Browsing by Author "Pratap, Harish B."
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Item Accumulation of Copper and Zinc and their Effects on Growth and Maximum Quantum Yield of the Brown Macroalga Padina Gymnospora(2008) Mamboya, Florence; Pratap, Harish B.; Mtolera, M.; Björk, MatsAccumulation and the effects of copper and zinc on the macroalga Padina gymnospora were assessed in the laboratory after artificial exposure to copper and zinc (separately or in combination). Exposure concentrations of copper used were 0, 25, 50, 100, 500 and 1,000 µg l-1. Concentrations of zinc exposure were 0, 50, 100, 250, 1,000 and 5,000 µg l-1. The simultaneous (or combined) addition of copper and zinc (Cu+Zn) involved 25+50, 50+100, 100+250, and 500+1,000 µg l-1. Accumulation patterns were determined by measuring tissue contents of copper and zinc, while the tolerance was assessed by measuring growth rate and photosynthetic performance, as maximum quantum yield (Fv/Fm). Furthermore, the influence of major nutrients (phosphates and nitrates) on algal-metal-accumulation was estimated after additions of nitrate (1, 10 and 20 mg l-1) and phosphate (0.1, 1 and 2 mg l-1). The data obtained showed that the accumulation increased linearly with the increase in metal concentration in the growth media. However, the presence of additional nitrate and phosphate reduced both the metal accumulation and their toxic effects. Both algal growth rate and maximum quantum yields were negatively affected in proportion to the increase in metal concentrations and exposure time. At exposures to 50, 100 and 500 µg l-1 copper, inhibition in growth was greater than 50%, while an exposure to 1,000 µg l-1of zinc was needed to cause the same effect on growth and Fv/Fm. Growth rate was a more sensitive indicator of stress than maximum quantum yield in response to exposure to copper and zinc Accumulation of Copper and Zinc and their Effects on Growth and Maximum Quantum Yield of the Brown Macroalga Padina GymnosporaItem Accumulation of Copper and Zinc and their Effects on Growth and Maximum Quantum Yield of the Brown Macroalga Padina Gymnospora. Western Indian Ocean J. Mar. Sci. 6(1):17-28 (2007)(2008) Mamboya, Florence A.; Pratap, Harish B.; Mtolera, Matern; Björk, MatsAccumulation and the effects of copper and zinc on the macroalga Padina gymnospora were assessed in the laboratory after artificial exposure to copper and zinc (separately or in combination). Exposure concentrations of copper used were 0, 25, 50, 100, 500 and 1,000 µg l-1. Concentrations of zinc exposure were 0, 50, 100, 250, 1,000 and 5,000 µg l-1. The simultaneous (or combined) addition of copper and zinc (Cu+Zn) involved 25+50, 50+100, 100+250, and 500+1,000 µg l-1. Accumulation patterns were determined by measuring tissue contents of copper and zinc, while the tolerance was assessed by measuring growth rate and photosynthetic performance, as maximum quantum yield (Fv/Fm). Furthermore, the influence of major nutrients (phosphates and nitrates) on algal-metal-accumulation was estimated after additions of nitrate (1, 10 and 20 mg l -1) and phosphate (0.1, 1 and 2 mg l-1). The data obtained showed that the accumulation increased linearly with the increase in metal concentration in the growth media. However, the presence of additional nitrate and phosphate reduced both the metal accumulation and their toxic effects. Both algal growth rate and maximum quantum yields were negatively affected in proportion to the increase in metal concentrations and exposure time. At exposures to 50, 100 and 500 µg l-1 copper, inhibition in growth was greater than 50%, while an exposure to 1,000 µg l-1of zinc was needed to cause the same effect on growth and Fv/Fm. Growth rate was a more sensitive indicator of stress than maximum quantum yield in response to exposure to copper and zinc.Item Calcium Homeostasis in Low and High Calcium Water Acclimatized Oreochromis Mossambicus Exposed to Ambient and Dietary Cadmium(2007) Pratap, Harish B.; Bonga, Sjoerd W.The effects of cadmium administered via ambient water (10 µg/l) or food (10 µgCd/fish/day) on plasma calcium, corpuscles of Stannius and bony tissues of Oreochromis mossambicus acclimated to low calcium (0.2 mM) and high calcium (0.8 mM) water were studied for 2, 4, 14 and 35 days. In low calcium water acclimated fish, ambient cadmium induced significant hypocalcemia, while the structure and morphometry of type-1 and type-2 cells of corpuscles of Stannius were not affected on day 2 and 4. Subsequently on day 14 and 35, recovery of plasma calcium to normal levels was observed followed by a decrease in corpuscles of Stannius index (CSI), cell size, volume of granular endoplasmic reticulum (p<0.05) of type-1 cells in both, fish exposed to ambient or dietary cadmium. The type-2 cells were not affected. In high calcium water acclimated fish both, ambient and dietary cadmium caused a significant reduction of plasma calcium levels on day 2 and 4. In these fish, there was a significant transient increase in the size of corpuscles of Stannius on day 4, followed by recovery on day 14 and 35. Ultrastructural observations of corpuscles of Stannius revealed that cadmium did not cause any cellular damage on type-1 and type-2 cells during 35 days exposure. In low or high calcium water acclimatized tilapia exposed to ambient or dietary cadmium had no effect on the calcium and phosphate composition of the scales, operculum and vertebrae. Thus, it is unlikely that recovery of hypocalcemia was due to the dissolution of calcium from bony tissues. This study also revealed that cadmium does not mediate stimulation of the corpuscles of Stannius gland, and that high Ca2+ water had a protective effect against ambient and dietary cadmium.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 Cyanobacteria blooms—A possible cause of mass mortality of Lesser Flamingos in Lake Manyara and Lake Big Momela, Tanzania(Elsevier, 2006) Lugomela, Charles; Pratap, Harish B.; Mgaya, Yunus D.Limnological studies were conducted in three alkaline lakes (Lake Big Momela, Manyara and Embagai) with the aim of investigating the cause of mass mortality of the Lesser Flamingos in Lake Manyara and Lake Big Momela during July–August 2004. High concentrations, up to 150 million filaments per liter of the potentially toxic planktonic cyanobacterium Arthrospira fusiformis were found in surface scum of Lake Big Momela where Lesser Flamingos were dying at a rate of between 15 and 50 individuals per day during the study period. Gut content analyses indicated that A. fusiformis was the main food item in moribund flamingos. Mouse bioassay suggested that the crude microalgal extract dominated by A. fusiformis was toxic with all mice close to death becoming lethargic, with loss of balance, uncoordinated movements, intermittent tremors, dyspnoea with gasping followed by respiratory arrest. This observation gives circumstantial evidence that A. fusiformis at such high concentrations was toxic to the Lesser Flamingo in Lake Big Momela. # 2005 Elsevier B.V. All rights reserved.Item Effect of Ambient and Dietary Cadmium on Pavement Cells, Chloride Cells, and Na+/K+-Atpase Activity in the Gills of the Freshwater Teleost Oreochromis Mossambicus at Normal and High Calcium Levels in the Ambient Water(Elsevier, 1993) Pratap, Harish B.; Bonga, Sjoerd W.The effects of cadmium on the gills of the African freshwater cichlid Oreochromis mossambicus in water with normal and relatively high calcium concentrations were studied for periods up to 35 days. The exposure was either through the ambient water or via the diet. Changes in the ultrastructure of the gill epithelium upon exposure to cadmium in the ambient water indicated degeneration of pavement cells and chloride cells, and acceleration in the turnover of the chloride cells. Studies of the Na+/K+-ATPase activity of the gills indicated that a transient increase in the total number of chloride cells was not associated with an increase, but rather a decrease of the total ion-exchange capacity of the chloride cells. Macrophages, lymphocytes, rodlet cells and neutrophilic granulocytes infiltrated the filament epithelium. Recovery of the gills was observed after 35 days. Dietary cadmium caused similar, although delayed, effects. High water calcium concentration reduced the impact of water-borne cadmium, but had no ameliorating effect on dietary cadmium. The data indicate that the disturbance of ion regulation in fish caused by sublethal levels of dietary cadmium is the result of effects of the metals on the gills rather than on the kidney.Item The Effect of Copper on the Daily Growth Rate and Photosynthetic Efficiency of the Brown Macroalga Padina Boergesenii(1999) Mamboya, Florence A.; Pratap, Harish B.; Mtolera, Matern; Björk, MatsThe effect of copper (Cu) on the daily growth rate (DGR) and photosynthetic efficiency (PE) of the brown macroalga Padina boergesenii was studied under controlled laboratory conditions. The DGR was measured as an increase in fresh weight while the PE was measured as the ratio of variable to maximal chlorophyll fluorescence (Fv /Fm ). Padina boegesenii were exposed to 25, 50, 100 and 500mg Cu/l for 21 days. The DGR and PE of P. boergesenii decreased significantly with an increase in copper concentration in the growth media. This study shows that copper is acutely toxic to P. boergesenii at concentrations higher than 500mg Cu/l. Low concentration of copper is toxic to P. boergesenii after a prolonged exposure of 21 days. Similarly, exposure time has a significant negative effect on both DGR and PE.Item Effect of Waterborne and Dietary Cadmium on Plasma Ions of the Teleost Oreochromis Mossamicus in Relation to Water Calcium Levels(1989) Pratap, Harish B.; Fu, H.; Lock, R. A. C.; Bonga, Sjoerd W.The effects of cadmium administered via ambient water or food on plasma ions of the African freshwater cichlidOreochromis mossambicus were studied for 2, 4, 14, and 35 days, in low calcium (0.2 mM) and high calcium (0.8 mM) water. In low calcium water, an environmentally relevant concentration of 10 g/L water-borne cadmium induced a significant and dramatic hypocalcemia on days 2 and 4. Recovery of plasma calcium was observed on days 14 and 35. Hypermagnesemia was observed on day 2, but normal levels were already found on day 4. In high calcium water adapted fish, the extent of hypocalcemia and hypermagnesemia was less pronounced than in fish from low calcium water. Water-borne cadmium caused no significant changes in plasma phosphate, sodium, potassium, or osmolality. On days 2 and 4, dietary cadmium (averaging 10 g Cd/fish/day) caused hypermagnesemia and hypocalcemia in low calcium wateradapted fish. Recovery was observed on days 4 and 14, respectively. In fish from high calcium water, dietary cadmium caused a significant reduction in plasma calcium on day 4 only; plasma magnesium was unaffected. Hyperphosphatemia was apparent on day 14, irrespective of the water calcium concentration. No changes in plasma sodium, potassium, or osmolality were found.The results show that sublethal concentrations of cadmium, administered via the water as well as via the food, affect calcium and magnesium metabolism in tilapia. High water calcium ameliorates the effects of both water and dietary cadmium on plasma calcium and magnesium levels.Among the various heavy metal pollutants, cadmium is frequently present in natural water bodies as a result of discharges from industrial processes or other anthropogenic contamination. The harmful effects of cadmium on mammals and other terrestrial animals have been widely studied and reviewed (Flicket al. 1971; Vallee and Ulmer 1972; Webb 1979; Korte 1983; Foulkes 1986). Aquatic vertebrates such as fish, live in very intimate contact with the environment through their gills. This makes them very susceptible to aquatic pollutants.Since it is well established that freshwater fish take up most of the ions necessary for homeostasis from the water via the gills (Eddy 1982), cadmiuminduced plasma ionic disturbances are apparently caused by impaired uptake and diffusional losses of ions via these organs (Larssonet al. 1981; Giles 1984). Ionic disturbances have also been reported after exposure of fish to sublethal concentrations of heavy metals. For example, changes in the plasma ionic composition have been observed in fish exposed to copper and zinc (Lewis and Lewis 1971; Spry and Wood 1985), mercury (Locket al. 1981), and chromium (Van der Putteet al. 1983). With respect to cadmium, exposure of rainbow trout to sublethal levels induced hypocalcemia, with reduced plasma sodium, potassium, chloride and increased plasma magnesium (Giles 1984). In European flounder, cadmium-induced hypocalcemia and elevated levels of plasma phosphate, magnesium and potassium were observed (Larssonet al. 1981).In addition to water, food could also be a source of cadmium for fish, since it accumulates in aquatic organisms through trophic transfers (Anonymous 1971; Williams and Giesy 1978; Coombs 1979). Indeed, Bryan (1976) concluded that food as a source of Zn, Mn, Co, and Fe for molluscs, crustaceans and fish was more important than water. From various studies on both water-borne and food-containing metals, reviewed by Dallingeret al. (1987), there is evidence that uptake of heavy metals such as Cd, Cu, Co, Pb, Hg, and Zn from food is also the predominant pathway in freshwater fish. Koyama and Itazawa (1977) reported significant hypocalcemia and elevated plasma phosphate levels in cadmium-fed carps. Similarly, plaice and thornback ray both accumulated more cadmium from food than from seawater (Pentreath 1977). In general, cadmium concentrations in natural waters are extremely low and a more important route of cadmium uptake by fish may be represented via the gut. Experiments with dietary cadmium may therefore yield more representative information for field situations.In this investigation, we have compared the effects of a sublethal concentration of cadmium administered via the water or via the food in the African cichlid fishOreochromis mossambicus (tilapia). Plasma ions and osmolality were determined. Cadmium was administered at sublethal concentrations, in the order of magnitude that may occur in natural waters (10 g Cd/L). In many studies aimed at evaluating the effects of cadmium on fishes, high concentrations (>1 mg Cd/L) of cadmium have been used. Hence severe physiological, behavioral and detrimental effects have been reported. Such high concentrations are rarely found in nature, except in cases of spillage or heavily polluted waters. The Working Group on Cadmium Toxicity (EIFAC 1977) has suggested that chronic exposure to low cadmium concentrations is more relevant to understanding the mechanisms involved in the intoxication process in teleost fish.We further studied the influence of relatively low and high calcium concentration of the water on the toxic effects of cadmium. The effects of water hardness (mainly Ca2+ and Mg2+ ions) on heavy metal toxicity have been demonstrated in various species of teleosts (Prtet al. 1985). Increased toxicity of cadmium to fish in soft water as compared to hard water has been demonstrated in catfish and guppies (Kinkade and Erdman 1975), goldfish (McCartyet al. 1978), striped bass (Palawskiet al. 1985), brook trout (Carrollet al. 1979) and rainbow trout (Calamariet al. 1980; Pascoet al. 1986). Similar observations on teleosts exposed to zinc, copper and lead (Sinleyet al. 1974; Zitko and Carson 1976; Judy and Davies 1979; Laurn and McDonald 1986) indicate a protective role of calcium against the toxic effects of heavy metals. It was also investigated whether the protective effect of the water-calcium concentration is limited to water-borne cadmium only, or also applies to dietary cadm Effect of waterborne and dietary cadmium on plasma ions of the teleost Oreochromis mossamicus in relation to water calcium levels (PDF Download Available).Item Effects of Ambient and Dietary Cadmium on Haematological Parametres in Oreochromis Mossambicus Acclimatised to Low- And High-Calcium Water(Springer Link, 2008) Pratap, Harish B.The haematological response to ambient (10µg Cd l−1 ) or dietary (10µg Cd fish−1 day−1 ) cadmium for 2 and 14days was investigated in tilapia (Oreochromis mossambicus) acclimatised to low-calcium (0.2mM Ca2+) and high-calcium water (0.8mMCa2+). Significant reduction of erythrocytes (red blood cells), haemoglobin (Hb), packed cell volume (PCV), mean cell haemoglobin (MCH) and mean cell volume (MCV) occurred in fish exposed to ambient cadmium in lowcalcium water. The anaemic response of significantly reduced Hb, PCV, MCH and MCV was also evident in fish exposed to dietary cadmium in low-calcium water. Except for increased mean cell volume of erythrocytes, both ambient and dietary cadmium had no effect on haematological indices in fish from high-calcium water. This study indicates that high-calcium water has a protective effect on cadmium toxicity.Item Effects of Water-borne Cadmium on Plasma Cortisol and Glucose in the Cichlid Fish Oreochromis Mossambicus(1990) Pratap, Harish B.; Bonga, Sjoerd W.1.1. Freshwater cichlids Oreochromis mossambicus (tilapia) were exposed to 10 μg Cd/l in ambient water for 2,4, 14 and 35 days. Plasma cortisol and glucose levels were determined to evaluate if cadmium induced a typical stress response in these fish.2.2. Exposure to cadmium for 2, 4 and 14 days elicited a significant elevation of plasma cortisol levels.3.3. A significant hyperglycemia occurred on days 2 and 4 in cadmium-exposed fish.4.4. During long-term exposure to cadmium (35 days), the plasma cortisol and glucose levels returned to control values. This recovery after 35 days indicates the ability of tilapia to adapt to low cadmium concentrations in the ambient water.Item Heavy Metal Contamination in the Western Indian Ocean (a review)(2003) Mamboya, Florence A.; Pratap, Harish B.; Björk, MatsWestern Indian Ocean Coast has many potential marine ecosystems such as mangrove, seagrass meadows, macroalgae, and coral reefs. It is largely unspoiled environment however, tourism and population growth in coastal urban centres, industrialization, are presenting a risk of pollutants input to the marine environment of the Western Indian Ocean. Mining, shipping and agricultural activities also input contaminants into the marine environment via runoff, vessel operations and accidental spillage. Heavy metals are among the pollutants that are expected to increase in the marine environment of the Western Indian Ocean. The increase in heavy metal pollution can pose a serious health problem to marine organism and human through food chain. This paper reviews studies on heavy metal contamination in the Western Indian Ocean. It covers heavy metal studies in the sediments, biota, particulates and seawater collected in different sites. In comparison to other regions, only few studies have been conducted in the Western Indian Ocean and are localized in some certain areas. Most of these studies were conducted in Kenyan and Tanzanian coasts while few of them were conducted in Mauritius, Somalia and Reunion. No standard or common method has been reported for the analysis or monitoring of heavy metals in the Western Indian Ocean.Item Heavy Metal Levels in the Sediments of Four Dar Es Salaam Mangroves - Accumulation in, and Effect on the Morphology of the Periwinkle, Littoraria Scabra (Mollusca : Gastropoda)(Elsevier, 2001) De Wolf, Hans; Ulomi, S.A.; Backeljau, T.; Pratap, Harish B.; Blust, R.Heavy metals were determined in the soft tissue and shells of the littorinid, Littoraria scabra, and in the sediments of four mangrove areas along the Dar es Salaam coastline where L. scabra was collected. Several metals accumulate, preferentially in the animals' soft body parts, but do not seem to affect the shell morphology of this species. Sediment-metal levels, measured in the direct vicinity of Dar es Salaam have increased dramatically over the last decade. Nonetheless, these levels are still lower compared to metal-sediment levels reported in polluted European and American estuaries. Soft-tissue metal levels detected in L. scabra are, nevertheless, with the exception of Cr and Zn, comparable to metal levels reported in other gastropod species. D 2001 Elsevier Science Ltd. All rights reserved.Item Histopathology of gills and gut of the edible cockle Anadara Antiquata (Bivalvia: Arcidae) exposed to acute level of Ammonium sulfate(2009) Matojo, Nicodemus D.; Pratap, Harish B.Toxicity studies with ammonium sulfate were scanty. Based on standard procedures, we estimated the 96 h acute toxicity of this agrochemical on the edible cockle, Anadara antiquata Linnaeus (Bivalvia: Arcidae), in a static in vitro bioassay at mean pH 8, temperature 28±1° C, salinity 33% and DO 6 mg/L. The LC50 was estimated at 270 mg/L±0.3 and mortality was 33.08% (4.56 probits), both at 95% significance level. Although the exposure was not acutely toxic, some uncontrolled massive deformities evidenced in the victims over 336 h. These postexposure injuries promoted mortality to 61.6% (5.3 probits) in which all samples exposed to 200 mg/L and above died. Stress manifestations involved excessive shell gaping, foot protrusion, mucus secretion coupled by necrosis, hyperplasia, cilial shortening, lamellar shrinkage, abscess formation and eventual epithelial ruptures and proliferations in the gills and gut. Prior to death, the victims lost mobility and sensitivity and their shell gaps were abnormally expanded. However, around 38.4% of all specimens survived this acute exposure, and the overall injury ranged between acute and chronic levels hence was subchronic. These results are indicating that A. antiquata has great potential of biomonitoring the toxicity of ammonium sulfate. A necessity for handling this agrochemical conscientiously is also justified.Item The Impact of Different Sprayable Surfaces on the Effectiveness of Indoor Residual Spraying Using a Micro Encapsulated Formulation of Lambda-Cyhalothrin Against Anopheles Gambiae S.S(BioMed Central, 2015) Mutagahywa, Joshua; Ijumba, Jasper; Pratap, Harish B.; Molteni, Fabrizio; Mugarula, Frances E.; Magesa, Stephen M.; Ramsan, Mahdi M.; Kafuko, Jessica M.; Nyanza, Elias C.; Mwaipape, Osia; Rutta, Juma G.; Mwalimu, Charles D.; Ndong, Isaiah; Reithinger, Richard; Thawer, Narjis G.; Ngondi, Jeremiah M.Background: The type of sprayable surface impacts on residual efficacy of insecticide used in indoor residual spraying (IRS). However, there is limited data on common types of wall surfaces sprayed in Zanzibar and mainland Tanzania where IRS began in 2006 and 2007 respectively. The study investigated residual efficacy of micro-encapsulated lambda-cyhalothrin sprayed on common surfaces of human dwellings and domestic animal shelters in Zanzibar and mainland Tanzania. Methods: An experimental hut was constructed with different types of materials simulating common sprayable surfaces in Zanzibar and mainland Tanzania. Surfaces included cement plastered wall, mud-daub, white-wash, wood, palm-thatch, galvanized iron-sheets, burnt-bricks, limestone and oil-paint. The World Health Organization (WHO) procedure for IRS was used to spray lambda-cyhalothrin on surfaces at the dose of 20–25 mg/m2 . Residual efficacy of insecticide was monitored through cone bioassay using laboratory-reared mosquitoes; Kisumu strain (R–70) of Anopheles gambiae ss. Cone bioassay was done every fortnight for a period of 152 days. The WHO Pesticide Evaluation Scheme (WHOPES) threshold (80% mortality) was used as cut-off point for acceptable residual efficacy. Results: A total of 5,800 mosquitoes were subjected to contact cone bioassay to test residual efficacy of lambda-cyhalothrin. There was a statistically significant variation in residual efficacy between the different types of wall surfaces (r = 0.24; p < 0.001). Residual efficacy decreased with increasing pH of the substrate (r = −0.5; p < 0.001). Based on WHOPES standards, shorter residual efficacy (42-56 days) was found in wall substrates made of cement, limestone, mud-daub, oil paint and white wash. Burnt bricks retained the residual efficacy up to 134 days while galvanized iron sheets, palm thatch and wood retained the recommended residual efficacy beyond 152 days. Conclusion: The study revealed a wide variation in residual efficacy of micro encapsulated formulation of lambda-cyhalothrin across the different types of wall surfaces studied. In areas where malaria transmission is bimodal and wall surfaces with short residual efficacy comprise > 20% of sprayable structures, two rounds of IRS using lambda-cyhalothrin should be considered. Further studies are required to investigate the impact of sprayable surfaces on residual efficacy of other insecticides commonly used for IRS in Zanzibar and mainland Tanzania.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 Macroalgae as Biofilters of Dissolved Inorganic Nutrients in an Integrated Mariculture Tank System in Zanzibar(2001) Mwandya, Augustine W.; Mtolera, Matern S. P.; Pratap, Harish B.; Jiddawi, Narriman S.A laboratory experiment was conducted to determine the capacity of themacroalgae Eucheuma denticulatum, Gracilaria crassa and Ulva reticulatato remove dissolved inorganic nutrients from finfish effluents in seriallyarranged tank systems. The aim was to determine the capacity ofmacroalgae which could be used in an integrated maricultre pond systemat Makoba, Zanzibar. Seawater from the reservoir entered the finfish tanksfirst, then drained through plastic pipes into the shellfish units and finallyinto the macroalgae units before being discharged back into the sea. Thewater residence time in each tank was 4 days. The performance of each ofthe different units was assessed in terms of total ammonia-N, phosphate-P and nitrate-N produced by finfish, and then, the removal of these nutrientsby shellfish and macroalgae biofilters. The levels of dissolved inorganicnutrients were highest in the finfish units and lowest in the macroalgaeunits. Increase in stocking density of macroalgae from 1g/l to 2g/l wasrelated to their increase in daily growth rates, specific growth rates andinorganic nutrient uptake rates. However optimum stocking densities werenot reached. Of the three inorganic nutrients, ammonia-N and phosphate-P was taken up by the macroalgae much more than nitrate-N. Ammonia-N removal efficiency in the system reached a maximum of about 63% at2g/l of Ulva reticulata whereas, phosphate-P and nitrate-N maximumremoval capacity were 58 and 54% respectively. Among the three species ofmacroalgae, Ulva reticulata seems to be the most efficient biofilter. It isconcluded that locally available macroalgae are good bioregulators of waterquality, thus can be applied in small scale mariculture activities and canalso generate income.Item Mineral Composition and Cadmium Accumulation in Oreochromis mossambicus Exposed to Waterborne Cadmium(2004) Pratap, Harish B.; Bonga, Sjoerd W.Item 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.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