海洋浮游介形类的多样性和生态学研究进展

海洋浮游介形类(ostracods)是一类分布较广的小型甲壳动物, 大多数是典型的有机碎屑摄食者, 本身又是中深层鱼类的饵料, 在海洋碳循环中起重要作用。目前海洋浮游介形类研究主要集中在海洋表层, 大约还有200—400 种的海洋浮游介形类未被发现, 尤其是栖息于深海的种类。今后介形类分类学研究的重要趋势之一是深海种类的发现。我国介形类研究起步晚, 积累少, 应加强我国不同海域深海介形类及其与环境关系的深入研究。文章综述了海洋浮游介形类的多样性和生态学等方面的研究进展, 重点概述了海腺萤科分类的发展, 比较分析了不同海域介形类的物种多样性和分布特征, 总结了浮游介形类的生态作用及其影响因素, 概括了我国海洋浮游介形类的研究现状, 以期为海洋生物多样性、海洋生物地球化学循环以及深海生态学等方面的研究提供基础依据。     

象山港网箱养殖区与非养殖区的细菌群落分布

近海集约化养殖是导致我国近海污染的主要来源之一。浮游细菌在近海生态系统的物质循环过程中发挥重要作用,研究海洋浮游细菌群落对养殖活动的响应,对于指示和评价海水养殖生态系统健康具有重要意义。采集了象山港网箱养殖区与非养殖区3个深度,包括表层(0.5 m)、中层(2.5 m)、底层(8.0 m)的水样,利用焦磷酸测序技术测定16S rRNA基因,研究浮游细菌的群落结构和多样性。结果表明:网箱养殖活动不仅使得附近区域水体理化性质发生改变,如化学需氧量浓度显著高于非养殖区域,而且显著地(P0.05)改变了浮游细菌的群落结构,但不同深度间群落结构和多样性的差异不显著。网箱养殖区和非养殖区中主要浮游细菌类群为α-变形菌(Alphaproteobacteria)、γ-变形菌(Gammaproteobacteria)、拟杆菌(Bacteroidetes)、放线菌(Actinobacteria)、β-变形菌(Betaproteobacteria)、ε-变形菌(Epsilonproteobacteria)和其它变形菌(Unclassified Proteobacteria),占细菌总序列数的98.64%。有些细菌类群的平均相对丰度从网箱区到非养殖区差异显著,如拟杆菌(P0.01)和放线菌(P0.05)显著降低,而γ-变形菌(P0.05)显著增加。相似度分析表明γ-变形菌、α-变形菌和拟杆菌是造成网箱区和非养殖区群落差异的主要类群,对群落差异总贡献率达到45.02%。偏冗余分析表明,影响细菌群落分布的主要环境因子有化学需氧量、磷酸盐、铵盐和总有机碳,共解释38.18%的群落变异,空间距离单独解释10.66%的群落变异。实验结果表明,养殖活动导致浮游细菌群落的改变,其中拟杆菌、放线菌和γ-变形菌的丰度显著变化,可能用于评价养殖水体的水质状况。     

珠江河口的浮游细菌生态学研究进展

河口地区是海陆交互作用的集中地带,生态环境十分脆弱敏感,物质循环机制复杂,而浮游细菌(bacterioplankton)参与的生态过程是河口生态系统物质循环的重要环节。珠江河口是独特的典型亚热带河口。近年的研究表明,浮游细菌在珠江河口生态系统物质循环中占有重要地位,其生产力和丰度受噬菌原生动物(鞭毛虫)和病毒的控制,而且其生物量与浮游植物的数量具有显著的相关性。珠江河口的优势浮游细菌类群为变型菌门(Proteobacteria)和蓝藻菌(Cyanobacteria)等,浮游细菌丰度和群落结构变化主要受到盐度、温度、营养盐水平等因素的影响。珠江河口浮游细菌与地球物质循环功能鲜有报道,而且珠江河口生态系统中有机质的浮游细菌转化机制和生态学效应更是没有深入研究。基于此,本文全面综述了珠江河口浮游细菌种类组成、分布、生物量、地球物质循环及其环境影响因素等方面的研究进展,有助于系统性地揭示近海生态系统的特征;同时,本文作者还对珠江河口浮游细菌生态学研究今后值得关注的科学问题进行了探讨。     

近海海洋生态连通性研究进展

生态连通性是空间生态学和保护生物学的重要概念和研究手段。国外越来越多的研究表明,开展近海海洋生态连通性研究对促进海洋生态系统保护和修复具有十分重要的现实意义。阐述了近海海洋生态连通性的概念与机制,回顾了目前近海海洋连通性的研究进展并分析了存在的问题,总结了近海海洋生态连通性研究的框架和具体方法,最后提出我国开展近海海洋生态连通性研究的建议,以期对今后国内开展海洋生态连通性相关研究工作有所启示。     

缀块性和缀块动态:Ⅱ.描述与分析

在生态学中,“缀块”(patch)的概念早已在植被群落和海洋生态系统中浮游动植物空间分布研究中广泛应用。A.S.Watte早在1947年就强调缀块在植物群落结构分析中的重要性。实际上,缀块存在于地球的任何地方。森林可     

昆明小型城市湖泊叶绿素a浓度与硅藻群落的时空分布及主控因子

水体叶绿素a浓度(Chla)与硅藻群落特征是指示湖泊水质的常用生物指标。本研究于2017年3月—2019年12月调查了昆明市4个小型湖泊(云南师范大学校园内北潭、北湖、南湖、龙潭)的水体环境指标、Chla浓度和硅藻群落的季节变化。结果显示：4个湖泊水体总氮(TN)、总磷(TP)和Chla浓度均呈现明显的季节波动。其中，营养水平最高的南湖水体Chla含量显著高于其他3个湖泊，影响南湖Chla变化的主要因子是TN;而在其他3个水体中，水温的增加显著促进了Chla浓度的上升。水温和TN是4个湖泊水体Chla时空变化的主要驱动因子。北潭、南湖和龙潭的硅藻群落以浮游硅藻占优，水深最浅的北湖以底栖硅藻为主，表明水深影响了硅藻群落的浮游物种占比与优势属种。水深、TN、TP、透明度以及水温驱动了硅藻群落的时空变化，其中，水温是影响硅藻群落季节差异的主要因子，而TN和TP是导致同一季节湖泊间硅藻群落差异的主要因子。     

陆源人类活动对近海生态系统的影响

随着海岸带快速城市化和经济发展,人类活动对近海生态系统的影响日益增加。通过对国内外大量相关文献的分析和与国际专家的研讨,分别从海洋资源开发、海岸带城市化和环境变化等几个方面概述了陆源人类活动对近海生态系统的影响。目前陆源人类活动导致近海生态系统出现的主要问题有:海洋生物资源过度捕捞、海岸带富营养化、海洋酸化、珊瑚礁退化、海洋垃圾、以及海岸带矿产开采等高强度开发活动引发的重金属和持久性有机污染物污染等。这些问题会直接导致海洋生物群落结构变化、影响水质、降低海洋生物多样性,最终影响海洋生态系统服务功能,威胁海洋生态系统健康。这些问题的根源多来自陆地,必须将海洋和陆地作为一个有机整体,整合海陆系统相互作用的科学计划,推进海洋资源和近海生态系统的可持续管理。     

我国土壤线虫生态学研究进展和展望

土壤线虫生态学主要探讨土壤线虫群落和其周围环境(包括生物和非生物)的相互关系, 包括不同生态系统中土壤线虫群落的分布和结构组成、线虫群落与土壤环境及其他土壤生物之间的相互作用等。本文回顾了我国研究者近年来在土壤线虫生态学研究领域的研究现状, 包括不同生态系统土壤线虫群落的分布、组成和多样性及其影响因素, 土壤线虫群落与全球气候环境变化的关系, 土壤线虫群落的生态功能以及土壤线虫群落生态学分析方法的发展及应用。重点评述近年来我国土壤线虫生态学的发展现状, 同时分析和比较了国内外土壤线虫生态学的发展态势, 提出建设全国范围的监测网络的重要性。未来我国土壤线虫生态学的发展方向应继续加强小尺度下土壤微食物网联通性和大尺度下全球气候变化对土壤线虫群落影响的研究以及加强相关新的研究技术方法的应用。     

中国近海入侵贝类及其影响

海洋贝类种类繁多,是近海底栖生态系统的优势种,在生态系统物质循环和能量流动中起着极其重要的作用;但因频繁的人类活动导致的贝类入侵问题,往往使该过程不能正常运转。大量研究表明,入侵贝类会抑制原著贝类或其他生物的生长及拓殖,形成单一优势群落,破坏当地生态系统的平衡,也会对海洋渔业生产和近海工程及作业等造成不可预测的危害。目前,欧美等国家针对该问题已开展了大量工作,十分重视入侵贝类的生物学、生态学与行为学特征及特性的研究,并根据其入侵途径与方式的不同开展了检测、监测、防控及管理工作。但在我国,入侵贝类还未引起相关部门及研究机构的足够重视。本文主要简述了我国近海的3种入侵贝类沙筛贝、指甲履螺和地中海贻贝的生物学、生态学及行为学等特征及其对当地生态系统的影响;同时,根据其特性及入侵过程控制的难易,建议在完善我国入侵贝类数据库的基础上加强早期预警与检测,以及安全防控和管理等工作。     

松花江哈尔滨段浮游植物群落格局及其与环境因子的相关性

松花江是黑龙江在我国境内的最大支流,流经吉林、黑龙江两省。松花江哈尔滨段是哈尔滨市工农业生产与生活用水的重要水资源,近年来由于人类活动的频繁影响,水体质量有所下降。鉴于此,于2018年春、夏、秋三季(4月、8月和10月),在松花江哈尔滨段设置14个采样点,对电导率、总氮和总磷等理化指标进行测定,同时对其浮游植物群落结构及环境因子相关性进行研究。利用群落相似性分析(ANOSIM)探讨浮游植物群落时空分布差异;通过SIMPER分析筛选出影响群落时空格局的关键物种。基于优势种和10项理化指标的冗余分析(RDA)揭示了浮游植物群落生态分布特征并对关键影响因子进行识别。研究结果表明,调查期间共鉴定浮游植物136种,其中优势种15种,群落结构主要以硅藻门和绿藻门的物种构成。松花江哈尔滨段浮游植物群落结构与过去10余年间相比较为稳定。ANOSIM和SIMPER分析表明,季节变化和人为活动干扰对浮游植物群落时空格局具有一定驱动作用,蓝藻门物种的空间分布活动干扰影响明显。RDA分析表明,浮游植物分布特征与水环境时空异质性关系密切,驱动松花江哈尔滨段浮游植物群落时空分布的主要水环境因子为电导率、总磷、浊度和pH。     

Vertical gradients in species richness and community composition across the twilight zone in the North Pacific Subtropical Gyre

Although metazoan animals in the mesopelagic zone play critical roles in deep pelagic food webs and in the attenuation of carbon in midwaters, the diversity of these assemblages is not fully known. A metabarcoding survey of mesozooplankton diversity across the epipelagic, mesopelagic and upper bathypelagic zones (0–1500 m) in the North Pacific Subtropical Gyre revealed far higher estimates of species richness than expected given prior morphology‐based studies in the region (4,024 OTUs, 10‐fold increase), despite conservative bioinformatic processing. Operational taxonomic unit (OTU) richness of the full assemblage peaked at lower epipelagic–upper mesopelagic depths (100–300 m), with slight shoaling of maximal richness at night due to diel vertical migration, in contrast to expectations of a deep mesopelagic diversity maximum as reported for several plankton groups in early systematic and zoogeographic studies. Four distinct depth‐stratified species assemblages were identified, with faunal transitions occurring at 100 m, 300 m and 500 m. Highest diversity occurred in the smallest zooplankton size fractions (0.2–0.5 mm), which had significantly lower % OTUs classified due to poor representation in reference databases, suggesting a deep reservoir of poorly understood diversity in the smallest metazoan animals. A diverse meroplankton assemblage also was detected (350 OTUs), including larvae of both shallow and deep living benthic species. Our results provide some of the first insights into the hidden diversity present in zooplankton assemblages in midwaters, and a molecular reappraisal of vertical gradients in species richness, depth distributions and community composition for the full zooplankton assemblage across the epipelagic, mesopelagic and upper bathypelagic zones.     

Bacterial diversity and community composition from seasurface to subseafloor

We investigated compositional relationships between bacterial communities in the water column and those in deep-sea sediment at three environmentally distinct Pacific sites (two in the Equatorial Pacific and one in the North Pacific Gyre). Through pyrosequencing of the v4–v6 hypervariable regions of the 16S ribosomal RNA gene, we characterized 450 104 pyrotags representing 29 814 operational taxonomic units (OTUs, 97% similarity). Hierarchical clustering and non-metric multidimensional scaling partition the samples into four broad groups, regardless of geographic location: a photic-zone community, a subphotic community, a shallow sedimentary community and a subseafloor sedimentary community (⩾1.5 meters below seafloor). Abundance-weighted community compositions of water-column samples exhibit a similar trend with depth at all sites, with successive epipelagic, mesopelagic, bathypelagic and abyssopelagic communities. Taxonomic richness is generally highest in the water-column O₂ minimum zone and lowest in the subseafloor sediment. OTUs represented by abundant tags in the subseafloor sediment are often present but represented by few tags in the water column, and represented by moderately abundant tags in the shallow sediment. In contrast, OTUs represented by abundant tags in the water are generally absent from the subseafloor sediment. These results are consistent with (i) dispersal of marine sedimentary bacteria via the ocean, and (ii) selection of the subseafloor sedimentary community from within the community present in shallow sediment.     

Variability in the macrozooplankton community off the Antarctic Peninsula

Summary This paper presents an analysis of zooplankton net sampling surveys carried out during four expeditions to the Antarctic Peninsula region. Cluster analysis documented two to three site groupings for the epipelagic zone and one mesopelagic site cluster below 200 to 300 m depth. Analysis of species dominance, constancy, diversity and evenness indices did not allow clear designation and separation of communities in terms of these parameters.Computation of a rank correlation matrix for each season allowed the characterization of species groups. There were no perfect indicator species in the very strict sense. The main differences in the composition of the zooplankton between the site clusters were due mainly to changes in abundance rather than to presence or absence of particular species. However, the interpretation of the complex species and site groupings led to the conclusion that we can define three distinct communities: an oceanic, a neritic, and a mesopelagic community beneath 200 to 300 m. A so-called transitional cluster represents a mixing zone created by frequent occurrence of species from both the oceanic and neritic community. The location of the described oceanic and neritic community sites seem to be relatively stable with minor latitudinal changes during the seasons, while occurrence and abundance of most species changes with the time of the year. The usefulness of particular species (e.g. Euphausia superba) as indicator species also change during the year     

Major imprint of surface plankton on deep ocean prokaryotic structure and activity

Deep ocean microbial communities rely on the organic carbon produced in the sunlit ocean, yet it remains unknown whether surface processes determine the assembly and function of bathypelagic prokaryotes to a larger extent than deep‐sea physicochemical conditions. Here, we explored whether variations in surface phytoplankton assemblages across Atlantic, Pacific and Indian ocean stations can explain structural changes in bathypelagic (ca. 4,000 m) free‐living and particle‐attached prokaryotic communities (characterized through 16S rRNA gene sequencing), as well as changes in prokaryotic activity and dissolved organic matter (DOM) quality. We show that the spatial structuring of prokaryotic communities in the bathypelagic strongly followed variations in the abundances of surface dinoflagellates and ciliates, as well as gradients in surface primary productivity, but were less influenced by bathypelagic physicochemical conditions. Amino acid‐like DOM components in the bathypelagic reflected variations of those components in surface waters, and seemed to control bathypelagic prokaryotic activity. The imprint of surface conditions was more evident in bathypelagic than in shallower mesopelagic (200–1,000 m) communities, suggesting a direct connectivity through fast‐sinking particles that escape mesopelagic transformations. Finally, we identified a pool of endemic deep‐sea prokaryotic taxa (including potentially chemoautotrophic groups) that appear less connected to surface processes than those bathypelagic taxa with a widespread vertical distribution. Our results suggest that surface planktonic communities shape the spatial structure of the bathypelagic microbiome to a larger extent than the local physicochemical environment, likely through determining the nature of the sinking particles and the associated prokaryotes reaching bathypelagic waters.     

Vision in the deep sea

The deep sea is the largest habitat on earth. Its three great faunal environments--the twilight mesopelagic zone, the dark bathypelagic zone and the vast flat expanses of the benthic habitat--are home to a rich fauna of vertebrates and invertebrates. In the mesopelagic zone (150-1000 m), the down-welling daylight creates an extended scene that becomes increasingly dimmer and bluer with depth. The available daylight also originates increasingly from vertically above, and bioluminescent point-source flashes, well contrasted against the dim background daylight, become increasingly visible. In the bathypelagic zone below 1000 m no daylight remains, and the scene becomes entirely dominated by point-like bioluminescence. This changing nature of visual scenes with depth--from extended source to point source--has had a profound effect on the designs of deep-sea eyes, both optically and neurally, a fact that until recently was not fully appreciated. Recent measurements of the sensitivity and spatial resolution of deep-sea eyes--particularly from the camera eyes of fishes and cephalopods and the compound eyes of crustaceans--reveal that ocular designs are well matched to the nature of the visual scene at any given depth. This match between eye design and visual scene is the subject of this review. The greatest variation in eye design is found in the mesopelagic zone, where dim down-welling daylight and bio-luminescent point sources may be visible simultaneously. Some mesopelagic eyes rely on spatial and temporal summation to increase sensitivity to a dim extended scene, while others sacrifice this sensitivity to localise pinpoints of bright bioluminescence. Yet other eyes have retinal regions separately specialised for each type of light. In the bathypelagic zone, eyes generally get smaller and therefore less sensitive to point sources with increasing depth. In fishes, this insensitivity, combined with surprisingly high spatial resolution, is very well adapted to the detection and localisation of point-source bioluminescence at ecologically meaningful distances. At all depths, the eyes of animals active on and over the nutrient-rich sea floor are generally larger than the eyes of pelagic species. In fishes, the retinal ganglion cells are also frequently arranged in a horizontal visual streak, an adaptation for viewing the wide flat horizon of the sea floor, and all animals living there. These and many other aspects of light and vision in the deep sea are reviewed in support of the following conclusion: it is not only the intensity of light at different depths, but also its distribution in space, which has been a major force in the evolution of deep-sea vision.     

Community Structure and Function of Planktonic Crenarchaeota: Changes with Depth in the South China Sea

Marine Crenarchaeota represent a widespread and abundant microbial group in marine ecosystems. Here, we investigated the abundance, diversity, and distribution of planktonic Crenarchaeota in the epi-, meso-, and bathypelagic zones at three stations in the South China Sea (SCS) by analysis of crenarchaeal 16S rRNA gene, ammonia monooxygenase gene amoA involved in ammonia oxidation, and biotin carboxylase gene accA putatively involved in archaeal CO₂ fixation. Quantitative PCR analyses indicated that crenarchaeal amoA and accA gene abundances varied similarly with archaeal and crenarchaeal 16S rRNA gene abundances at all stations, except that crenarchaeal accA genes were almost absent in the epipelagic zone. Ratios of the crenarchaeal amoA gene to 16S rRNA gene abundances decreased ~2.6 times from the epi- to bathypelagic zones, whereas the ratios of crenarchaeal accA gene to marine group I crenarchaeal 16S rRNA gene or to crenarchaeal amoA gene abundances increased with depth, suggesting that the metabolism of Crenarchaeota may change from the epi- to meso- or bathypelagic zones. Denaturing gradient gel electrophoresis profiling of the 16S rRNA genes revealed depth partitioning in archaeal community structures. Clone libraries of crenarchaeal amoA and accA genes showed two clusters: the “shallow” cluster was exclusively derived from epipelagic water and the “deep” cluster was from meso- and/or bathypelagic waters, suggesting that niche partitioning may take place between the shallow and deep marine Crenarchaeota. Overall, our results show strong depth partitioning of crenarchaeal populations in the SCS and suggest a shift in their community structure and ecological function with increasing depth.     

Links between viruses and prokaryotes throughout the water column along a North Atlantic latitudinal transect

Viruses are an abundant, diverse and dynamic component of marine ecosystems and have a key role in the biogeochemical processes of the ocean by controlling prokaryotic and phytoplankton abundance and diversity. However, most of the studies on virus–prokaryote interactions in marine environments have been performed in nearshore waters. To assess potential variations in the relation between viruses and prokaryotes in different oceanographic provinces, we determined viral and prokaryotic abundance and production throughout the water column along a latitudinal transect in the North Atlantic. Depth-related trends in prokaryotic and viral abundance (both decreasing by one order of magnitude from epi- to abyssopelagic waters), and prokaryotic production (decreasing by three orders of magnitude) were observed along the latitudinal transect. The virus-to-prokaryote ratio (VPR) increased from ∼19 in epipelagic to ∼53 in the bathy- and abyssopelagic waters. Although the lytic viral production decreased significantly with depth, the lysogenic viral production did not vary with depth. In bathypelagic waters, pronounced differences in prokaryotic and viral abundance were found among different oceanic provinces with lower leucine incorporation rates and higher VPRs in the North Atlantic Gyre province than in the provinces further north and south. The percentage of lysogeny increased from subpolar regions toward the more oligotrophic lower latitudes. Based on the observed trends over this latitudinal transect, we conclude that the viral–host interactions significantly change among different oceanic provinces in response to changes in the biotic and abiotic variables.     

海洋生态系统稳定同位素基线的选取

稳定同位素技术在海洋食物网研究中得到了广泛的应用,但在分析海洋生物食性和营养级时,需要选择某种生物或物质的稳定同位素值作为基线.本文综述了河口和海湾、浅海、大洋及深海4类典型海洋生态系统稳定同位素基线的选取,分析了影响稳定同位素基线选择的因素,以及特定化合物稳定同位素在消除基线时空异质性中的潜在价值,并对目前存在的问题以及今后的研究方向进行了展望,以期为国内学者进一步深入开展海洋生态系统的稳定同位素生态学研究提供有益参考.     

Evolution in the deep sea: Biological traits, ecology and phylogenetics of pelagic copepods

Deep-sea biodiversity has received increasing interest in the last decade, mainly focusing on benthic communities. In contrast, studies of zooplankton in the meso- to bathypelagic zones are relatively scarce. In order to explore evolutionary processes in the pelagic deep sea, the present study focuses on copepods of two clausocalanoid families, Euchaetidae and Aetideidae, which are abundant and species-rich in the deep-sea pelagic realm. Molecular phylogenies based on concatenated-portioned data on 18S, 28S and internal transcribed spacer 2 (ITS2), as well as mitochondrial cytochrome c oxidase subunit I (COI), were examined on 13 species, mainly from Arctic and Antarctic regions, together with species-specific biological traits (i.e. vertical occurrence, feeding behaviour, dietary preferences, energy storage, and reproductive strategy). Relationships were resolved on genus, species and even sub-species levels, the latter two established by COI with maximum average genetic distances ranging from ?5.3% at the intra-specific, and 20.6% at the inter-specific level. There is no resolution at a family level, emphasising the state of Euchaetidae and Aetideidae as sister families and suggesting a fast radiation of these lineages, a hypothesis which is further supported by biological parameters. Euchaetidae were similar in lipid-specific energy storage, reproductive strategy, as well as feeding behaviour and dietary preference. In contrast, Aetideidae were more diverse, comprising a variety of characteristics ranging from similar adaptations within Paraeuchaeta, to genera consisting of species with completely different reproductive and feeding ecologies. Reproductive strategies were generally similar within each aetideid genus, but differed between genera. Closely related species (congeners), which were similar in the aforementioned biological and ecological traits, generally occurred in different depth layers, suggesting that vertical partitioning of the water column represents an important mechanism in the speciation processes for these deep-sea copepods. High COI divergence between Arctic and Antarctic specimens of the mesopelagic cosmopolitan Gaetanus tenuispinus and the bipolar Aetideopsis minor suggest different geographic forms, potentially cryptic species or sibling species. On the contrary, Arctic and Antarctic individuals of the bathypelagic cosmopolitans Gaetanus brevispinus and Paraeuchaeta barbata were very similar in COI sequence, suggesting more gene flow at depth and/or that driving forces for speciation were less pronounced in bathypelagic than at mesopelagic depths.     

Diel vertical migration of the loosejaw dragonfishes (Stomiiformes: Stomiidae: Malacosteinae): a new analysis for rare pelagic taxa

The diel vertical migration (DVM) of three genera of the stomiid subfamily Malacosteinae (Photostomias, Aristostomias and Malacosteus) was analysed from capture records of nearly 300 specimens in the Atlantic Ocean. To account for broad temporal and geographic scales encountered in this study, local time of capture was transformed to a corrected time representing position in a solar day. Species of Photostomias and Aristostomias undertake asynchronous DVMs characterized by a residence in the mesopelagic zone during the day and separate migrating and non‐migrating subpopulations at night. Species of Photostomias displayed an asynchronous DVM pattern characterized by a residence in the lower mesopelagic zone (>500 m) during the day and a segregated distribution at night. Specimens of Photostomias guernei captured at night in the mesopelagic were nearly identical in size to those captured in the epipelagic; however, day epipelagic specimens were stratified by size. In species of Aristostomias, few specimens were caught in the mesopelagic zone during the day and only small specimens were captured in the mesopelagic zone at night, indicating that sampling depth may not have been adequate to capture the bulk of mesopelagic daytime residents and the entire size range of the non‐migrating night‐time residents. In contrast, Malacosteus niger was distributed below 600 m, did not regularly migrate to the epipelagic zone and was stratified across the 700 m isobath. From these data, relationships between DVM patterns, morphology and foraging ecology are inferred and biases and applications of this method are discussed.