披山岛海区浮游动物种类组成及数量分布特点

根据2007年披山岛海区春季和夏季2个季度浮游动物调查资料,分析和研究了浙江省玉环县披山岛海区浮游动物种类组成和数量分布特点.结果表明:浮游动物共有18种,属3门12属,其中桡足类的种类最多,占总种数的72.22%;主要优势种为中华哲水蚤(Calanus sinicus)、瘦拟哲水蚤(Paracalanus gracilis)、针刺拟哲水蚤(Paracalanus aculeatus)和红小毛猛水蚤(Microsetella rosea).浮游动物的平均丰度及生物量均为春季比夏季高,春季的平均丰度为6.55×103个/m3,夏季为6.13×103个/m3;春季的平均生物量为216.49 mg/m3,夏季为98.26 mg/m3.桡足类的生物量占浮游动物总量的75.97%～97.55%,是决定披山岛浮游动物数量分布和变动的主要成分.与历史资料和邻近海域相比较,披山岛海区生物量与其接近或大于东海各海域.春、夏两季生物多样性(H′)有显著性差异(P<0.05),春季具有较高的生物多样性,且远海的生物多样性大于近海.     

莱州湾春、夏季鱼卵、仔稚鱼群落结构及环境因子相关性

于2014年5月、8月和2015年5月、8月,利用大型浮游生物网,对莱州湾海域20个站位进行4个航次拖网调查,分析了鱼卵、仔稚鱼的种类组成、数量分布、优势种以及群落结构特征与环境因子的相关性。结果表明:4个航次共采获鱼卵、仔稚鱼22种,其中1种仔稚鱼未鉴定出种类,1种仔稚鱼鉴定到科,其余20种隶属于8目16科20属;鱼卵、仔稚鱼优势种季节变化明显;鱼卵、仔稚鱼数量分布与环境因子数据的多元分析表明,盐度对鱼卵数量影响较为明显,温度对仔稚鱼数量影响较为明显,仔稚鱼数量还与溶解氧(DO)、亚硝酸盐、无机氮、活性磷酸盐呈显著相关(P0.05),与氨氮(NH_3~-N)、叶绿素a含量呈极显著相关(P0.01),鱼卵数量与桡足类密度呈显著正相关(r=0.479,P=0.032),而仔稚鱼数量与桡足类密度呈显著负相关(r=-0.510,P=0.022)。     

三亚珊瑚礁分布海区浮游生物的群落结构

为了更好地了解珊瑚礁区生物群落应对环境变化的生态响应机制,以及浮游生物群落结构与珊瑚礁发展发育的关系,我们于2006年10月26日至11月10日对三亚珊瑚礁保护区9个有珊瑚礁分布的站点进行了浮游生物群落结构的调查.共鉴定出浮游植物种类61属130种(包括变种、变型),其中硅藻门48属101种,甲藻门10属25种,蓝藻门2属3种,金藻门1属1种.硅藻门的角毛藻属(Chaetoceros)种类最多,根管藻属(Rhizosolenia)的种类次之.调查海区浮游植物的细胞丰度范围为348-11,320个/L,平均为3,247个/L.在浮游植物群落中硅藻占绝对优势,平均丰度为3,230个/L,占总密度的99.5％.调查海区共鉴定出浮游动物76种,其中桡足类29种,水母类17种,浮游幼虫10种,毛颚类7种,被囊类6种,浮游腹足类4种,十足类、多毛类和介形类各1种.调查海区浮游动物的密度范围为43-190个/m3,平均为114个/m3.优势类群为桡足类、各类幼虫和毛颚类,平均分别占浮游动物总密度的28.5％,27.7％和13.6％.各站位浮游植物的多样性指数和均匀度平均分别为3.98和0.70,浮游动物的多样性指数和均匀度平均分别为4.37和0.87.鹿回头和大东海海域的浮游植物密度大,而生物多样性指数低.活的造礁石珊瑚种数和覆盖率高的站点的浮游生物多样性也较高.     

湛江港湾浮游桡足类群落结构的季节变化和影响因素

2009年2月、5月、8月和11月分别对湛江港湾浮游动物进行了季度月调查,并对该海域浮游桡足类群落结构的季节变化及影响因素进行了分析.结果共鉴定出桡足类72种,其中冬季36种,占浮游动物种类数的29.5％;春季33种,占浮游动物种类数的39.3％;夏季24种,占浮游动物种类数的29.6％;秋季19种,占浮游动物种类数的40.4％.主要优势种为中华哲水蚤Calanus sinicus、强额拟哲水蚤Paracalanus crassirostris、短角长腹剑水蚤Oithona brevicornis、亚强真哲水蚤Eucalanus subcrassus、刺尾纺锤水蚤Acartia spinicauda和桡足类幼体.季节变化模式为:夏季丰度最高,达960.0个/m3,春季次之为421.0个/m3,冬季为303.4个/m3,秋季最低仅为252.8个/m3.平面分布冬春季丰度内湾高,往湾口逐渐降低,夏季内湾低往湾口逐渐增大,而秋季分布较均匀.调查海区桡足类丰度与水温、叶绿素a和浮游植物细胞丰度呈极显著的正相关,与DIN和PO3-4呈显著的负相关,与盐度、pH值和活性硅酸盐相关性不明显.     

2016年夏季长江口邻近海域浮游动物群落结构

根据2016年8月长江口邻近海域27个站位的浮游动物样品数据,对长江口邻近海域的浮游动物群落结构和多样性进行分析,研究了浮游动物群落结构与环境因子的关系.结果表明: 该海区共鉴定出浮游动物93种,隶属于6门12大类群,另有浮游幼体及鱼卵仔鱼15种.其中,桡足类为绝对优势类群,共鉴定出48种,占44.4%;水母类为第二优势类群,共鉴定出12种,占11.1%.该海域出现的主要贡献类群为桡足类、海樽类、毛颚类、枝角类和水母类,平均丰度依次为273.9、115.0、67.1、63.6和61.1 ind·m^-3,其中绝对优势类群为桡足类,贡献率占20.3%.根据环境因子聚类结果,将该海区分为冲淡水影响区和外海水团影响区.单因子相似性分析检验发现,两个区域群落结构差异显著(平均差异性为4.0 %).SIMPER分析发现,对差异性的贡献比例依次是桡足类20.3%、海樽类18.0%、枝角类14.1%、毛颚类13.4%和水母类11.8%.     

长江口及邻近海域浮游动物群落结构及季节变化

根据2006—2007年长江口及其邻近海域(29°30'N—32°30'N,120°00'E—127°30'E)150个站位4个季节的调查资料,对长江口海域浮游动物群落结构、种类组成、优势种及其季节变化进行研究。结果表明,长江口及其邻近海域浮游动物群落物种多样性丰富,四季共鉴定浮游动物460种,隶属7个门,246属,此外,另有54类浮游幼体。其中,桡足类是最优势类群,有193种,占41.96%;端足类为第二优势类群,有51种,占11.09%;水螅水母为第三优势类群,有34种,占7.39%。长江口及其邻近海域浮游动物的物种多样性呈现明显季节变化,其特征为:夏季(317种)秋季(309种)春季(230种)冬季(138种)。中华哲水蚤和百陶带箭虫为长江口及其邻近海域的四季优势种。长江口及其邻近海域浮游动物大体可划分为5种生态类群:近岸低盐类群、广温广盐类群、低温高盐类群、高温广盐类群和高温高盐类群。结合同步调查的水文和水化学数据,进行浮游动物群落丰度与环境因子的相关分析表明:盐度是影响长江口及其邻近海域的浮游动物群落丰度的主要环境因子。     

2000～2001年柘林湾浮游动物的群落结构及时空分布

20 0 0年 7月至 2 0 0 0 1年 7月的周年调查结果表明 ,粤东柘林湾浮游动物有桡足类 2 9属 5 7种 ,枝角类 3属 3种 ,及端足类、磷虾、糠虾、多毛类、毛颚类、被囊类、水母和各种浮游幼体。其中 ,强额拟哲水蚤 Paracalanuscrassirostris、短角长腹剑水蚤 Oithona brevicornis和鸟喙尖头 Penilia avirostris为优势种 ,合计占浮游动物总个体数的 6 2 .7%。浮游动物的种类数、生物量和总个体数都表现为湾外大于湾内的平面分布格局 ,周年变化基本上为单峰型 ,高峰期位于 6～ 1 0月份 ,最低谷位于冬季 1月份。因此 ,总个体数与水温成显著正相关关系。柘林湾是一个浮游动物相对丰富的海湾 ,年均生物量为 1 1 5 .7mg· dw / m3 ,总个体数达 6 .8× 1 0 3 ind/ m3 ,但群落结构的小型化趋势比较明显。回归分析结果表明 ,浮游动物总个体数与浮游植物密度成显著正相关关系。     

烟台四十里湾浮游动物群落特征及与环境因子的关系

2009年3月—2010年12月在烟台四十里湾海域对浮游动物群落结构及其环境因子进行了连续20个航次的综合调查,记录到浮游动物8大类共计64种(类)。浮游动物主要类群为桡足类和浮游幼虫,分别发现22种、18类,占总种(类)数34%、28%;其次为水螅水母类,发现13种,占20%;毛颚动物和栉水母类各发现1种。浮游动物的优势种为中华哲水蚤(Y=0.183)、腹针胸刺水蚤(Y=0.078)、强壮箭虫(Y=0.078)和洪氏纺锤水蚤(Y=0.026)。浮游动物的生态类型主要为温带近岸种和广布性种。四十里湾海域浮游动物群落结构的季节变化较为明显,春、夏、秋、冬四季之间群落结构有显著性差异(P0.05),同一季节内群落结构相似度较高,达55%以上。浮游动物丰度中位值在5月份达到最高(546.3个/m~3);种类数、多样性指数中位值均在8月达到最高,分别为18种、3.20;浮游动物生物量呈现出双峰变化模型,5月份达到第1峰值(中位值870.4 mg/m~3),10月份为第2峰值(中位值362.0 mg/m~3)。浮游动物种类数高值区主要分布在养马岛北部海域,而丰度高值区主要分布在近岸尤其是辛安河口海域。浮游动物种类数及多样性指数与水温、化学需氧量、硅酸盐显著正相关(P0.01),与盐度、溶解氧、无机氮显著负相关(P0.01);水温和盐度是影响浮游动物分布的主要环境因子,其次是硅酸盐、叶绿素a和化学需氧量,活性磷酸盐、溶解氧、透明度以及无机氮对浮游动物分布的影响较小。     

兴化湾浮游动物群落季节变化和水平分布

兴化湾为福建北部最大的海湾,于2006年对该海湾浮游动物群落进行了四季9个站位的调查。共检出浮游动物及幼虫124种,其中春季42种,夏季89种,秋季71种,冬季20种;分属近岸暖温、近岸暖水和广布外海3个生态类群;优势种15种,春季以水母和桡足类占优势,夏季以水母占优势,秋季以水母、桡足类和箭虫占优势,冬季则以桡足类占优势。不同季节兴化湾浮游动物生物量湿重和丰度水平分布特征变化明显,并与温度和盐度呈显著相关。聚类分析显示兴化湾浮游动物群落夏季类群和秋季类群相似度较高;各季节水平分布基本可分为湾口区和湾内区两大类群。与20世纪80年代相比,尽管本次调查浮游动物群落没有表现出显著差异,但随着电厂等大规模工程的投产,兴化湾海域生态系统健康面临着极大威胁,其环境压力需引起持续关注。     

华南地区典型抽水型水库后生浮游动物群落的种类组成与结构

大镜山水库位于广东省珠海市,是一座富营养抽水型中型水库,为了解富营养过程中抽水型水库后生浮游动物群落的种类组成与结构特征,于2006年3～12月在水库敞水区进行每月1次或2次调查.共检到轮虫32种、枝角类4种和桡足类9种.其中,臂尾轮属为轮虫优势属,角突臂尾轮虫(Brachionus angularis)和剪形臂尾轮虫(B. forficula)为最主要的优势种.长额象鼻溞 (Bosmina longirostris)为枝角类的优势种,中华窄腹剑水蚤(Limnoithona sisnensis)为桡足类第1优势种,温中剑水蚤(Mesocyclops thermcyclopoides)为次优势种.中华窄腹剑水蚤个体较小(成体体长为0.3～0.5mm),对咸水有较强的适应能力,该种是通过河流调水引入大镜山水库.后生浮游动物的个体体重分布范围为0.01～81.92 μg,种类主要分布的个体体重区间为0.08～0.32 μg,在该区间的浮游动物主要为轮虫.浮游动物的丰度与生物量以桡足类占优势,丰度峰值出现在个体体重为0.08～0.16 μg的区间上,并以无节幼体为主;生物量的峰值出现在2.56～5.12 μg的等级上,峰值为46.43 μg/L,主要由桡足类构成.水库中后生浮游动物的丰度和生物量范围分别为21.9～876 ind./L和17.47～1089.73 μg/L,丰水期丰度较高,丰度和生物量的峰值分别出现在5月和9月份.与同地区的其它水体相比,大镜山水库浮游动物种类数低,与水体咸度高和鱼类养殖导致的高强度捕食压力有关.抽水入库量、降雨量是影响后生浮游动物丰度的主要因子,它们明显地削弱了温度的作用;在水温下降的枯水期,鱼类捕食压力下降导致了枝角类丰度的增加.     

Paralarvae of the jumbo squid,Dosidicus gigas

Abstract. The rhynchoteuthion stage of the jumbo squid, Dosidicus gigas, has morphological characteristics similar to the paralarvae of the purpleback squid, Sthenoteuthis oualaniensis, making it difficult to determine the locations, seasons, and conditions where spawning of jumbo squid occurs. In this study, 180 paralarvae of D. gigas were collected off the west coast of the Baja California peninsula and identified by sequencing a 369-bp fragment of the cytochrome oxidase I gene. Of these, 77 specimens, 0.8–6.0 mm in mantle length, were described. Indices based on morphometric ratios were used to determine whether the shapes of different body structures were reliable for identifying the paralarvae. For two ratios, the results appear to discriminate members of D. gigas from those of S. oualaniensis. Additionally, eye or intestinal photophores were not observed in any paralarvae of D. gigas. Morphological and morphometric information provided a valuable basis for the discrimination and identification of these two species.     

北部湾近岸海域浮游动物群落结构特征及季节变化

2017年3月(枯水期)、7月(丰水期)和10月(平水期)分别对北部湾近岸海域44个站位的浮游动物进行了调查。结果共检出浮游动物251种和浮游幼体24类,其中枯水期138种(类),丰水期134种(类),平水期191种(类),分属河口低盐、近岸暖温、近岸暖水和外海暖水4个生态类群。优势种9种,其中枯水期以原生动物占绝对优势,丰水期以枝角类、桡足类和浮游幼体类占优势,平水期以十足类和浮游幼体类占优势。浮游动物丰度年均值为789.95个/m~3,呈现出枯水期(1540.19个/m~3)明显高于平水期(457.58个/m~3)和丰水期(372.08个/m~3)的季节变化特征;浮游动物生物量年均值为252.40 mg/m~3,生物量的季节变化与丰度变化不一致,平水期生物量(385.01 mg/m~3)明显高于枯水期(221.41 mg/m~3)和丰水期(150.78 mg/m~3)。多样性指数平水期最高(3.16),丰水期(2.35)次之,枯水期(2.22)最低。枯水期和丰水期北部湾近岸海域浮游动物生物量和丰度水平分布特征基本呈现自河口近岸海域向外海递增的趋势,平水期浮游动物生物量与丰度的空间分布较为均匀。浮游动物的种类组成结构以及优势种的演替对浮游动物的生物量和丰度季节变化有着重要的决定作用。径流导致的悬浮物、营养盐等的变化可能是决定北部湾近岸海域浮游动物生物量和丰度空间分布的主要因素。研究还表明与其他海湾相比,北部湾近岸海域浮游动物群落结构趋于小型化,需加大关注。     

Community characteristics and of zooplankton in Qinzhou Bay

Qinzhou Bay, the biggest bay in Guangxi Province, is very species-rich and is developing a robust marine economy. In recent years, as human impact has increased, problems associated with the environment have become more complicated. Measuring zooplankton diversity and abundance is a way to monitor environmental conditions. According to the data from four ecological surveys of the zooplankton in Qinzhou Bay during 2008 and 2009, a total of 134 species of zooplankton were identified, including 52 Copepoda species, 27 Medusa species, 14 Planktonic larvae, 9 Chaetognatha species, 8 Pteropoda species, 5 Amphipoda species, 4 Cladocera species, 4 Ostracoda species, 3 Thaliacea species, 2 Appendiculata species, 2 Sergestdae species, 2 Protlsta species, 1 Rotiera species and 1 Cumacea species. The fauna was clearly characterized as tropical population. The total species number was highest in autumn, followed by spring, winter and summer. Zooplankton species diversity in Qinzhou Bay has increased compared with the results obtained in 1983–1985 (83 species). However, compared with other bays, the number of zooplankton species in Qinzhou Bay is close to Daya Bay (128), higher than in Zhilin Bay (60), Jiaozhou Bay (81) and Luoyuan Bay (70), and far lower than in the north South Sea (709). We adopted the dominant index Y > 0.02 as the distinguishing standard of dominant species. The number of dominant species in spring, summer, autumn and winter were six, nine, eight and five. There was only one common dominant species (Penilia avirostris) appeared in different seasons, For summer and autumn, the shared dominant species numbered about four. Between other seasons, the shared dominant species varied between two and three. The number of uniquely dominant species was four in summer, three in autumn and one in both spring and winter. The dominant species in different seasons have some overlaps and some differences. The average biomass of zooplankton was 378 mg/m³ at all times of year. The average biomass was largest in autumn, followed by winter, and was the least in spring and summer. The average density of zooplankton for the entire year was 805.11 ind/m³. The average density was largest in summer, followed by winter, and was least in autumn and spring. Copepoda and Planktonic larvae were the major components of zooplankton in spring and summer at Qinzhou Bay, with the other species’ densities under 10%. In autumn, Copepoda, Planktonic larvae and Chaetognatha were the major components of the biomass, and in winter, the major species were Copepoda and Cladocera, with the others species’ density under 10%. The average value of the Shannon–Wiener diversity index (H′) was 3.84 and the evenness index (J′) was 0.77. The zooplankton diversity index and community evenness overall were good and the community organization had a complete and stable state, but the status of the community was relatively weak. The relationship between biomass/density of zooplankton and environmental factors is remarkable. Biomass and density are positively correlated with temperature and nutrient concentration, and are negatively correlated with salinity.     

田湾核电站海域浮游动物生态特征

2009年8月在田湾核电站附近海域进行了海洋浮游动物及环境因子的调查,在14个调查站位共鉴定浮游动物10大类43种.其中原生动物5种,水螅水母类17种,栉水母类2种,枝角类2种,桡足类11种,糠虾2种,樱虾类1种,磷虾1种,毛颚类1种,被囊类1种.浮游动物的丰度范围为99-2546个/m3,平均值为834个/m3.主要优势种为薮枝螅水母、太平洋纺锤水蚤、背针胸刺水蚤、鸟喙尖头潘、异体住囊虫、汤氏长足水蚤、强壮箭虫.优势度分别为0.804、0.586、0.569、0.485、0.197、0.140、0.116.各类指数变幅较大(种类数为9-17,丰富度指数为0.913-1.770,多样性指数为1.170-3.212,均匀度指数为0.369-0.803).多样性指数均值为2.188,均匀度指数均值为0.587,丰富度指数均值为1.336.相关性分析表明,水温与浮游动物丰度及种类数之间具有显著的相关性,相关系数(r)分别为-0.615和-0.574,P＜0.05;种类数与多样性指数、丰富度指数及均匀度指数有显著的正相关,相关系数(r)分别为0.730、0.759(P＜0.01)和0.552( P＜0.05),水温升高使浮游动物种类数减少;水温与氨氮含量之间有极显著的正相关性,氨氮含量与浮游动物种类数之间有极显著的负相关性,水温升高使氨氮上升引起浮游动物种类数下降,温排水导致调查海域水温升高引起了浮游动物群落多样性指数、丰富度指数及均匀度指数的下降.调查海域水质状况的生物多样性指数评价显示,目前该海域水质总体处于轻度污染.     

南沙群岛美济礁海域夏季浮游动物群落特征

浮游动物是珊瑚礁生态系统中的重要组成部分,但国内相关研究相对较少。利用2012年7月在南沙群岛美济礁海域开展的13个站次的海洋生物调查数据,对美济礁浮游动物的群落特征进行研究,表明:(1)美济礁浮游动物种类组成丰富,共出现15个类群138种(类)浮游动物;(2)优势种组成复杂、区域变化明显,单一种的优势度不高;(3)浮游动物平均密度和湿重生物量分别为117.70个/m3、69.01 mg/m3,浮游幼虫在总密度中所占比例最大;(4)浮游动物非常丰富,多样性程度较高。平均丰富度、多样性指数和均匀度分别为4.93、3.33和0.67;(5)浮游动物可划分为2个群落,分别为潟湖-礁坪区群落和向海坡群落;(6)受珊瑚礁不同生物地貌带的空间异质性和水动力条件的影响,美济礁浮游动物群落区域差异明显。潟湖区浮游动物多样性较高,生物量最低;礁坪区浮游动物数量大,但分布不均匀,且多样性水平最低;向海坡区浮游动物种类最多、多样性非常丰富,但栖息密度最低。     

Features of the structure and spatial distribution of plankton in the Sheksna Reservoir

Based on the field studies conducted in August 2005 and 2007, the distributions of zooplankton structure and abundance, as well as chlorophyll content, in the Sheksna Reservoir are analyzed. A total of 107 zooplankton species have been found (46 Cladocera, 18 Copepoda, and 43 Rotifera), including 24 species (10 Cladocera, 2 Copepoda, and 12 Rotifera) new for the reservoir. In the surface layer of water, where blue-green algae concentrate, zooplankton abundance and biomass are 1.5–5 times lower and the zooplankton structure is simpler than in deeper layers. The highest zooplankton biomass (>3 g/m³) are observed in Lake Beloe and the upper area of the Sheksna section, while in the near-shore sites it did not exceed 1 g/m³. There are no significant changes in zooplankton abundance when compared to the abundance recorded at the end of the past century.     

Seasonality and abundance of some dominant crustacean zooplankton in Lake Awasa,a tropical rift valley lake in Ethiopia

The zooplankton of a Rift Valley lake in Ethiopia, Awasa, was sampled at 3 stations for 2 years (1986 and 1987) concurrently with various meteorological and limnological measurements. The spatial and temporal variation in abundance of some numerically dominant crustaceans, Mesocyclops aequatorialis similis (Copepoda), Thermocyclops consimilis (Copepoda) and Diaphanosoma excisum (Cladocera) is discussed. Temporal (months, sampling dates) rather than spatial (station) variability accounts for more than 50% of the total variance in zooplankton abundance but horizontal patchiness exists during periods of high zooplankton density. Sampling errors were generally low, except for counts of cyclopoid nauplii (subsampling) and Diaphanosoma (inter-replicate variance). Zooplankton showed distinct seasonality associated with the mixing cycle of the lake. Total numbers increased to more than 200 000 m⁻³ during the unstratified period (July to September). Low numbers were evident during stratification (February to May) when zooplankton numbers did not exceed 15 000 m⁻³. Individual zooplankton species and age classes showed variable seasonal amplitudes, ranging from 6.4 (nauplius 3) to 44.8 (copepodite 3 of Mesocyclops). We discuss some possible causes for zooplankton seasonality in Lake Awasa, and also review zooplankton seasonal cycles in other tropical lakes, especially African ones.     

State of the Ichthyoplankton Community along the Crimean Peninsula in August 2011

Data on species composition, spatial distribution of ichthyoplankton, and feeding of fish larvae in August 2011 are presented for the shelf and the open waters along the Crimean Peninsula from Kerch Strait to Karkinit Bay. In the ichthyoplankton, fish eggs and larvae represented 19 species from 16 families. The average egg abundance was 111 egg/m² and larvae abundance was 22 ind./m². The elimination ratio of the European anchovy Engraulis encrasicolus, which dominates in the plankton from the final stages of development to the prelarvae in 2011, was similar to that observed in 1957. The high number of larvae of the older age group in the western halistatic zone is explained by the peculiarities of the hydrological regime. Decrease in the pressure of predatory jelly macroplankton and an fodder zooplankton (zooplankton abundance) contribute to the survival of the fish larvae.     

福建中部近海浮游动物数量分布与水团变化的关系

根据2009—2010年在福建中部近海24°55'—25°13'N、119°11'—119°32'E水域冬、春、夏3个季节的调查资料,探讨了该水域浮游动物总丰度与生物量的平面分布、季节变化及其与台湾海峡水团变化的关系。结果表明,调查水域浮游动物的数量在冬、春之交变化较大,而在春、夏季变化较小。浮游动物冬、春两季的平均丰度分别为8.90 个/m³和245.65 个/m³,夏季为236.82 个/m³。冬、春两季,该水域浮游动物的分布特征相近。其数量在近岸较高,向外侧水域逐渐降低。冬季浮游动物的丰度最高为31.56 个/m³,春季最高达到831.67 个/m³。中华哲水蚤(Calanus sinicus)是冬、春季影响总丰度变化最主要的种类。与冬、春季不同,夏季浮游动物的数量在离岸水域较高,丰度最高达1053.13 个/m³,而在近岸较低,最低值仅19.17 个/m³。汉森莹虾(Lucifer hanseni)、双生水母(Diphyes chamissonis)是影响总丰度变化最主要的种类。浮游动物在各季的不同分布特征与台湾海峡的季节性水团变化有关。受季风转换影响,从冬季到夏季,海峡内沿岸流势力逐渐减弱,台湾暖流水势力逐渐增强,并影响到沿岸的水文环境。这导致调查水域内浮游动物的优势种类由暖温种向暖水种演替。由于冬、春季的重要优势种类中华哲水蚤与夏季的汉森莹虾、双生水母具有不同的温度适应性,受不同性质水团的影响,在近岸和离岸水域各自呈现出不同的数量高低。从而进一步影响到各季浮游动物总数量的分布。     

Biases in determining the diet of jumbo squid <Emphasis Type="Italic">Dosidicus gigas</Emphasis> (D’ Orbigny 1835) (Cephalopoda: Ommastrephidae) off southern-central Chile (34°S–40°S)

The diet of jumbo squid (Dosidicus gigas) off southern-central Chile is described to examine potential biases in the determination of their main prey. Specimens were collected from catches using different fishing gear (jigging, trawl and purse-seine), from July 2003 to January 2004, and from December 2005 to October 2006. The stomach contents were analyzed in terms of frequency of occurrence, number, and weight of prey items and the diet composition was analyzed using Detrended Correspondence Analysis. In the industrial purse-seine fleet for jack mackerel (Trachurus murphyi), the dominant prey of D. gigas was T. murphyi. In the industrial mid-trawl fishery for Patagonian grenadier (Macruronus magellanicus), the dominant species in the diet of D. gigas was M. magellanicus. Similarly, Chilean hake (Merluccius gayi) was the main prey in the diet of D. gigas obtained in the industrial trawl fishery for Chilean hake; and, in both artisanal fisheries (purse-seine for small pelagics and jigging), small pelagic fish and D. gigas were the main prey in the stomach contents of D. gigas. Cannibalism in D. gigas varied between different fleets and probably is related to stress behavior during fishing. The Detrended Correspondence Analysis ordination showed that the main prey in the diet of D. gigas is associated with the target species of the respective fishery. Consequently, biases are associated with fishing gear, leading to an overestimate in the occurrence of the target species in the diet. We recommend analyzing samples from jigging taken at the same time and place where the trawl and purse-seine fleets are operating to avoid this problem, and the application of new tools like stable isotope, heavy metal, and fatty acid signature analyses.