鄱阳湖刀鲚生殖群体特征及状况分析

研究鄱阳湖刀鲚群体的生殖特征和条件状况,为制定开发利用渔业资源的政策提供基础资料,以实现鄱阳湖刀鲚资源的可持续开发和保护。2013、2014年4-7月,分别在鄱阳湖及湖口八里江段进行了实地渔业资源调查,随机抽样定置网、流刺网和拖网采集的鄱阳湖刀鲚样本共658尾,测量了体长、体重、净重、性腺重和性别。雌性287尾、雄性371尾,体长18.6~38.1 cm、体重16.3~198.2 g。雌性刀鲚的体长和体重均大于雄性(P0.01),雌、雄个体的体长和体重差异均为极显著(P0.01)。随着体长的增加,雌雄体重差异越大;同等体长的雌性体重大于雄性。6月中旬、下旬的刀鲚卵巢发育仍参差不齐,有些可挤出卵粒,已发育到Ⅳ期末和Ⅴ期,有些还处在Ⅳ期初,但成熟系数在2.0以下的个体数量已显著减少。绝对繁殖力为960~13 820粒,相对繁殖力为123.4~753粒/g。平均丰满度为0.30±0.03(0.19~0.45)。鄱阳湖刀鲚雌雄比在1∶1.25~1.44,表现出雄多雌少的现象;刀鲚繁殖种群已呈现出逐渐变小的趋势,资源已出现严重的过度利用。     

鄱阳湖湖口水域鲚鱼的物种属性及资源现状

从外部形态和内部结构等方面阐述了鄱阳湖湖口水域鲚鱼的物种属性,同时分析了它的年龄组成及资源现状。结果表明,鄱阳湖湖口水域的鲚鱼为短颌鲚,其种群的年龄结构简单,渔获物中以小个体居多;鄱阳湖湖口水域在9、10月份出现鲚鱼渔汛。     

鄱阳湖刀鲚繁殖群体生物学参数及生长特性的初步分析

基于渔业资源调查数据,运用软件FiSATⅡ分析了鄱阳湖刀鲚繁殖群体的生物学参数及生长特性。分析结果表明,鄱阳湖刀鲚体长16.0~38.1cm;体长和体质量的关系式为m=0.002L3.139(r=0.949;P0.05;n=1014),von Bertalanffy生长方程的各参数为:渐近体长为40.95cm,生长系数为0.240,理论生长起点年龄t0=-0.568。鄱阳湖刀鲚的拐点体质量为67.94g,平均丰满度为0.29±0.04(0.14~0.49),总死亡系数为1.36a-1,自然死亡系数为0.52a-1,捕捞死亡系数为0.84a-1。鄱阳湖刀鲚开发率为0.61,处于资源过度利用状态。     

鄱阳湖通江水道短颌鲚生长特性初探

鄱阳湖是我国最大的季节性淡水湖泊,鱼类资源丰富,但湖区水深较浅、换水周期短,丰水期、枯水期、平水期的水面差异大,致使其稳定性和抗干扰能力差,鱼类资源安全风险大。水利枢纽工程建设是鄱阳湖生态经济区的重要支撑和保障,但工程建设同时也将对区域生态环境产生不利影响,包括水质水量和渔业资源等诸多方面,科学高效的评估将为鄱阳湖生态环境保护提供技术支持。2012年3月至2013年2月在鄱阳湖通江水道屏峰段逐月随机抽样测定定置网采集的短颌鲚(Coilia brachygnathus),2013年12月至2014年11月每月在湖口江段整船次或整网次随机采集渔获物,共获得短颌鲚样本1 403尾、18.8 kg,测定其体长和体重数据,运用Fi SAT II软件对短颌鲚的生物学参数及生长特性进行了初步分析。结果表明,鄱阳湖通江水道短颌鲚体长范围为5.6~32.5 cm,平均体长14.3 cm;体重范围为0.6~125.5 g,平均体重13.4 g;体长与体重关系式为W=0.003L3.022(R=0.985,P<0.05,n=1403);von Bertalanffy生长方程得出鄱阳湖短颌鲚渐近体长L∞=34.65 cm,生长系数k=0.390,理论生长起点年龄t0=-0.359;其拐点体重为38.6 g,拐点体长为22.8 cm,平均丰满度为0.32;总死亡系数Z=1.20,自然死亡系数M=0.75,捕捞死亡系数F=0.45,开发率E=0.37。     

鄱阳湖凤尾鱼出现罕见渔汛

凤尾鱼，俗称毛花鱼、七丝鲚、刀鲚，为溯河鱼类。每年春末夏初，凤尾鱼亲鱼由江河进入湖泊产卵繁殖；秋末，成群随湖水游入长江，因而形成了凤尾鱼渔汛。2003年10月，在鄱阳湖与长江接口的江西省湖口等水域出现了继1998年来少见的凤尾鱼渔汛。此次渔汛11月9日结束，汛期20d，品种以短颌鲚为主，占渔获物重量的98％。     

鄱阳湖刀鲚的鉴定与资源动态研究

为研究潘阳湖刀鲚资源状况, 2019—2020 年在鄱阳湖开展鱼类资源调查工作, 采集到大量鲚属(Coilia)鱼类, 对这些样本进行了形态学和分子生物学的鉴定。随机测量 112 尾样本的上颌骨长度显著大于头长, 长颌长/头长的范围为 1.00~1.46, 平均为 1.17±0.07。使用线粒体 Cyt b 基因和 D-loop 控制区序列作为分子标记, 对 22 尾随机样本进行物种鉴定, 结果显示 22 尾样本均为刀鲚(Coilia nasus)。对其中 5 尾样本耳石的微化学特征进行了测定, 结果显示耳石锶钙比(Si/Ca)均有大于 3 的过程出现, 表明样本为溯河洄游型刀鲚。2019—2020 年, 刀鲚在鄱阳湖中的单船产量分别达到 8.1 ind/d 和 142 ind/d, 与历史数据相比, 出现了一定的增长。鄱阳湖刀鲚资源量的恢复表明长江禁渔制度实施和取消刀鲚特许捕捞制度取得了良好的效果, 建议进一步开展鄱阳湖刀鲚产卵场调查并加强栖息地保护, 促进刀鲚资源恢复。     

安徽无为长江段刀鲚生殖洄游群体年龄结构的变化分析

为了分析我国名贵鱼类长江刀鲚(Coilia ectenes)数量不断减少的趋势及原因,从而提出资源保护与恢复对策,2006年3～7月在安徽无为长江段,对捕捞刀鲚的渔具、渔法和刀鲚渔获量、种群年龄结构、平均体长、体重进行了野外调查.结果表明,86个网次共捕获刀鲚536尾、34.57 kg,最高网次捕获量仅0.85 kg;经抽样,对100尾刀鲚进行测定,体长为21.7～42.1 cm、体重为20～235 g;体长、体重相关式为W=0.0011L3.3312(R2=0.969);种群年龄组成中以2+龄和3+龄个体为主,也能捕获1+和4+龄个体,5+和6+龄个体较少;与1972年相比,捕获量由41.56 t降至2～3 t.分析认为,刀鲚资源衰退的主要原因是长江水文条件的变化使刀鲚产卵场受到破坏,不断升高的市场价格引起对刀鲚的过度捕捞,而水质污染程度的日趋加重也不利刀鲚的生长繁殖.保护与恢复刀鲚资源的对策应该是建立刀鲚繁殖场保护制度,取缔网目5 cm以下的网具或禁捕2～3年.     

鄱阳湖鲤的年龄与生长特征

为了解大型通江湖泊鄱阳湖中鲤(Cyprinus carpio Limaeus)的种群状况,根据2001年采集的448尾标本,对鲤的年龄和生长特征进行了研究.鄱阳湖鲤鳞片上的年轮表现为切割与疏密特征,尤以切割为主.渔获物群体平均体长为32.6 cm,平均体重为941.7 g,年龄结构为0+～4+龄,其中3+龄以下个体约占94.0%.鳞径(R)与体长(L)的关系为L=6.7963+29.421R(r=0.9128),体重(W)与体长(L)的关系为形=0.0219L3.0018(r=0.9979),拟合的Von Bertalanffy生长方程参数为L∞=97.26 cm,W=20315.39 g,k=0.2073,t0=-0.7841.与其它水域相比,鄱阳湖鲤生长较快,其生长拐点年龄为4.52龄,建议将其捕捞年龄确定在4.5龄左右.与20世纪70年代相比,鄱阳湖鲤表现出小型化趋势,应采取实施春季禁渔制度、控制捕捞强度、提高捕捞年龄、保护湖滩草洲生态环境等措施,实现渔业资源增殖.     

鄱阳湖刀鲚产卵场调查

为了解鄱阳湖刀鲚产卵场的现实情况,于2014年5~7月,通过实地走访渔民、现场GPS定位并查询历史资料,对鄱阳湖刀鲚产卵场的状况进行了调查,利用ArcMap软件绘制和计算了刀鲚产卵场的分布和面积,建立了鄱阳湖刀鲚产卵场的动态数据库,旨在为鄱阳湖名贵鱼类资源保护和动态管理提供科学依据。     

东平湖刀鲚生物学参数、单位补充量渔获量及产卵亲体量评估

为完善东平湖刀鲚(Coilia nasus)的基础生物学数据, 并为实现其资源的可持续利用提供技术指导和理论依据, 本研究根据 2021—2023 年东平湖定置三层多目刺网调查获得的刀鲚体长、体重数据, 利用 ELEFAN_GA 技术对刀鲚的生长和死亡参数进行估算, 拟合 Von Bertalanffy (VBGF)生长方程, 构建了基于体长结构的单位补充量渔获量(YPR)和单位补充量产卵亲体量(SSBPR)模型。结果显示, 东平湖刀鲚体长范围为 4.9~26.2 cm, 平均体长为 (12.2±2.4) cm, 体重范围 1.1~51.8 g, 平均体重为(6.6±4.5) g; 使用基于 bootstrap 的 ELEFAN_GA 方法估算刀鲚渐进体长 L_∞=31.65 cm, 生长速率 K=0.66, 理论生产起点年龄 t₀= ‒0.23, 季节性生产振幅 C=0.65, 1 年中生产最快的时间段 t_s=0.40; 刀鲚的总死亡系数 Z=2.71, 自然死亡系数 M=1.074, 捕捞死亡系数 F=1.641、开发率 E=0.604, 平均选择体长 L₅₀=9.15 cm; YPR 模型结果显示, 随着 F 增大, YPR 值呈现先上升后下降的趋势, 生物学参考点 F_0.1 和 F_max 的值分别为 0.978 和 2.204; SSBPR 模型结果显示随着捕捞强度的增大, SSBPR 呈下降趋势, 现阶段捕捞强度介于 F_20%(2.848)与 F_40%(1.065)之间, 略大于 F_35%(1.286)。综上所述, 东平湖刀鲚生长表现出明显的季节性变化规律, 在与其他地理群体对比中, 东平湖刀鲚在生物学参数上的差异体现了其生长过程的空间异质性, K 值最大表明其可以用最短的时间生长到接近极限体长, 说明东平湖饵料丰富, 而同时较高的开发率和较低的开捕体长则表明目前东平湖刀鲚已处于过度开发状态, SSBPR 曲线得出现阶段捕捞强度小于极限值 F_20%, 略大于生物学参考点 F_35%。研究结果表明, 为使东平湖刀鲚资源达到生态、经济效益平衡, 可在适当减少渔船数量以降低捕捞强度的情况下, 通过增大网目尺寸以增加开捕体长来保持其可持续发展。     

Population size estimation of the pond smelt Hypomesus nipponensis in Lake Kasumigaura and Lake Kitaura,Japan

We estimated the population size of the pond smelt Hypomesus nipponensis at the beginning of the fishing season in Lake Kasumigaura and Lake Kitaura, Japan using two DeLury methods and cohort analysis. A growth curve was estimated on the basis of monthly standard length. The relationship between standard length and weight was utilized for calculating the mean weight on the survey day in a particular month. Total monthly catches in Lake Kasumigaura and Lake Kitaura were calculated using partial monthly pond smelt catch obtained from processing plants located near the lakes between July and December. The total monthly catch was calculated from the total monthly catch weight and the monthly mean weight. The number of boats operating each month, compiled by the Kasumigaura-Kitaura Fisheries Office of Ibaraki Prefecture, was also employed. The estimated initial population sizes were compared with the population level index (PLI) estimated from survey data before the start of the fishing season. No significant differences were detected among the initial population sizes estimated by DeLury method, cohort analysis and PLI. The estimates ranged from 7.4 million to 410 million in Lake Kasumigaura, and from 7.7 million to 44 million in Lake Kitaura.     

Discards from the commercial gillnet fishery for dusky flathead, Platycephalus fuscus, in New South Wales, Australia: spatial variability and initial effects of change in minimum legal length of target species

A scientific observer programme was used to quantify the composition and magnitude of discards in the gillnet fishery for dusky flathead, Platycephalus fuscus (Cuvier), in three barrier estuaries in New South Wales, Australia, during the 2001 fishing season. Regulations only permit the retention of legal‐sized dusky flathead and legal‐sized blue swimmer crab, Portunus pelagicus L., and mud crab, Scylla serrata (Forskål); all other organisms were discarded. Sampling was stratified into two time periods; before and after 1 July 2001 which coincided with the increase in the minimum legal length (MLL) of dusky flathead from 33 to 36 cm total length (TL). Eighty one catches were sampled, yielding 38 finfish species and two portunid crab species. Legal‐sized dusky flathead were the most abundant organism captured, accounting for 23–47% by number and 34–54% by weight of the mean observed catch depending on the estuary and survey period, with a mean catch of 25–59 flathead weighing 13–25 kg per fishing‐night. Species composition and relative abundance of catches differed among estuaries, but not between sampling periods. Predominant bycatch species included legal and undersize blue swimmer crab, sea mullet, Mugil cephalus L., luderick, Girella tricuspidata (Quoy & Gaimard), bream, Acanthopagrus australis (Günther) and yellowfin leatherjacket, Meuschenia trachylepis (Günther). These five species accounted for 82% of total bycatch by number and 71% by weight, pooled across the three estuaries. More crabs were retained than discarded, with retained legal‐size crabs (byproduct) accounting for 16% of total bycatch by number and 13% by weight, with an average of 5–22 crabs weighing 1–6 kg being caught per fishing‐night, depending on the estuary. Overall, 7% of dusky flathead captured (number) were below the MLL of 36 cm and discarded, suggesting the nets as currently configured may be relatively selective in catching legal‐size flathead. However, 41% of dusky flathead were <40 cm TL, indicating that if the MLL for this species is increased to this length as proposed, new nets must be introduced into the fishery. The findings are discussed in terms of making the flathead fishery more sustainable, including alternative management strategies for the fishery.     

太湖翘嘴红鮊的生物学及其增殖问题的探讨

本文从研究翘嘴红鲌的生长、各个时期的食性和繁殖生物学出发,对于翘嘴红鲌在太湖渔业资源中的地位及作用作了比较深入的探讨。作者认为,过去把翘嘴红鲌简单地当作有害于太湖鱼类资源的凶猛鱼类而不加节制地加以捕杀,是造成目前太湖鱼类组成小型化和渔获物经济价值下降的原因之一。因此提出了保护和增殖翘嘴红鲌的主张,并且具体地提出了有关翘嘴红鲌的起捕规格、禁渔期和禁渔区、限制有害渔具、实行人工放流和保护水域环境等一系列建议。     

长江近口段鳗苗捕捞量的时间格局及其与生态因子的GAM模型分析

为研究长江口鳗苗捕捞量与生态因子的相互关系,于2012年汛期对长江靖江段鳗苗的捕捞量进行了监测,采用广义可加模型(GAM)对日捕捞量与水温、潮差、气压、浑浊度等生态因子之间的相关性作了分析。结果显示,靖江段鳗苗汛期为1月下旬—4月上旬,单船总捕捞量为221~443尾,平均(344.8±83.4)尾。1月均值仅0.4尾/d,且空网率高达90.9%;4月为旺汛期,均值10.4尾/d,空网率仅为10.0%。GAM模型显示,潮汐周期—月份交互项、水温和潮差对鳗苗日捕捞量的影响显著,而气压、浊度和月相周期对鳗苗日捕捞量的影响不显著。潮汐周期—月份交互项、水温和潮差对鳗苗日捕捞量的偏差解释率分别为42.4%、19.1%和13.1%,均呈现正相关关系。统计也显示,日捕捞量表现出上、下弦月较低、新月或满月前后较高的半月周期波动。鳗苗捕获的最低水温为6.3℃,而10~15℃为适宜捕捞水温。高潮期和低潮期分别占总捕捞量的76.8%和23.2%。研究表明,长江口鳗苗在借助潮汐流而快速溯河的过程中,部分在口门水域即被捕获,部分滞留在了长江河口段,而影响鳗苗溯河的重要生态因子是潮汐和水温。     

南海北部金线鱼流刺网渔业情况分析

根据“粤阳东18023”渔船2006年1月至2007年12月的渔获销售记录，结合春、秋2季的渔获抽样测量数据，对使用单片刺网在南海北部作业的大型金线鱼流网船的生产情况进行了分析。结果显示，渔获以底层和近底层种类为主，带鱼Trichiurus haumela、长尾大眼鲷Priacanthus tayenus和金线鱼Nemipterus virgatus为渔获优势种，占产量的29．7％、13．3％和10．5％，占产值的27．4％、24．4％和15．7％；渔船全年作业，汛期在11月至翌年3月，其中1月为旺汛期，休渔期的产量和产值在全年中所占比重很小；优势种渔获以成鱼为主，其CPUE的高值期与汛期基本一致。     

Effects of mesh size,fishing depth and season on the catch and discards of short mackerel Rastrelliger brachysoma gillnet fishery at the mouth of Pattani Bay,Thailand

This study evaluates the impacts of mesh size of the net, fishing depth and season on the catches of target, non-target and discarded species for short mackerel Rastrelliger brachysoma gillnet fishery in the vicinity of Pattani Bay, Gulf of Thailand. The catches were examined for species composition, catch efficiency and size of catch. Samples were obtained monthly from February 2019 to February 2020 at three fishing depths (2.0, 4.0 and 6.0 m) using gillnets with three different mesh sizes (3.0, 4.0 and 4.5 cm). Including the target species, 112 species were collected, the majority of which were non-targeted fishes and crustaceans. The target species, Rastrelliger brachysoma, contributed only 6.0% by number and 8.76% by weight to the total catches. The 111 non-target species were classified into five categories based on potential sale prices. A total of 18 species, equivalent to 3.04% by weight of the total catches, were considered to be of negligible value and discarded or sold for the production of fish meal. Temporal variability was observed for number of individuals and biomass of total catches; the compositions of the catches clustered to two distinct seasons from December to March and from April to November, respectively. Spatial variability in this study focused on the depth profile which was found to significantly influence species richness and sizes of some fish species. For 12 species, mesh sizes of the gillnets significantly affected the number of individuals caught, as well as their weight and sizes. The novel findings of this study provide essential information that can be used for the sustainable management of the Rastrelliger brachysoma fishery in the Gulf of Thailand.

     

Status of the fishery of Pimbmrettewa wewa, a man-made lake in Sri Lanka

Abstract. The status of the fishery of Pimburctlewa wewu, a man-made lake in Sri Lanka, was studied from January 1985 to January 1986. The annual fish yield in the reservoir is 441 kg/ha, one of the highest in the south-east Asian region. Oreochromis mossambicus (Peters) is the dominant species in the fishery and accounted for about 90% by weight of the total catch. Although there were monthly variations in catch per unit effort, the daily catch per fisherman was not adversely affected. A possibility of having a more productive fishery is suggested In reducing The minimum permissible mesh size in the gillnet fishery during the peak recruitment season in May–June. The possible effects of reducing the mush size are discussed. Using the length-frequency data of O. mossambicus , the asymptotic length and the growth constant were estimated to be 39.3cm and 0.34 respectively. The estimates of total mortality (2.42). natural mortality (0–82) and mean selection length (24.6 cm) were based on these growth parameters Yield-per-recruit analysis indicated that the O. mossambictus fishery in the reservoir was optimally exploited.     

Relationships between Stocking and Anglers' Catches in Draycote Water Trout Fishery

The trout fishery at Draycote Water was investigated during the 1980 fishing season. Fish stocked were batch-marked according to the date of introduction by freeze branding, and catch data were obtained by the cooperation of anglers. Population estimates were made at the end of the fishing season using gill nets and mark-recapture techniques. Of the 32,960 marked brown and rainbow trout stocked, 69.8% were caught and declared by anglers. Returns of rainbow trout were better (78.1%) than those of brown trout (44.2%). Over 90% of all fish caught were taken within 45 days of stocking. Catch per unit effort fluctuated widely but was closely associated with stockings of fish. Catchability (Q) of stocked fish was found to diminish rapidly with time after stocking. At the end of the fishing season the estimated population of marked trout was 4045 (2 × SE = 250), compared with a theoretical number (stock less total catch) of 10,802, giving a mean daily apparent natural mortality, made up of the true natural mortality plus the undeclared catch, of 1.36%.