Analysis of mesh breaking loads in cotton gill nets: Possible solution to ghost fishing     

Yoshiki Matsushita  Shusuke Machida  Haruyuki Kanehiro  Fumio Nakamura  Naoto Honda 《Fisheries Science》2008,74(2):230-235

ABSTRACT:   A small number of fishers in Chiba Prefecture of eastern Japan use cotton gill nets to catch Japanese spiny lobster Panulirus japonicus. To examine the advantages of cotton gill nets, we analyzed changes in mesh breaking load of a new cotton gill net used in a fishing operation. A new cotton gill net was also soaked in a seawater tank to simulate ghost fishing conditions. The average mesh breaking load of new cotton mesh was 50.3 N. This value decreased to 19.0 N after 38 days (∼912 h), and after 82 days (∼1968 h) the mesh could be easily torn (breaking load 0.07 N). Under fishing conditions, the cumulative soak time was only 744.4 h over 19 months. The average breaking load at the end of this period was 43.1 N, a strength 86% that of the presoaked mesh. The mesh breaking load of a cotton gill net continuously soaked for 744.4 h was 26.1 N, as estimated from tank experiment data. Thus, a cotton gill net maintains reasonable strength under typical use conditions, but will degrade if lost at sea.  相似文献   

广东东莞松木山水库鱼类群落结构及其与环境因子的关系     

袁晨  裴瑞华  郑梓瑶  吴鹏举  黄娜  李一帆  胡忠军 《上海海洋大学学报》2022,31(4):940-949

为探讨广东东莞松木山水库鱼类群落结构特征及其与环境因子的关系,分析其结构特征在沉浮网间的差异性,在该水库设置3个采样点采用多网目刺网对鱼类进行了调查。结果显示,共采集到鱼类17种,隶属4目、6科,物种数以鲤形目为主（占58.82%）。相对重要性指数（IRI）显示,优势种为海南似鱎（IRI占比29.66%）、?（18.98%）、尼罗非鲫（18.46%）、鲢（14.85%）和莫桑比克非鲫（11.36%）,其中单位努力捕捞数量（NPUE）以海南似鱎（45.72%）占优、单位努力捕捞重量（BPUE）以尼罗非鲫（34.60%）为主。聚类分析表明,鱼类物种组成在季节间无显著差异,物种数、NPUE和BPUE亦无季节变化（P>0.05）。鱼类群落物种数、NPUE和BPUE沉浮网间无显著差异（P>0.05）,但鱼类数量组成沉浮网间存在显著差异（P<0.001）,与海南似鱎有关,其NPUE浮网显著高于沉网（P<0.05）,其他5种主要鱼类沉浮网间无显著差异（P>0.05）。透明度、pH和总磷是影响鱼类物种数量时空分布的关键环境因子。研究表明,松木山水库鱼类多样性低,可能与水面积较小、连通性低、外来种入侵及入库河道以人工排渠为主有关,为科学合理评估鱼类数量组成建议水库鱼类调查需要同时使用沉浮网。  相似文献   

Blood chemistry and acid-base balance in rainbow trout Oncorhynchus mykiss with experimentally-induced acute bacterial gill disease     

P. J. Byrne  V. E. Ostland  J. S. Lumsden  D. D. MacPhee  H. W. Ferguson 《Fish physiology and biochemistry》1995,14(6):509-518

Rainbow trout were experimentally infected with the causative agent of bacterial gill disease (BGD) (Flavobacterium branchiophilum) via bath challenge. All fish were cannulated with dorsal aortic catheters, had nasogastric tubes sutured in place for feeding, and were maintained individually, in plexiglass boxes with a flow-through water system. Fish were either fed, or unfed during the trial. Acute changes in blood gas, serum biochemistry and clinical parameters were monitored. By 24h post-challenge, BGD-infected trout that had been fed had significant hypoxemia, hypercapnia, increased blood ammonia, hypoosmolality, hyponatremia, hypochloremia, and increased cough and respiratory rates when compared to control levels. Unfed BGD-infected trout had similar, but less severe blood gas and clinical changes, and no electrolyte disturbances. The BGD-induced hypoxemia is likely exacerbated by increased oxygen demands brought on by feeding. It is not known what association feeding has with the development of low serum ion levels in BGD-infected trout. This is the first study to report the use of fed fish, as opposed to unfed or starved trout, in obtaining blood chemistry values from indisturbed and cannulated animals.  相似文献   

Hormonal influences on in vitro [35S]-sulfate uptake by gill arches from the goldfish (Carassius auratus L.)     

Tracy A. Marchant  Brenda M. Moroz 《Fish physiology and biochemistry》1993,11(1-6):393-399

A bioassay for insulin-like growth factor (IGF), based on the in vitro incorporation of [³⁵S]-sulfate into gill arch tissue was used to study the hormonal regulation of proteoglycan synthesis in the goldfish (Carassius auratus). [³⁵S]-sulfate incorporation into gill arch tissue was found to be time-dependent with maximal uptake occurring by 48h, suggesting that proteoglycan synthesis in this tissue was maintained for at least 48h in vitro. The addition of human recombinant IGF-I (IGF-I) to the incubation medium was found to significantly stimulate [³⁵S]-sulfate uptake into the gill arches, whereas bovine growth hormone (GH) was without effect. Porcine insulin was also stimulatory, but results indicate that the effects of porcine insulin and IGF-I may be mediated by a single receptor system. Finally, arches from hypophysectomized fish were significantly less responsive to IGF-I than were arches from sham-operated fish. Furthermore, administration of ovine GH in vivo appeared to increase subsequent responsiveness in vitro. Together, these results provide evidence that the growth-promoting actions of GH in the goldfish may be mediated, at least in part, by a peptide related in structure to mammalian IGF-I.  相似文献   

Production of salmonid amoebic gill disease by exposure to Paramoeba sp. harvested from the gills of infected fish     

D Zilberg  A Gross  & B L Munday 《Journal of fish diseases》2001,24(2):79-82

Atlantic salmon, S almo salar L., were exposed to different concentrations of Paramoeba sp. The lowest concentration which induced amoebic gill disease (AGD) was 230 Paramoeba sp. L^–1 and the severity of infection increased with increasing concentration. The concentration of Paramoeba sp. positively correlated with the number of gill lesions ( R ² > 0.7). This study provides evidence that Paramoeba sp. is the causative agent of AGD and describes an experimental model that enables the severity of the induced disease to be controlled.  相似文献   

The wheat germ agglutinin binding sites and development of the mitochondria-rich cells in gills of tilapia (Oreochromis mossambicus)     

J.C. Tsai  P.P. Hwang 《Fish physiology and biochemistry》1998,19(1):95-102

By labelling with gold-colloid-conjugated wheat germ agglutinin (WGA), the WGA-binding sites were identified in the apical region of certain mitochondria-rich (MR) cells in gills of freshwater-adapted tilapia (Oreochromis mossambicus). Bromo-deoxyuridine (BrdU) injection was used to discern the differentiation of the WGA binding sites during development of MR cells. Double labeling of gill sections of fish 2, 4, 6, and 8 days after a single BrdU injection showed that the BrdU labeled MR cells 2 and 4 days after injection were mostly WGA negative, whereas 6 and 8 days after injection, WGA and BrdU-labeled MR cell increased gradually in number. Furthermore, the ratio of the WGA-positive to total MR-cells was higher in gills of tilapia adapted to low calcium ([Ca] = 0.015 mm) freshwater than in hard freshwater ([Ca] = 1.898 mm). The results indicate that WGA binding site may be a marker expressed late during differentiation of MR cells, and physiologically functional in assisting uptake of calcium when environmental calcium is low. According to their WGA binding and also characteristics their likely function in calcium absorption, the WGA positive MR cells shown in this study are considered to be similar to the cells described by Pisam et al. (1995).  相似文献   

A method for calculating numerical estimates of gear selectivity curve   总被引：1，自引：0，他引：1  

EIJI  TANAKA 《Fisheries Science》2002,68(5):1081-1087

The present paper proposes a method for estimating the numerical curve of gear selectivity without the assumption of function of selectivity curve and estimating confidence intervals, using data of catch per unit effort at length for several nets of different mesh sizes obtained from fishing experiments. The paper assumes such geometric similarity as the selectivity is the same if the rate of fish length to mesh size is the same. The basic idea is due to a technique of numerical integration that uses the derivatives at various points. The natural logarithm of selectivity is expressed by an approximation equation using its cumulated derivatives. The values of derivatives at various lengths are calculated from the data. The confidence intervals are made from the bootstrap samples. The method was applied to the data of catch at length by mesh size of gill net for pink salmon Oncorhynchus gorbuscha . Data collection, modification and issues of the method are discussed.  相似文献   

Reduced total hardness of fresh water enhances the efficacy of bathing as a treatment for amoebic gill disease in Atlantic salmon, Salmo salar L     

Roberts SD  Powell MD 《Journal of fish diseases》2003,26(10):591-599

The current treatment for amoebic gill disease (AGD)-affected Atlantic salmon involves bathing sea-caged fish in fresh water, often sourced from local dams, for 3-4 h. In both a small-scale laboratory and an on-farm field experiment, the effects of water hardness on the efficacy of freshwater bathing were assessed. Results showed that soft fresh water (19.3-37.4 mg L(-1) CaCO3), whether it be naturally soft city mains water or artificially softened dam water, was more efficacious at alleviating AGD in affected fish than hard fresh water (173-236.3 mg L(-1) CaCO3). Soft freshwater bathing significantly reduced viable gill amoebae numbers (from 73.9 to 40.9% of total count) and significantly alleviated gill pathology, both gross and histological. Following bathing, gross gill pathological scores of soft freshwater bathed fish lagged 2 weeks behind hard freshwater bathed fish. Significant gill lesion fragmentation, and shedding of lesion-associated hyperplastic tissue, was accompanied by a significant reduction in AGD-affected gill filaments in soft freshwater bathed fish. Furthermore, soft freshwater bathing alleviated the blood plasma electrolyte imbalance seen in control (sea water) and hard freshwater bathed fish. This study showed that the use of soft fresh water for bathing AGD-affected Atlantic salmon could be an improvement to the current method of treatment. Not only does it reduce gill amoeba numbers, but also, it is of a therapeutic advantage with the potential to reduce bathing frequency.  相似文献   

Fusarium incarnatum isolated from black tiger shrimp, Penaeus monodon Fabricius, with black gill disease cultured in Vietnam   总被引：1，自引：0，他引：1  

Khoa LV  Hatai K  Aoki T 《Journal of fish diseases》2004,27(9):507-515

Fusarium incarnatum was isolated from gill lesions of cultured black tiger shrimp, Penaeus monodon, in every crop during 2000-2002 in Nghe An province, Vietnam. Infected shrimps showed typical signs of black gill disease and mortalities about a month prior to harvest. Detailed morphological examinations, as well as molecular phylogenic analyses based on partial nucleotide sequences of ribosomal DNA, were made on the isolates. An artificial infection of kuruma prawn, Penaeus japonicus, using two selected isolates was also conducted and their pathogenicity determined.  相似文献   

The effect of acid water on oxygen consumption,circulating catecholamines and blood ionic and acid-base status in rainbow trout (Salmo gairdneri,Richardson)     

Xuemin Ye  D. J. Randall  Xiqin He 《Fish physiology and biochemistry》1991,9(1):23-30

Chronically cannulated rainbow trout were exposed in acid water (pH 4.0) for 72h. The gill potential was strongly dependent on water pH, being blood side negative in neutral water, but positive in acid water. Catecholamine levels increased irregularly during acid exposure, and the Bohr and Root effects were not completely erased by the effect of catecholamines during acid exposure. Long term exposure to low water pH, although causing an acidosis in the fish, did not suppress resting oxygen consumption. Prolonged exposure to acid conditions, however, resulted in an increase in ammonia excretion. Changes in plasma sodium and chloride were similar to that reported previously for trout exposed to low calcium, acid water. We conclude that exposure of trout to pH 4 soft water, although impairing oxygen transport, does not limit resting oxygen consumption but does reduce the scope for activity. More extreme acid conditions do impair resting oxygen uptake.  相似文献