Metal pollution loading,Manzalah lagoon,Nile delta,Egypt: Implications for aquaculture

High cultural enrichment factors are found for Hg (13×), Pb (22.1×), and other potentially toxic metals (e.g., Sn, Zn, Cu, Ag) in the upper 20 cm of sediment cores from the southeastern Ginka subbasin of Manzalah lagoon, Nile delta, Egypt. Cores from other areas of the lagoon show little metal loading. Metal loading followed the closure of the Aswan High Dam, the availability of abundant cheap electricity, and the development of major power-based industries. Industrial wastes containing potentially toxic metals are dumped into the Nile delta drain system. The load carried by Bahr El-Baqar drain discharges into the Ginka subbasin, which acts as a sink and results in metal loading of the sediment deposited there. Further development of aquaculture in this subbasin, of food-stuff agriculture on recently reclaimed lagoon bottom, or where irrigation waters come from Bahr El-Baqar drain or its discharge should be halted or strictly limited until potentially toxic metals in the drain waters and sediment are removed and polluted input drastically reduced. This environmental assessment of heavy metals in aquaculture or agriculture development should extend to other waterbodies in the northern Nile delta, particularly Idku lagoon and lake Mariut, where industrial metal-bearing wastes discharge into the waterbodies.     

Water renewal estimates for aquaculture developments in the Richibucto estuary,Canada

Water renewal in semi-enclosed coastal areas is crucial for the supply of oxygen and seston and for the removal of organic loadings from finfish or shellfish aquaculture sites. Water renewal depends on hydrodynamic processes and can have a complex spatial distribution due to irregular topographic features. This study describes some physical oceanography observations gathered in the Richibucto estuary, New Brunswick, Canada, and provides an estimate of the spatial distribution of water renewal in the North Arm, a location in the estuary where the largest American oyster (Crassostrea virginica) aquaculture operation in eastern Canada is located. The estuary changes from a well mixed estuary to a partially stratified estuary depending on runoff conditions. Tides are mixed but mainly diurnal due to the nearby presence of the second M₂ amphidromic point in the Gulf of St. Lawrence. Tidal amplitudes vary from 0.3 to 0.6 m and show a slight increase some 35 km upstream. Currents in the main channel can reach over 0.60 m s⁻¹ during ebb and 0.3 m s⁻¹ during flood, with a slack water period of approximately 8 h. Low frequency sea level fluctuations have a range of 0.5 m at the mouth and are coherent within the estuary. Hydrodynamic and advection-dispersion models are used to calculate the spatial distribution of the local renewal time (LRT) in the North Arm for high and low freshwater discharge conditions, using the dissolved tracer method. Results show that the LRT varies from less than 5 d at the downstream end of the North Arm to over 100 d further upstream. When averaged over the entire North Arm, the integral renewal time (IRT) is estimated to vary only from 8 to 21 d depending on the season. The LRT and IRT estimates are major improvements over conventional renewal estimates using tidal prism methods.     

Constraints and perspectives in aquaculture development

Aquaculture can be considered as a rapidly growing industry in many parts of the world. The impressive overall upward trend in production is likely to continue for the rest of the century. However, aquaculture will still be a minor contributor to the world's protein supply, even though the projected annual output of about 30 million tons can be realized by the year 2000. Nevertheless, aquaculture can play an important role in many developing countries not only within the context of rural development, but also as a commercial activity that focuses on export markets. Progress in aquaculture will always be accompanied by a number of constraints that occur with or through expansion of this industry. Some of the most important problem areas are briefly addressed, including those related to environmental degradation, disease control, human health and competition for resources. Finally, gaps in science and technology as well as research priorities are identified.     

Recent advances in aquaculture in Japan

Conclusions During the last ten years, aquaculture, especially mariculture has undergone remarkable expansion to counter-balance the gap between the supply and demand of fishery products in Japan. Its expansion has also been supported by the traditional preference of the Japanese people for seafood. Mariculture is now being forced to change its structure due to adverse economic circumstances such as the rise in the cost of energy, feeds and other materials for culture, low market prices, deterioration of environmental conditions, and many other factors. Before these constraints can be resolved, advanced scientific knowledge and technologies must be integrated to develop new types of aquaculture. Expansion of maricultural activities to more open-sea and off shore areas would be one route to follow. Technologies for the development of formulated diets not only for young but also for adults and larvae, establishment of feeding standards, prevention of epizootic diseases must support the establishment of modern aquaculture.The culture-based fisheries, or marine ranching, is becoming a subject for further development in Japan. Much research work has been conducted with a great degree of governmental support. Establishment of a net work of seedstock production farms has made it possible to carry out releasing experiments on a large scale. A newly integrated restoration system could be developed on the basis of these experiments, even though the profits resulting from the artificial restoration of stocks is not thouroughly verified at present. The commencement of a national scheme for culture-based fisheries would be a manifestation of the enthusiasm of the Japanese fish industry.     

Preliminary investigation of chloramphenicol in fish, water and sediment from freshwater aquaculture pond

Analytical methods of chloramphenicol in the aquaculture environment have been developed using high-performance liquid chromatography and liquid chromatography-tandem mass spectrometry. The contents of chloramphenicol were determined using high-performance liquid chromatography for sediment and liquid chromatography-tandem mass spectrometry for fish and water collected from a freshwater aquaculture pond in China. Chloramphenicol in the water and sediment were 112.3 ng/L and 0.1957 mg/kg, respectively. The chloramphenicol residues in 3 kinds of fish, including carp, chub and grass carp were different. Only the muscle and head of grass carp were under the minimum required performance limit (0.3 μg/kg) and were safe to eat. The chloramphenicol in other tissues of grass carp, carp and chub exceeded the minimum required performance limit. The highest content of chloramphenicol was in the branchia of carp and the lowest was in the head of grass carp. The results showed the chloramphenicol in the aquaculture environment was serious, although the government of China had banned the use of chloramphenicol in aquaculture a few years ago.     

The role of aquaculture in human nutrition

Aquaculture, the farming and husbandry of freshwater and marine organisms furnishes about 12% of the food man obtains from the waters of the globe. It is most important in Asia and has grown rapidly in the last decade. The development of aquaculture must rely on control over production sites, in most cases, and on the application of various bio-technical inputs. It dates back to antiquity and has relied on fish and molluscs as its mainstays. Freshwater species predominate among the former but increasing competition for the freshwater resources of the globe indicate that the cultivation of marine species (mariculture) will be of increasing importance. Many species are partly or fully cultured with very few having assumed domesticated, i.e., genetically improved status. The world's tropics with their warmer climate present greater development potential for aquaculture than the temperate zone, a fact that promises to make it especially valuable in policies to improve the diets of developing nations. An overview is given here over species and methods of aquaculture with the latter seen as a continuum having at one pole feedlot types of management with strong control over environmental variables and high inputs, also resulting in high yields, and at the other an approach that could be likened to pasturage. Feeding is not excluded in it but recycling and astute steering of ecological processes are equally if not more important management mechanisms here. Biological and engineering research in aquaculture is being pursued widely. However, pollution, site competition, security of tenure to a site and the like have to be addressed in equal measure for aquaculture to hold its promise of furnishing important quantities of high quality protein food.     

Cyanobacteria in aquaculture systems: linking the occurrence,abundance and toxicity with rising temperatures

The presence of toxic cyanobacteria in aquaculture systems is a matter of concern due to its capability to produce toxin known as microcystin. This study was carried out to determine the presence, abundance and toxic potential of cyanobacteria in selected aquaculture systems in Perak, Malaysia, as well as to identify the potential main trigger of toxic cyanobacterial blooms in aquaculture water. In this study, a total of 40 freshwater fish ponds were sampled from 10 different aquaculture farms in Perak, Malaysia. Results revealed that the most frequently found cyanobacterial taxa in Perak aquaculture water was Microcystis spp., where it was detected in all of the studied ponds. During the sampling period, 75 % of the sampled ponds water contained unsafe levels of microcystin with concentrations up to 295.86 µg MC-LR equivalent L^?1. This study also discovered that a combination of temperature and pH was the key environmental factor that triggered the proliferation and toxicity of cyanobacteria, whereby temperature was statistically proven to be a more powerful predictor in comparison with pH. This study has implied that cyanobacteria can present health risk to human through aquaculture fish consumption. Moreover, the risk posed by cyanobacteria in aquaculture systems will be amplified by the influence of global warming, with rising water temperatures up to 32 °C.     

Impact of aquaculture on eutrophication in Changshou Reservoir

1INTRODUCTION EUTROPHICATIONCANBEUNDERSTOODASAPHENOME NONOFTHEENRICHMENTOFNUTRIENTSINAWATERBODY.THE MOSTIMPORTANTNUTRIENTSTHATCAUSEEUTROPHICATIONARE PHOSPHATES,NITRATESANDAMMONIA(CAIQINGHUA,1993;HORNEANDGOLDMAN,1994).THEMOSTPROMI NENTFEATURESOFEUTROPHICWATERSARETHEHIGHCONTENTS OFNUTRIENTSANDTHEABUNDANCEOFPLANKTONSORATTACHED ALGAE.EUTROPHICATIONISACOMMONPHENOMENO…     

Modeling hydrodynamics and aquaculture waste transport in coastal maine

Net-pen aquaculture results in the introduction of excess fish food and fecal matter in coastal waters. These wastes may modify the benthic environment. Mathematical models are developed in this study to simulate tidal and wind-driven currents, waves, and the resulting dispersion of fish food and fecal matter in coastal Maine, a region where limited modelling studies have been performed. Cobscook Bay and Toothacher Bay in Maine are studied in detail through the use of mathematical models and field data. We find that a systematic, site-specific, step-by-step modeling strategy involving the use of numerical models to simulate the overall hydrodynamic environment in combination with a waste-particle transport model can be an extremely powerful method of determining a priori whether aquaculture operations will cause high rates of net-pen waste accumulation at a particular site.     

Coastal pollution due to increasing nutrient flux in aquaculture sites

The supply of nitrogen and phosphorus in coastal zones through time is reflected in the nutrients’ concentration in the sediment record. Five aquaculture sites in the Philippines were investigated in an effort to establish how long-term changes in land and coastal water use could have led to biogeochemical modifications affecting the coastal ecosystem. Samples from study sites show a narrow concentration range for nitrogen and did not reveal any significant trend through time. In contrast, phosphorus concentrations in most sites start at less than 20 ppm in sediments 30 years and older. The phosphorus value continuously increase in younger sediments, with each site having a different magnitude change as well as timing of when the major increase happened. The uppermost 10 cm, representing the last 15 years in sites with age control, typically show a 2- to 3-fold increase in P load values. Historical increase in nutrient load also coincides with harmful algal bloom events in each area; when effective P input exceeded 130 kg/km² per year. Lastly, the observed increase may be attributed to several factors including physical attributes of the area, urbanization of coastal zones, but most importantly in the proliferation of aquaculture activities.     

江苏如东北部水产养殖区地面沉降现状分析与防控建议

江苏如东北部水产养殖区自规模化运营以来,长期对区内浅部地下水进行集中式开采,区内地下水水位持续下降形成水位漏斗,继而导致地面沉降的发生,是苏北地区典型水产养殖引起的地面沉降区,为全省地面沉降研究新的拓展区和实践区。根据2017—2020年度高精度InSAR监测数据,圈定研究区地面沉降重点沉降区及影响范围,通过39个开采井水位统测数据对比研究,证实区内地下水水位漏斗与地面沉降展布形态和特征具有较好的一致性,科学佐证了地下水开采是研究区地面沉降形成的主要诱因。     

The opportunities for engineering and technology in addressing the environmental,institutional, and economic constraints of marine aquaculture in the United States

Profound changes have taken place in agriculture over the past 50 yr. Science, engineering, and innovation have transformed agriculture from a way of life into a business. Most of these changes occurred during an era when the public took the environment for granted, accepting the practices of agriculture. Aquaculture has entered a similar period of rapid expansion over the last decade; however, the public (and their governments) are now acutely aware of the environment. Aquaculture will face scrutiny unknown during the development of agriculture. Science and technology have opportunities to address the environmental, institutional, and economic constraints associated with marine aquaculture, including the interface between the environment and production, technology to assist with problems of production and environmental impacts, and the pursuit of new options in siting and culturing.     

Multiple step ahead river flow modelling for south east tasmanian aquaculture

We develop multiple step ahead prediction models of river flow for locations in Tasmania (Australia) for decision support in aquaculture. In predicting river flows for multiple days ahead, we first statistically determine the maximum input lags of rainfall and river flow. We then use machine learning techniques in building models. In multiple step ahead prediction, we consider both static and dynamic approaches. In dynamic approach, one day prediction is served as input to two days ahead prediction. The experimental results demonstrate that, in general, a dynamic approach provides better accuracy in multiple day’s ahead prediction. For Duck Bay location using dynamic approach, support vector regression performs best over linear regression, M5P and multilayer perceptron. However, at Montagu Bay location, we find that M5P performs best over methods. We find that multiple step ahead prediction of river flow for each location requires modelling of lags with associated machine learning techniques.     

A multidisciplinary approach to evaluating impacts of shellfish aquaculture on benthic communities

The impact of suspended mussel culture (Mytilus edulis, M. trossulus) on the benthos of a small Nova Scotia cove (7 m depth) was assessed using meehods involving both benthic metabolism and community structure. Due to deposition of mussel feces and pseudofeces, sedimentation rate was higher under the mussel culture lines than at an adjacent reference site of similar sediment texture. Porewater profiles of sediment sulfate and sulfide indicated greater anaerobic metabolism at the mussel site than at the reference site, but sulfide was absent from the upper centimeters of sediments under the mussels. Seasonal measures of sediment oxygen demand showed little change between sites, but maximum rates of ammonium release at the mussel site were twice the highest rates measured at the reference site. Abundance of benthic macrofauna was higher at the reference site, but biomass was generally lower. Biomass at the mussel site was dominated by molluscs (Ilyanassa spp. andNucula tenuisulcata), that were attracted to mussels fallen from the culture and/or enriched organic matter due to biodeposition. Species diversity was lower at the reference site due to the dominance of the polychaeteNephtys neotena. Abundance-biomass comparisons (ABC method) of faunal analysis did not indicate any impact of biodeposition at this site: however, disturbance did not result in a typical assemblage of small opportunistic species anticipated with this method. Cluster analysis of macrofauna usually provided a clear separation between the sites. Since the contruction of a causeway (1968), foraminifera species composition showed a temporal response to temperature changes in the cove by shifting toward calcareous species, but assemblages downcore showed little or no relationship to aquaculture impacts. Although there is a shift toward anaerobic metabolism at the mussel lines, the impact of mussels falling to the sediments was more noticeable in benthic community structure than was any impact due to organic sedimentation or hypoxia. In general the impact of aquaculture on the benthos appeared to be minor. Furtyher assesment of these consequences may mandate both taxonomic and energetic approaches to impact assessment.     

The rôle of aquaculture in the industrial regions of the temperate zone

The prosperous industrial areas of North America and Europe support a diverse and vigorous aquaculture industry. Although climatic restrictions of temperature, photosynthetic energy and exposure may limit the potential, the relatively intensive forms of production of the area are supported by good and expanding market demand. Thus, many forms of production are technically sophisticated. Capital and operating cost levels are generally high and technically difficult. Poorly marketable products are not economically viable. The bulk of production is therefore concentrated on three fish groups: rainbow trout, Atlantic and Pacific salmon, channel catfish, and two mollusc groups: oysters and mussels. The potential for growth and development of the industry is good but is increasingly controlled by market expansion rather than by technical innovation.     

A numerical model for far-field tsunamis and its application to predict damages done to aquaculture

The 1960 Chilean tsunami which traveled the Pacific Ocean and caused much damages to Japan is simulated from its generation to the terminal effects on coastal areas. In the computation of ocean propagation by the linear longwave theory, a new technique is introduced to keep the same accuracy as the linear Boussinesq equation and reduce the CPU time as well as the computer memory. In the coastal transformation computation, the energy dissipation due to sea-bottom scouring is suggested to be included, particularly in the case of long bays. To obtain accurate results, the current velocity requires finer spatial grids than the water surface elevation. Damage done to pearl culture rafts are explained in terms of the computed current velocity.     

Diversity of marine and brackish water nitrite-oxidizing consortia developed for activating nitrifying bioreactors in aquaculture

Nitrite is a well-known toxicant in aquaculture, produced as intermediate in nitrification. Two nitrite-oxidizing bacterial consortia, one from marine environment and the other from brackish water, were developed by enrichment technique at National Centre for Aquatic Animal Health, for removal of nitrite from recirculating aquaculture systems. In the present study, bacterial diversity of the consortia was assessed based on 16S ribosomal RNA and the functional gene analysis. Clone libraries of 16S ribosomal RNA gene and nitrite oxidoreductase A gene were constructed, and amplified ribosomal DNA restriction analysis was carried out to cluster the clones. Dendrograms generated through molecular characterization showed 29 and 27 clusters in marine and brackish water consortia, respectively. Phylogenetic analyses of representative clones from each cluster depicted profound diversity in the consortia consisting autotrophic nitrifiers belonging to Proteobacteria, anaerobic ammonia oxidizers, Actinobacteria, Bacteroidetes and heterotrophic denitrifiers. Functional gene analysis corroborated with the presence of specific nitrite oxidizers. Quantitative polymerase chain reaction showed the abundance of nitrite oxidizers in the order of 1.51 ± 0.38 × 10⁹/g and 4.88 ± 0.42 × 10⁷/g in marine and brackish water consortia, respectively. Diversity indices and pattern of distribution of organisms within the consortia were analyzed using Geneious, VITCOMIC, Mega 5 and Primer software. The marine nitrite-oxidizing consortium showed higher Shannon–Wiener diversity and mean population diversity than brackish water consortium, suggesting that the former was having more diverse flora and higher potential to be used as startup cultures for activating nitrifying bioreactors subsequent to acclimatization to the required salinity.     

Influence of intertidal aquaculture on benthic communities in Pacific Northwest estuaries: Scales of disturbance

We reviewed the scale and intensity of disturbance, and the response of benthic and epibenthic communities, to intertidal aquaculture activities in Pacific Northwest estuaries. Available data indicate a spectrum of influences on the ability of estuaries to sustain biota unrelated to the cultured species. Certain disturbances, such as adding gravel to mudflats and sandflats to enhance clam production, may subtly impact certain benthic and epibenthic invertebrates without changing the carrying capacity for estuarine-dependent taxa, such as juvenile Pacific salmon (Oncorhynchus spp.). However, habitat shifts might alter the relative suitability for different salmon species. In contrast, acute disturbances that produce large-scale changes in community dominants, such as manipulation of burrowing shrimp or eelgrass with pesticides or mechanical harvesting and manipulation of oyster grounds, strongly influence the carrying capacity for many fish and macroinvertebrates. Ensuring that estuarine ecosystems are sustainable for the breadth of processes and resources requires a comprehensive assessment of both natural and anthropogenic disturbance regimes, landscape influences, and the effects of local management for particular species on other resources.     

电解脱氮除磷技术在海产养殖废水治理中的研究

海产养殖迅速发展造成水域富营养化、赤潮频发,海产养殖废水污染的治理迫在眉睫。为解决此问题将电解脱氮除磷技术应用在海产养殖废水处理中,并探讨电压、pH、极板间距和电解时间对脱氮除磷去除率的影响。结果表明:脱氮除磷的去除率与电压成正相关,与极板间距成负相关。在电压为30V,极板间距10cm,pH为7时,NH_4~+-N、NO_3~--N和TP的去除率达到最大分别为72%、90%、85%。