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1.
郑鹤亭  钱爱珍 《水产学报》1988,12(4):359-365
合成纤维的伸长度大;抱合力差,制成网片后结节容易滑动。若不经过定型处理,势必导致网具变形,影响捕捞效果。绝大部份国营渔业公司和绳网厂在网片编织后,均采用热定型,以加强结节牢度。但群众渔业由于设备条件差和其特殊的编织方法,目前还只是使用拉伸定型而不进行热处理。广东国营渔业公司也是如此。  相似文献   

2.
网具是由网片、纲绳、浮沉子装配而成。一、网片:1.网片的种类及编织方法。网片按其结构形式分为有结节网片和无结节网片两类。淡水网具大多是用有节结网片。网片结节的编结方法为活节,死节和变形节三种,见图(1)  相似文献   

3.
(四) 烂鱼试验试验对处于相同烂鱼腐蚀条件下,着色网片与染色网片的色光变化及强力保持情况下进行了对比。 1.样品试样A——原液着色锦纶_6网片,未经树脂处理,73年试制。试样B——染色锦纶_6网片,未经树脂处理,样品取自上海网具厂。试验C——染色锦纶_6网片,树脂处理,样品取自上海网具厂。  相似文献   

4.
<正> 捕捞作业过程中,流体对网具的阻力主要归结于对网片的阻力.历来在计算网片水中阻力时,都是以网片在运动方向的投影面积作为网衣阻力的计算依据,即网衣网线的粗度或直径是与阻力相关的主要参数,对于网片相对于流体作垂直运动时,这样的计算是正确的.但大部分的渔捞作业工况,如拖网拖曳时上下身网与水流的相对运动;围网放网时网衣迅速垂直下降与水流的相对运动以及流刺网的拖曳等等,其网衣与流体的相对运动夹角极小,几  相似文献   

5.
网片缩结就是将拉紧的网片长度加以缩短,使网片网目张开,保持一定形状,以便有效地捕捞,并将缩短后的长短与拉紧时长度的比值,称为缩结系数。缩结系数分为水平缩结系数和垂直缩结系数两种,通常用u_1和u_2来表示。有的渔业生产单位在网具装配时,往往忽视网片缩结的作用,常因缩结系数选择不当,耗线量大,网片利用率低,或者造成因网具的质量、规格等问题,而影响捕捞效果。因此要针对网具的种类和用途,将网片进行合理缩结。  相似文献   

6.
<正> 机编矩形网片具有成本低和适宜成批生产等优点,已被广泛采用。网具是由各种不同形状的网片构成,在装配的过程中,需将机编的矩形网片剪裁成不同尺寸和形状,然后缝合成所需的网具。一、网片的剪裁单元(一)边傍:沿网片纵向剪断结节处相邻的2个  相似文献   

7.
王平 《海洋渔业》1988,10(1):48-48
<正> 工业捕鱼是渔业部门的一个重要组成部分,它捕捞的主要对象是水中的动物资源和植物资源.在捕捞中.渔具是一个必不可少的工具,而网典则是它的主要组成.纵观网具发展史,我们可以看到制网纤维材料起了很大的变化,从原来的植物纤维材料发展到今天有各种类型的合成纤维制成的各种特色的网.使用的结果表明,合成纤维可使网具的牢度和抗机械磨损能力增强1~2倍.提高渔具的荷重能力和延长渔具的使用寿命.网具主要由网片和  相似文献   

8.
王尔光 《海洋渔业》1988,10(3):110-114
<正> 网渔具水阻力的计算是渔具设计的基础,因此,迄今为止,已有国内外许多学者对此进行了大量的研究。特别是对于平面网片水动力的研究,目前已经取得了较可靠,完整的计算方法,但实际网具大都呈曲面形状,对曲面网片水阻力的计算能否运用平面网片的公式,借助数学上曲面积分的方法来解决,至今尚设有切实可行的研究成果。本  相似文献   

9.
对虾幼虾计数是虾苗暂养最后阶段的一个重要步骤,完成这个步骤必须要有一种能够做到得心应手的收集网具。这里推荐一种新型结构的幼虾收集网,是我们根据近年来在闽东一些虾塘试用,并加以总结经验、改进设计的新式网具。这种网具制作比较简单,可采用聚氯乙烯网衣拼成,整个网身摊开来,就是一张长方形网片(如图所  相似文献   

10.
<正> 为了发展围网生产,提高围网产量,延长网具的使用寿命,1979年大连海洋渔业公司与大连合成纤维研究所、东海水产研究所等单位合作,共同研究生产国产第一批纺前着色涤纶围网丝,编织成涤纶有结围网片和经编无结围网片.同时近几年来还使用了涤纶绞捻无结围网片,用这三种不同网片结构的网衣先后设计了不同类型的深水围网,并在实践生产中应用,经过多年的试验,取得了一些经验和教训.  相似文献   

11.
Previously, we reported 10 PEGE types of 85 tilapia Streptococcus agalactiae(GBS), which shifted from Streptococcus iniae in China, by using PEGE method. Presently, larger and more representative tilapia GBS were isolated, for the ?rst time in China, to characterize their serotypes and genetic diversities more precisely than had done before. 168 GBS strains were distributed in ?ve provinces of China, in which Guangdong, Guangxi and Hainan were the major ones, holding36.9%(62/168), 37.5%(63/168) and 19.6%(33/168), respectively. Serotypes, Ia, Ib and III, were observed in these strains and the most predominant one was Ia(95.2%), which mainly distributed in Guangdong, Guangxi and Hainan. Ia initially occurred in 2009, it shoot up to 32.1% in 2010,but decreased to 16.1% in 2011 before went up to 45.2% in 2012. Ib sporadically occurred during2007–2011, III onlyoccurred in 2012. 14 different PFGE types, including 4 new types(N, O,P and Q), were observed, in which B, D, F and G were the predominant types, holding 83.9%(141/168) of the total GBS strains. Ia corresponded to 11 PFGE types(A–H, N–P), in which type D predominated(51%). Ib represented 3 genotypes(I, J and Q) and III harbored only 2genotypes(N and F). Type N and Fsynchronously presented in Ia and III. In summary, the genetic diversity of tilapia GBS varied by serotypes and changed with geographical locations and years.Although Iastillpredominated, new rareserotypeIII alreadyoccurred in China.  相似文献   

12.
13.
The environmental processes associated with variability in the catch rates of bigeye tuna in the Atlantic Ocean are largely unexplored. This study used generalized additive models (GAMs) fitted to Taiwanese longline fishery data from 1990 to 2009 and investigated the association between environmental variables and catch rates to identify the processes influencing bigeye tuna distribution in the Atlantic Ocean. The present findings reveal that the year (temporal factor), latitude and longitude (spatial factors), and major regular longline target species of albacore catches are significant for the standardization of bigeye tuna catch rates in the Atlantic Ocean. The standardized catch rates and distribution of bigeye tuna were found to be related to environmental and climatic variation. The model selection processes showed that the selected GAMs explained 70% of the cumulative deviance in the entire Atlantic Ocean. Regarding environmental factors, the depth of the 20 degree isotherm (D20) substantially contributed to the explained deviance; other important factors were sea surface temperature (SST) and sea surface height deviation (SSHD). The potential fishing grounds were observed with SSTs of 22–28°C, a D20 shallower than 150 m and negative SSHDs in the Atlantic Ocean. The higher predicted catch rates were increased in the positive northern tropical Atlantic and negative North Atlantic Oscillation events with a higher SST and shallow D20, suggesting that climatic oscillations affect the population abundance and distribution of bigeye tuna.  相似文献   

14.
Growth hormone (GH) and reproduction: a review   总被引:5,自引:0,他引:5  
Interaction between growth and reproduction occurs in many vertebrates and is particularly obvious at certain stages of the life cycle in fish. Endocrine interactions between the gonadotropic axis and the somatotropic axis are described, the potential role of GH being emphasised. A comparative analysis of these phenomena in mammals, amphibians and fish, suggests a specific role of GH in the physiology of puberty, gametogenesis and fertility. It also shows the original contribution made by studies on the fish model in this field of investigations.  相似文献   

15.
16.
In this experiment, a feeding trial was performed to determine the effects of fructooligosaccharide (FOS) on growth performance, digestive enzyme activity and immune response of Japanese sea bass, Lateolabrax japonicus juveniles (initial weight 38.3 ± 0.5 g), and the fish were examined following feeding with six levels of FOS (0, 0.5, 1, 2, 4 and 6 g/kg) for 28 days. Significant enhancement of weight gain (WG) and specific growth rate (SGR) was found in fish fed 1 g/kg FOS incorporated diets (p < .05), while the feed conversion ratio (FCR) in the 1, 2 g/kg FOS groups reduced significantly compared with the control (p < .05). Besides, the crude lipid in the 4, 6 g/kg FOS groups increased significantly compared with the control (p < .05). On the other hand, the erepsin and lipase activities significantly elevated in intestine of fish fed 2 g/kg FOS (p < .05) and the lysozyme activity in serum of fish fed 2 g/kg FOS were significantly higher than that in the control (p < .05). Moreover, the alkaline phosphatase activities in serum of fish fed 0.5, 1, 2 g/kg FOS were significantly higher than in control (p < .05). Regression analysis showed that the relationships between dietary FOS levels and either SGR, FCR, erepsin or lysozyme activities were best expressed by regression equations, and the optimal inclusion levels are 1.37, 1.80, 3.06, 3.11, 1.93 and 1.80 g/kg for SGR, FCR, erepsin, lipase, lysozyme and total superoxide dismutase activities, respectively. Overall, this study revealed that FOS incorporated diets could beneficial for L. japonicus culture in terms of increasing the growth, digestion and immune activities. Under the present experimental condition, the optimal supplementary level of FOS in the diet of L. japonicus is 1–3 g/kg.  相似文献   

17.
Two gonadotropins (GtH; Qa and Qb) were purified by gel filtration and ion exchange chromatography from the pituitaries of Indian walking catfish (Clarias batrachus). The presence of GtH during purification was assessed by in vitro oocyte maturation and in vivo steroidogenic activity, and their identities were determined by elution profiles, molecular weight, biological activities and yield. The molecular weights of Qa and Qb were 37 and 42 kDa, respectively, and composed of distinct subunits (Qa: 20 and 14 kDa and Qb: 26 and 18 kDa). Polyclonal antibodies raised against Qa immunostained Qa, Qb and pituitary GtH cells. A competitive Qa‐ELISA was developed whose sensitivity was 6.25 ng mL?1 (1.25 ng well?1) with intra‐ (3.5%) and inter‐ (12.4%) assay coefficients of variation. Displacement curves parallel to the standard were obtained with plasma and pituitary extracts of catfish, Qb and carp GtHII. The assay was validated by measuring the plasma Qa levels after LHRH treatment and in relation to ovarian growth in the female catfish during different reproductive phases. Based on the results, Qa and Qb corresponded to fish LH and FSH respectively. The findings will increase the knowledge of the mechanisms controlling fish reproduction and identification of sensitive phases in fish in captivity for hormonal manipulation.  相似文献   

18.
Protein and amino acid composition of the mantle of juvenile O ctopus vulgaris (Cuvier, 1797) during fasting for 27 days were determined. Average protein content of octopus mantle was of 711.19 ± 46.80 g kg?1 DW, and it decreased with increasing fasting days. The non‐essential amino acids content was higher (486.18 ± 11.08 g kg?1 protein) than essential amino acids (425.82 ± 9.15 g kg?1 protein) at the start of the experiment (unstarved animals). The results suggest that the amino acid profile of the mantle where the most abundant amino acids are Arg, His, Lys, Gly, Leu and Pro could indicate a prolonged fasting condition (>20 days) or poor nutrition of O . vulgaris. This study supports the idea of using mantle for metabolic needs of starved O . vulgaris suggesting that the degradation pathway of amino acids to pyruvate and tricarboxylic acid cycle intermediates was favoured contrary to the degradation pathway of ketogenic amino acids. Special considerations should be taken concerning Thr, Ile, Ser, Ala, Asx (Asp, Asn), Glx (Glu, Gln) (because of their fast intake) and Lys and His (due to their stable contents) during a prolonged period of fasting.  相似文献   

19.
Tetrahymena is a protozoan parasite, which infects guppy, Poecilia reticulata Peters, and causes substantial economical losses in commercial farms worldwide. Studies of guppy infected by Tetrahymena require standardized infection protocols. The LD50 for Tetrahymena infection of guppies by intraperitoneal (IP) injection was calibrated, and the level obtained was 946 parasites per fish. Guppy infection with Tetrahymena by immersion, imitating the natural route of infection via the integument, was studied under normal or stress conditions. Exposure to cold and netting (CNI) and to cold only (CI) followed by immersion exposure to 10 000 Tetrahymena per mL resulted in 22.5% and 19.2% mortality, respectively, as compared to 14.2% and 10% in groups that were netted only (NI) or non‐stressed (I). Histopathology revealed that immersion infection resulted in a systemic infection. Lysozyme levels, measured 3 weeks after infection, were significantly higher in the CNI group (288 μg per mg protein) compared with CI‐, NI‐ and I‐treated groups (94.5, 64 and 62.3 μg mg?1, respectively). There was no evident parasite immobilization activity in body homogenates, suggesting no development of acquired immunity. Re‐infection by IP injection revealed no increase in protection in any of the treatment groups, mortality range of 56.3–75%, higher than in the non‐exposed control (40.6% mortality).  相似文献   

20.
The endemic, anadromous cyprinidChalcalburnus tarichi is the only fish species known to occur in alkaline Lake Van (Eastern Anatolia, Turkey). EightC. tarichi were maintained individually in Lake Van water (17 – 19°C; pH 9.8; 153 mEq·I–1 total alkalinity; 22 total salinity) and tank water samples analyzed for 24 h in 2 to 4 h intervals. At zero time, < 1µM ammonia was present and urea was undetectable in the tank water; at 24 h, total ammonia and urea made up 114±32 and 35±25µM, respectively. Over the experimental period, ammonia-N and urea-N excretion averaged 1041±494 and 607±169moles·kg–1 fish·h–1, respectively. The extent of urea excretion was highly variable between specimens. Uric acid excretion was not detectable.Urea was present at high concentrations in all tissues and plasma (25 – 35moles·g–1·ml–1) of freshly caughtC. tarichi; total ammonia content of the tissues was by a factor of 1.9 (liver) to 3.0 (brain) lower. High arginase activity (2.4±0.2 U·min–1·g–1) was detected in the liver ofC. tarichi but ornithine carbamoylphosphate transferase, a key enzyme of the ornithine-urea-cycle, was absent. Ureagenesis is likely through degradation of arginine and/or uricolysis. High glutamine synthetase activity (11±0.6 U·min–1·g–1) and low ammonia content in brain suggest that, like other teleosts,C. tarichi has an efficient ammonia detoxification in the brain, but in no other tissue.Nitrogenous waste excretion at alkaline pH is discussed. The ability ofC. tarichi to excrete high levels of ammonia at extremely alkaline pH is unique among teleosts studied so far. The mechanism of ammonia excretion under Lake Van conditions remains to be elucidated.  相似文献   

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