在自然横流冷却塔内利用余热进行工业化流水养鱼的试验报告

<正> 开封火电厂内的自然横流冷却塔,是我国七十年代从国外引进的先进技术,是我国第一座试验型横流冷却塔。目前,在横流塔内养鱼国外还未见报道,因此该试验将会产生有益的影响,开拓一条电厂余热利用的新途径。该试验的主要目的是:研究在横流塔内特殊环境中的养殖设备以及在横流塔内特殊环境中的养殖规律。该试验的主要意义在于:1)充分利用塔内的空闲场地,在不重新占用土地的前提下     

南海北部拖网方形和菱形混合网目网囊的渔获性能研究

为评价南海北部拖网方形和菱形混合网目网囊对主要渔获物的网目选择性，使用套网法，开展混合网目网囊(试验网)和传统菱形网目网囊(对照网)的对比选择性试验，结合Logistic和Richards曲线拟合选择性曲线，分析2种不同网目结构网囊对南海北部蓝圆鲹的选择性能。试验结果显示：试验网中数量逃逸率和质量逃逸率均高于80%的渔获种类有8种，而对照网只有5种；蓝圆鲹作为2种网囊中渔获质量最高的渔获种类，试验网中蓝圆鲹的数量逃逸率和质量逃逸率分别为25.35%和20.98%,而对照网中分别为16.39%和15.48%。选择性结果表明，试验网和对照网2种网囊Richards曲线拟合更好，模型残差和赤池信息指数更小，其拟合的蓝圆鲹的50%选择叉长分别为14.31 cm和13.60 cm。因此，方形和菱形混合网目网囊对多种副渔获的释放率较高，使用该网囊可以有效提高拖网的选择性能，保护渔业资源的可持续利用。     

三层刺网缩结系数的确定

正确选择刺网的缩结系数，是设计刺网的一个重要方面。缩结系数的大小，一方面影响到网片的利用面积，另一方面又影响到网线的张力。缩结系数大，网片利用面积大，但网线张力增加，其刺缠性能降低，直接影响到刺网的渔获效果。     

小水池养殖龙虱技术

为研究小水池养殖成虱的效果，试验选择大水池和小水池，组成二个饲养组。饲养8周后测定各组龙虱的生长性能、饲料效率和成活率。结果表明，两组水池饲养效果相似。     

根据食欲选择后备母猪/饲槽颜色及形状对断奶仔猪有影响/单独圈养或四只群养青年母猪生长性能及消化和代谢的反应/新的脲酶抑制因子NBPT对反刍家畜氮代谢的影响/给母鸡喂加碘饲料有利繁殖/检测母猪妊娠和空怀的新技术

在荷兰,一个重要协作试验的最初结果业已公布。它研究的是选择青年母猪作未来种畜所普遍采用的程序。研究结果表明,育种者假设生产性能测定期间青年母猪表现出的食欲和它们分娩后的饲料采食量之间有联系,是正确的。简单地说,在试验圈中食欲好的青年母猪,在她的第一个哺乳期内会采食大量的饲料。虽然这看起来很明显,但以前这种联系从未被证实,也未给选择方案的设计者提供必要的信息。遗传学家认为,这种联系有助于我们解释根据参数配种的母猪,进食量少则使用年限短的原因。     

鱼粉中油脂酸价测量不确定度的评定

测量不确定度是判断测量结果的依据和评定测量水平的指标，现今不确定度在世界各国许多实验室和计量机构使用。中国合格评定国家认可委员会对实验室采用测量不确定度描述测量结果质量已提出明确的要求，测量不确定度在检测、校准实验室中已得到越来越广泛的重视和应用，测量不确定度在检测工作中的正确使用可以衡量实验室科学管理和检测技术的水平。通过对鱼粉中油脂酸检测的测量不确定度进行分析，找出影响不确定度的因素，对不确定度进行评定，如实反映测量的置信度和准确度。     

祖国各地

“天邦”中华鳖饲料饲养效果好选择品质优良的人工配合饲料，是养鳖取得成功，提高经济效益的关键之一。浙江省湖州市德清县种养技术研究所于１９９８年１０月５日至１１月１５日进行了四种饲料的饲养效果对比试验，现将其结果报告如下：试验于保温性能良好的大棚温室中进...     

抗风浪网箱材料性能的研究

报道了抗风浪网箱材料的选择、材料性能和测试结果。试验表明，开发的网箱框架高密度聚乙烯管材性能优良，其抗屈服应力达23MPa，断裂伸长率达525％～763％，纵向回缩率仅为0．3％。采用的六边形锦纶网衣网片纵向断裂强度为315～342daN，比进口挪威网衣强度高1．9％～10．7％。     

鱼饲料消化率测定方法的研究

消化率测定是饲料营养价值评定的重要内容．也是配制平衡日粮的前提。我国原料品种多、加工方式各异，准确测定饲料的消化率对鱼饲料配方选择尤为重要。 选择消化率测定方法的原则是准确可靠、适用范围广。近年来、有关鱼饲料消化率测定方法的研究较多．但仍以体内间接测定法为主。由于费时费工、部分学者也进行了体外消化法的研究。本文主要对各种方法进行比较、评述．以供参考。１ 体外消化试验 该方法是利用酶制剂或研究对象的消化器官的酶提取液在试管内进行的消化试验。其测定值近似反映鱼对饲料的消化率。１．１ 消化液测定法 根据胃…     

利用电厂余热水进行淡水白鲳苗种越冬试验

在总面积为135m~2的3个水泥池中利用电厂冷却塔的余热水进行淡水白鲳苗种越冬试验,并放养7.4万尾,经过250d,收获100～250g/尾的淡水白鲳鱼种3874kg,收入116630元,纯利润69330元,单位利润为513.6元/m~2。     

人工湿地植物的功能与选择

植物在人工湿地中起着非常重要的作用，它可以拦截大颗粒污染物，吸收降解营养物质；能够稳固湿地床表面基质，降低冰雪在湿地表面的凝结速率；可以改善处理系统景观，为野生生物及微生物的生长提供适宜的环境，具有生态美学和经济价值。选择植物应考虑植物的适应性、净化能力、抗逆性、经济和观赏价值以及物种间的合理搭配。本文阐述了植物在人工湿地中的作用和选择人工湿地植物的一些基本原则，提出了植物在人工湿地实际运用时仍存在的一些问题，对其应用前景做了展望与讨论。     

Participation of local fishermen in scientific fisheries data collection: a case study from the Bangweulu Swamps, Zambia

The feasibility of participation by local fishermen in scientific fisheries data collection for stock assessment is described. Artisanal fishermen from the Bangweulu Swamps, Zambia, collected length-frequency data for 1 year from their catch using the main fishing methods employed in the swamps as well as experimental gears. It is shown that with this method, it is possible to obtain large quantities of reliable and relatively cheap length-frequency data that allow for a full length-based stock assessment, including cohort analysis. There are also indications that with a proper feedback of the findings by the research institutions to the fishing communities, this sampling method might enhance the awareness of exploitation patterns and the management consequences. This may be seen as a first step in preparing the communities to take up their role in a community-based approach in the management of the fish resources.     

Experimental evaluation of mass selection to improve red body colour in Fijian hybrid tilapia (Oreochromis niloticus × Oreochromis mossambicus)

Mass selection was trialed on Fijian hybrid tilapia (Oreochromis niloticus × Oreochromis mossambicus) to reduce the amount of black spots on otherwise red phenotypes. The responses of two selection intensities (low‐selection line, top 50% – L) and (high‐selection line, top 30% – H) were compared with that of a control line (no selection – C) across three generations. The relative growth performance of treatments (C, L and H) was examined in parallel in each generation to assess whether mass selection had a correlated negative effect on growth performance. The results show clearly that red phenotype can be improved significantly by applying mass selection, without affecting growth performance. We propose that black spots on an otherwise red phenotype could represent the allelic products of a second genetic locus influencing skin colour, which can be expressed in red individuals (genotype Rr) but which may be masked in black individuals (genotype rr).     

Intraspecific Differences in Physiological Efficiency of Juvenile Atlantic Halibut Hippoglossus hippoglossus L.

We compared growth efficiency, feeding consumption, metabolism, excretion, and energy allocation in populations of juvenile Atlantic halibut from Norway, Iceland, and Canada reared at low (8 C), medium (12 C, 15 C) and high (18 C) experimental temperatures. Our findings show that protein utilization and energy allocation in juvenile Atlantic halibut varies among different populations, as the Norwegian population displayed the highest protein efficiency ratio, protein production value, and energy conversion efficiency compared to the Canadian population, while the Icelandic population showed overall intermediate growth performance. The results do not conform to a simple thermal adaptation model but might represent an example of: 1) local adaptation of fish populations; or 2) countergradient variation where shorter growing season at higher latitudes is compensated with higher physiological efficiency. These findings have implications for halibut culture, particularly in selection work focusing on growth performance.     

Diversified aeration facilities for effective aquaculture systems—a comprehensive review

The growing intensive aquaculture system around the world maintains a high stocking density, wherein it is essential to increase and sustain the optimum dissolved oxygen concentration (DO) through the provision of artificial aeration systems. The selection of an aerator is a crucial aspect of aquaculture operations. The selected aerator must be economically efficient and should be able to fulfill the requirement of oxygen supply in the pond water. The present study provides an extensive literature review on the importance of artificial aeration in aquaculture, the standard method of test for performance evaluation of an aerator, various aeration systems and their mechanisms, method to determine the numbers of aerator requirement, comparative studies of different type of aerators, and economic consideration in selection of aerators. In addition, a thorough analysis has been done to suggest the type of aerator that is economically viable and efficient for different pond volumes based on the performance data reported in the reviews. Therefore, this study may help the end-users (fish farmers) to select the best aerator based on their requirements.

     

Oxygen recharge and ammonia stripping capabilities of various closed culture configurations

A packed tower (trickling filter), empty, half full and full of a medium (styrofoam packing material) and a rotating biological contactor (RBC, rotating disc) were tested at various recirculating flow rates, with and without supplemental aeration, to determine oxygen recharge and ammonia stripping capabilities. Oxygen recharge capabilities increased with increasing flow rates, but at different rates for each filter. Oxygen recharge efficiencies decreased as flow rates increased in the half full and empty towers, were about constant for the full tower and increased in the RBC. Oxygen recharge capabilities were significantly increased with the addition of surface agitation; greater than the sum of the component contributions. With supplemental aeration, the full tower with a recirculation flow of 45·4 liters/min was most efficient and capable of supplying the most oxygen. Ammonia stripping was found to be insignificant in all systems tested.     

Change in habitat associations and geographic distribution of thorny skate (Amblyraja radiata) in the southern Gulf of St Lawrence: density‐dependent habitat selection or response to environmental change?

We describe changes in the habitat associations and geographic distribution of thorny skate during their feeding season in the southern Gulf of St Lawrence, based on 32 yr of monitoring by a bottom‐trawl survey. In the 1990s, geographic range contracted sharply and distribution shifted into a narrow band of warm deep waters. These changes appeared to reflect altered habitat selection by individual skates, rather than local depletion of the skates that had habitually occupied the vacated areas or a change in the timing of seasonal migrations. Changes in skate distribution coincided with a decline in skate biomass and a cooling of bottom waters. The contraction in the geographic range of skates appeared to be a density‐dependent response, more closely linked to the decline in skate abundance than to the change in environmental conditions. The cause of the shift in habitat associations is less certain. An index of the distribution shift was more strongly correlated with skate biomass than with an index of temperature conditions, and the change in temperature associations is in the direction predicted by density‐dependent bioenergetic considerations. However, the shift into deeper waters is into a depth zone where skate condition is relatively low, contrary to the expectation that fish should be concentrated in optimal habitat at low population size. On the other hand, while the shift into warm deep waters coincided with a cooling of waters at intermediate depths, distribution failed to shift back to the earlier pattern as these waters warmed in the late 1990s.     

Markers for selection of disease resistance in fish: a review

Aquaculture is the fastest growing food producing sector in the world. However, diseases result in a major loss in production. Among the several management techniques, selective breeding for resistant trait is one of the most reliable methods and provides long-term control over disease problems. Field survival or challenge survival records provide initial information of resistant stocks. However, selection programmes demand a proper marker which can identify the resistant stock easily with much accuracy. Several immunological indicators associated with resistance to a particular disease have been reported. These include positively correlated markers such as level of natural and specific antibody, respiratory burst activity of phagocytes and level of acute-phase ceruloplasmin protein and negatively correlated markers such as serum lysozyme, haemolytic and haemagglutination activities. However, for few fish species and pathogen-specific markers viz., myeloperoxidase activity, cortisol and glucose levels, macrophage aggregation and the level of plasma proteins, a confined conclusion of association has not been established. Besides immunological markers, molecular markers are in use because of their reliable screening methods. Genome can be scanned for molecular markers which provide the full linkage map of a species or stock. Association of these molecular markers with resistant traits gives rise to quantitative trait loci (QTL) for resistance to a particular pathogen. Screening of resistant stock can be carried out using these markers. Among the several marker systems, amplified fragment length polymorphism, microsatellites and single-nucleotide polymorphism play a major role in the process of selection for disease resistance. With the use of these marker techniques, we can avoid challenge testing where a huge number of animals were being killed. Multiple trait selection can also be possible with multiple QTL identification for resistance to two or more diseases simultaneously.     

Variation analysis and sample size estimation for growth indicators during PIT-tag-assisted family construction of channel catfish (Ictalurus punctatus)

Passive integrated transponder (PIT) tags can be used to overcome environmental variations caused by individual fish tanks during family selection of the channel catfish (Ictalurus punctatus), which thus permits growth comparisons among different families under identical environmental conditions. Power analysis was used to analyse variations in various growth performance measures during PIT-tag-assisted family construction of channel catfish, and this allowed sample sizes to be estimated. The experimental data suggested that, for a particular fish species, when having a low variation coefficient of fish body weight at the time of PIT marking and maintaining consistent individual sizes, the sample size required during a family growth experiment could be effectively reduced. This present study lays a theoretical foundation for analyzing variations in growth performance indicators and estimating the sample sizes during PIT-tag-assisted family construction of fish experiments.