390 resultados para Rivers


Relevância:

10.00% 10.00%

Publicador:

Resumo:

About 18% of Uganda’s surface area is covered with water from which about 300,000 metric tonnes of fish are produced. Fish are currently the second most important export commodity generating approximately US$100 million annually. Fish provides 50% of protein diet for the 20 million people translating into per capita consumption of 12 kg. Close to the production system, this figure rises to 50 – 100 kg. It is estimated that fishery-related activities employ at least one million people countrywide (i.e. 5% of the population). Fish exports to regional markets are worth at least US $ 20 million annually. Fish flesh contains an anticholesterol which assists in reducing heart diseases. Some fishes are of medicinal value e.g. haplochromines (Nkejje) are used to treat measles. Most of the fish in Uganda is got from lakes Victoria, Kyoga, Albert and Albert Nile, Edward and George production systems as well as from the 160 minor lakes and rivers and the associated wetland systems. Capture fisheries based in these systems contribute up to 99% of the fish production in Uganda but aquaculture is also picking up. The fishing industry employs up to one million Ugandans

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Lake wamala was opened to commercial fishing in 1960. Interviews with the local fishermen during 1975/78 (Okaronon 1975, 1976, 1977, 1989) revealed that fishing for subsistence had been going on long before stocking was done. The subsistence fishing was conducted along rivers and at river mouths using basket traps (mainly made of papyrus stems), weirs and hooks and that the fish species caught were predominantly clarias (mudfish/male) and protopterus Lungfish/Mamba). These interviews did not, however, reveal the presence of tilapiine species in Lake wamala prior to stocking. These interviews did not however reveal the presence of tillapine species in lake wamala prior to stocking. Following the opening of the lake to commercial fishing in 1960, Lake Wamala provided a very profitable commercial fishery throughout the 1960s. However, during the early 1970s the fishermen started complaining of continued decline in catch rates from about 8 kg (15 fish) of O. niloticus per net per night if in 1966 to less than 1 kg per net per night by 1975.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

A study was conducted to evaluate the effects of feed made from locally available ingredients on polyculture of shrimp and three brackishwater finfish species. Hatchery produced post-larvae (PL) of shrimp Penaeus monodon (0.005g) were stocked at the rate of 15,000 PLs/ha. Brackishwater finfish species Liza parsia, Mugil cephalus and Rhinomugil corsula of 0.63-1.4lg collected from local rivers were stocked at the rate 8,000, 1,000 and 2,000/ha, respectively in four treatments. Shrimp and finfishes were fed four different experimental diets composed of fish meal, mustard oil cake, rice bran, oyster shell power and vitamin premixes at the rate of 3-5% estimated crop/day for 195 days. Among four treatments, P. monodon showed comparative better growth in T4 and T3. Finfish L. parsia showed its better performance in treatment T2. Species M. cephalus and R. corsula showed insignificant production. P. monodon showed better growth with diet of fish meal and mustard oil cake@ 28.84 and 33.65%, respectively in T 3 and 19.22 and 43.27%, respectively in treatment T4.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The bed Shakla, comprising an average area of 75.0 ha is located in the northeastern region (Brahmanbaria district) of Bangladesh. The study was carried out to assess the ecological aspects of bed ecosystem. Surface run-off and increase inflow of rain water from the upper stretch during monsoon cause inundation and resumption of connection between beel and parent rivers. The range of dissolved oxygen (DO) content ( 4.5-8.9 mg/L) was found congenial for aquatic life. pH was in the alkaline range (7.3-8.5) and free C02 was reletavely high. Lower values of total hardness and total alkalinity indicated less nutrients in the beel water. A wide variation (1.4-27.2 x 103 ceHs/L) in the standing crop of total plankton was recorded during study period of which phytoplankton alone contributed about 90%. Phytoplankton diversity in the beel represented by three groups viz. Chlorophyceae, Myxophyceae and Bacillariophyceae in order of abundance. A total of 52 fish species belonging to 36 genera, 20 families and 1 species of prawn were identified so far from the beel. About l3 types of fishing method were found in operation. Seine nets (moshari berja, ghono berjal) and gill net (current jal) were identified as detrimental gear killing juveniles of different species during post spawning period. Kua fishing was also found harmful due to dewatering nature. A total of 11 species belonging to 11 genera and 10 families of aquatic weeds were identified from the beet The eggs of Macrobrachium Jamarrei were identified into the Najas najas vegetation during April-September.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The marine environment of Pakistan has been described in the context of three main regions : the Indus delta and its creek system, the Karachi coastal region, and the Balochistan coast. The creeks, contrary to concerns, do receive adequate discharges of freshwater. On site observations indicate that freshwater continues flowing into them during the lean water periods and dilutes the seawater there. A major factor for the loss of mangrove forests as well as ecological disturbances in the Indus delta is loss of the silt load resulting in erosion of its mudflats. The ecological disturbance has been aggravated by allowing camels to browse the mangroves. The tree branches and trunks, having been denuded of leaves are felled for firewood. Evidence is presented to show that while indiscriminate removal of its mangrove trees is responsible for the loss of large tracts of mangrove forests, overharvesting of fisheries resources has depleted the river of some valuable fishes that were available from the delta area. Municipal and industrial effluents discharged into the Lyari and Malir rivers and responsible for land-based pollution at the Karachi coast and the harbour. The following are the three major areas receiving land-based pollution and whose environmental conditions have been examined in detail: (l) the Manora channel, located on the estuary of the Lyari river and serving as the main harbour, has vast areas forming its western and eastern backwaters characterized by mud flats and mangroves. The discharge of industrial wastewater from the S.I.T.E. and municipal effluents from the northern and central districts into the Lyari has turned this river into an open drain. This, in turn, has caused a negative impact on the environment of the port, fish harbour, and the adjacent beaches. (2) The Gizri creek receives industrial and municipal effluents from the Malir river as well as from several industries and power stations. The highly degraded discharges from the Malir have negatively impacted the environment in this creek. (3) The coastline between the Manora channel and Gizri creek where the untreated municipal effluents are discharged by the southern districts of Karachi, is responsible for the degraded environment of the Chinna creek, and also of the beaches and the harbour. The Balochistan coast is relatively safe from land-based pollution, mainly because of the lack of industrial, urban or agricultural activity, except the Hingol river system where some agricultural activities have been initiated.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

A survey conducted to evaluate the present status of harvesting, transportation and marketing of freshwater SIS of Bangladesh showed that among the 56 to 73 species of small indigenous fish species (SIS), mola (Amblypharyngodon mola), dhela (Osteobrama cotio cotio), puti (Barbodes sarana), tit puti (Puntius ticto), tengra (Mystus vitatus), chapila ( Gudusia chapra), batashi (Pseudotropius atherinoides), buzuri tengra (Mystus tengra), katchki (Corika soborna), gol chanda (Chanda ranga), lamba chanda (Chanda nama), phul chela (Chela phulo) and lata (Channa punctatus) are the most common. But the abundance of the mola, puti, tengra, batashi and chapila are higher than the other SIS species. Puti was at the top of the list in percentage abundance (7-9%), followed by mola (7-8%), tengra 6-7% and chapila 5-6% in all the investigated areas. Three levels of market or marketing systems were observed in the distribution channel of fish trade: primary, secondary/higher secondary and final consuming markets. Primary market is the catching point in the rural area. In secondary market, the collectors bring the fish from primary market to the landing ghats, usually to the nearest thana market or at a place well linked by rivers, road and rail transport. On purchasing the fish from the higher secondary market, the paikars sell the fish to the retailers who take it to the final consumer market. Different types of crafts and gears are used for catching the SIS in Bangladesh. Monofilament gill nets (20%), traps and line nets (25%) and seine nets (25%) are the dominant gears in respect of the total catch followed by lift net (10%) and cast net (20%). A total of 10 types of gear are listed according to their mode of operation which used for catching SIS. The processors in consumer market received higher marketing profit followed by primary market and secondary market, respectively.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

In total 68 phytoplankton species were identified at the mouth of the Maheshkhali channel with the Bay of Bengal, among them 41 belong to Bacillariophyceae, 17 Dinophyceae, 7 Cyanophyceae and 3 to Chlorophyceae. The highest phytoplankton production was observed in November (578.0 x 105 cells/L) and the lowest in June (37.5 x 105 cells/L). Some hydrographic parameters e.g., surface water temperature, salinity and nutrients (N03-N and P04-P) were recorded and their relationship with the occurrence and abundance of phytoplankton population were also studied. Nutrient concentration was higher during the autumn months, when rain water provided the maximum outflow of rivers discharging into the channel. During the nutrient peak period, the total phytoplankton production was maximum. Bacillariophyceae was the dominant group of phytoplankton throughout the study period except in June and September, when Dinophyceae was dominant. Cyanophyceae was abundant in spring months when temperature began to rise.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Studies on the abundance, migration and management of Jatka (juvenile hilsa, Tenualosa ilisha) were conducted in the Gajner Beel, located at the south-east corner of the Pabna Irrigation and Rural Development Project (PIRDP) in Sujanagar Upazila of Pabna district, Bangladesh. The main Jatka season was found to be extended from mid August to mid October. Veshal/Bandh/Khora Jal (lift net) and Ber Jal (beach seine net) were found as the major gears involved in Jatka fishing. The estimated total amount of Jatka caught from the Beel during the studied season was 46.2 t. The migratory route of Jatka is extended from the Padma and/or Jamuna rivers to the Badai river and then to the Beel through the sluice gate. The possibility of breeding of hilsa in the Beel was nullified. Finally, a community based management plan was suggested for implementation by the Gajner Beel management committee.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The fisher folk used to catch small indigenous species of fish (SIS) from rivers, canals, wetlands and floodplains at little or no cost for their livelihood. Surplus fish was sold at the local market to generate some little capital for the households. The livelihood and consumption of SIS in fishing community of two upazilas viz. Trisal and Ishwarganj under Mymensingh district were studied for 3 months in 2004. Most of the fisher folk of the study areas belong to resource-poor section of the society living below the poverty level. Majority of them had no cultivable land. As professional fishers they face many problems during lean fishing period from January to April due to little or non-availability of fish. Majority of the fisher households consumed SIS three to four days a week. The fisher households of Trisal upazila consumed more small fish than those of Ishwargonj upazila. More than 50% respondents consumed <20 g SIS/day and 20% consumed >40 g SIS/day in Trisal upazila. On the other hand, in Ishwargonj upzila, most of the fisher households (66%) were found to consume <20 g SIS/day. SIS was mostly available from July-December in rivers, wetlands (beels), and canals, and income from fishing was reported to be good. The dominant SIS was Puntius spp., Mystus spp., Anabas testudineus, catfishes, mola, and small prawns. Non-indigenous species like tilapia was also dominant in Trisal upzila where aquaculture practices were well established.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The contents of the heavy metals Fe, Zn, Cu, Mn, Pb, Cd and As were examined in the liver, heart, gills, kidney and muscles of the fish Clarias gariepinus from Eko-Ende dam in Ikirun, the capital of Ifelodun Local Government of Osun State, Nigeria. C. gariepinus is the fish of choice and the most demanded in the southwest of Nigeria. The highest metal concentrations were in the liver and the gills while the lowest was in the muscles. The general deceasing order of metal accumulation in the organs was Fe > Zn > Cu > Mn > Cd. Lead and arsenic were not detected in any organ. The values were of lower concentrations than found in many other dams and rivers in Nigeria and some other countries. The values were also lower than the FAO/WHO recommended maximum limits in fish samples, making the fish to be safe and not of any hazards for the consumers.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Dried fish constitutes a regular item of trade in India, particularly in the interior parts far away from the sea and rivers. The poor section of the society is the main consumer. The quality of dried fish never receives much attention at any stage of processing (drying) and storage. A good amount of these fish is discarded during drying due to fungal growth to avoid the danger of mycotoxin production. A survey of the dried fish from the Cochin markets had revealed that they do carry fungal infestations and their chances of mycotoxin production cannot be ruled out as the strains of Aspergillus flavus, Aspergillus ochraceus and Fusarium spp. have been isolated.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Linear alkylbenzene sulfonate (LAS) are widely used in detergent industry. Due to contaminants entering the water, and the effects of their accumulation in fish, LAS, has a great importance in environmental pollution. In the present study, accumulation of LAS and its histological effects on gill tissue, liver and kidney of Caspian kutum (Rutilus frisii kutum) were studied. Caspian kutum is the most important and most valuable teleosts of the Caspian Sea. Due to releasing Caspian Kutum in rivers and Anzali Lagoon and unlimited entry of wastewater to the aquatic ecosystem, research on the impact of LAS on Caspian kutum is important. In the present study, fish exposed to sublethal concentrations of LAS (0.58, 1.16 and 2.32 mg/l) for 192 hours. Control treatments with three replicates at 0, 24, 48, 72, 96 and 192 hours were done. For assessments of the histological effects of LAS, tissue sections prepared and by using Hematoxylin - Eosin were stained, then the prepared sections, examined by light microscopy. For determination of the bio accumulation of LAS, the soxhlet extraction and solid phase extraction was performed to determine the amount of LAS using HPLC with fluorescence detector. According to results average of bioconcentration factor and LAS concentrations in fish had reached stable levels after approximately 72 h and thus represented steady state BCF values in this species. The value of steady-state bio-concentration factor of total LAS was 33.96 L.Kg- 1 and for each of the homologous C10-n-LAS, C11-n-LAS, C12-n-LAS and C13-n- LAS were 3.84, 6.15, 8.58 and 15.57 L.Kg-1 respectively. According to the results obtained in gills exposed to LAS, histopathological alteration include hypertrophy, lifting of lamella epithelium, edema, clubbing of lamellae hyperplasia, lamellar fusion and aneurysm were seen. In liver tissue exposed to three concentrations of LAS, congestion and dilation of sinusoids, irregular-shaped nuclei and degeneration in the hepatocyte, vacuolar degeneration and necrosis were observed. In kidney exposed to three concentrations of LAS, reduction of the interstitial haematopoietic tissue, degeneration in the epithelial cells of renal tubule, tubular degeneration, necrosis, shrinkage and luminal occlusion were observed. According to the results the most alteration due to exposure to LAS was seen in the gill tissue. None of the control samples showed histological effects of LAS.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Lar lake, with the international UTM specification of 39S 579680 3976567 & 39S 589930 3976184 is Situated in Lar national Park with an aerial distance of 55 Km of Tehran along Haraz road. The present research is carried out as part of a comprehensives Plan for assessment of bioresearches of Lar lake & the rivers flowing into it. This research includes examination of there benthic Samplings performed in Lar lake and each of the related rivers including Delichaee, Ab-e-sefid , Alarm & Lar (Kamardasht).Tubifex and Chironomus genus were found to have the highest frequencies of occurrence in the lake with %77.117 & %21.823 respectively followed by Chironomidae and Simulidae from the Diptera order which accounted for %72.328 and %13.812 occurrences in four rivers examined in the Study. The benthic biomass at various examined Sites and the average wet weight of the benthic biomass in station No one in the lake Was 17.397g and the figure for the examined site in Alarm was 20.242 g which were the highest level among Other examination stations the index for the abundance of species in Alarm river was greater than the rest of the examined rivers with 12.57. A sum of 354 Pieces of brown trouts was caught in the course of sampling which were closely investigated in terms of their digestive tract Content. It was identified that Daphniidae and Chironomus constituted the bulk of eaten items from the lake with %17.985 and %63.973 respectively. Meanwhile, Chironomidae and Simuladae were the most frequently eanten benthos by the fish with %81.47 and %7.93 respectively.The index for the relative length of gut was recorded at 0.49± 0.08 which is well indicative of the carnivorous diet of the fish.The index for the feeding intensity amounted to 138  83 showing that the one year old fish were of more feeding intensity.The coefficient of condition (K) was estimated at 1.02  0.142 for all the caught fish. The average wet weight of the benthos was 10.348 g per square meter which if extended to 700ha surface area of the lake, the total macrobenthic production in the lake would amount to 72730Kg of wet weight or 6510 Kg of dry weight. Since the Secondary Production of macrobenthos have always been double that of their biomass, it is reasonable to assume that the Secondary Production of macrobenthos amount to 145640 Kg by their wet weight and Since the energy transfer in the food chain of the lake from benthos to fish is 10 percent, the fish production Capacity Coming from benthic resources of the lake (Lar) would be 14.5 MT, half of which (7000-8000MT) could annually be harvested. Further more, the actual fish Production Capacity might exceed the projected level Since Daphnia, Rotifers and Ostracoda which belong to Zooplanktons, play a part in the natural diet of trout. Meanwhile, rivers Play a major role in fish nutrition and the annual fish production in Delichaee river is about 4481.8Kg while the figures for Ab-e-sefid, Alerm and Lar rivers are 2370.7 4848.7 and 2586.2 Kg respectively, that further increase fish Production in the area and every year half of these resources can be exploitable from the river & the lake.Nevertheless, due to ecological & biological importance of rivers and the probability of environmental Pollution, devastation of natural fish habitats & their nursery grounds, Sport fishing is not recommended at all.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

A total of 361 caudal fin samples were collected from adult A. stellatus specimens caught in the north Caspian Sea, including specimens from Kazakhstan (Ural River), Russia (Volga River), Azerbaijan (Kura River), specimens caught in the south Caspian Sea including specimens from Fishery Zone 1 (from Astara to Anzali), Fishery Zone 2 (from Anzali to Ramsar), Fishery Zone 3 (from Nowshahr to Babolsar), Fishery Zone 4 (from Miyankaleh to Gomishan) as well as from specimens caught in Turkmenistan (all specimens were collected during the sturgeon stock assessment survey). About 2 g of fin tissue was removed from each caudal fin sample, stored in 96% ethyl alcohol and transferred to the genetic laboratory of the International Sturgeon Research Institute. Genomic DNA was extracted using phenol-chloroform method. The quality and quantity of DNA was assessed using 1% Agarose gel electrophoresis and Polymerase Chain Reaction (PCR) was conducted on the target DNA using 15 paired microsatellite primer. PCR products were electrophoresed on polyacrylamide gels (6%) that were stained using silver nitrate. Electrophoretic patterns and DNA bands were analyzed with BioCapt software. Allele count and frequency, genetic diversity, expected heterozygosity and observed heterozygosity allele number, and the effective allele number, genetic similarity and genetic distance, FST and RST were calculated. The Hardy Wienberg Equilibrium based on X2 and Analysis of Molecular Variance (AMOVA) at 10% confidence level was calculated using the Gene Alex software. Dendrogram for genetic distances and identities were calculated using TFPGA program for any level of the hierarchy. It is evident from the results obtained that the 15 paired primers studied, polymorphism was observed in 10 pairs in 12 loci, while one locus did not produce DNA bands. Mean allele number was 13.6. Mean observed and expected heterozygosity was 0.86 and 0.642, respectively. It was also seen that specimens from all regions were not in Hardy Wienberg Equilibrium in most of the loci (P≤0.001). Highest Fst (0.063) was observed when comparing specimens from Fishery Zone 2 and Fishery Zone 4 (Nm=3.7) and lowest FST (0.028) was observed when comparing specimens from the Volga River and those from the Ural River (8.7). Significant differences (P<0.01) were observed between RST recorded in the specimens studied. Highest genetic distance (0.604) and lowest genetic resemblance (0.547) were observed between specimens from Fishery zones 2 and 4. Lowest genetic distance (0.311) and highest genetic resemblance (0.733) was observed between specimens from Turkmenistan and specimens from Fishery zone 1. Based on the genetic dendrogeram tree derived by applying UPGMA algorithm, A. stellatus specimens from Fishery zone 2 or in other words specimens from the Sepidrud River belong to one cluster which divides into two clusters, one of which includes specimens from Fishery zones 1, 3 and 4 and specimens from Turkmenistan while the other cluster includes specimens from Ural, Volga and Kura Rivers. It is thus evident that the main population of this species belongs to the Sepidrud River. Results obtained from the present study show that at least eight different populations of A. stellatus are found in the north and south Caspian Sea, four of which are known populations including the Ural River population, the Volga River population, the Kura River population and the Sepidrud River populations. The four other populations identified belonging to Fishery zones 1, 3, and 4 and to Turkmenistan are most probably late or early spawners of the spring run and autumn run of each of the major rivers mentioned. Specific markers were also identified for each of the populations identified. The Ural River population can be identified using primers Spl-68, 54b and Spl-104, 163 170, 173, the Volga River population can be identified using primers LS-54b and Spl-104, 170, 173 113a and similarly the population from the Kura River can be identified using primers LS-34, 54b and Spl-163, 173 and that from the Sepidrud River can be identified using primers LS-19, 34, 54b and Spl-105, 113b. This study gives evidence of the presence of different populations of this species and calls for serious measures to be taken to protect the genetic stocks of these populations. Considering that the population of A. stellatus in Fishery zone 2 is an independent population of the Sepidrud River in the Gilan Province, the catch of these fishes in the region needs to be controlled and regulated in order to restore the declining stocks of this species.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Morphological assessment of sexually mature Rutilus frisii kutum Kamenskii 1901 caught from the rivers (Shirud, Khoshkrud, Sepidrud and Chelavand Rivers) flowing in the southwest Caspian Sea region was conducted and sperm volume, total sperm count and sperm concentration of abnormal sperms were determined after exposing the spawners to 60% herbicide butachlor (machete). Spawners under study were maintained in tanks (1000 l) at the Shahid Ansari Teleost Fish Hatchery and exposed to two different concentrations (25% and 75% of its LC50 value) of butachlor. Results obtained indicate that exposure to high butachlor toxicity (75% of its LC50 value) decreased sperm volume to 0.61 ± 0.42 cc in 2-3 year old fishes and to 0.55 ± 0.42 cc in fishes above 3 years of age, while that in fish exposed to low butachlor toxicity (25% of its LC50 value) decreased to 1.55 ± 0.42 cc in 2-3 year old fishes and to 1.28 ± 0.42 cc in fishes above 3 years of age. The sperm volume under normal conditions in R. frisii kutum is 4.6 ± 0.42 cc in 2-3 year olds and 4.58 ± 0.42 cc in fishes above 3 years of age. The total sperm count in R. frisii kutum is 39.74 ± 2.5 billion spermatozoa/cc in 2-3 year olds and 42.99 ± 2.5 billion spermatozoa/cc in fishes above 3 years of age. When exposed to high butachlor toxicity, total sperm count dropped to 16.92 ± 2.5 billion spermatozoa/cc in 2-3 year olds and to 15.98 ± 2.5 billion spermatozoa/cc in fishes above 3 years of age. Similarly total sperm count in R. frisii kutum exposed to low butachlor toxicity was recorded as 23.6 ± 2.5 billion spermatozoa/cc in 2-3 year olds and 29.4 ± 2.5 billion spermatozoa/cc in fishes above 3 years of age. Under normal conditions, on the basis of morphology, spermatozoa showed only 10 ± 1.92% of abnormal sperms. The number of abnormal sperms increased by 28.6 ± 1.92% in fishes exposed to high butachlor toxicity, while that in fishes exposed to low butachlor toxicity increased by 19.7 ± 1.92% in 2-3 year olds and 16.6 ± 19.2% in fishes above 3 years of age. It is evident from the results obtained that increase in level of pollution caused a decrease in sperm volume but an increase in the percentage of abnormal sperms. Results obtained indicate that exposure to high butachlor toxicity (75% of its LC50 value) decreased testostron hormone to 0.31 ± 0.22 ng/ml in high butachlor toxicity, and to 0.45 ± 0.22 ng/ml in low butachlor toxicity (25% of its LC50 value). Testostron hormone dropped to 0.53 ± 0.22 ng/ml in 2-3 year olds and to 0.79 ± 0.22ng/ in fishes above 3 years of age. The testostron hormone under normal conditions in R. frisii kutum is 2.7 ± 0.22 ng/ml. It is evident from the results obtained that increase in level of pollution caused a decrease in testostron hormone