防城港市红沙养殖区营养盐状况分析与评价

根据2007年6～9月和2008年6～10月6个航次的监测资料,分析了红沙养殖区海域水质变化特征,并对PO4-P、SiO3-Si、DIN、pH值、盐度、DO、COD和叶绿素a等进行了分析,对该海域进行了富营养化评价及有机污染评价。结果表明,该海域营养盐随月份呈现不同的变化规律。从营养结构看,与Redfield值比较,符合P限制条件;根据富营养化评价,红沙养殖区海域营养指数秋季较低,而夏季较高,属富营养化状态;有机污染评价的结果显示,红沙养殖区海域属于水质开始受污染类型。     

Employment of Marine Polysaccharides to Manufacture Functional Biocomposites for Aquaculture Feeding Applications

In this study, polysaccharides of marine origin (agar, alginate and κ-carrageenan) were used to embed nutrients to fabricate biocomposites to be employed in animal feeding. The consistency of biocomposites in water has been evaluated up to 14 days, by several methods: swelling, nutrient release and granulometric analysis. Biocomposites were produced with varying percentages of nutrients (5%–25%) and polysaccharides (1%–2%–3%). All possible biopolymer combinations were tested in order to select those with the best network strength. The best performing biocomposites were those manufactured with agar 2% and nutrients 10%, showing the lowest percentage of water absorption and nutrient release. Biocomposites made of agar 2% and nutrients 10% were the most stable in water and were therefore used to analyze their behavior in water with respect to the release of quercetin, a phenolic compound with demonstrated high antibacterial and antioxidant activities. The leaching of such molecules in water was therefore employed as a further indicator of biocomposite water stability. Altogether, our results confirm the suitability of agar as a binder for biocomposites and provide a positive contribution to aquaculture.     

Growth variations within a farm of mussel (Mytilus galloprovincialis) held near fish cages: importance for the implementation of integrated aquaculture

Fish farming releases extensive amounts of particulate organic waste that can be exploited by bivalves in integrated culture. We tested if mussels Mytilus galloprovincialis cultured at two depths (1 and 6 m) in a raft, moored 170 m from a fish farm had greater growth than bivalves held 550 m from the fish cages. Mussel growth was monitored monthly, covering the second phase of the culture, from thinning‐out to harvest (March to November 2011). We also studied if fish solid and dissolved nutrients increased the organic content of the seston and chlorophyll‐a levels near the fish cages through weekly samples. Results showed no differences in seston, chlorophyll and physiochemical characteristics of the water among rafts. Maximum growth and Condition Index (CI) occurred during spring–summer (April–August), when mussels had access to greater food quality and quantity. Mussels cultivated close to the cages showed similar shell length, weight and CI compared with mussels distant from the fish farm. Average shell length, meat dry weight and CI at harvest were 76.31 mm, 2.51 g and 23%. Bivalves cultured distant from the fish cages displayed 26% higher biomass than the other raft at the end of the experiment. Differences in biomass were explained by the significantly higher recruitment of mussel seed observed at the raft distant from the fish cages from June to November. The lack of a significant enhancement in growth of the bivalves cultured next to finfish is discussed.     

Influence of temperature on yolk resorption in common snook Centropomus undecimalis (Bloch, 1792) larvae

To determine the optimal rearing temperature for Centropomus undecimalis larvae during the yolk resorption period, changes in larval development were measured at four different temperatures (23, 25, 28 and 31°C). Yolk and oil‐globule volume was recorded for 25 larvae at four different times. This involved an initial measurement at hatch and at 24, 48 and 72 h posthatch (hph). Additional morphological measurements included standard length, body height and eye diameter. On average, at the end of the three trials, larvae reared at 25°C had a longer mean standard length than larvae reared at 23, 28 and 31°C. Larvae reared at 25°C also had more yolk and oil globule reserves than larvae raised at 28 and 31°C. The body height:length residuals were also the highest at 25°C (i.e. larvae had deeper or stockier bodies). The yolk sac was present up to 72 hph at 23 and 25°C, while it was entirely consumed after 48 hph in larvae held at 28 and 31°C. Larvae showed the fastest growth during the first 24 hph in all temperature treatments; this period corresponded to the highest energy consumption as determined by the decrease in yolk sac and oil‐globule volume. Eye diameter did not vary significantly with time during yolk‐resorption. We conclude that a temperature near 25°C is optimal for raising snook larvae during the yolk‐resorption period.     

The effectiveness of several commercial antifouling treatments at reducing biofouling on finfish aquaculture cages in British Columbia

Biofouling in finfish aquaculture is an important issue because copper based antifoulants contribute to marine pollution and biofouling management incurs heavy costs to the industry. The purpose of this study was to assess the effectiveness five treatments (non‐biocidal: Dyneema, Netpolish, Aquacoating and ThornD; biocidal using cuprous oxide: Netrex) as compared with an untreated nylon net. After 8 months, effectiveness was determined by quantifying changes in: per cent net occlusion, per cent cover of major fouling groups, and biomass. Only one non‐biocidal treatment performed better than the control in one performance index (Dyneema had lower biomass), and overall, the copper treatment was most effective. The results from this study demonstrated that the effectiveness of copper treatments will continue to be a barrier to the implementation of non‐biocidal antifoulants, and that more research is needed to develop effective, non‐biocidal antifoulant coatings for aquaculture operations.     

Greening the blue revolution of small‐scale freshwater aquaculture in Mymensingh,Bangladesh

Rapid development of small‐scale freshwater aquaculture in the Mymensingh district of north‐central Bangladesh has been linked to a ‘blue revolution’. Mymensingh is ranked first among districts of pond fish production in Bangladesh. Aquaculture in Mymensingh plays an important role in the local economy, contributing to food production, livelihood opportunities, income generation, poverty alleviation and social transformation. However, a number of challenges, particularly social, economic and environmental issues, will need to be overcome to translate its benefits effectively. We propose a conceptual framework for greening the blue revolution of aquaculture, which links social, economic and ecological aspects for promoting the importance of socio‐ecological, ecological‐economic and socio‐economic interactions. We conclude that active community participation, institutional collaboration and policy support are needed for greening the blue revolution of aquaculture in Mymensingh.     

Depletion of florfenicol amine in tilapia (Oreochromis sp.) maintained in a recirculating aquaculture system following Aquaflor®‐medicated feed therapy

Aquaflor^® [50% w w^?1 florfenicol (FFC)], is approved for use in freshwater‐reared warmwater finfish which include tilapia Oreochromis spp. in the United States to control mortality from Streptococcus iniae. The depletion of florfenicol amine (FFA), the marker residue of FFC, was evaluated after feeding FFC‐medicated feed to deliver a nominal 20 mg FFC kg^?1 BW d^?1 dose (1.33× the label use of 15 mg FFC kg^?1 BW d^?1) to Nile tilapia O. niloticus and hybrid tilapia O. niloticus × O. aureus held in a recirculating aquaculture system (RAS) at production‐scale holding densities. Florfenicol amine concentrations were determined in fillets taken from 10 fish before dosing and from 20 fish at nine time points after dosing (from 1 to 240 h post‐dosing). Water samples were assayed for FFC before, during and after the dosing period. Parameters monitored included daily feed consumption and biofilter function (levels of ammonia, nitrite and nitrate). Mean fillet FFA concentration decreased from 13.77 μg g^?1 at 1‐h post dosing to 0.39 μg g^?1 at 240‐h post dosing. Water FFC concentration decreased from a maximum of 1400 ng mL^?1 at 1 day post‐dosing to 847 ng mL^?1 at 240 h post‐dosing. There were no adverse effects noted on fish, feed consumption or biofilter function associated with FFC‐medicated feed administration to tilapia.     

First report on the autochthonous gut microbiota of brown trout (Salmo trutta Linnaeus)

A study was conducted to characterize the autochthonous gut microbiota present in the pyloric caeca (PC), anterior mucosa (AM) and posterior mucosa (PM) of brown trout (Salmo trutta). Total viable counts (TVC) bacterial populations were enumerated using tryptone soy agar, lactic acid bacteria (LAB) levels were enumerated on de Man, Rogosa & Sharpe agar and PCR‐DGGE was employed as a culture‐independent method to assess the total communities. No significant differences were observed between the different gut regions for TVC or LAB levels. 16S rRNA sequencing identified all LAB isolates as Carnobacterium maltaromaticum. In contrast, the TVC community was more diverse; Firmicutes and Bacteroidetes were present but all gut regions were dominated by Proteobacteria, accounting for 88.4–92.6% of the communities. Citrobacter freundii was the dominant species and accounted for 51.0–57.8% of the isolates. Complex bacterial communities were observed using PCR‐DGGE and a trend towards the reduction in the number of operational taxonomic units (OTUs), microbial richness and microbial diversity was observed from the PC to the PM. The similarity between regions was low (52–68%) and cluster analysis revealed that the communities grouped into two distinct clusters; one dominated by the PM samples and the other contained the AM and PC samples. OTUs from the DGGE were identified as members of the phyla Proteobacteria and Firmicutes. Many OTUs were detected in all gastrointestinal regions, however, some OTUs showed regional specialization. Further studies are required to elucidate the activity of these genera in situ and how their actions impact the host.     

复合养殖系统中浮游植物群落结构及其与水环境因子的关系

本研究以主养团头鲂搭配少量鲢鳙鱼的人工湿地-池塘复合养殖系统为研究对象,在人工湿地运行期间调查了该复合养殖系统池塘中浮游植物的生态特征,并分析了浮游植物的群落结构与水环境因子间的关系。结果表明：复合养殖池塘中共鉴定出浮游植物8门91种,其中绿藻种类最多,而蓝藻在数量上占据了绝对的优势。人工湿地运行期间养殖池塘中浮游植物的种类、数量、生物量无显著变化,数量和生物量的平均值分别为3.04×108cells/L,7.14×106mg/L,主要优势种有双对栅藻、四足十字藻、苇氏藻、微小平裂藻、点形粘球藻、泥污颤藻、优美平裂藻、微小色球藻、为首螺旋藻、不定微囊藻;池塘的Shannon-Wiener多样性指数为2.77~3.27,Margalef多样性指数为2.75~3.18,Pielou均匀性指数为0.45~0.55。同时将浮游植物种类丰度与水环境因子进行冗余分析(RDA),结果表明：池塘中绿藻主要受温度、溶氧、pH的影响,而蓝藻主要受pH和氨氮的影响。     

Puffy skin disease (PSD) in rainbow trout,Oncorhynchus mykiss (Walbaum): a case definition

Puffy skin disease (PSD) is a disease that causes skin pathology in rainbow trout, Oncorhynchus mykiss (Walbaum). Incidence of PSD in UK fish farms and fisheries has increased sharply in the last decade, with growing concern from both industry sectors. This paper provides the first comprehensive case definition of PSD, combining clinical and pathological observations of diseased rainbow trout from both fish farms and fisheries. The defining features of PSD, as summarized in the case definition, were focal lateral flank skin lesions that appeared as cutaneous swelling with pigment loss and petechiae. These were associated with lethargy, poor body condition, inappetance and low level mortality. Epidermal hyperplasia and spongiosis, oedema of the dermis stratum spongiosum and a mild diffuse inflammatory cellularity were typical in histopathology of skin. A specific pathogen or aetiology was not identified. Prevalence and severity of skin lesions was greatest during late summer and autumn, with the highest prevalence being 95%. Atypical lesions seen in winter and spring were suggestive of clinical resolution. PSD holds important implications for both trout aquaculture and still water trout fisheries. This case definition will aid future diagnosis, help avoid confusion with other skin conditions and promote prompt and consistent reporting.