共查询到20条相似文献，搜索用时 78 毫秒
1.
Changes in Hemocyte Counts in Litopenaeus stylirostris Subjected to Sublethal Infection and to Vaccination 总被引：1，自引：0，他引：1
Abstract.— A study was conducted with juvenile Litopenaeus stylirostris to evaluate the impact on total hemocyte counts of the injection of (1) formalin-killed Vibrio penueicida cells (vaccine) and (2) a sublethal infection with a moderately pathogenic strain of Vibrio alginolyticus . After an initial decrease in hemocyte counts, both the vaccination and the sublethal infection induced higher hemocyte counts than controls. In order to investigate the possibility of increasing the number of circulating hemocytes in pond-reared juvenile shrimp, the vaccine was added to the diet. No effect on the hemocyte counts was observed over a 20-d feeding period. 相似文献
2.
3.
通过加温刺激克氏原螯虾(Procambarus clarkii)雌虾在冬季抱卵,并对卵及幼体在不同水温下的发育过程进行观察。结果显示:经过38 d的加温刺激,在26℃下陆续观察到有虾抱卵,18℃以下未观察到抱卵虾,但该水温能促进雌虾性腺发育。雌虾经加温刺激后所抱卵在18℃,21℃和26℃下均能正常孵化出幼虾。18℃,21℃和26℃下孵化时间分别为(39.67±3.06)d,(28.33±2.52)d和(15.00±2.00)d,孵化所需时间随着温度的提升而减少(P<0.05)。孵化的幼虾经45 d养殖后,在18℃,21℃和26℃下体长分别为(1.90±0.25)cm,(2.73±0.38)cm和(3.78±0.70)cm,体重分别为(0.223±0.100)g,(0.688±0.331)g和(2.145±1.272)g。18℃,21℃水温下的幼虾在此生长阶段为非异速生长(b=3),26℃水温下的幼虾为异速生长(b>3)。在3种温度下,幼体生长速度随温度的升高明显加快(P<0.05)。 相似文献
4.
Radula development in abalone Haliotis discus hannai from larva to adult in relation to feeding transitions 总被引：1，自引：0，他引：1
ABSTRACT: The radula morphology of Haliotis discus hannai was examined by scanning electron microscope from the larval to the adult stage. The radula of competent larvae contained 11–13 transverse rows of teeth after 6–7 days at 20°C. The number of rows increased to 25–30 during the first several days after settlement, but then remained approximately constant throughout the post-larval period, increasing again in abalone larger than 4 mm in shell length (SL). In post-larvae < ~1 mm SL, only two pairs of lateral teeth (L1, L2) were present in the larval radula. An additional three pairs of lateral teeth (L3–L5) were added progressively as post-larvae grew from 0.9 mm to 1.9 mm SL. Marginal teeth were added steadily from one pair in larvae to 30–40 pairs at 3–4 mm SL, 70–80 pairs in 30–40 mm juveniles, and 70–90 pairs in 90–100 mm adults. The serrations on the working edges of the rachidian (R) and lateral teeth became less pronounced as the abalone grew. Nearly all serrations disappeared from the rachidian (R) and inner lateral teeth (L1, L2) by ~2 mm SL, and from the outer lateral teeth (L3–L5) by 20 mm SL. For abalone larger than 1.5 mm SL, the L3–L5 teeth became longer and more pointed, which increased the space between adjacent rows of teeth. Post-larvae < 1 mm SL had highly curved teeth with clearance angles of approximately or less than zero, whereas larger abalone had positive clearance angles. These radula developments appear to be related to transitions in feeding habits from microbial to macroalgal diets. 相似文献
5.
Biodiversity in aquatic systems in relation to aquaculture 总被引：12，自引：0，他引：12
This paper first considers the perception and dimensions of biodiversity. We suggest that biodiversity can be viewed as a biospatial, hierarchically distributed structure of variability among living organisms with five levels of complexity (and including agricultural systems). Loss of biodiversity, value of biodiversity and knowledge of aquatic biodiversity are reviewed briefly. Methods for measuring biodiversity, especially at the genetic level, are discussed and considerable emphasis is laid on effective population size as a controlling factor in biodiversity. Finally, a range of impacts of aquaculture upon biodiversity are considered, including competitive and introgressive effects from farmed stocks. The development and use of reversibly sterile strains is seen as highly beneficial to both aquaculture and the maintenance of biodiversity. 相似文献
6.
7.
8.
9.
水产养殖的实质是一种以"物"换"物"的过程,也就是通过水产养殖,把饵料或肥料转化为水产品的过程.水产养殖单位面积产量的高低和经济效益的好坏,在很大程度上取决于使用的饵料是否合理和投饵的技术是否科学.对于水产养殖来说,正确合理地选用饵料,科学合理地投喂,是促进养殖动物快速生长,提高饵料转化率,降低饵料成本,提高经济效益的关键.饵料投喂是水产养殖中的一大关键环节,只有正确把握饲养鱼类的投饵数量,科学投喂,才能提高饵料的利用率,保证养鱼增产增收增效.目前对于鱼类的研究多集中于鱼类养殖技术、营养和饵料开发方面,对于科学的饵料投喂的报道较为少见.而这方面的研究结果对于我们开展水产养殖业、提高效益、节省成本以及在环境保护方面是很重要的.因此,科学把握水产养殖中饵料投喂显得尤为重要.投饵技术包括投饵量的确定、投饵时间、投饵次数、投饵方法和投饵原则.下面就投饵技术几个方面以及饵料投喂存在的问题进行阐述,期望能使读者对科学投饵有一个清晰的认识,并且对于解决饵料投喂存在的问题提供借鉴. 相似文献
10.
肥料在水产养殖中的应用及前景 总被引：4，自引：0，他引：4
水中的浮游动物和浮游植物是鱼类的天然饵料 ,能弥补饲料中缺乏的某些营养素。合理的施肥能促进水中浮游生物的生长 ,是提高鱼塘产量、增加养鱼效益的有效方法 ,也是发展渔业生产的重要措施之一。在鱼苗、鱼种培育到成鱼饲养的整个过程中 ,施肥都是其中关键的一环。1 水产养殖施用肥料的必要性近年来 ,由于饲料原料的大幅度涨价 ,尤其是鱼用饲料的价格飞涨 ,致使养鱼成本急剧上涨 ,效益逐年降低。研究表明 ,鱼类对饵料中的蛋白质含量要求较高 ,一般在 30 %～ 4 5 %之间 ,如草鱼鱼苗要求 35 % ,鱼种及成鱼要求 2 5 % ;鲤鱼 30 % ;团头鲂 35 … 相似文献
11.
The direct effect of osmolality on growth and mRNA population were investigated in the rainbow trout cell line (RTG-2). These cells can grow in the media of osmolalities ranging from 200 to 600 mosmol kg-1. With two-dimensional electrophoresis, the in vitro translation of poly(A+) RNA isolated from these cells showed osmoresponsive changes in the population of translatable mRNAs. Using differential mRNA display polymerase chain reaction, however, we identified inducible cDNA products in hyper-osmotic and hypo-osmotic media as third component of complement, and as homologues of known genes: an atypical protein kinase regulated by the thyrotropin-dependent mitogenic pathway, nucleolin and CHD3. The remaining cDNAs have no significant homology in GenBank. Northern blots demonstrate that their mRNA levels were induced in hyper-osmotic and hypo-osmotic media, but not by other stresses. The expressed proteins of these mRNAs may be involved directly or indirectly in the adaptation of RTG-2 cells to different osmolalities probably through the osmotic signal transduction and adjustment in cellular metabolism to osmotic stress. 相似文献
12.
近年来,外来物种入侵已引起人们的忧虑与重视。本文就水生“外来物种”入侵温州水域的现状进行调研,并提出对策。 相似文献
13.
Energy acquisition and allocation to egg production in relation to fish reproductive strategies 
下载免费PDF全文
下载免费PDF全文 Richard S McBride Stylianos Somarakis Gary R Fitzhugh Anu Albert Nathalia A Yaragina Mark J Wuenschel Alexandre Alonso‐Fernández Gualtiero Basilone 《Fish and Fisheries》2015,16(1):23-57
Oogenesis in fishes follows a universal plan; yet, due to differences in the synchrony and rate of egg development, spawning frequency varies from daily to once in a lifetime. Some species spawn and feed in separate areas, during different seasons, by storing energy and drawing on it later for reproduction (i.e. capital breeding). Other species spawn using energy acquired locally, throughout a prolonged spawning season, allocating energy directly to reproduction (i.e. income breeding). Capital breeders tend to ovulate all at once and are more likely to be distributed at boreal latitudes. Income breeding allows small fish to overcome allometric constraints on egg production. Income breeders can recover more quickly when good‐feeding conditions are re‐established, which is a benefit to adults regarding bet‐hedging spawning strategies. Many species exhibit mixed capital‐ and income‐breeding patterns. An individual's position along this capital–income continuum may shift with ontogeny or in relation to environmental conditions, so breeding patterns are a conditional reproductive strategy. Poor‐feeding environments can lead to delayed maturation, skipped spawning, fewer spawning events per season or fewer eggs produced per event. In a few cases, variations in feeding environments appear to affect recruitment variability. These flexible processes of energy acquisition and allocation allow females to prioritize their own condition over their propagules' condition at any given spawning opportunity, thereby investing energy cautiously to maximize lifetime reproductive value. These findings have implications for temporal and spatial sampling designs, for measurement and interpretation of fecundity, and for interpreting fishery and ecosystem assessments. 相似文献
14.
15.
A cointegration analysis is conducted to examine the effect of fishery subsidies on fisheries production using data compiled
over more than 30 years in Japan. The results illustrate that one fishery production indicator (production value per fishermen)
shows a positive relationship with one particular group of government financial transfer (GFT) (that is, government general
service expenditures including cost for fishery managements, scientific researches, and other administrative activities).
No other tested results between GFTs and fishery indicators showed a real relationship. Although further scrutiny is awaited,
this study could provide an empirical basis for an argument that, under an effective fishing management system, fisheries
subsidies do not necessarily cause production increases or negative impact on fishing stocks. 相似文献
16.
In the coastal zone of the Sea of Okhotsk off Hokkaido, Japan, the giant ezo scallop ( Patinopecten yessoensis ) is widely cultivated on the sea bed, making its fishery a major industry. However, the area experiences intense cyclones, including typhoons, about once a decade and the scallop resources appear to have received severe damage from the storms. Such an event occurred on 29 October 1988. The storm caused 12-m-high wind waves, which appeared to be fully developed sea waves. The water above the sea bed repeatedly moved back and forth at speeds of 1∼2 m s-1 causing damage to the scallops due to collisions and rubbing with gravel and other scallops. From a comparison of wind data with the annual catch of scallops, intense cyclones seem to play an important role on the year-to-year fluctuations in the scallop fishery. 相似文献
17.
An econometric analysis, known as a panel data analysis, was conducted to understand the nature and the magnitude of the effect
caused by subsidies to fishery productions. Published data on government financial transfers for OECD member countries from
1996 to 2002 were used for this purpose. The result of the panel data analysis indicated that certain financial transfers
have brought small but positive influences to economic indicators on fisheries of aggregated OECD countries, while either
no or negative effects were recognized in other financial transfers. Different magnitudes of influences were observed according
to the types of the transfers. Also, there are cases where two types of financial transfers provide offsetting effects to
a single economic indicator. Specifically, the total volume of fishery production for OECD countries is positively influenced
by government direct payment programs, but negatively affected by the amount of general services provided by the governments.
This study can be regarded as a useful first attempt to examine the empirical link between productions and subsidies of the
fishery sectors. 相似文献
18.
19.
Abstract. Histopathological studies on natural and experimental infections of nineteen microsporidian species from fishes distinguished two types of tissue reactions.
The first type is characteristic of infections with xenoma-inducing microsporidian species and comprises three successive stages: a weakly reactive stage, a productive stage with the formation of granulomas and a stage of granuloma involution. Following the first stage, tissue reactions are directed towards the isolation of the parasite and result in its complete elimination and host tissue repair. The extent of pathological changes probably depends on the number of parasite cells which initiated the infection.
The second type is represented by Pleistophora species infecting muscles or oocytes. Host tissue reaction is surprisingly slight during the schizogony and sporogony and does not tend to isolate the invaded muscle fibres. A slight lymphocytic infiltration of myosepta indicates the first stage of tissue reaction. The tissue reaction only reaches the productive stage when mature spores completely fill the contents of the infected muscle fibre. A thick wall of fibroblasts may be formed to demarcate the parasite mass as soon as it undergoes necrotic changes. The extent of pathological changes probably depends on the ability of early developmental stages of the parasite to spread the infection within the host.
In both types of tissue reaction, the spores are destroyed by complete digestion within host phagocytic cells. 相似文献
The first type is characteristic of infections with xenoma-inducing microsporidian species and comprises three successive stages: a weakly reactive stage, a productive stage with the formation of granulomas and a stage of granuloma involution. Following the first stage, tissue reactions are directed towards the isolation of the parasite and result in its complete elimination and host tissue repair. The extent of pathological changes probably depends on the number of parasite cells which initiated the infection.
The second type is represented by Pleistophora species infecting muscles or oocytes. Host tissue reaction is surprisingly slight during the schizogony and sporogony and does not tend to isolate the invaded muscle fibres. A slight lymphocytic infiltration of myosepta indicates the first stage of tissue reaction. The tissue reaction only reaches the productive stage when mature spores completely fill the contents of the infected muscle fibre. A thick wall of fibroblasts may be formed to demarcate the parasite mass as soon as it undergoes necrotic changes. The extent of pathological changes probably depends on the ability of early developmental stages of the parasite to spread the infection within the host.
In both types of tissue reaction, the spores are destroyed by complete digestion within host phagocytic cells. 相似文献
20.
庭院养龟规模小 ,可采用土法进行加温或降温 ,使龟池形成一个特殊的小生境 ,促进龟的生长和发育。要使龟池的温度维持在一个相对恒定的范围内 ,龟池应建在坐北向南、冬天有阳光照射的地方 ;池面上搭建一个框架 ,盖上塑料薄膜 ,龟舍中垫上干草或碎布 ,以起到一定的保温作用。在严寒季节 ,除采用热水加温、炭炉加温、电暖器加温等办法之外 ,还可用土法太阳能加温节省能源 ,效果也好 ,做法是 :用薄木板钉一个宽 1 1 0 cm、长 1 50cm、四边高 5cm的基板 ,底板涂上黑漆 ,上面铺上 1～ 2层遮光布。用长 1 0 0 cm、直径 1～ 1 .5cm的玻璃管 ,按 2 c… 相似文献