Effect of water exchange on effluent and sediment characteristics and on partial nitrogen budget in semi-intensive shrimp ponds in New Caledonia

An experiment was conducted in six earthen ponds with 20 shrimps m^?2Litopenaeus stylirostris (Stimpson) during the warm season in New Caledonia to study the dynamics of wastes in relation with water exchange rate (WER). The nitrogen budget was established, taking into account the different forms of nitrogen in the water, sediment, feed and shrimp. Data from a wide range of treatments applied in unreplicated ponds were treated using regression analysis to establish the relationship between WER and partial nitrogen budget, sediment characteristics and shrimp performance. To compare effluent quality between treatments during the season, data were analysed using the non‐parametric sign test. The water outflow was characterized by a decrease in the concentrations of N‐mineral forms (TAN, NO₂^?–NO₃^?), an increase in the concentration of organic soluble and sestonic organic forms (expressed in terms of particulate nitrogen, particulate organic carbon, chlorophyll a) compared with the water inflow. Increasing WER increased the amount of exported wastes and mainly in the organic forms and TAN can be considered as negligible. The nitrogen budget showed that 19–46% of nitrogen input (feed+water) was exported into the coastal environment. The results showed that the quality of the sediment decreased as WER decreased. The potential negative impact of the developing industry in New Caledonia on the costal environment could be partially reduced in a first step by decreasing WER. However, if applied in the farms, this practice should be linked to a close survey of the evolution of sediment quality.     

环境因子对对虾弧菌致病性的影响

对虾弧菌病是对虾养殖过程中危害最严重的细菌性疾病之一。文章对对虾弧菌病的病理特征、弧菌种类以及环境因子对对虾弧菌致病性影响作以简述。     

Evaluation of different concentrations of adult live Artemia (Artemia franciscana,Kellogs 1906) as natural exogenous feed on the water quality and production parameters of Litopenaeus vannamei (Boone 1931) pre-grown intensively

A 7-week experimental study was performed to evaluate the effect of five concentrations of adult live Artemia (0, 1, 2, 3 and 4 L⁻¹) as exogenous natural feed on the water quality and production parameters of juvenile (0.2 ± 0.01 g) shrimp (Litopenaeus vannamei) pre-grown intensively (125 organism m⁻²) under laboratory conditions (80 L plastic tanks). No significant differences were observed in the environmental variables among treatments. Total ammonium nitrogen, nitrates and phosphates recorded higher concentrations in all the treatments using artemia, as compared with the treatment without Artemia. In all the cases, the levels remained within or close to the ranges considered necessary for the farming of the species. The highest weight gain and biomass were obtained in the treatments with 3 and 4 Artemia L⁻¹. The best feed conversion ratio were recorded using 2 Artemia L⁻¹ and the highest with 0 Artemia L⁻¹. No differences in survival were detected among treatments. The greatest concentrations of nitrogenous metabolites achieved at the highest densities of Artemia were lower than the LC₅₀ for penaied shrimp and no negative effect was observed on the survival of the shrimp. These results clearly indicate that the use of adult live Artemia as exogenous natural feed significantly increased the production parameters of the Pacific white shrimp.     

我国北方地区繁育凡纳滨对虾试验

凡纳滨对虾(Litopenaeus vannanei)自然产于拉丁美洲太平洋沿岸,是西半球的主要养殖虾类。它具有生长速度快、抗病能力强、适盐范围广(5~50)、出肉率高等特点。凡纳滨对虾于1988年由中国科学院海洋研究所引进中国,并在1994年工厂化人工育苗取得成功,1995年江苏省大丰县贝类苗种     

竹炭的微波处理方法与效果的研究

研究了竹炭吸附前,利用微波进行预处理的处理方法与效果。结果表明：微波处理后竹炭的比表面积与吸附能力有显著的提高,不同的竹炭用微波或NaOH加微波处理后．亚甲基蓝吸附值提高了34％-92％。该法用于吸附Pb^2＋后的竹炭的洗脱,竹炭的吸附能力恢复到原来的90％以上。该法有望成为竹炭活化的有效手段。     

Environmental influences on the availability of smooth pink shrimp, Pandalus jordani, to commercial fishing gear off Vancouver Island, Canada

Short time scale (less than seasonal) variability in commercial catch rates of smooth pink shrimp, Pandalus jordani, off the west coast of Vancouver Island, Canada, was examined in relation to changes in environmental conditions. Catch per unit of effort (CPUE) data were used as a proxy for catchability to identify environmental conditions affecting the availability of shrimp to the two main gear types in this fishery: otter trawls and beam trawls. Correlogram analyses of the 1996 CPUE (log-transformed) data from each gear type, and autocorrelation analyses of wind stress, tidal current speed, sea surface temperature and salinity, and hours of bright sunshine (the latter three as residuals from their seasonal trends) for 1996 indicated a mean decorrelation time scale of 7.7 days. This was used to construct smoothed time series of these CPUE and environmental data for 1996. Multiple regression analyses with CPUE as the dependent variable and the environmental data as independent variables were significant, explaining 44% of the variability in otter-trawl data and 35% of the beam-trawl variability. Three hypotheses are proposed to explain these results, involving interactions between the shrimp's behaviour and environmental conditions. A significant proportion of the within-season variability in CPUE (and therefore in the availability of shrimp to fishing gear) for P. jordani off Vancouver Island can result from variations in environmental conditions which, if included in stock analyses, should reduce the variability of population abundance estimates.     

浅谈猪繁殖与呼吸综合征的防控措施

猪繁殖与呼吸综合征(Porcine reproductive and respiratory syndrome,PRRS)是由猪繁殖与呼吸综合征病毒(PRRSV)引起的猪的一种高度传染性疾病,又称\"猪蓝耳病\"。笔者通过引种管理、生物安全、生产流程、疫苗免疫以及实验室监测这五项措施帮助不同的猪场实现对猪蓝耳病的有效防控。