The Migrations of North Esk Sea Trout

The migrations of North Esk sea trout were studied by tagging all stages of sea trout taken in a stationary trap situated on Kinnaber Mill Lade which drains its water from the main river. The majority of recaptures were reported from the Montrose area, and evidence of a great deal of intermixing between the sea trout of the North Esk and neighbouring rivers was found. After their initial migration as smolts a proportion of the tagged sea trout returned to fresh water within the same year. Some tagged fish undertook several journeys back and forth between sea water and fresh water during (his period. Numerous examples of tagged sea trout travelling appreciable distances (>100 km) along the coast were obtained. In addition four tagged fish were recaptured in excess of 500 km from the North Esk, three off the Scandinavian coast and one in the River Barvas, North West Lewis.     

虹鳟海水驯养试验报告

对４批１８８１尾不同规格的虹鳟进行由淡水过渡到海水的驯养试验。过渡时间５－７天，最小体长３．５ｃｍ，过渡成活率９９．５％。在海水中饲养６４天，增重率为８０％。利用对虾育苗池进行的自然水温海水越冬试验，存活率８７％。１９８５年底专家鉴定认为，本研究成果处于国内同类研究先水平。     

Size and MEP-2* variation in juvenile Atlantic salmon (Salmo salar) in the River North Esk,Scotland

The relationship of size to MEP-2* genotype was investigated in 0+ juvenile Atlantic salmon (Salmo salar) in the River North Esk, Scotland. Significant temperature-associated MEP-2* heterogeneity was observed among tributaries and, in the two tributaries studied, size and MEP-2* genotype were significantly associated. No size association, or heterogeneity among tributaries, was found for the other allozyme polymorphisms screened. The results suggest that the association between size and MEP-2* variation, noted by others, is likely to be widespread in wild populations, and potentially linked to habitat temperature.     

Differences in the time of river entry of Atlantic salmon,Salmo salar L., spawning in different parts of the River North Esk

Abstract Spawning adult Atlantic salmon, Salmo salar L., were sampled in five tributaries of the River North Esk, Scotland, during the winters 1989/90 and 1990/91. The fish furthest upriver had higher sea- and smolt-ages and the one-sea-winter fish were smaller and more coloured than those spawning further downstream. These differences indicate that the uppermost tributaries are populated by fish which enter the river early in the year and the lowest tributaries by fish entering late in the year. Exactly why such a structure exists is not clear, but it is suggested that these differences may be adaptive and that selection effects may continually be modifying these populations.     

The economic feasibility of seaweed production in the North Sea

Seaweeds are increasingly seen as an alternative to land-grown products in food and feed applications. Interest in production of seaweeds in temperate waters is rising, in particular in combination with offshore wind energy generation. This article reports an investigation of the economic feasibility of seaweed production in the North Sea using economic modelling. Often, an overly positive picture of the costs and benefits of seaweed production is sketched. Based on current available information, offshore seaweed production in the North Sea is not economically feasible. Sensitivity analysis shows that revenues would have to increase by roughly 300%, all other things equal, to make a profit. A number of opportunities to improve the economic feasibility of a North Sea seaweed value chain are identified. Technical innovation and the design of systems that enable multiple harvests per year can reduce production costs. Successful marketing of seaweed as human food, and the development of biorefinery concepts can increase the value of the produced seaweed.     

The Economic Impact of the Trout,Oncorhynchus mykiss,Industry on Transylvania County,North Carolina

Abstract

The commercial culture of rainbow trout, Oncorhynchus mykiss, in Transylvania County, North Carolina, generated approximately $9 million in economic output in 2002. Commercial trout farming began in North Carolina more than 45 years ago. Twenty of the 57 commercial trout farms in production in North Carolina are located in Transylvania County, ranging in size from 1,135 to 204,300 kg annual production in 2002. North Carolina presently ranks second in the United States in commercial trout production, behind Idaho. The study shows that, in 2002, the trout industry generated about $9 million in economic output, created 201 jobs, and generated $3 and $0.9 million, respectively, as labor income and tax revenue in 2002. This is particularly important for Transylvania County where economic prosperity depends on locally available jobs and diversification of economic activities.     

东海北部和黄海南部鲐鱼年龄和生长的研究

本研究采用2002年11月～2003年8月在东海北部和黄海南部海域(30°～34°N、126°E以西)所获取的鲐鱼渔获样品,合计采集777ind,通过对鲐鱼耳石生长轮的观察和基础生物学测定,研究了鲐鱼的年龄和生长。结果表明叉长与体重的关系雌雄间没有显著性差异;所鉴定鲐鱼年龄组成为1～3龄鱼,共3个年龄序列,并补充20世纪80年代4～5龄鱼对鲐鱼的生长规律进行研究,采用Walford方法拟合,其生长参数K、L∞、t0分别为0.31993、451.3514和-1.20307;鲐鱼的生长拐点年龄为2.7yr,拐点体重为450g,拐点叉长为320mm。比较分析东海群系鲐鱼的渔业生物学历史状况,在目前所能观察得到的鲐鱼年龄段内(1～3龄),东海区鲐鱼个体平均叉长比20世纪80年代的都要小;与闽南、粤东近海地方群系的相比,东海群系的平均叉长在鲐鱼的整个生长阶段都明显的大。     

Spawning of North Sea fishes linked to hydrographic features

Spawning of fishes takes place across a wide area of the North Sea. However, more intense spawning is seen in restricted areas, indicating that such areas present favorable conditions. To update information on fish spawning in the North Sea and analyze potential linkages to hydrographic characteristics, an internationally coordinated survey was conducted in the winter/spring of 2004. Oblique hauls for fish eggs and larvae and vertical profiles of temperature and salinity were carried out at 393 stations across the entire North Sea. The hydrography was strongly influenced by the interfacing of water masses of different salinity, and frontal zones were seen along all coastal areas and off the Dogger and Fisher Banks. Total abundances of eggs and larvae, including fish species such as cod, haddock, plaice, long rough dab and sandeel, peaked in the vicinity of the frontal areas. Hence our findings indicate that the main spawning locations of fish are linked to recurrent hydrographic features such as salinity fronts. Such a linkage may provide survival advantages, as the fronts present favorable feeding conditions, and the related physical processes may confine egg and larval dispersal and transport them towards suitable nursery habitats.     

Climate fluctuations and the spring invasion of the North Sea by Calanus finmarchicus

The population of Calanus finmarchicus in the North Sea is replenished each spring by invasion from an overwintering stock located beyond the shelf edge. A combination of field observations, statistical analysis of Continuous Plankton Recorder (CPR) data, and particle tracking model simulations, was used to investigate the processes involved in the cross-shelf invasion. The results showed that the main source of overwintering animals entering the North Sea in the spring is at depths of greater than 600 m in the Faroe–Shetland Channel, where concentrations of up to 620 m⁻³ are found in association with the overflow of Norwegian Sea Deep Water (NSDW) across the Iceland–Scotland Ridge. The input of this water mass to the Faroe–Shetland Channel, and hence the supply of overwintering C. finmarchicus , has declined since the late 1960s due to changes in convective processes in the Greenland Sea. Beginning in February, animals start to emerge from the overwintering state and migrate to the surface waters, where their transport into the North Sea is mainly determined by the incidence of north-westerly winds that have declined since the 1960s. Together, these two factors explain a high proportion of the 30-year trends in spring abundance in the North Sea as measured by the CPR survey. Both the regional winds and the NSDW overflow are connected to the North Atlantic Oscillation Index (NAO), which is an atmospheric climate index, but with different time scales of response. Thus, interannual fluctuations in the NAO can cause immediate changes in the incidence of north-westerly winds without leading to corresponding changes in C. finmarchicus abundance in the North Sea, because the NSDW overflow responds over longer (decadal) time scales.     

黄海北部对虾增殖业发展的探讨

黄海北部对虾增殖业历经17年，有了较快发展。目前，苗种、资金、回捕效果等制约因素，影响了对虾增殖业的可持续发展。应采取稳定苗种来源、加大资金投入、提高增殖效果的综合措施，推动对虾增殖业的进一步发展。     

Variability in growth rates of larval haddock in the northern North Sea

The large-scale distribution of haddock ( Melanogrammus aeglefinus ) larvae in the northern North Sea was mapped in a grid survey carried out in late April 1996. A drifting buoy was deployed in the centre of one of the areas of concentration of larvae located off the east coast of the Shetland Isles, where intensive sampling was carried out for ≈ 10 days. Daily larval haddock growth variability, estimated from otolith microstructure analysis, was independent of the measured variability of the physical and biological environment of the larvae. The survey coincided with the onset of the spring plankton production bloom, and a likely explanation for the absence of environmental effects on larval growth was high food availability and larval feeding rates. Nevertheless, differences in growth were observed between cohorts, with larvae hatched later in the spring displaying higher growth at age than those hatched earlier. Particle-tracking modelling suggested that differences in temperature history between cohorts, on their own or compounded by a potential interaction between temperature and the development of plankton production, may explain the higher growth rate of the larvae hatched later in the season.     

虹鳟饲料配方对比试验

饲料的好坏直接影响到虹鳟的产量和效益 ,因此 ,有必要不断改进虹鳟饲料配方。为此 ,我们进行了该试验 ,并取得了良好效果。1　材料与方法试验在本溪虹鳟渔场进行。用条件相同的 1号和 2号两口水泥池 ,面积各为 2 0ｍ2 ,均为头水位池。各池放虹鳟鱼 2 2 2 0尾 ,放养规格 1号池1 0 2 6ｇ/尾 ,2号池 1 1 2 0ｇ/尾。 1号池溶氧为9 37ｍｇ/Ｌ ,氨氮为 0 46ｍｇ/Ｌ ;2号池溶氧为9 0 5ｍｇ/Ｌ ,氨氮为 0 2 3ｍｇ/Ｌ。两池水温 1 1～1 2℃。 1号池投喂改进配方的虹鳟饲料 ,2号池投喂原有配方的虹鳟饲料 ,两种饲料配方见表 1。改进配方中的“6号…     

黄海北部近岸海域渔业生物群落结构

为摸清黄海北部近岸海域渔业生物群落结构现状,并揭示其时空变化的主要环境驱动因子,于2021年4—11月在该海域开展了6航次底拖网及环境调查。运用丰度-生物量比较曲线、聚类分析和非度量多维标度排序等方法分析了海域渔业资源种类组成及优势度、群落多样性及年内演替;运用典范对应分析 (CCA) 探讨了群落结构时空变化与环境因子之间的关系。结果显示,调查采集到的种类共有89种,包括鱼类50种和无脊椎动物39种。鳀已成为海域主要中上层优势鱼种,大泷六线鱼、细纹狮子鱼和脊腹褐虾等冷温性种类成为季节性主要渔业生物,小黄鱼、蓝点马鲛和鲐等传统资源仍在衰退过程中。调查发现部分真鲷幼体及集群蓝圆鲹幼体,海域或有其育幼场存在。调查期间内群落大部分时间处于不稳定状态,其中4月群落显示中等干扰,5—11月群落均显示严重干扰。在所选环境因子中,海表温(SST)、海底温(SBT)、海底盐(SBS)和叶绿素(Chl.a)是导致群落结构时空变化的主要环境因子,其中SST和SBT的影响尤为显著。本研究系统阐明了黄海北部近岸海域渔业生物群落结构特征和季节性演替,为进一步了解该海域渔业生物群落结构现状及其对环境因子的响应提供了参考。     

基于不同空间插值法的黄海和东海北部游泳动物多样性空间分布研究

物种多样性空间分布是生态学研究的重要内容之一,空间插值法在该领域应用广泛。本研究以2017年5月黄海和东海北部游泳动物多样性为例,选取种类数(S)、Shannon-Weaver多样性指数(H′)、Pielou均匀度指数(J)和Margalef丰富度指数(d)来衡量该海域物种多样性,应用反距离加权法(Inverse distance weighted, IDW)、径向基函数法(Radial basis function, RBF)、局部多项式法(Local polynomial interpolation, LPI)、普通克里格法(Ordinary kriging, OK)和协同克里格法(Ordinary cokriging, COK)对上述4种多样性指数进行插值,通过jackknife检验的方法选择适合每种多样性指数的空间插值法。结果表明,对于4种多样性指数,COK结果均最好,而其他4种方法精度较低,且差别不大。COK预测结果表明,S和d都呈现出东南部高,北部次之,中部最低的格局。H′和J也是中部最低,在南部和北部海域差异不大。4种多样性指数在32?N以南海域的高值区范围大致相同。COK可以作为黄海和东海北部游泳动物多样性空间插值的方法。     

Modelling the transport of particles in the North Sea with reference to sandeel larvae

The transport of particles representing sandeel larvae in the North Sea is simulated with a three-dimensional circulation model for the years 1976 to 1990. A great year-to-year variability in drift patterns is demonstrated. The results may explain some of the observed differences in recruitment between the main sandeel areas in the North Sea. In the northern sandeel area it seems that strong year classes are unlikely if the retention due to unfavourable currents is poor, and that a high retention in the summer may favour a good year class. In the southern sandeel area no clear coupling between year class strength and larval drift is found, possibly because the retention always seems large enough for a potentially good year class. For more quantitative use of such models in relation to sandeel recruitment, more biological knowledge is obviously needed on larval vertical distribution and timing of sandeel hatching and settling.     

Development of the Trout Fishery at Grafham Water

The paper describes the development of the trout fishery at Grafham Water, and considers the various factors having a bearing on the changing nature of the fishery as the lake becomes more mature.