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1.
珠江口南沙海域秋季渔业资源群落结构特征   总被引：2，自引：0，他引：2  
根据2015年11月珠江口南沙海域的渔业资源调查资料,对该海域秋季渔业资源群落组成、优势种和生物多样性等群落结构特征进行了初步研究。结果表明,该海域共出现渔业生物40种,以鱼类和甲壳类为主。其中,底层鱼类21种,中上层鱼类3种,甲壳类16种。相对重要性指数(IRI)可用来度量物种的生态优势度,秋季优势种类有亨氏仿对虾(Parapenaeopsis hungerfordi)和锐齿(Charybdis acuta)2种(IRI≥1 000)。该区域内各站位质量渔获率为0.63~11.15 kg·h~(-1),平均为4.23 kg·h~(-1);尾数渔获率为84~885尾·h~(-1),平均为433尾·h~(-1)。Shannon-Wiener多样性指数(H')为2.07,Margalef丰富度指数(D)为1.64,Peilou均匀度指数(J')为0.59。分析表明,该海域渔获物以小型经济甲壳动物和经济幼鱼为主,渔获个体偏小,总体上多样性空间差异不大。与该区域2002年同月份的调查数据相比,目前渔获物多样性下降明显,群落结构相对简单。  相似文献   

2.
  1. The structure of food webs provides important insight into biodiversity, organic matter (OM) pathways, and ecosystem functioning.
  2. Stable isotope analysis (δ13C and δ15N) was used to characterize the trophic structure and the main OM pathways supporting food webs in the Rapa Nui coastal marine ecosystem.
  3. The trophic position of consumers and isotopic niche metrics were estimated for different assemblages (i.e. mesozooplankton, emergent zooplankton, reef invertebrates, reef fishes, pelagic fishes, and seabirds). Furthermore, the relative importance of different OM sources (i.e. macroalgae, zooxanthellate corals, and particulate OM [POM]) was assessed for heterotrophic consumers using Bayesian mixing model (MixSIAR).
  4. Results show a clear pattern of 13C and 15N enrichment from small-sized pelagic and benthic invertebrates, to reef and pelagic fishes, and seabirds. Most invertebrates were classified as primary consumers, reef fishes as secondary consumers and pelagic predators and seabirds as tertiary and quaternary consumers.
  5. Isotopic niche metrics indicate a low trophic diversity for pelagic assemblages (mesozooplankton and pelagic fishes), in contrast to reef fauna (invertebrates and fishes), whose higher trophic diversity suggest the exploitation of a wider range of trophic resources. Overlapping of standard ellipses areas between reef invertebrates and reef fishes indicates that both assemblages could be sharing trophic resources.
  6. Mixing models results indicate that POM is the main trophic pathway for mesozooplankton, macroalgae (Rhodophyta) for emergent zooplankton, and a mix of coral-derived OM and Rhodophyta for coral reef assemblages such as macrobenthos and reef invertebrates. In contrast, POM contribution was notably more important for some pelagic fishes and seabirds from upper trophic levels.
  7. This study provides key elements for conservation efforts on coral reefs, management planning and full-implementation of the recently created Rapa Nui Multiple Use Marine Protected Area.
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3.
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4.
中东太平洋金枪鱼延绳钓渔获物组成分析   总被引：4，自引：2，他引：2  
根据2000年9月至2002年8月两年的中东太平洋金枪鱼延绳钓探捕调查结果,对延绳钓渔获物组成进行了初步分析。结果显示,延绳钓的主要渔获种类有肥壮金枪鱼(Thunnus obesus)和黄鳍金怆鱼(Thunnus albacares)等15种大洋性鱼类,渔获物中金枪鱼类分别占重量和尾数的76．41％和76．91％,旗鱼类占11．05％和7．83％．鲨鱼类占10．80％和12．08％,其他鱼类占1．73％和3．18％。相对重要性指标(IRI)表明,延绳钓渔业以肥壮金枪鱼和黄鳍金枪鱼为目标鱼种,其他大型中上层经济鱼类为兼捕对象。各渔获种类的渔获重量组成比例月间变化和海域变化明显。  相似文献   

5.
Hypoxia-based habitat compression of tropical pelagic fishes   总被引：2，自引：0，他引：2  
Large areas of cold hypoxic water occur as distinct strata in the eastern tropical Pacific (ETP) and Atlantic oceans as a result of high productivity initiated by intense nutrient upwelling. We show that this stratum restricts the depth distribution of tropical pelagic marlins, sailfish, and tunas by compressing the acceptable physical habitat into a narrow surface layer. This layer extends downward to a variable boundary defined by a shallow thermocline, often at 25 m, above a barrier of cold hypoxic water. The depth distributions of marlin and sailfish monitored with electronic tags and average dissolved oxygen (DO) and temperature profiles show that this cold hypoxic environment constitutes a lower habitat boundary in the ETP, but not in the western North Atlantic (WNA), where DO is not limiting. Eastern Pacific and eastern Atlantic sailfish are larger than those in WNA, where the hypoxic zone is much deeper or absent. Larger sizes may reflect enhanced foraging opportunities afforded by the closer proximity of predator and prey in compressed habitat, as well as by the higher productivity. The shallow band of acceptable habitat restricts these fishes to a very narrow surface layer and makes them more vulnerable to over‐exploitation by surface gears. Predictably, the long‐term landings of tropical pelagic tunas from areas of habitat compression have been far greater than in surrounding areas. Many tropical pelagic species in the Atlantic Ocean are currently either fully exploited or overfished and their future status could be quite sensitive to increased fishing pressures, particularly in areas of habitat compression.  相似文献   

6.
Anthropogenic changes to the Great Plains rivers of North America have had a large, negative effect on a reproductive guild of pelagic‐broadcast spawning (PBS) cyprinid fishes. The group is phylogenetically diverse, with multiple origins of the PBS mode. However, because of incomplete life‐history information, PBS designation often relies only on habitat and egg characteristics. We identified 17 known or candidate PBS fishes and systematically synthesized the literature on their biology and ecology in relation to major threats to persistence. Research output on an individual species was unrelated to conservation status, but positively correlated with breadth of distribution. The PBS species have opportunistic life‐history strategies and are typically short‐lived (generally 1–3 years) fishes. Many PBS species have truncated ranges showing declines in both distribution and abundance, especially those endemic to the Rio Grande catchment. Fundamental habitat associations are unknown for many species, particularly regarding seasonal shifts and early life stages. Critical thermal tolerances have been quantified for five PBS species and are generally >35°C. Turbidity and salinity changes are linked to responses at multiple life stages, but information is lacking on interactions between water quality and quantity. Hydrologic alteration appears to be a primary threat to PBS species, through complex interactions with landscape fragmentation, and habitat change. We highlight areas where scientific and management communities are lacking information and underline areas of potential conservation gain.  相似文献   

7.
莱州湾水域鱼类生物完整性评价   总被引：1，自引：0，他引：1       下载免费PDF全文
采用莱州湾水域鱼类生物完整性指数评价生态系统健康状况,为该水域的生态修复和渔业资源的可持续管理提供科学依据。2016-2017年在莱州湾采用底拖网开展鱼类资源调查,共捕获鱼类52种。参照1982-1983年的历史资料确定评价标准,从鱼类种类组成与丰度、繁殖共位群和营养结构等角度,筛选适用于莱州湾水域鱼类生物完整性(Fish index of biological integrity,F-IBI)评价的指标体系,得到鱼类总种类数、冷温性鱼类比例、中上层鱼类种类数比例、平均单位网次渔获量、多样性指数、产浮性卵鱼类比例、产粘着性卵鱼类比例、低耐污鱼类种数比例、广食性鱼类比例、底栖动物食性鱼类比例、浮游动物食性鱼类比例和杂食性鱼类比例等12个参数指标。根据评价指标体系计算F-IBI,结果显示:莱州湾水域的F-IBI得分为30,其完整性等级为“差”,表明莱州湾水域生态健康状况差。建议采取面源污染控制和基于生态系统保护的渔业管理恢复莱州湾水域生态系统健康。  相似文献   

8.
渤海主要渔业生物资源变动的研究   总被引：10，自引：3，他引：7  
根据１９５９年、１９８２～１９８３年、１９９２～１９９３和１９９８～１９９９年在渤海进行的周年分季度底拖网调查数据,分析了渤海主要渔业生物种类的资源变化特征。１９５９～１９８２年间,优势种发生了很大的变化,经济价值较高的小黄鱼、带鱼和对虾等由黄鲫、Ｔｉ鱼、枪乌贼等小型低值种类所替代。８０年代以来,年间优势种有一定的变动,但小型中小层鱼类Ｔｉ鱼、黄鲫、斑Ｊｉ等一直是渤海渔业生物优势种类。１９９８～１  相似文献   

9.
Generalist feeding strategies are favoured in stressful or variable environments where flexibility in ecological traits is beneficial. Species that feed across multiple habitat types and trophic levels may impart stability on food webs through the use of readily available, alternative energy pools. In lakes, generalist fish species may take advantage of spatially and temporally variable prey by consuming both benthic and pelagic prey to meet their energy demands. Using stomach content and stable isotope analyses, we examined the feeding habits of fish species in Alaska's Arctic Coastal Plain (ACP) lakes to determine the prevalence of generalist feeding strategies as a mechanism for persistence in extreme environments (e.g. low productivity, extreme cold and short growing season). Generalist and flexible feeding strategies were evident in five common fish species. Fish fed on benthic and pelagic (or nektonic) prey and across trophic levels. Three species were clearly omnivorous, feeding on fish and their shared invertebrate prey. Dietary differences based on stomach content analysis often exceeded 70%, and overlap in dietary niches based on shared isotopic space varied from zero to 40%. Metrics of community‐wide trophic structure varied with the number and identity of species involved and on the dietary overlap and niche size of individual fishes. Accumulation of energy from shared carbon sources by Arctic fishes creates redundancy in food webs, increasing likely resistance to perturbations or stochastic events. Therefore, the generalist and omnivorous feeding strategies employed by ACP fish may maintain energy flow and food web stability in extreme environments.  相似文献   

10.
王靓  花传祥  朱清澄  李非 《中国水产科学》2020,27(11):1379-1392
小型中上层鱼类是北太平洋海域重要的渔业资源,具有生命周期短、生长速度快、高集群性等特点,其资源年间波动显著,且受气候-海洋变化的影响。本文围绕秋刀鱼（Coloabis saira）、鲣（Katsuwonus pelamis）、鲐（Scomber japonicus）、鳀（Engraulis japonious）、竹䇲鱼（Trachurus japonicus）、沙丁鱼（Sardinops sagax）6种主要的小型中上层鱼类,回顾了厄尔尼诺-南方涛动（El Niño/La Niña-southern oscillation,ENSO）、太平洋年代际振荡（the Pacific decadal oscillation,PDO）、黑潮-亲潮（Kuroshio-Oyashio,KR-OY）等关键气候-海洋指数的特点及对鱼类栖息地环境和资源变动的影响。概括了气候-海洋变化对小型中上层鱼类的洄游分布和资源丰度的直接影响过程,以及对亲体繁殖产卵、仔稚体成活率和资源量波动间接的滞后影响过程。建议：（1）在多种气候-海洋指数基础上添加种群动态过程、捕捞方式系数、自然死亡率等参数构建生物量动态模型,揭示气候-海洋变化对渔业资源量的影响过程;（2）结合北太平洋涛动（North Pacific oscillation,NPO）、北极涛动（Arctic oscillation,AO）、北太平洋环流振荡（North Pacific gyre oscillation,NPGO）等其他北太平洋主要气候,基于物理海洋模型及空间耦合水动力学模型研究大尺度海流、中尺度涡旋对小型中上层鱼类影响。  相似文献   

11.
Since the 1950s, invertebrate fisheries catches have rapidly expanded globally to more than 10 million tonnes annually, with twice as many target species, and are now significant contributors to global seafood provision, export, trade and local livelihoods. Invertebrates play important and diverse functional roles in marine ecosystems, yet the ecosystem effects of their exploitation are poorly understood. Using 12 ecosystem models distributed worldwide, we analysed the trade‐offs of various invertebrate fisheries and their ecosystem effects as well as ecological indicators. Although less recognized for their contributions to marine food webs, our results show that the magnitude of trophic impacts of invertebrates on other species of commercial and conservation interest is comparable with those of forage fish. Generally, cephalopods showed the strongest ecosystem effects and were characterized by a strong top‐down predatory role. Lobster, and to a lesser extent, crabs, shrimp and prawns, also showed strong ecosystem effects, but at lower trophic levels. Benthic invertebrates, including epifauna and infauna, also showed considerable ecosystem effects, but with strong bottom‐up characteristics. In contrast, urchins, bivalves, and gastropods showed generally lower ecosystem effects in our simulations. Invertebrates also strongly contributed to benthic–pelagic coupling, with exploitation of benthic invertebrates impacting pelagic fishes and vice versa. Finally, on average, invertebrates produced maximum sustainable yield at lower levels of depletion (~45%) than forage fish (~65%), highlighting the need for management targets that avoid negative consequences for target species and marine ecosystems as a whole.  相似文献   

12.
  • 1. Fishing spans all oceans and the impact on ocean predators such as sharks and rays is largely unknown. A lack of data and complicated jurisdictional issues present particular challenges for assessing and conserving high seas biodiversity. It is clear, however, that pelagic sharks and rays of the open ocean are subject to high and often unrestricted levels of mortality from bycatch and targeted fisheries for their meat and valuable fins.
  • 2. These species exhibit a wide range of life‐history characteristics, but many have relatively low productivity and consequently relatively high intrinsic vulnerability to over‐exploitation. The IUCN — World Conservation Union Red List criteria were used to assess the global status of 21 oceanic pelagic shark and ray species.
  • 3. Three‐quarters (16) of these species are classified as Threatened or Near Threatened. Eleven species are globally threatened with higher risk of extinction: the giant devilray is Endangered, ten sharks are Vulnerable and a further five species are Near Threatened. Threat status depends on the interaction between the demographic resilience of the species and intensity of fisheries exploitation.
  • 4. 4. Most threatened species, like the shortfin mako shark, have low population increase rates and suffer high fishing mortality throughout their range. Species with a lower risk of extinction have either fast, resilient life histories (e.g. pelagic stingray) or are species with slow, less resilient life histories but subject to fisheries management (e.g. salmon shark).
  • 5. 5. Recommendations, including implementing and enforcing finning bans and catch limits, are made to guide effective conservation and management of these sharks and rays.
Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

13.
Resource polymorphism is a widespread phenomenon in post‐glacial fishes where multiple morphotypes of a species occur sympatrically and exhibit distinct resource use. Availability of open niches and high levels of within and among species competition are thought to drive differences in morphology and may provide insights into early stages of speciation. Hovsgol grayling (Thymallus nigrescens) are endemic to Lake Hovsgol, a lake colonised by fish following the Pleistocene, and are threatened with habitat loss due to climate change and illegal harvest. Previous analysis of Hovsgol grayling diet inferred through C and N stable isotopes suggested the presence of littoral and pelagic foraging groups. We hypothesised that morphology of the two foraging groups would reflect predictions of functional morphology, indicating the presence of resource polymorphism. To test this hypothesis, we evaluated evidence from C and N stable isotopes, stomach contents, fish ages, capture location and morphology. Two foraging groups of Hovsgol grayling were identified through stomach content and C and N stable isotope analysis. Individuals with greater zooplankton consumption were more frequently captured in the pelagic zone, exhibited higher gill raker counts, larger orbit (eye) sizes, longer paired fins, narrower head width, larger maxilla and smaller size at age than the group with greater reliance on benthic invertebrate prey. These differences were generally consistent with those described in other fish species exhibiting littoral–pelagic resource polymorphism. Our study provides the first example of littoral–pelagic resource polymorphism in the salmonid subfamily Thymallinae and highlights the potential influence of competition on fish evolution.  相似文献   

14.
  1. Dam construction threatens global aquatic biodiversity by fragmenting stream networks and altering flow regimes. The negative effects of dams are exacerbated by increased drought periods and associated water withdrawals, especially in semi-arid regions. Stream fishes are particularly threatened owing to their mobile nature and requirement for multiple habitats to complete their life cycles. An understanding of relationships with fragmentation and flow regimes, particularly as coarse-scale (e.g. catchment) constraints on species distributions, is essential for stream fish conservation strategies.
  2. Prairie chub (Macrhybopsis australis) is a small-bodied minnow (Cyprinidae) with poorly understood ecology endemic to the North American Great Plains. Suspected declines in abundance and extirpations have resulted in conservation interest for prairie chub at state and federal levels. Prairie chub is thought to share its reproductive strategy with pelagic-broadcast spawning minnows (pelagophils). Freshwater pelagic-broadcast spawning fishes have been disproportionately affected by fragmentation and streamflow alteration globally.
  3. Relationships of prairie chub occurrence with coarse-scale fragmentation and streamflow metrics were examined in the upper Red River catchment. Occurrence probability was modelled using existing survey data, while accounting for variable detection. The modelled relationships were used to project the distribution of prairie chub in both a wet and dry climatic period.
  4. The probability of prairie chub occurrence was essentially zero at sites with higher densities of upstream dams, but increased sharply with increases in flow magnitude, downstream open mainstem, and flood duration. The projected distribution of prairie chub was broader than indicated by naïve occurrence, but similar in both climatic periods. The occurrence relationships are consistent with the hypotheses of pelagic broadcast spawning and represent coarse-scale constraints that are useful for identifying areas of the stream network with higher potential for finer-scale prairie chub conservation and recovery efforts. In addition to informing pelagophil conservation, the relationships are also applicable to pelagic-broadcast spawning fishes in marine environments.
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15.
根据2011年春季南海中南部海域灯光罩网渔业海上调查数据,对南海中南部海域灯光罩网渔获组成、主要鱼种的生物学特性进行了研究。结果表明,鸢乌贼（Symplectoteuthis oualaniensis）是南海中南部灯光罩网的主捕鱼种,占绝对地位,优势胴长组为110～130 mm;其他主要鱼种有长体圆！（Decapterus macrosoma）、黄鳍金枪鱼（Thunnus albacaes）、鲔（Euthynnus affinis）和鲣（Katsuwonus pelami）。运用相对重要性指数（IRI）作为鱼种优势度的度量指标,得出灯光罩网渔获优势种只有鸢乌贼一种,IRI 值高达19418.013（IRI≥1000）,重要种有2种,长体圆！和黄鳍金枪鱼,IRI 值分别为176.731和175.703（1000﹥ IRI≥100）。灯光罩网是南海捕捞中上层鱼类的主要作业方式之一,发展前景好,应合理开发,实现南海渔业的更好发展。  相似文献   

16.
Pelagic fishes are typically considered mobile and wide-ranging open ocean foragers. However, many species have also been recorded in association with nearshore topographic structures. The relative abundance of four pelagic species at and away from topographic features on the continental shelf, as inferred from fine-scale catch data collected over a 7-year period, was examined for southern Western Australia. A total of 1056 captures were recorded from 890 h of trolling over 102 days: the top four species accounted for 97.5% of all captures. Eight distinct topographic features received 13.7% of the total trolling effort and produced 43.8% of captures. The percentage of all captures within 1 km of these features were 80% for yellowtail kingfish (Seriola lalandi, YTK), 50% for bonito (Sarda australia, BON), 27% for southern bluefin tuna (Thunnus maccoyii, SBT), and less than 5% for skipjack tuna (Katsuwonus pelamis, SKJ). Catch rates were 26, 6.59, and 2.47 times higher than catch rates away from the topographic features for YTK, BON, and SBT, respectively. In contrast, SKJ catch rates were 1/3rd lower at topographic features, indicating avoidance rather than preference. The mean distance at which species were captured from the center of each feature differed significantly, with YTK closest (303 m), followed by SBT (442 m), BON (493 m), and SKJ (539 m). These findings indicate habitat partitioning in pelagic fishes at topographic features and offer a way to increase catch of a targeted species, or reduce the capture of unwanted or quota-limited species.  相似文献   

17.
《水生生物资源》1999,12(3):177-185
Two trawl surveys were carried out in the summer months (June–July) of 1996 and 1997 along the whole South Adriaticarea (Mediterranean sea) for the first time, using the same vessel and the same sampling gear (European Community Research Project `MEDITS'); previous research data referred only to the south-western Adriatic side. A total list of 168 demersal species (fishes, cephalopods and crustaceans) was obtained during the surveys; species abundance data (individuals/trawling hour) were processed accordingto multivariate techniques in order to describe the composition and the distribution of the main species assemblages within the investigated area (10–800-m bathymetric range). Multivariate analysis of MEDITS survey catch data showed a strong relationship betweenfish assemblages and depth, while the influence of depth was lower with respect to cephalopod and especially crustacean assemblage distribution.  相似文献   

18.
Large pelagic fishes are assessed and managed by tuna Regional Fisheries Management Organizations (tRFMOs). These organizations have been criticized for not meeting conservation objectives, which may relate to aspects of governance and management. No previous studies have systematically evaluated why management performance differs among tRFMOs and among stocks within each tRFMO. In this study, we collected data on the nature of research, management, enforcement and socioeconomics of management systems in the five principal tRFMOs of the world's oceans. We quantified influences of economic and fishery‐related factors on these management characteristics and examined how these factors vary among tRFMOs. We found that tRFMOs with a greater number of member countries, a greater economic dependency on tuna resources, a lower mean per capita gross domestic product, a greater number of fishing vessels and smaller vessels were associated with less intensive research, management and enforcement in these tuna fisheries. We also quantified the influence of specific management attributes and of biological, economic and fishery‐related factors on the trends and current status of large pelagic fish stocks in these regions. The most important factors correlated with trends and current stock status were external to the management systems, and included stock size, age at maturity, ex‐vessel price and economic dependency of countries on tuna fisheries. To improve the overall status of large pelagic fish stocks in the global high seas, more intensive data collection, research and management are needed in certain areas, especially in the Indian Ocean, and for certain stocks, especially non‐target species.  相似文献   

19.
1997年12月到1998年11月，利用尖尾罟网和掺缯网船在珠江口水域进行了周年月度渔业资源调查，共捕获268种游泳生物，其中鱼类167种，足类7种，虾蛄类10种，虾类31种，蟹类53种。采用主成份分析、回顾分析和聚类分析等统计方法分析游泳生物的组成、生物学及季节变化等特征。结果表明，珠江口水域的游泳生物主要是沿岸性或河口性的小型种类，基本由当年生个体组成，它们与高温低盐水环境特征相适应，构成珠江口游泳生物组成的主体。游泳生物组成的季节变化明显，但对于鱼类的底栖类群和中上层类群则存在着时间上的差异。  相似文献   

20.
ABSTRACT:   It is important to clarify trophic dynamics in marine ecosystems for management of the fishing ground. Organic carbon sources and trophic position of pelagic fishes in the coastal waters of the south-eastern Izu Peninsula, Japan, were examined on the basis of carbon and nitrogen stable isotope distributions. The δ13C of the fishes was mostly distributed from −19 to −16‰ for nektonic fishes (13 species of adults and immatures) and planktonic fishes (10 species of larvae and juveniles), close to the δ13C values of particulate organic matter and planktonic decapods. These δ13C signatures for the inhabitants of the water column were in contrast with the high δ13C values (mainly −16 to −13‰) for demersal fishes of Scorpaeniformes and benthic polychaetes collected in the surf zone. These results indicate that nektonic and planktonic fishes depend on phytoplankton for carbon supply. The δ15N signatures suggest that the trophic position ranged 3.1–4.5 for the nektonic fishes and 2.9–3.7 for the planktonic fishes, premised on trophic level 3 for larval Japanese anchovy Engraulis japonicus . Thus, planktivorous fishes should be mainly assigned to trophic levels 3 and 4 in this area.  相似文献   

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