102 resultados para invertebrate


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The impact of Petrochemical Special Economic Zone (PETZONE) activities on the health status of Jafari Creek was studied by assessing the changes in macroinvertebrate assemblages in nine sites during September 2006- January 2008. Furthermore to evaluate the ecological status of the Jafari Creek the WFD indices (i.e. AMBI, M-AMBI) were used. The relationship between spatial pattern of macro invertebrate assemblages and ambient factors (i.e. water temperature, salinity, pH, dissolved oxygen, turbidity, electrical conductivity, total dissolved solid, total hardness, total nitrogen, ammonia, total phosphorous, chemical oxygen demand, biological oxygen demand, sediment grain size distribution, sediment organic content, heavy metals contents) was measured. Background Enrichment indices, Contamination factor and Contamination degree, were used to assess the health status in the study area based on Nickel, Lead, Cadmium and Mercury contents of the sediments. The macrobenthic communities had a low diversity and were dominated by opportunistic taxa, and the AMBI and M-AMBI indices need to be calibrated before using in Persian Gulf and its coastal waters. The BIO-ENV analysis identified pH, dissolved oxygen, TDS, and the total organic content of sediments as the major environmental variables influencing the infaunal pattern. This suggests that management should attempt to ensure minimal disturbance to environmental variables underlying the spatial variation in macroinvertebrate assemblages. Background Enrichment indices showed that the health of Jafari Creek has declined over time due to the constant discharge of heavy metals to the Creek system. Furthermore WQS index shows that the quality condition of the water column in Jafari Creek, regard to the calculated number (3) is week. These indices also identified a significant degree of pollution in the study area. The decrease in the ecological potential of Jafari Creek was best highlighted by the alteration in macrobenthic assemblages.

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Distribution and growth biology of rock oyster (Saccostrea cucullata) in the northern shores of Oman sea have been struied. During this one-year study, samples have been taken monthly from ten different stations. quantity of vertical distribution of this species was obseredl in the mid - intertidal zone. After determining the spread pattern, the following subjects were studied: - Growth parameters - Distionction of the "cohorts" - Determination of "spawning Season" - Condition of the "Gonado Somatic Index" - Sex ratio - Length of the species during the first year of maturation. - Identification and determination of percentage of "Biofouler Organisms." Results obtained from the above - mentioned studies show that considering a growth factor (k) of 0.52, the value of "Loo " for this species is equal to 114 (mm).Five to six different age groups were observed among the samples taken. In the areas where this study was conducted, this species grows 24 to 30 (mm) in the first year of its life this growth rate is lower in the higher - aged grpups relative to the lewer - aged groups, so that the longest size classes grow between 4 to 6 (mm) per year. • The maxinum Value of the "Condition Index" is in the pozm area and the minimum value of it belongs to Darak and Tang areas. Along with the increase in the growth of gonads the above mentioned condition index increases gradually simultaneous with the onset of spawning. Also, study of the influence of environmental factors on the maturation process suggests that the most important factors affecting maturation and spawing are temperature and salinity. The study of GSI shows that this species has a coordinated bimodal spawing trend, with its spring peak in june and its autumn peak, being still higher than the spring peak, in september. The recruitment curve confirms the above spawning peaks with its peaks occuring after a delay of one month or maximum two months in comparison to the spawning peaks. The results of calcuation of "Sex Ratio" of this species in each area show that sex ratio is 1:1. Among the first size classes that reach maturity, nearly 67% of the samples are male and the remaining 33% are female. with the increase in the shell size, the percentage of males decreases and the percentage of females increases. , The above facts prove the protandrous nature of this species the diagram showing the sizes of the first samples which reach maturity suggests that more than 50% of the samples mature after their length exceeds 36 (mm). The shortest mature sample was found to have a length of 22(mm). After studying "Biofouler Organism" nine different invertebrate groups were indentified. Barnacles and Tunicates have the highest and lowest percentages respectively. According to zonal observations, Barnacles and polychacta do the greatest damage to this species.

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Ecological study on Kolahy and 'flab estuaries were carried out during 1996-1997. Water and sediment sampling was done seasonally. In order to study the physical and chemical characteristic of the water, various animal fauna from different material niches including planktons and fish from water, benthousi from the sediment , and surface living animal such as Arthropod (Crabs) and Waterbirds were identified. I he result shoved, that water salinity of both estuaries was the same as the general salinity existing its the Persian Gulf water, and its variation is same IN those waters Minimum water salinity in both estuaries are seen during Bahairdan or early winter mooth(Jaa.), which is about 31ppt and Maximum is during .rirldlun.) or summer mouth at about 19 ppt. Dissolved otygen and pH are slime as the general Persian Gulf waters., Dissolve Oxygen being directly associated to temperature and its fluctuation is between 7- Sing/I and pH between 7.5-LS. The animals of both estuaries are almost similar having a sal factory species diversity . The birds of the region are often seasonal migrants , the maximum population of which occurs in winter season and the minimum during summer month. Nam coverage is richer in Tiab than Kolahy estuary, where in Kolahy a signal Mangrove tree is in exigence. 'Ile total coverage of Mangrove forest in Tiab is estimated about -29 hec.Both estuaries are included with in the international Ramsar Convention sites in 1971. Due to national importance of these estuaries inproviding refugee for various birds species and also hinting grounds and access traffic for local fishing vehicles, Actiog as an important access for various inhabitancy living with these area of the Persian Gulf. Due to importance or prawn aquacultur for the economical well being of local inhabitance, these areas provide a suitable grandees for prawn production. I-test statistics show, there are no significant difference among various invertebrate and vertebrate animals. In over all out look 21) phytoplankton genera, 21) zeoplankton genera 17 miafauna and 32 roaerofauna genera , 11 different species Carcineacearions and 119 species of walerbirds were identified with in the Tiab and Kolahy estuariesregioos. The X statistic show that the animal density is directly associated to season. Where density of miofauna and maerofauna in both estuaries are in maiticrourn during summer and the minimums existing during the winter season. In addition the bentic invertebrate population density in closlly association to birds population density since , the later, feeds on the former animals. Where the increasing in bird population density during the winter season, the bentic invertebrate animal population density decreases. The over all trend of animal population density in winter tend to increased towards the summer seasons, which this is due to climatic conditions of the region. The bird population on the contrary to other animals of both estuaries tend to increase from summer towards the winter seasons and which this bird population density is in maximum in winter with in the region.

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Source of the Nile Fish farm (SON) is located at Bugungu area in Napoleon Gulf, northern Lake Victoria. The proprietors of the farm requested for technical assistance of NaFIRRI to undertake regular environment monitoring of the cage site as is mandatory under the NEMA conditions. As the SON is a key collaborator/client of the institute, NAFIRRI agreed to undertake the assignment subject to facilitation by the client. The institute agreed to conduct quarterly surveys of key environmental parameters at the site including selected physical-chemical and biological factors, nutrient status, column depth, water transparency and sedimentation. Samples and field measurements were to be taken at 3 sites: within and/or close to the fish cages (WIC), upstream (USC) and downstream (DSC) of the cages. The first environmental monitoring survey was undertaken in February 2011; the second in May 2011 and the third in September 2011. The surveys cover physical-chemical parameters, nutrient status, invertebrate and fish communities. The present report presents field observations made for the fourth quarter survey undertaken in November 2011 and provides a scientific interpretation and discussion of the results with reference to possible impacts of the cage facilities to the water environment and the different aquatic biota at and around the cage site including natural fish communities.

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Source of the Nile Fish farm (SON) is located at Bugungu area in Napoleon Gulf, northern Lake Victoria. The proprietors of the farm have a collaborative arrangement with NaFIRRI to undertake quarterly environment monitoring of the cage site as is mandatory under the NEMA conditions. The monitoring surveys cover selected physical-chemical factors i.e. water column depth, water transparency, water column temperature, dissolved oxygen, pH and conductivity; nutrient status, algal and invertebrate communities (micro-invertebrates/zooplankton and macroinvertebrates/ macro-benthos) as well as fish community. The second quarter survey for the calendar year 2015, which is the subject of this report, was undertaken in June 2015. Results/observations made are presented in this technical report along with a scientific interpretation and discussion of the results with reference to possible impacts of the cage facilities to the water environment and aquatic biota.

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Rastrineobola argentea is the only native fish species which is still abundant in Lakes Victoria and Kyoga, the others being two introduced species; Lates niloticus and Oreochromis niloticus. It forms an important commercial fishery in Lake Victoria and is very important as food of Lates niloticus in both lakes. The depletion of the originally abundant insectivorous and zooplanktivorous hap lochromines due to predation by Lates niloticus appears to have favoured it by reducing potential competitors for food. It now consumes a wide range of invertebrate organisms that originally used to be eaten by different specialised species of haplochromines which include: larvae and pupae of chironomids and chaoborids, copepods and ostracods. Its size in Lake Kyoga (where the Nile perch was introduced earlier) has, however, decreased and is smaller than that in Lake Victoria probably due to high predation pressure. The twin effect of predation and fishing are likely to exert heavy pressure on the species. Research is therefore required to provide information for its management.

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The National Fisheries Resources Research Institute (NaFIRRI) on behalf of OPEP Consult Ltd undertook a baseline survey of the transition zone (basically along the shoreline) and near shore habitats of the Uganda apart of Lake Edward and Kazinga channel during December 2007 to January 2008. A major objective of the baseline survey was to generate baseline information on the aquatic ecosystem features related to the fisheries and socio-economics of the fish catch including issues raised by residents in the fish landing sites. Therefore, the baseline survey captured information on water quality, the aquatic invertebrate fauna, aspects of fish biology and ecology, the fish catch including facilities at fish landings, value in the catch and related fisheries socio-economic issues perceived by residents in the settled areas along the shores.

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Under the Implementation of the Fisheries Management Plan (IFMP) for Lake Victoria Result area 4, quarterly gillnet surveys are undertaken to monitor changes in fish stocks and environmental parameters in the shallow nontrawlable areas of the lake For purposes of monitoring surveys, the Ugandan sector of Lake Victoria is divided into 3 zones as shown in Figure 1. During the second quarter of APE2, two gillnet surveys were undertaken in zones 1 and 3 in February and March 2006 respectively. The purpose of the surveys was to monitor changes in the fish stocks and their biological characteristics, water quality, algal dynamics and invertebrate communities; as detailed in the various sections of the report. The surveys followed those conducted in November and December 2006 in the same zones. Results of the surveys showed that the number of fish taxa was higher in the near-shore fleets (0-100m) decreasing towards offshore. The near-shore areas were also associated with high primary productivity and hence secondary production to which Caridina and other invertebrates are part. These organisms are an important source of food for the fish and this may partly account for the high number of fish species recorded in this area of the lake. It was also observed that although Nile perch was the most dominant fish species recorded in all the stations during the surveys, haplochromines, Brycinus sadleri, Brycinus jacksonii Oreochromis niloticus and various mormyrid species contributed significantly to the fish biomass. The presence of many fish species and their coexistence with the predator, Nile perch is attributed to the presence of macrophyte cover and rocky habitats which serve as refugia in the shallow inshore habitats of Lake Victoria. In addition, the vegetated habitats are an important source of food for the fishes. As reported in macro-invertebrate studies, big populations of Caridina and other invertebrates were recorded among macrophyte beds. Caridina is an important source of food for juvenile Nile perch and other fish species so are the other invertebrates especially chironomid larvae, odonata nymphs and molluscs. Resurgence in haplochromine cichlids was observed during the surveys. The presence of haplochromines cichlids in all the sites especially Thruston Bay where it ranked the second by percentage contribution in number, is evidence of the recovery of this group of fishes which had declined largely due to predation by L. niloticus. Caridina nilotica has also increased in biomass and is a major component of the Nile perch diet. This could have reduced predation pressure on the haplochromines by Nile perch and has possibly contributed to recent resurgence in haplochromines cichlids in the lake in the shallow nontrawlable areas of the lake Rastrineobola argentea was found to be an important prey item for Nile perch and other fish species such as Clarias gariepinus. Measures should therefore be taken to ensure sustainable harvesting of Dagaa so that there is enough left to sustain the fishery of Nile perch and other species.

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The government of the People's Republic of China through a 2007 agreement with the Government of the Republic of Uganda, has establishment of an Agricultural Technology Demonstration Center (ATDC). The first phase covering the building of aquaculture infrastructure at Kajjansi ARDC is complete and the second operation phase has started in which facilities for cage culture have been set up in the Napoleon gulf, northern Lake Victoria near Jinja. The cage facility is aimed at boosting fish farming within the lake as a diversification to the traditional pond fish culture technology. NaFIRRI scientists as well as Chinese experts undertook a baseline survey in the chosen cage site on 12 March 2012. The survey covered determination of water depth, water transparency, measurement of selected physical-chemical parameters (temperature,dissolved oxygen, conductivity and pH; determination of the nutrient status and study of algae, invertebrate and fish communities at the site. Materials and methodologies used in the survey were based on the Standard Operating Procedures (SOPs) of NaFIRRI. The study area was divided into three study sites. Site 1 (upstream) was at 8.9 metre depth while site 2 (proposed cage site) and site 3 (downstream) were 6 and 4.3 metres deep respectively. Water transparency was lowest at site 1 (1.58 m) and highest at site 3 (1.64 m). Dissolved oxygen at the three sites ranged from 6.0 to 8 mg/I. Water temperature profiles fluctuated within narrow limits between 26.5 and 27.5 DC. Measurements of pH were between 7 (neutral) and 8 (alkaline) while electrical conductivity was between 98 and 101 uS/em. These observed physical-chemical parameters at the study site were considered suitable for cage fish rearing purposes. Nitrite-nitrogen levels varied within narrow limits from 0.043 to 0.0453 mgtl. Similarly, Ammonia-nitrogen varied between 0.015 and 0.0185 mg/1. Soluble reactive phosphorus (SRP) level was highest at site 3 (O.012mgll) compared to that at sites 1 and 2 (0.009mgll). Total suspended solids (TSS) were higher at site 1 (83.3mgll), thereafter decreasing to lower levels at sites 2 (24.8mgtl) and 3 (19.8mgl) respectively. The nutrient level results observed here all fall below the maximum permissible limits by NEMA and therefore the site is recommended for cage culture The algal community was constituted by four major groups: Blue greens,Greens, Cryptophytes, and Diatoms with blue greens as the common and dominant group. High algal biomass (19944961 ugtL) of the dominant blue green algae was observed at site 1 compared site 2 and 3 (58655.2 & 27487. 7 ugtL) respectively. Occurrence of toxicin producing algae: microsytis and cylindrospermopsis in the proposed cage area was considered to be of not much significance as their concentrations were below harmful levels. However, monitoring their presence, biomass and seasonality will be critical in order to follow when and where they occur and at what time of the year for ease of management of the cages

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Knowledge of how biota can be used to monitor ecosystem health and assess impacts by human alterations such as land use and management measures taken at different spatial scales is critical for improving the ecological quality of aquatic ecosystems. This knowledge in Uganda is very limited or unavailable yet it is needed to better understand the relationship between environmental factors at different spatial scales, assemblage structure and taxon richness of aquatic ecosystems. In this study, benthic invertebrate community patterns were sampled between June 2001 and April 2002 and analysed in relation to water quality and catchment land use patterns from three shallow near-shore bays characterized by three major land uses patterns: urban (Murchison Bay); semi-urban (Fielding Bay); rural (Hannington Bay). Variations in density and guild composition of benthic macro-invertebrates communities were evaluated using GIS techniques along an urban-rural gradient of land use and differences in community composition were related to dissolved oxygen and conductivity variation. Based on numerical abundance and tolerance values, Hilsenhoff's Biotic Index ofthe invertebrates was determined in order to evaluate the relative importance of water quality in the three bays. Murchison Bay supported a relatively taxa-poor invertebrate assemblage mainly comprising stenotopic and eurytopic populations of pollution-tolerant groups such as worms and Chironomus sp. with an overall depression in species diversity. On the contrary, the communities in Fielding and Hannington bays were quite similar and supported distinct and diverse assemblages including pollution-intolerant forms such as Ephemeroptera (mayflies), Odonata (dragonflies). The Hilsenhoff Biotic Index in Murchison Bay was 6.53. (indicating poor water quality) compared to 6.34 for Fielding Bay and 5.78 for Hannington Bay (both indicating fair water quality). The characterization of maximum taxa richness balanced among taxa groups with good representation of intolerant individuals in Hannington Bay relative to Fielding and Murchison bays concludes that the bay is the cleanest in terms of water quality. Contrary, the dominance of few taxa with many tolerant iqdividuals present in Murchison Bay indicates that the bay is degraded in terms of water quality. These result are ofimportance when planning conservation and management measures, implementing large-scale biomonitoring programs, and predicting how human alterations (e.g nutrient loading) affect water ecosystems. Therefore, analysis of water quality in relation to macro-invertebrate community composition patterns as bio-indicators can lead to further understanding of their responses to environmental manipulations and perturbations.

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The mobile water hyacinth, which was produced in growth zones, especially Murchison bay, was mainly exported to three sheltered storage bays (Thruston, Hannington and Waiya). Between 1996 and May 1998, the mobile form of water hyacinth occupied about 800 ha in Thruston bay, 750 ha in Hannington bay and 140 ha in Waiya bay). Biological control weevils and other factors, including localised nutrient depletion, weakened the weed that was confined to the bays and it sunk around October 1998. The settling to the bottom of such huge quantities of organic matter its subsequent decomposition and the debris from this mass was likely to have environmental impacts on biotic communities (e.g. fish and invertebrate), physico-chemical conditions (water quality), and on socio-economic activities (e.g. at fish landings, water abstraction, and hydro-power generation points). Sunken water hyacinth debris could also affect nutrient levels in the water column and lead to reduction in the content of dissolved oxygen. The changes in nutrient dynamics and oxygen levels could affect algal productivity, invertebrate composition and fish communities. Socio-economic impacts of dead sunken weed were expected from debris deposited along the shoreline especially at fish landings, water abstraction and hydropower generation points. Therefore, environmental impact assessment studies were carried out between 1998 and 2002 in selected representative zones of Lake Victoria to identify the effects of the sunken water hyacinth biomass.

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A first list of the marine invertebrate species collected along the coast of Nhatrang (Vietnam) is presented.