The species showed continuous breeding with peaks between May and September and December. The average size at first maturity in H. scabra was 16.8 cm.
The Structuring Role of Microhabitat Type in Coral Degradation Zones: A Case Study with Marine Nematodes from Kenya and Zanzibar
(Springer Link, 2007) Raes, Maarten; De Troch, Marleen; Ndaro, Simon G. M.; Muthumbi, Agnes; Guilini, Katja; Vanreusel, Ann
Nematode genus assemblages were identified from four locations in coral degradation zones (CDZs) along the African east coast: Watamu and Tiwi Beach (Kenya) and Matemwe and Makunduchi (Zanzibar). Three microhabitat types were distinguished: coralline sediment, coral gravel and coral fragments. Nematode community composition was comparable to that of other studies dealing with the same habitat. The presence of a common genus pool in CDZs was reflected in the considerable similarities between samples. The addition of coral fragments as a habitat for nematodes resulted in an increased importance of taxa typical for coarse sediments and large substrata. Local and regional turnover were of the same order of magnitude. The structuring effect of microhabitat type clearly overrode the effect on a local and regional scale. Differences in sediment characteristics were more important in structuring the nematode assemblages than differences between the coralline sediment and coral fragments. No effect related to the three-dimensional structure of coral fragments was found. Differences between nematode assemblages in the coralline sediment and on coral fragments were attributed to the exposed nature of the latter habitat, its large surface area and its microbial or algal cover. Differences in available food sources were reflected in nematode trophic composition.
Study of the Inshore Cichlid Fish Potential of Lake Tanganyika around Kigoma, Tanzania
(1990) Ndaro, Simon G. M.

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