中国远洋渔业企业规模经济效应研究——基于数据包络分析方法     

谭春兰  胡红 《中国农学通报》2015,31(23):36-42

为了研究中国远洋渔业企业的规模经济效应并最终促进远洋渔业企业的发展,通过运用DEA（数据包络分析）模型,对中国3家远洋渔业上市公司总共30个年份的投入和产出数据进行了实证分析,并对远洋渔业企业的规模经济效率和综合技术效率等进行了评估和测算。结果表明,中国远洋渔业企业的整体规模经济系数较高,但并未充分发挥规模经济的作用。远洋渔业企业综合技术效率偏低,不利于企业规模经济效应的发挥,对企业的生产经营效率形成制约。远洋渔业企业的劳动力投入成本偏高,劳动力投入过剩,投入要素结构不合理。通过对非DEA有效单元的分析,为远洋渔业企业达到DEA有效指明改善的方向和途径。  相似文献   

Non-stationary effects of multiple drivers on the dynamics of Japanese sardine (Sardinops melanostictus,Clupeidae)     

Shuyang Ma  Caihong Fu  Jianchao Li  Peng Sun  Yang Liu  Zhenjiang Ye  Yoshiro Watanabe  Yongjun Tian 《Fish and Fisheries》2023,24(1):40-55

Non-stationary driver-response relationships are increasingly being recognized by scientists, underlining that a paradigm shift out of conventional stationary relationships is crucial. Japanese sardine (Sardinops melanostictus, Clupeidae) is a typical small pelagic fish in the northwestern Pacific with considerable fluctuations in productivity, bringing about great economic and ecological concerns. Numerous studies suggest that the population dynamics of Japanese sardine is an integrated process affected by multiple density-dependent, fishing and climatic drivers. However, little has hitherto been done to incorporate the non-stationary effects of multiple drivers, impeding progresses in understanding the population dynamics and in developing management strategies. In this study, we adopted variable coefficients generalized additive models to reveal the non-stationary effects of density dependence, fishing pressure and climatic conditions on the population dynamics of Japanese sardine. Results suggest that the dynamics of Japanese sardine from 1976 to 2018 could be divided into four periods: the 1980s when suitable climatic conditions from strong Siberian High pressure system sustained high abundance; the 1990s when negative density-dependent effects and degrading climatic conditions due to temperature increase led to population collapse; the 2000s when negative triple effects, particularly high fishing pressure, restricted the population increase; and the 2010s when favourable climatic conditions with re-strengthening Siberian High pressure system accompanied by low fishing pressure contributed to the population recovery. The study highlights that precise identifications of population status and climatic conditions are helpful to achieve good trade-offs between resource exploitation and protection and to facilitate ecosystem-based management for Japanese sardine fisheries.  相似文献   

台湾海峡及其邻近海域鲐鲹鱼类群聚资源的评估   总被引：7，自引：1，他引：6       下载免费PDF全文

卢振彬  戴泉水  颜尤明 《中国水产科学》2000,7(1)

:以初级生产力为基础 ,应用Steele模式估算台湾海峡及其邻近海域中上层鱼类资源年生产量为16 9.88× 10 4 t。估算鲐鱼类群聚资源量为 10 2 .0 8× 10 4 t。Gulland模式和简单模式估算鲐鱼类群聚资源的MSY分别为 50 .6 6× 10 4 t和 51.0 4× 10 4 t。Schaefer和Fox 2种剩余产量模式所估算的MSY分别为52 .4 1× 10 4 t和 51.73× 10 4 t,估算的fMSY换算为福建灯围渔船分别为 10 17组和 10 75组 ,并从海峡南、北 2个不同群系的鲐鱼类主要种群结构和生态学变化及渔业现状 ,讨论该 2个鲐群聚资源的开发利用程度  相似文献   

闽南_台湾浅滩渔场六种主要中上层鱼类的脂肪酸研究   总被引：7，自引：1，他引：6  

吴志强 《水产学报》2000,24(1):61-64,65,66

研究了蓝圆Ｓｈｅｎ、金色小沙丁鱼、颌圆Ｓｈｅｎ、鲐鱼、竹Ｊｉａ鱼、羽鳃鲐肌油中的脂肪酸组成及含量变化。结果表明：鱼油中都含有Ｃ１２－Ｃ２２系列脂肪酸。饱和脂肪酸（ＳＦＡ）占总脂肪酸（ＴＦＡ）的３５．２４％￣３８．６０％,单不饱和脂肪酸（ＭＵＦＡ）占２３．５９％￣３０．０７％,多不饱和脂肪酸（ＰＵＦＡ）占３３．０６％￣４０．３３％,ＥＰＡ占２．３５％￣３．６２％,ＤＨＡ占１７．９５％￣２４．４９％。  相似文献   

东海浮游十足类优势种环境适应的研究   总被引：6，自引：0，他引：6  

徐兆礼 《水产学报》2005,29(6):762-768

根据1997-2000年东海23°30′~33°N、118°30′~128°E海域4个季节海洋调查资料,对东海浮游十足类优势种的生态特征进行了研究,探讨这些优势种对环境的适应及与渔场的关系。结果表明:主要优势种有中型莹虾Lucifer intermedius、刷状莹虾Lucifer penicillifer、细螯虾Leptochela gracilis和汉森莹虾Lucifer hanseni。前2个优势种是近海暖水种,细螯虾是广温高盐种,汉森莹虾是外海暖水种。近海暖水种不但平均丰度高,而且优势度和占浮游十足类总丰度的百分比均大于其它优势种。广温高盐优势种具有较高的出现率,细鳌虾丰度不高,但在每个季节、各个海区均有出现。在夏季,低温环境适应力差的暖水种往往有很高的聚集强度。与东海其它类群的浮游动物不同,浮游十足类以夏季丰度最大。就个体数量而言,以近海暖水种个体居多,主要分布在位于东海沿岸河口附近的鱼类产卵场。  相似文献   

Which are the best environmental conditions for catching the beach‐seine target species? A Portuguese case study     

Clia M. Teixeira  Priscila M. Silva  Rita Gamito  Sandra Amoroso  Nuno Lopes  Catarina Freitas  Henrique N. Cabral  Jos L. Costa 《Fisheries Oceanography》2020,29(3):276-289

The beach‐seine fishery is a commercial fishing activity on the Portuguese coast, with reports dating as far back as the early 15th century. The main target species of this fishery are small pelagic fish such as Atlantic chub mackerel, Atlantic horse mackerel and sardine. To identify the best conditions for fishing the target species, catches of beach seine (2007–2017) were used and generalized linear models were applied, using a binomial and gamma distributions. The logistic model explained between 36.3% and 45.7% of the catches variability; the gamma model explained 9.1% and 46.9% of the catches variability, being month and wind direction the best covariates for the occurrence and/or abundance of the three small pelagic fishes in analysis. If the effort is directed to the days that meet the conditions found for each species (sardine: between May and October, wind NW, daytime; Atlantic horse mackerel: May, NW/NE wind, 800 m from the coastline; Atlantic chub mackerel: from July to August, NW moderate wind), a reduction in bycatch and discards can be achieved. This approach can have a positive economic and social impact, since it provides information for turning fisheries more efficient.  相似文献   

Spawning habitat of the Atlantic menhaden in Onslow Bay, North Carolina   总被引：2，自引：0，他引：2  

Checkley  Jr  Ortner  Werner  Settle  & Cummings 《Fisheries Oceanography》1999,8(S2):22-36

The Continuous, Underway Fish Egg Sampler (CUFES) was used to sample pelagic eggs of the Atlantic menhaden ( Brevoortia tyrannus ) from 3-m depth off North Carolina in winter 1993–94 and 1994–95. Simultaneous measurements were made of temperature, salinity, and the concentration of chlorophyll a . The maximal concentration of eggs was 346 eggs m⁻³. Eggs were highly aggregated in patches which occurred between the Gulf Stream and mid-shelf fronts (17–23°C, 36.0–36.4‰). Unexpectedly, eggs were found almost exclusively in water of 20–60 m (mode 20 m) bottom depth. Thus, spawning appears related to bathymetry as well as hydrography. Variograms for egg concentration indicated a mean (± SE) patch scale of 3.6 ± 1.7 km and a high degree of spatial variance explained by CUFES sampling. Lagrangian modelling of particles moving in response to tides, winds, and a prescribed flow from the north indicated that the region of observed, maximal occurrence of eggs is favourable for the retention of eggs and larvae on the shelf adjacent to inlets used to enter nursery areas.  相似文献   

Simulations of the Black Sea pelagic ecosystem by 1-D, vertically resolved, physical–biochemical models     

TEMEL OGUZ  HUGH W. DUCKLOW  PAOLA MALANOTTE-RIZZOLI  & JAMES W. MURRAY 《Fisheries Oceanography》1998,7(3-4):300-304

The present paper summarizes the results of several simulations of the central Black Sea pelagic food web using three different 1-D, physical–biochemical, water column process models. The most simplified, five-compartment version is used to explore the robust biological features of the ecosystem and the role of upper-layer physics on the evolution of the euphotic zone biological processes. The other models, introducing additional biological complexities, show how these biologically structured models become more capable of simulating intensified subsurface summer production, more dynamic plankton structure arising after the increasing role of gelatinous carnivores in the ecosystem during the 1980s, and fairly sophisticated nitrogen cycling in the water column.  相似文献   

中东大西洋中部海域中上层鱼类资源结构与渔场分布   总被引：1，自引：0，他引：1  

逄志伟  张鹏  李显森 《水生态学杂志》2017,38(6):57-63

为了解中东大西洋中部海域中上层鱼类资源结构与渔场分布,对2007-2014年入渔FAO34渔区3.11和1.32小区(毛里塔尼亚专属经济区)从事中上层鱼类捕捞的7艘国内渔船的生产数据进行了分析。结果表明,我国入渔船只数量、入渔渔船总产量和作业渔船平均日产量均呈现先增加、后减少的趋势,且在2011年入渔渔船总产量和作业渔船平均日产量到达最大值,2012年入渔船只数量到达最大值。渔获种类主要包括沙丁鱼(Sardina pilchardus)、短体小沙丁鱼(Sardinella maderensis)、金色小沙丁鱼(Sardinella aurita)、日本鲭(Scomber japonicus)和竹筴鱼(Trachurus trachurus),各渔获种类的渔获量年际间波动较为明显。月均产量在17.2~23.6 t/haul,最高值和最低值分别出现在12月和8月;月均总产量在1 279.0~2 414.2 t,最高值和最低值分别出现在1月和8月,12月至次年3月为渔汛旺期。渔场季节变化现象明显,夏秋季向北移动,冬春季向南移动,20.0°~20.8°N、17.4°~18.0°W区域为高产量海域。该海域中上层鱼类洄游现象明显,这可能主要与该海域的不同洋流在不同月份的强弱变化有关,该海域整体渔业资源呈现一定衰退现象。建议渔船入渔该海域从事中上层鱼类捕捞持谨慎态度,加强该海域渔业资源的研究与保护。  相似文献   

Does upwelling intensity determine larval fish habitats in upwelling ecosystems? The case of Senegal and Mauritania          下载免费PDF全文

Maik Tiedemann  Heino O. Fock  Patrice Brehmer  Julian Döring  Christian Möllmann 《Fisheries Oceanography》2017,26(6):655-667

European sardine (Sardina pilchardus) and round sardinella (Sardinella aurita) comprise two‐thirds of total landings of small pelagic fishes in the Canary Current Eastern Boundary Ecosystem (CCEBE). Their spawning habitat is the continental shelf where upwelling is responsible for high productivity. While upwelling intensity is predicted to change through ocean warming, the effects of upwelling intensity on larval fish habitat expansion is not well understood. Larval habitat characteristics of both species were investigated during different upwelling intensity regimes. Three surveys were carried out to sample fish larvae during cold (permanent upwelling) and warm (low upwelling) seasons along the southern coastal upwelling area of the CCEBE (13°–22.5°N). Sardina pilchardus larvae were observed in areas of strong upwelling during both seasons. Larval habitat expansion was restricted from 22.5°N to 17.5°N during cold seasons and to 22.5°N during the warm season. Sardinella aurita larvae were observed from 13°N to 15°N during cold seasons and 16–21°N in the warm season under low upwelling conditions. Generalized additive models predicted upwelling intensity driven larval fish abundance patterns. Observations and modeling revealed species‐specific spawning times and locations, that resulted in a niche partitioning allowing species' co‐existence. Alterations in upwelling intensity may have drastic effects on the spawning behavior, larval survival, and probably recruitment success of a species. The results enable insights into the spawning behavior of major small pelagic fish species in the CCEBE. Understanding biological responses to physical variability are essential in managing marine resources under changing climate conditions.  相似文献