Aquaculture Zone Research Articles

Introduced Pacific oysters Crassostrea gigas in South Africa: demographic change, genetic diversity and body condition

Successful aquaculture species are often chosen for their fast growth rates and fecundity, which are also characteristics of invasive species. The Pacific oyster Crassostrea gigas, which constitutes 80% of global oyster trade, has been confirmed as invasive in 17 of the 66 countries where it is cultured. The single study of its status in South Africa reported populations in six South Coast estuaries in 2001, dropping to three sites in 2003. We resurveyed these estuaries, visited others in the Eastern and Western Cape provinces, and sampled oyster tissue for molecular analyses of population structure. Pacific oysters have disappeared from Knysna and, following our collections, possibly also from the GouKou Estuary. Between 2003 and 2012, the Breede Estuary population decreased by 87%, from an estimated 184 206 to 23 760 individuals. Within this estuary, oysters 12 km upriver had denser shells and higher body condition indices than did those within 1.4 km of the river mouth, presumably reflecting higher availability of suspended organic matter. However, low salinity over most of the species’ range in the estuary probably inhibits recruitment. New populations of Pacific oysters in the Swartkops and Kaaimans estuaries urgently require monitoring and eradication. Haplotype (h) and nucleotide (π) diversities across all oyster populations sampled (h = 0.2300 [SD 0.0595], π = 0.0006 [SD 0.0007]) were lower than those of co-occurring indigenous Cape rock oysters Striostrea margaritacea from the GouKou and Breede estuaries (h = 0.9076 [SD 0.0386], π = 0.00589 [SD 0.00347]). Pacific oysters either have been introduced to South African estuaries infrequently, or have experienced genetic bottlenecks following river floods or human exploitation, or both. Populations growing outside culture infrastructure are restricted to estuaries in the Eastern and Western Cape provinces, with no evidence of occurrence in fully marine shelf environments. Given the species’ considerable socio-economic importance, estuarine and coastal surveillance coupled with aquaculture zoning are required to integrate biodiversity and food security considerations.

Social Status of the Fish-farmers of Floating-net-cages in Lake Maninjau, Indonesia

The study surveyed the social status of fish-farming in Lake Maninjau of Indonesia. The stuctured interview using scheduled questionnaires were used in obtaining information from 240 fish farmers randomly selested from eight local sub-districts as the study areas. The eighth sub-districts were divided into three areas which involved the aquaculture zone of the lake. Data obtained were analyzed using descriptive statistics. The findings revealed that majority (39.16%) of the fish farmers were male with the age range of 31-40 years. It was about 55.41% of the fish farmer having household size 4-6 person, and 45.83% educational level was Senior High School graduates. The total annual income from sales of fish were IDR 10000000-IDR 20000000, 37.92% of fish farmers practiced the integrated fish-farming, and only 52.08% of the farmers practiced fish-production. 51.25% of the fish farmers got their information from their friends and fellow farmers. 73.33% of the fish farmers cultured Tilapia species, 77.91% of the fish farmers obtained their fingerlings from private hatchery, 96.66% of fish farmers stated that poor water quality as a major constraints to fish production. The results indicated that floating net-cages activities at the Lake Maninjau played essential role in the lives of fish-farmers for survival.

SWOT Analysis and Countermeasures of Ecological Agricultural Development of Jianshan Farm

At present, the excessive use of the fertilizers and pesticides in the agricultural production has result in hardening of the soil and decrease of the wild animals and can not maintain the sustainable using of land resources. To develop ecological agriculture is a powerful measure to reduce energy consumption, protect environment, and realize the sustainable development of the agriculture. In order to promote the sustainable development of agriculture in Jianshan Farm, this paper by using SWOT analysis method analyzed the strength, weakness, opportunity and threat in the development of the ecological agriculture in Jianshan Farm, based on the experience from domestic and foreign ecological agricultural development, and put forward the countermeasures for the development of the ecological agriculture in order to develop ecological circular agriculture and non-genetic soybean crop protected areas, and to establish soybean-corn rotation area and healthy aquaculture zone, as well as develop new energy industry.

Phosphorus, organic matter and nitrogen distribution characteristics of the surface sediments in Nansi Lake, China

Nansi Lake is the largest and most important freshwater reservoir for the South-North Water Diversion Project located in Shandong Province, China. The characteristics of the nutrient compositions and distribution in the lake sediment may significantly influence the upper-level water quality, which has not been well studied. In this study, the distribution characteristics of the total phosphorus (TP), total organic matter (OM) and total nitrogen (TN) contents in the shallow sediments of Nansi Lake were investigated. The experimental results showed that the sedimentary TP, OM, and TN levels of the entire Nansi Lake (expressed as dry weight percentage) were (0.030 ± 0.003)–(0.129 ± 0.018) %, (1.14 ± 0.18)–(10.60 ± 1.30) % and (0.105 ± 0.021)–(0.71 ± 0.08) %, respectively. The three nutrient indicators appeared to be higher in the upstream lake than in the downstream lake. Concentrations of TN and OM were both particularly higher in aquaculture zones of Nansi Lake, where excessive fish feed may largely contribute to the high TN and OM in the sediment. Furthermore, there was a significantly positive correlation (n = 28, R 2 = 0.7870) between TN and OM. According to the pollution index (P i ) and enrichment factor, there is moderate enrichment of TN and OM in the sediment, while minor enrichment of TP in Nansi Lake. Calculations of the OM index and organic nitrogen index suggested that the surface sediment of the entire Nansi Lake has been contaminated by OM and organic nitrogen. Therefore, there is a pressing need to further investigate the release characteristics of these nutrient contaminants from the sediment of Nansi Lake and potential impacts on the surface water quality.

Lipophilic shellfish toxins in Dinophysis caudata picked cells and in shellfish from the East China Sea

We reported previously that okadaic acid (OA) and dinophysistoxin-1 (DTX1) were responsible for diarrhetic shellfish poisoning (DSP) incidents due to consuming cultivated mussels (Mytilus galloprovincialis) in coastal cities near the East China Sea in May 2011. Pectenotoxin-2 (PTX2) and its seco acids were also present in these mussels. Causative species of microalgae were not identified because detailed information on the location of the contaminated shellfish was not recorded. In order to explore potential causes for these poisoning events, the lipophilic toxin profiles in picked cells of Dinophysis and in shellfish samples collected from two mariculture zones in the East China Sea were analyzed in the present study. Single-cell isolates (100 cells total for each location) of Dinophysis were collected from the aquaculture zones of Gouqi Island (Ningbo City, Zhejiang Province) and Qingchuan Bay (Ningde City, Fujian Province) in July and September 2013, respectively, for lipophilic toxin profiling. Shellfish samples collected over the course of a year from the Gouqi Island aquaculture zone and mussels (M. galloprovincialis) collected four times from the Qingchuan Bay aquaculture zone were tested for lipophilic toxins by LC-MS/MS. The Dinophysis cells isolated from both sampling sites were identified under the light microscope as Dinophysis caudata. Average quota of PTX2, the predominant toxin in D. caudata isolated from the coastal waters of Gouqi Island and Qingchuan Bay, was 0.58 and 2.8 pg/cell, respectively. Only trace amounts of OA and DTX1 were detected in D. caudata. PTX2, PTX2sa, 7-epi-PTX2sa, OA, and/or DTX1 were found in samples of mussels (M. galloprovincialis and Mytilus coruscus) collected in the Gouqi Island aquaculture zone from the end of May to the beginning of July 2013. PTX2, PTX2sa, and 7-epi-PTX2sa were also detected in oyster (Crassostrea gigas) during that period, but almost no OA and DTX1 were present. Gymnodimine (GYM) was detected in almost all mussel (M. coruscus) samples, with the highest levels occurring in winter. Trace amounts of pectenotoxins (PTXs) and OAs were also found in mussels (M. galloprovincialis) collected from Qingchuan Bay. D. caudata is suggested as an important source of PTXs in shellfish cultivated in the East China Sea. This is the first report of toxin profiles for single-cell isolates of Dinophysis in the East China Sea.

Factors affecting the abundance of Caligus rogercresseyi (Boxshall and Bravo) on farmed salmonids in Chile in the period 2006–2007

An epidemiological study was carried out in the period 2006–2007 to identify the factors that affected the abundance of Caligus rogercresseyi in the two susceptible salmonid species reared in Chile, rainbow trout (Oncorhynchus mykiss) and Atlantic salmon (Salmo salar). The differences recorded between four aquaculture zones were mainly a consequence of the geographical and oceanographic characteristics of each location. The values of abundance were significantly influenced by the environmental variable salinity, temperature and water transparency. In addition, the stocking density, the season of year, level of exposure, depth of water at the farm and cage location, were important variables influencing the abundance of sea lice. No significant differences in sea lice abundance were recorded between rainbow trout and Atlantic salmon.

Harbour dredging and fish mortality in an aquaculture zone: assessment of changes in suspended particulate matter using multi-sensor remote-sensing data

The semi-closed Rushan Bay is one of the largest aquaculture bases in North China, with its only navigation channel connecting the Rushan harbour and the Yellow Sea. Recent economic growth with increased import and export demands have stimulated a dredging operation, starting on 26 March 2010, which was paused on 17 June 2010 after numerous reports of mortality of cultured shellfish, such as clam (Ruditapes philippinarum), among other precious marine animals. A lawsuit was filed to settle the dispute between the dredging company and an aquaculture company, yet there was endless debate on whether the mortality was caused by the dredging operations. Here, using multi-sensor remote-sensing data collected by Landsat/ETM+, HJ-1A&1 B/CCD, and Aqua & Terra/MODIS, we addressed the two critical questions of (1) whether there was a significant increase in the suspended particulate matter (SPM) in the aquaculture area during and after the dredging operations; and (2) if the answer is yes, whether such an increase was a direct result of the dredging. After careful selection of the satellite data and algorithms, the results from all three sensors suggested positive answers to both questions. In the 2 km2 aquaculture zone where significant mortality of cultured clam was reported, SPM derived from all three sensors during the dredging period was found to be at least 20 mg l–1 higher than that during the same period in previous years, far exceeding the 10 mg l–1 threshold value that has been used to gauge water quality degradation.

Coastal surface sediment quality assessment in Leizhou Peninsula (South China Sea) based on SEM–AVS analysis

Surface sediments from the coastal area of the Leizhou Peninsula in the South China Sea were collected and analyzed and the potential ecological risks in the area were assessed based on acid-volatile sulfide (AVS) model. The AVS levels are between 0.109 and 55.6μmolg−1, with the average at 4.45μmolg−1. The high AVS-concentration zones include the aquaculture areas of Liusha Bay and the densely populated areas of Zhanjiang Bay. The simultaneously extracted metals (SEM) range from 0.026μmolg−1 to 8.61μmolg–1, with the average at 0.843μmolg–1. Most of high SEM-concentration stations were located in ports or aquaculture zones. Most of the coastal surface sediments of the Leizhou Peninsula (90%) had no adverse biological effects according to the criterion proposed by USEPA (2005); while adverse effects were uncertain in some stations (8%); even in 2 stations (2%) adverse biological effects may be expected.

Understanding the spatio-temporal variability of phytoplankton biomass distribution in a microtidal Mediterranean estuary

Understanding the spatio-temporal variability of phytoplankton in aquaculture zones is necessary for the prevention and/or prediction of harmful algal bloom events. Synoptic cruises, time series analyses of physical and biological parameters, and 3D modeling were combined to investigate the variability of phytoplankton biomass in Alfacs Bay at basin scale. This microtidal estuary located in the NW Mediterranean is an important area of shellfish and finfish exploitation, which is regularly affected by toxic outbreaks. Observations showed the existence of a preferential phytoplankton accumulation area on the NE interior of the bay. This pattern can be observed throughout the year, and we show that it is directly linked to the physical forcing in the bay, in particular, the interplay between freshwater input and wind-induced turbulence. Both drivers affect the strength of the estuarine circulation, explaining nearly 75% of the variability in phytoplankton biomass. More cells are retained when stratification is weakened and the estuarine circulation reduced, while flushing rates are higher during times of increased stratification and stronger estuarine flow. This has been confirmed by using a 3D hydrodynamic model with Eulerian tracers. Nutrients, while important to support phytoplankton populations, have been found to play only a secondary role in explaining this variability at basin scale.

基于GIS的虾夷扇贝养殖适宜性综合评价——以北黄海大小长山岛为例

由于水产养殖缺乏科学空间规划，近年来中国最大的虾夷扇贝（<em>Patinopecten yessoensis</em>）养殖基地长山群岛发生了扇贝大规模死亡现象。当地渔业主管部门急需水产养殖空间格局优化的技术手段和科学依据。采用叶绿素a浓度、海水表面温度、水深、透明度以及评价单元到渔港、城镇、旅游区和自然保护区的距离等指标，构建了虾夷扇贝养殖适宜性评价模型，并以大小长山岛海域为示范区，对该海域的虾夷扇贝的养殖适宜性进行了空间分析。结果表明：大小长山岛海域虾夷扇贝养殖适宜性较高且具有较大的空间变异，在不考虑海域使用冲突情形下，养殖适宜性指数在6.0-7.0以及7.0以上的海域占示范区的面积比例分别为26.04%（167.75 km²）和4.73%（44.06 km²），且高适宜性（SSI > 7.0）区主要分布在大长山岛西北和西南海域；而由于航道和水产养殖存在海域使用冲突，高适宜区面积大幅下降为19.56 km²。在此基础上对大小长山岛海域虾夷扇贝养殖空间格局优化提出了建议。利用一些简单的距离指标反映了陆地基础设施因素对水产养殖选址的影响，体现了海陆统筹的理念并可为海陆统筹技术方法研究提供重要借鉴。;Changshan archipelago in North Yellow Sea, the biggest base for Japanese scallop aquaculture in China, has recently experienced a series of problems including large-scale scallop death, environmental degradation and sea use conflicts. Most of them are attributed to the shortage of scientific spatial planning for Japanese scallop aquaculture and the subsequent over-density issue to great extent. The local government and farmers are in urgent need of the technology and scientific foundation for spatial adjustment and optimization of current scallop aquaculture. It is widely accepted that the definition and characterization of suitable aquaculture zones is pivotal for the success and sustainable development of aquaculture, GIS based suitability studies for aquaculture site selection, however, are surprisingly very rare in China. With the islands of Dachangshan and Xiaochangshan (IDX) as a case, a GIS-based aquaculture site suitability index (SSI) model was used in the spatial suitability analysis of Japanese scallop aquaculture. The distances to towns, biological conservation zones, island tourism zones, fishery harbors and navigation lines in addition to SST, bathymetry, water transparency, Chl a were used as criteria or parameters for site selection, which were selected according to the current sea uses and ecological issues of concern in IDX and the requirements of Japanese scallop for environments as well. Field surveyed data were used to obtain the parameters for Chl a and water transparency whereas the other parameters were extracted from basic geospatial vector data or raster data(only ocean color SST here) for the study area to produce thematic layers in the form of raster by means of distance tool or interpolation tool in ArcGIS 10. All data were re-sampled or interpolated to the same resolution of 250 meters and a suitability score for each criterion was established using a scoring system from 1 to 8, with 8 being the most suitable and 1 being the least suitable for developing scallop culture. To make full use of the expertise and research results of foreign scientists in this field, the weights and scoring system for these parameters were mainly determined according to relevant references and slightly adjusted based on the opinions of local aquaculture experts and farmers. After that, a site suitability index model based on a liner weighted combination of suitability score for each parameter was used to calculate the site suitability index (SSI) for each assessment unit(pixel here). Due to the sea use conflicts between scallop aquaculture and navigation, biological conservation and island recreation, some water areas cannot be used as scallop aquaculture sites and form spatial constraints. Given that the issue of sea use conflicts is a big concern in marine aquaculture site selection, the spatial and areal distribution of SSI for IDX were analyzed both in the scenarios of no spatial constraints and spatial constraints, on which basis aquaculture structure optimization plan for IDX was proposed in this paper. The results showed that IDX were fairly suitable for Japanese scallop aquaculture and of big spatial variation. 32.06% of the potential water area (211.81 km²) had suitability index bigger than 6.0 in the scenario of no spatial constraints. The highly suitable sites with SSI above 7 (accounting for 4.73% of the potential water area) were mainly distributed to the northwest and southwest of Dachangshan Island with an area of 44.06 km². In addition, it was found that the spatial constrains mainly resulted from the sea use conflict between aquaculture and marine navigation, which made the area of highly suitable level (SSI > 7.0) drop from 44.06 km² to 19.56 km². The adjustment of navigation line can improve the potential of scallop aquaculture potential greatly. In this paper, the impact of scallop aquaculture on nature reserve of wild fishery species was considered in the scallop site suitability model, highlighting the concern of biodiversity conservation. Besides, the role of land based social-infrastructure resources such as fishery harbors and towns in site selection reflected the thought of land-ocean overall planning. In the end, advice on the spatial pattern adjustment of Japanese scallop aquaculture in IDX was given based on the aquaculture site suitability analysis. The results are expected to provide an important scientific foundation for spatial structure optimization of Japanese scallop aquaculture in IDX whereas the methodology can be used as an important reference for the spatial pattern adjustment of marine aquaculture in China.

Larval growth response of the Portuguese oyster (Crassostrea angulata) to multiple climate change stressors

Rising anthropogenic carbon dioxide (CO2) dissolving into coastal waters is decreasing the pH and carbonate ion concentration, thereby lowering the saturation state of calcium carbonate (CaCO3) minerals through a process named ocean acidification (OA). The unprecedented threats posed by such low pH on calcifying larvae of several edible oyster species have not yet been fully explored. Effects of low pH (7.9, 7.6, 7.4) on the early growth phase of Portuguese oyster (Crassostrea angulata) veliger larvae was examined at ambient salinity (34ppt) and the low-salinity (27ppt) treatment. Additionally, the combined effect of pH (8.1, 7.6), salinity (24 and 34ppt) and temperature (24°C and 30°C) was examined using factorial experimental design. Surprisingly, the early growth phase from hatching to 5-day-old veliger stage showed high tolerance to pH 7.9 and pH 7.6 at both 34ppt and 27ppt. Larval shell area was significantly smaller at pH 7.4 only in low-salinity. In the 3-factor experiment, shell area was affected by salinity and the interaction between salinity and temperature but not by other combinations. Larvae produced the largest shell at the elevated temperature in low-salinity, regardless of pH. Thus the growth of the Portuguese oyster larvae appears to be robust to near-future pH level (>7.6) when combined with projected elevated temperature and low-salinity in the coastal aquaculture zones of South China Sea.

Potential Influence of Climate Change on Shellfish Aquaculture System in the Temperate Region

Aquaculture is challenged by a number of constraints with future efforts towards sustainable production. Global climate change has a potential damage to the sustainability by changing environmental surroundings unfavorably. The damaging parameters identified are water temperature, sea level, surface physical energy, precipitation, solar radiation, ocean acidification, and so on. Of them, temperature, mostly temperature elevation, occupies significant concern among marine ecologists and aquaculturists. Ocean acidification particularly draws shellfish aquaculturists' attention as it alters the marine chemistry, shifting the equilibrium towards more dissolved CO2 and hydrogen ions (<TEX>$H^+$</TEX>) and thus influencing signaling pathways on shell formation, immune system, and other biological processes. Temperature elevation by climate change is of double-sidedness: it can be an opportunistic parameter besides being a generally known damaging parameter in aquaculture. It can provide better environments for faster and longer growth for aquaculture species. It is also somehow advantageous for alleviation of aquaculture expansion pressure in a given location by opening a gate for new species and aquaculture zone expansion northward in the northern hemisphere, otherwise unavailable due to temperature limit. But in the science of climate change, the ways of influence on aquaculture are complex and ambiguous, and hence are still hard to identify and quantify. At the same time considerable parts of our knowledge on climate change effects on aquaculture are from the estimates from data of fisheries and agriculture. The consequences may be different from what they really are, particularly in the temperature region. In reality, bivalves and tunicates hung or caged in the longline system are often exposed to temperatures higher than those they encounter in nature, locally driving the farmed shellfish into an upper tolerable temperature extreme. We review recent climate change and following environment changes which can be factors or potential factors affecting shellfish aquaculture production in the temperate region.

Characterisation of the wave field and associated risk of sediment resuspension in a coastal aquaculture zone

The interaction between extreme environmental events and the marine aquaculture industry has, in the past, led to substantial economic losses for the industry. In 1996, the aquaculture industry based near Port Lincoln in South Australia experienced a sediment resuspension event linked to the passage of a vigorous ex-tropical cyclone. A key process that drives the sediment dynamics in coastal environments is the physical forcing due to surface gravity waves. The numerical model Simulating WAves Nearshore (SWAN) has been applied to hindcast two years of wave fields for the central South Australian coastline and is validated against five datasets, using both in-situ observations and satellite derived wave heights. Using the calibrated model, we investigate the spatial variability in the relative contribution of locally generated wind waves versus incoming swell to the mean wave energy budget. The potential for sediment resuspension is then assessed using theoretical thresholds for the initiation of sediment resuspension which are derived using the Shields parameter and observed sediment grain size. Linear wave theory in conjunction with the model hindcast is used to identify the conditions that could lead to a sediment resuspension event. Incoming swell from the Southern Ocean poses the greatest risk of a sediment resuspension event, while locally generated wind waves are only able to resuspend sediments in the shallow near shore regions. We have developed a simple tool that will allow policy makers and farm managers to identify the likely combination of significant wave height and mean wave period for a particular depth, that is likely to result in the mobilisation of unconsolidated particulate matter on the seafloor.

Soil organic carbon content and storage of raised field wetlands in different functional zones of a typical shallow freshwater lake, China

Soil samples were collected in raised-field wetlands of five typical functional zones (inlet zone, water reserve zone, outlet zone, aquaculture zone, industrial zone) in Baiyangdian Lake, China, from a depth of 0–30 cm. The soil organic carbon (SOC) content, density, and storage, and carbon pool index (CPI) were calculated for each typical zone, and spatial distribution of SOC storage in the region was estimated using the ordinary kriging, interpolated value method. Our results showed that the average values of SOC content and storage decreased with depth along the soil profiles. Lowest values of SOC content and storage were observed in the inlet zone, whereas the outlet zone showed the highest SOC content and the water reserve zone showed the highest SOC storage. Surface soils had higher heterogeneity with higher values of SOC content and storage than deeper soils. Storage of SOC was much lower in the south-east of the water reserve zone and the east of the inlet zone than in the north-west of the water reserve zone or in the east of the whole Baiyangdian Lake. Values of CPI followed the order water reserve zone &gt; aquaculture zone &gt; outlet zone &gt; industrial zone &gt; inlet zone. The SOC was positively correlated with water content and negatively correlated with soil bulk density (P &lt; 0.01), but had no significant correlation with other soil properties.

Genetic diversity and species identification ofArgulusparasites collected from major aquaculture regions of India using RAPD-PCR

Argulus is one of the most important fish parasites that cause heavy economic loss to aquaculture industry. The present investigation was undertaken to study the genetic diversity of the Argulus sp. collected from 13 locations representing major aquaculture zones in India by RAPD analysis and to develop species-specific markers. Thirteen random decamer primers were used to amplify DNA fragments from three individual parasites of each location. Of the 172 bands scored by the primers, 168 were polymorphic. The per cent polymorphic loci and gene diversity values varied within a range of 8.14–43.02 and 0.0342–0.1727 respectively. Nei's genetic similarity between populations across all the primers ranged from 0.363 to 0.969. The dendrogram based on Nei's genetic distance showed two clusters; Bangalore and Mandi populations forming one cluster, and the rest in another cluster. The clusters also revealed strong correlation with the species identified as A. japonicus and A. siamensis respectively by morphological method. The study thus indicated A. siamensis as the major prevalent species in carp culture farms in India. Species-specific primers were designed from unique sequences cloned from RAPD fragments that could able to identify A. siamensis and A. japonicus separately.

Persistent halogenated compounds in two typical marine aquaculture zones of South China

Samples of two seawater farmed fish (crimson snapper (Lutjanus erythopterus) and snubnose pompano (Trachinotus blochii)), water, air, sediment, fish feed, macroalgae and phytoplankton were collected from two estuarine bays (Daya Bay and Hailing Bay) in South China. The concentrations of persistent halogenated compounds (PHCs) including polybrominated diphenyl ethers (PBDEs), organochlorine pesticides and polychlorinated biphenyls (PCBs) varied widely with the different sample matrices under investigation. The compositional patterns in fish, fish feed, macroalgae and phytoplankton, as well as the good correlations between the abundances of p,p′-DDT and BDE-209 and their metabolites (i.e., p,p′-DDD and p,p′-DDE for p,p′-DDT and BDE-47 for BDE-209) in fish indicated the occurrence of DDT and PBDE biotransformation in fish body. Finally, the marine aquaculture environment in South China is somewhat biologically impaired by DDT-contaminated water, sediment and fish feed, and there may be some cancer risk associated with fish consumption for humans, especially for urban residents.

A comparison of primer sets for detecting 16S rRNA and hydrazine oxidoreductase genes of anaerobic ammonium-oxidizing bacteria in marine sediments

Published polymerase chain reaction primer sets for detecting the genes encoding 16S rRNA gene and hydrazine oxidoreductase (hzo) in anammox bacteria were compared by using the same coastal marine sediment samples. While four previously reported primer sets developed to detect the 16S rRNA gene showed varying specificities between 12% and 77%, an optimized primer combination resulted in up to 98% specificity, and the recovered anammox 16S rRNA gene sequences were >95% sequence identical to published sequences from anammox bacteria in the Candidatus "Scalindua" group. Furthermore, four primer sets used in detecting the hzo gene of anammox bacteria were highly specific (up to 92%) and efficient, and the newly designed primer set in this study amplified longer hzo gene segments suitable for phylogenetic analysis. The optimized primer set for the 16S rRNA gene and the newly designed primer set for the hzo gene were successfully applied to identify anammox bacteria from marine sediments of aquaculture zone, coastal wetland, and deep ocean where the three ecosystems form a gradient of anthropogenic impact. Results indicated a broad distribution of anammox bacteria with high niche-specific community structure within each marine ecosystem.

Wave energy potential in Galicia (NW Spain)

Wave power presents significant advantages with regard to other CO 2-free energy sources, among which the predictability, high load factor and low visual and environmental impact stand out. Galicia, facing the Atlantic on the north-western corner of the Iberian Peninsula, is subjected to a very harsh wave climate; in this work its potential for energy production is assessed based on three-hourly data from a third generation ocean wave model (WAM) covering the period 1996–2005. Taking into account the results of this assessment along with other relevant considerations such as the location of ports, navigation routes, and fishing and aquaculture zones, an area is selected for wave energy exploitation. The transformation of the offshore wave field as it propagates into this area is computed by means of a nearshore wave model (SWAN) in order to select the optimum locations for a wave farm. Two zones emerge as those with the highest potential for wave energy exploitation. The large modifications in the available wave power resulting from relatively small changes of position are made apparent in the process.

Integrated Sediment Habitat Mapping for Aquaculture Zoning

Integrated Sediment Habitat Mapping for Aquaculture Zoning

Response of demersal fish communities to the presence of fish farms

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 288:241-250 (2005) - doi:10.3354/meps288241 Response of demersal fish communitiesto the presence of fish farms A. Machias1,*, I. Karakassis2, M. Giannoulaki1, K. N. Papadopoulou1, C. J. Smith1,S. Somarakis3 1Hellenic Centre of Marine Research, PO Box 2214, 71003 Iraklion, Crete, Greece2Department of Biology, University of Crete, PO Box 2208, 41409 Iraklion, Crete, Greece3Department of Biology, University of Patras, 26500 Patras, Greece *Email: amachias@her.hcmr.gr ABSTRACT: The hypothesis that the presence of fish farms affects the communities of wild fish at large spatial scales was investigated through experimental trawl surveys. Three regions of the Aegean Sea with aquaculture zones were sampled in May and September (reproductive and recruitment periods, respectively for most species in the Aegean Sea). In each region, 2 sub-areas were sampled: 1 located nearby the fish farming zones (within 2 to 3 n mile) and a similar site (‘reference site’) far away from these zones (>20 n mile). Three replicate hauls were made in each sub-area for each of the 3 investigated regions. Significant differences were observed in community structure between farming and reference sites, which were mainly due to quantitative rather than qualitative aspects. The overall abundance and/or biomass of wild demersal fish was significantly higher near the fish farms in every region studied during May without any significant change in diversity or biodiversity. During the recruitment period in September, total abundance and biomass were fairly similar. These findings support the hypothesis that the presence of fish farms affects the wild fish populations in the oligotrophic eastern Mediterranean at a spatial scale larger than the immediate vicinity of fish cages. It seems that during the recruitment period all sites were stocked with fish close to the carrying capacity of the respective areas, and by late spring the areas close to fish farming zones had suffered little losses during winter, whereas populations at the reference sites had decreased substantially. KEY WORDS: Fish communities · Fisheries · Aquaculture · Mediterranean Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 288. Online publication date: March 10, 2005 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2005 Inter-Research.