长江口日本鳗鲡苗的时空分布与捕捞生产现状

为掌握长江口日本鳗鲡的苗汛特征与捕捞生产现状,于2017—2020年在长江口开展了定点监测和走访调查,分析了长江口鳗苗的汛期规律、捕捞努力量及捕捞产量和产值。研究发现,长江口鳗苗旺发期为2-4月,主要捕捞区域分布在东旺沙、佘山岛和南汇嘴附近水域。长江口鳗苗捕捞努力量呈现下降趋势,有效网口面积从2017年的78.72万m²,下降到2020年的50.40万m²,下降了36%。长江口鳗苗汛期的单位捕捞努力量渔获量(CPUE)和总捕捞产量呈现波动变化趋势,2017和2020年较高,分别为(4 474±256)尾/100 m²和(5 220±1 063)尾/100 m²,2018和2019年较低,分别为(1 917±335)和(1 365±257)尾/100 m²。研究表明,长江口鳗苗生产值受到捕捞总产量影响,近4年来逐渐下降。建议进一步加强长江口鳗苗的资源监测和科学评估,指导规范鳗苗捕捞生产。     

江苏海域日本鳗鲡苗资源时空分布特征初步研究

根据2012~2016年1~5月在东台、如东、启东和海门4个监测区域的捕获数量和渔获规格,研究了江苏海域日本鳗鲡(Anguilla japonica)苗的时空分布特征。结果表明:2012~2016年,江苏海域鳗苗主汛期为2~4月,各区域监测船在主汛期的2~4月捕捞数量占该年总捕捞数量的比例为61.96%~100.00%,平均为88.18%。东台、如东、启东三地鳗苗逐旬捕捞量分布形态5年均呈单峰型,而海门除2015年和2016年呈双峰型外,其余3年均为单峰型。单网月捕获数量均值最高的年份为2014年,最高的区域为海门,最高的月份为3月;最低的年份为2013年,最低的区域为如东,最低的月份为1月。白天苗量比夜间苗量高出约30%。江苏海域鳗苗全长平均为56.1 mm,体质量为95.14 mg。为实现江苏海域鳗苗资源可持续利用,建议将捕捞期调整为2~3月,在捕捞价值较低的1月以及处于鱼类繁殖季节的4~5月实施禁捕。     

长江口九段沙水域中华绒螯蟹汛期特征及影响因子

对长江口九段沙水域中华绒螯蟹(Eriocheir sinensis)洄游群体渔获规格及汛期特征进行了调查研究.2006—2011年单船全汛期捕捞量为93.3~769.5 kg,年均值为481.5 kg;日均捕捞量为6.2~26.5 kg,均值为18.5 kg;总捕蟹个数为984~7547只,均值为4129只;平均体质量为89.5~114.5 g/ind,均值为100.7 g/ind;雄蟹比例为65.80%~80.54%,均值为74.35%;2006—2011年单船全汛期捕捞量呈波动上升趋势,峰值出现于2010年;平均体质量则先升后降,峰值出现于2008年.各年汛期内最高日捕捞量基本出现于12月初,其中最早出现于11月24日(2009年),最晚出现于12月12日(2010年).初汛期、旺汛期和尾汛期捕捞量比例分别为4.25%~38.48%、37.92%~72.81%和1.77%~34.00%.各年汛期内初汛期渔获物中大规格个体所占比例较高,雄蟹比例显著高于雌蟹;随着汛期后延,小规格个体的数量逐渐增多,总体渔获规格呈下降趋势,同时雌蟹比例逐渐增加,雌雄比例相对接近.水温和潮汛与捕捞量关系密切,通常水温降至13℃附近时开始进入旺汛期,各年份最高日捕捞量对应的水温介于10℃至13.5℃之间,平均为11.7;℃调查期间小潮期捕捞量占汛期总捕捞量的比例显著高于大潮期,其中小潮期捕捞量比例最高为95.79%(2008年),最低为73.41%(2010年).     

长江口汛期凤鲚捕捞量年际变化研究

根据1982—2014年33年的长江口汛期凤鲚(Coilia mystus)捕捞数据,采用多元统计分析研究凤鲚捕捞量的年际变化,利用格局转变贯序t检验(sequential t-test testing analysis of regime shifts, STARS)的方法研究捕捞量年际转变规律,并结合广义可加模型(generalized additive model,GAM)定量分析了凤鲚捕捞量与捕捞船数及环境因子长江口水温、泥沙量和径流量的相关性。结果显示,1982—2014年长江口凤鲚汛期总捕捞量和单船全汛捕捞量变幅分别为7.9～3 252.0 t·年~(-1)和130.0～12 945.5 kg·年~(-1),总体都呈波动下降趋势。总捕捞量在1997年和2007年发生2次格局转变,年际格局转变指数RSI值分别为-0.580和-0.405;单船全汛捕捞量在1990年和2007年发生格局转变,RSI值分别为-0.806和-0.371。捕捞船数变幅为59～330艘·年~(-1),分别在1990年、2000年和2006年发生3次年际格局转变,对应RSI值分别为0.992、-0.412和-0.763。通过对环境因素与捕捞因素的分析发现,凤鲚单船全汛捕捞量发生第一次格局转变主要受过度捕捞因素的影响,而第二次发生转变主要受环境和捕捞因素的共同影响。GAM模型结果揭示,输沙量与凤鲚单船全汛捕捞量呈正相关关系,表现为随着输沙量的增加,单船全汛捕捞量随之增加;反之,水温与单船全汛捕捞量呈负相关关系,即随着水温升高,单船全汛捕捞量随之降低。     

鰻苗捕捞、暫养和运輸

在温州地区沿海,鳗苗一般在农历十二月至翌年二月出现,十二月下旬至正月中旬为旺汛期。三月后鳗苗(每公斤4,000—8,000尾)几乎绝迹,继而出现规格为每公斤2,000尾以下的幼鳗。群众在鳗苗捕捞、暂养和运输方面积累了不少经验,现结合我们工作中的体会,总结如下。     

鳗苗捕捞、暂养和运输

在温州地区沿海．鳗苗一般在农历十二月至翌年二月出现．十二月下旬至正月中旬为旺汛期。三月后鳗苗(每公斤4,000-8,000尾)几乎绝迹．继而出现规格为每公斤2,000尾以下的幼鳗。群众在鳗苗捕捞、暂养和运输方面积累了不少经验．现结合我们工作中的体会,总结如下。     

长江口区鳗苗资源利用的调查

<正> 长江口区江苏、浙江、上海二省一市的沿海及沿江水域是我国鳗苗重要出口地之一。七十年代初期,在上海市主要河口性鱼类苗种资源的调查一文中曾提及部分闸口鳗苗情况。1987年,又详细报道了长江口北支崇明岛北岸闸口鳗苗生产量等问题。1987年在进行上海市污水集中排放对长江口生态环境影响的课题任务时,作者在长江南支、北支和杭州湾北岸带等水域,就有关鳗苗分布、生态和捕捞生产利用等进行了较全面的调查,探讨了资源变动因子和开发利用问题。     

1999年中国鳗苗生产和投放情况

２月中旬,大潮前后１周时间,以江浙为中心的鳗苗主产区迎来了生产高潮,日捕捞量在５００ｋｇ以上（５８００～６０００尾／ｋｇ）。到目前为止,日本鳗苗捕捞量和投苗量估计已超过２０ｔ,每尾入池价由３８元回升到４２～４３元。另据报道,目前中国已进口欧洲鳗...     

中国鳗苗生产和投放情况

2月中旬大潮前后一周时间,以江浙为中心的鳗苗主产区迎来生产高潮,日捕捞量在500公斤以上(每公斤5800—6000尾)。到目前为止,日本鳗苗捕捞和投苗量估计已超过20吨,每尾入池价由3．8元回升到4．2—4．3元。另据报导,目前中国已进口欧洲鳗苗近100吨,全部投入养殖,每尾入池价为0．76元。     

坚持实践第一的观点 姚江闸口鳗苗大丰收

目前,正是捕鳗苗的季节。宁波市姚江渔业公社广大贫下渔民在批林批孔运动的推动下,遵循毛主席“实践出真知”的教导,为支援国家出口鳗苗和自己养殖的需要,从3月上旬开始,在姚江大闸口捕捞鳗苗。经过一个多月的奋战,到4月3日已捕获鳗苗375斤,约计140万尾,出现了从未有过的好成绩。过去,由于受孔老二、林彪所散布的“唯上智与下愚不移”等反动谬论影响,有的人形而上学地     

Effects of environmental variables on recruitment of <Emphasis Type="Italic">Anguilla japonica</Emphasis> glass eels in the Yangtze Estuary,China

The recruitment pattern of Anguilla japonica glass eels into the Yangtze Estuary, China was studied during five successive migration seasons (2012–2016). The variation in daily catch was analyzed in relation to environmental factors that affect inshore migration. Two large migration waves of glass eels were observed in each recruitment season: one in the winter (January/February) and the other in the spring (March/April). A generalized additive model indicated that daily changes in glass eel catch were partially affected by local water temperature and tidal range. Water temperature seemed to have a threshold effect in winter, and there were optimal temperature ranges of 6–8 °C and approximately 10.5–12.0 °C associated with different recruitment waves to the Yangtze Estuary. The influence of tides was complex, with an overall positive correlation. The annual glass eel catch fluctuated greatly, but generally did not show a significant downward trend. To achieve sustainable use of glass eels, it is proposed that relevant management and conservation activities be reinforced.     

On the actual recruitment of European eel (Anguilla anguilla) in the River Ems,Germany

Data from the historical River Ems glass eel fisheries in the 20th Century have been used for the ICES recruitment series. Commercial catches ceased from 1980 and dropped to zero; thus, eel recruitment data are since lacking. The present study assessed the actual eel recruitment to the River Ems with regard to the local tidal conditions. Standardised measurements were performed on relative glass eel occurrence at the tidal weir from 2014 and quantitative sampling at the next weir upstream from 2013. Eel migration at the tidal weir was dominated by glass eels and increased 2–3 month earlier than at the upstream weir, where migration was dominated by pigmented eels. In 2016, glass eels were marked at the tidal weir and pigmented elvers were sampled at the upstream weir. The 2016 eel recruitment was estimated at about 1% of the mean historical recruitment. Eel recruitment at the two weirs was not directly linked. Many eels seem not to pass the upstream weir. Further investigations are needed to reveal whether the results represent a regular pattern. In the long run, the perpetuation of the recruitment series is also foreseen.     

Dynamics of upstream migration of the European eel, Anguilla anguilla (L.), in the Rivers Severn and Avon, England, with special reference to the effects of man-made barriers

The upstream migration of European eels, Anguilla anguilla (L.), was studied during 1991–1993 in the Rivers Severn and Avon using traps mounted on weir or sluice barriers. Only pigmented elvers and juvenile eels were trapped at the tidal limits, catches being equivalent to about 0.8% of the commercial glass eel catch in the lower estuary. First catches were made as temperatures rose above 10–11 °C. Pigmentation-stage analyses and body size data indicated that estuarine migration was slow and that natural mortality was probably very high. Relatively more eels were trapped in the Severn compared with the Avon, but in both rivers the number of immigrants decreased rapidly upstream of the tidal limits, whilst the average size and age increased. The number and severity of weir and sluice barriers to be surmounted exerted a greater effect than distance alone. Recapture rates of marked eels were low (1–2%), implying variable migratory tendencies and/or high mortality. Mean migration rate in the non-tidal rivers was 0.64 ± 0.6 km day^–1 and some eels were not recaptured until one or two years after release. Speed of migration increased with temperatures above 15–16 °C. Relationships between migration dynamics, barriers and the scarcity of upriver stocks of eels and distorted population structures in the two rivers are discussed. Recommendations are made for the provision of passes and/or stocking to enhance migration and recruitment.     

The Effects of Water Temperature and Flow upon Angling Success in the River Severn

Angling catch data was gathered by a postal questionnaire system from angling clubs holding competitions in three sections of the River Severn over a period of 3 years (1975–78). Angling success was measured as the percentage of anglers taking part that caught fish and as the overall catch rate (g/man/h) of the competing anglers. Species composition of the catch was also recorded. Angling success was closely related to water temperature. Parabolic regressions were fitted to the data. Optimum temperatures for angling success were between 18 and 20°C, except for the Lower Severn section where maximum catch rates were achieved at 14.9°C. Flow had little effect upon angling success until a critical flow was reached, above which success was considerably reduced. Critical flows for the upper, mid and lower sections were approximately 3,000, 5,000 and 10,000 Ml/day, respectively. Species composition of catches within river sections was influenced by water temperature. Some species (bleak, bream, dace and eels) were relatively more abundant in catches made at high temperatures whilst others (chub and roach) predominated at tow temperatures. It is suggested that the percentage of anglers catching fish is the most reliable indicator of angling success.     

长江靖江段鱼虾资源调查与分析

在对长江靖江段近岸鱼虾资源进行调查的基础上,通过种类鉴定、渔获物统计和分析,初步摸清了这一江段的渔业资源组成和时空变化状况,并就如何合理开发和养护长江鱼类资源进行了分析。     

长江口最大浑浊带浮游植物的生态研究↑（*）

研究海区浮游植物数量的时空变化具有相当明显的潮汐节律特殊。具体表现为：１、洪、枯水期均为大潮的数量高于小潮的数量，洪季前者为后者的６．８倍；估季前者为后者的６．１倍。２、洪、估期的大小潮期，基本上都以涨憩的数量高于落憩的数量。３、洪、枯季均为大潮期的数量空间分布不均，疏密分布现象明显。     

奉贤海域秋季浮游动物群落对潮汐运动的生态响应研究

根据2009年11月份大潮、小潮时期对奉贤附近海域进行的浮游生物生态调查资料,对大、小潮时期浮游动物的种类组成、密度与生物量分布、生物多样性及优势种的生态特征进行了比较分析。结果表明,大潮时浮游动物密度比小潮大,而浮游动物的种类数、生物量、生物多样性比小潮时低,大潮时优势种真刺唇角水蚤（Labidocera euchaeta）和火腿许水蚤（Schmackeria poplesia）的优势度（Y≥0．02）及其所占的数量比例高于小潮,优势种虫肢歪水蚤（Tortanus vermiculus）的优势度及其所占数量比例明显低于小潮。海洋浮游动物对潮汐变化的生态响应强烈。     

中东大西洋中部海域中上层鱼类资源结构与渔场分布

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。     

Catch forecasting and relationship between water temperature and catch fluctuations in snow crab <Emphasis Type="Italic">Chionoecetes opilio</Emphasis> in the western Sea of Japan

Catch forecasting and the relationship between water temperature and catch in the snow crab Chionoecetes opilio in the western Sea of Japan were investigated. Catch was used as an index of abundance on the basis of high correlations between catch per unit effort for the period when the latter data were available. The pattern of fluctuations, in catches and index coincided well with each other. Therefore, catch data were regarded as an index of abundance and the correlation coefficient between catch and water temperature was calculated at several depths from 1964 to 1999. Catch forecasting models were composed using significantly correlated variables with the following results: (i) in April and September, the catch showed high positive correlation with water temperatures (depth 50, 100, and 200 m, time lag 4–6 years); and (ii) a model using water temperatures in April alone (depth 100 m, time lag 4–7 years) forecasted the catches with a coefficient of determination of 0.504, where models using more variables (water temperatures in the 2 months and catches) showed a coefficient of 0.587 at most. Environmental conditions during the early life stages of the snow crab are thought to deeply influence the fluctuations, in abundance.