Temperature,discharge and development shape the larval diets of threatened green sturgeon in a highly managed section of the Sacramento River

Feeding at early fish life stages is a key determinant of survival to recruitment. To understand the environmental and developmental determinants of early life stage feeding in ESA‐threatened green sturgeon (Acipenser medirostris), we performed a diet study in a highly managed section of California's Sacramento River, where temperature and discharge are controlled by dam releases. Utilising field collections from 2012 to 2016, we assessed the impacts of temperature, discharge and morphological development on the composition and number of prey items in larval green sturgeon diets. Results show that there are more empty stomachs at colder temperatures. Higher discharge conditions decreased prey taxon richness and counts, especially the abundance of cyclopoid copepods in diets. Fish smaller than 30 mm had teeth on the oral jaws and showed a strong reliance on zooplankton prey. The developmental loss of teeth in fish greater than 30 mm was associated with decreased zooplankton consumption and increased richness of benthic macroinvertebrates in diets. Our results show that river management through dam releases has the potential to impact the earliest life stage of green sturgeon by reducing the prevalence of favoured zooplankton prey in diets.     

Physical forcing on fish abundance in the southern California Current System

The California Current System (CCS) is an eastern boundary current system with strong biological productivity largely due to seasonal wind‐driven upwelling and transport of the California Current (CC). Two independent, yet complementary time series, CalCOFI ichthyoplankton surveys and sampling of southern California power plant cooling‐water intakes, have indicated that an assemblage of predominantly cool‐water affinity fishes spanning nearshore to oceanic environments in the southern CCS has declined dramatically from the 1970s to the 2000s. We examined potential oceanographic drivers behind this decline both within and north of the CalCOFI survey area in order to capture upstream processes as well. Empirical orthogonal function (EOF) analyses using output from a data‐assimilative regional ocean model revealed significant relationships between the fish time series and spatial patterns of upwelling, upper ocean heat content and eddy kinetic energy in the CCS. Correlation and linear regression analyses indicated that the declining trend in fish abundance was correlated with a suite of factors: reduced offshore and increased inshore upwelling; a long term warming trend combined with more recent interannual variability in ocean temperature; weaker eddy kinetic energy north of Point Conception (35°N), potentially indicating reduced transport of the California Current (CC); increased influence of the California Undercurrent (CUC); and a decline in zooplankton displacement volume across the southern CCS. Understanding how changes in oceanography affect fish populations will offer insights into managing fisheries in a changing climate.     

鱼类免疫增强剂的研究现状与进展

现代水产养殖业追求优质高产,但在大规模高密度的养殖生产中,往往会导致鱼体的抗应激能力下降,病害增多,成活率下降,造成重大经济损失。近年来,国内外学者对鱼类免疫机制及其病害防治方法已进行了大量研究,其中免疫增强剂因能增强机体抗疾病感染的能力,其免疫增强作用所需时间较短,且没有记忆成分,被认为是一种提高鱼体免疫活性及疾病抵抗力的有效方法,具有重要的应用价值。     

云南境内南盘江水系鱼类种质资源现状及保护对策

为了解南盘江鱼类资源现状,保护和恢复南盘江鱼类多样性,2008年6月至2010年3月,对云南省境内南盘江鱼类现状进行实地考察,结合中国科学院昆明动物研究所馆藏标本和历年相关记录,分析南盘江鱼类种质资源现状。结果表明,云南境内南盘江及其附属湖泊共有鱼类8目、20科、71属、160种;其中,土著种137种,特有种93种,外来种23种。鲤科鱼类最多,有94种,占鱼类总数的58.8%,其次为条鳅科32种,占总数的20.0%,爬鳅科7种,占总数的4.4%。南盘江鱼类种类众多,但由于人为影响,河流污染比较严重,目前已有24种鱼类被列为濒危种类。分析南盘江近两年的鱼类种质资源现状,发现土著种类的数量大幅下降,这与南盘江河流环境恶化和水电开发力度增大密切相关。     

有害赤潮藻对鱼类影响的研究进展

赤潮灾害的多发性和普遍性极大危害了海产养殖业和渔业资源,严重破坏了正常的海洋生态系统,直接威胁着人类的生存环境和健康水平[1,2]。在赤潮灾害中,鱼类的大量死亡带来的危害和损失占相当大的比重[3],在我国,1998年春季南海的一次特大赤潮造成了大规模的养殖鱼死亡,直接经济损失超过3亿元。在这类赤潮灾害中不仅渔业资源和鱼类养殖业遭受了极大的破坏,海洋生物的种群结构乃至整个海洋生态系统也受到了影响,毒素在鱼类体内的累积威胁着食用者的生命安全[4]。因此,科学家们针对有害赤潮藻及其毒素对鱼类的影响开展了一些调查和研究工作…     

鱼类和水生动物基因组作图研究的现状及前景

鱼类和水生动物基因组作图（ｇｅｎｏｍｅ ｍａｐｐｉｎｇ）研究落后于陆生动物。水生经济动物的遗传图谱只是最近二、三年才有报道［１－３］。虽然起步晚，但以鱼类为代表的水生动物的基因组研究已经有了可观进展。本文试图从如下几个方面作一综述：１．分子遗传标记及其在基因组作图研究中的应用，２．水生动物基因组研究的现状，３．水生动物基因组作图的前景。１ 分子遗传标记及其在基因组作图研究中的应用１．１ 分子遗传标记 遗传标记一般可分为形态学标记、细胞学标记、生化标记和ＤＮＡ分子标记。其中只有ＤＮＡ分子标记是核苷酸水…     

云南境内南盘江水系鱼类种质资源现状及保护对策

为了解南盘江鱼类资源现状,保护和恢复南盘江鱼类多样性,2008年6月至2010年3月,对云南省境内南盘江鱼类现状进行实地考察,结合中国科学院昆明动物研究所馆藏标本和历年相关记录,分析南盘江鱼类种质资源现状。结果表明,云南境内南盘江及其附属湖泊共有鱼类8目、20科、71属、160种;其中,土著种137种,特有种93种,外来种23种。鲤科鱼类最多,有94种,占鱼类总数的58.8%,其次为条鳅科32种,占总数的20.0%,爬鳅科7种,占总数的4.4%。南盘江鱼类种类众多,但由于人为影响,河流污染比较严重,目前已有24种鱼类被列为濒危种类。分析南盘江近两年的鱼类种质资源现状,发现土著种类的数量大幅下降,这与南盘江河流环境恶化和水电开发力度增大密切相关。     

Current status of parasitic ciliates Chilodonella spp. (Phyllopharyngea: Chilodonellidae) in freshwater fish aquaculture

Freshwater fish farming contributes to more than two‐thirds of global aquaculture production. Parasitic ciliates are one of the largest causes of production loss in freshwater farmed fishes, with species from the genus Chilodonella being particularly problematic. While Chilodonella spp. include ‘free‐living’ fauna, some species are involved in mortality events of fish, particularly in high‐density aquaculture. Indeed, chilodonellosis causes major productivity losses in over 16 species of farmed freshwater fishes in more than 14 countries. Traditionally, Chilodonella species are identified based on morphological features; however, the genus comprises yet uncharacterized cryptic species, which indicates the necessity for molecular diagnostic methods. This review synthesizes current knowledge on the biology, ecology and geographic distribution of harmful Chilodonella spp. and examines pathological signs, diagnostic methods and treatments. Recent advances in molecular diagnostics and the ability to culture Chilodonella spp. in vitro will enable the development of preventative management practices and sustained freshwater fish aquaculture production.     

Effects of ocean climate on the length and condition of forage fish in the Gulf of Alaska

Climatic drivers of the size and body condition of forage fish in the North Pacific are poorly known. We hypothesized that length and condition of forage fish in the Gulf of Alaska (GoA) vary in relation to ocean temperature on multiple scales. To test this hypothesis, we analyzed morphometric data for capelin (Mallotus catervarius) and Pacific sand lance (PSL; Ammodytes personatus) sampled by a seabird (Cerorhinca monocerata) in two regions of the GoA, 1993–2016. Based on previous studies, we predicted that capelin length and body condition (Fulton's K) would be negatively related to the Pacific Decadal Oscillation (PDO) and sea surface temperature (SST), whereas PSL length and condition would be positively related. Interannual variation in length and body condition was evaluated relative to seasonal values of ocean climate using regression. Forage fish length and condition varied interannually, between sampling regions, and were dependent on the size/age class of the fish sampled. As predicted, length and body condition of capelin (mostly age 1+) were negatively related to the PDO and SST. Relationships with ocean climate for PSL varied by size/age class: positive for putative age‐0 fish and negative for putative age‐1+ fish. We conclude that our hypothesis was supported for capelin and partially supported for PSL. This study demonstrates that ocean climate determines key morphometric characteristics of forage fish that may relate to interannual variation in the energetic value of prey, and provides an example of how seabirds can be used to obtain specimens for evaluations of potential prey quality.     

Distribution and community structure of ichthyoplankton from the northern and central California Current in May 2004–06

The distributions, concentrations, and community structure of pelagic larval fishes collected from the central and northern California Current in the northeast Pacific Ocean during May 2004, 2005, and 2006 were analyzed to investigate inter-annual, latitudinal, cross-shelf, and depth-stratified variability. The inter-annual climate-induced variability during the sampling period provided a unique opportunity to observe how larval fish communities adjust to rapidly changing environmental conditions. The 170 depth-stratified samples collected from three cruises yielded 14 819 fish larvae from 56 taxa representing 23 families. Dominant larval taxa were Engraulis mordax , Citharichthys spp., Sebastes spp., and Stenobrachius leucopsarus . Larval concentrations decreased significantly in 2006 from 2004 and 2005 levels following the anomalous oceanic conditions observed in 2005 and decreased water temperature in 2006. Larvae were generally found in higher concentrations at northern (>43°N) versus southern (<43°N) stations, with larval E. mordax and Citharichthys spp. found almost exclusively in the north during all sampled years. Inter-annual variability related to dynamic upwelling intensity was observed in cross-shelf larval distributions, although concentrations of S. leucopsarus larvae consistently increased in the offshore direction, while larval Sebastes spp. were generally found in highest concentrations at intermediate stations along the shelf. Multivariate analyses revealed that latitude, station depth, and sea-surface temperature were the most important factors explaining variability in larval concentrations. The present study shows that the ichthyoplankton community of the central and northern California Current changed dramatically in response to the variable environmental conditions of 2004–06.     

Establishing survey and monitoring protocols for the assessment of conservation status of fish populations in river Special Areas of Conservation in the UK

• 1. Under the EC Habitats Directive (92/43/EEC), several rivers in the UK have been designated Special Areas of Conservation (SACs) because they support important populations of fish species. Several factors need to be considered when establishing survey protocols to assess the conservation status of fish species in these rivers.
• 2. It is important to understand the biology and habitat requirements of fish species and to design appropriate monitoring surveys that adequately assess the status of the fish populations. This information can, in turn, provide the basis for establishing sustainable conservation targets for specific stocks, a process known as condition assessment.
• 3. Favourable condition of fish species in SAC rivers is assessed using three criteria. The first relates to density of fish in various life stages against pre‐set targets, assuming that an appropriate number of sites is surveyed to account for natural spatial and temporal variations in fish populations. The second is evaluation of the demographic structure to demonstrate continued recruitment success. Third, by mapping the distribution of the target species in individual rivers and where favourable condition is only achieved where there has been no reduction in the distribution range river between surveys.
• 4. The framework described was developed from limited survey data. As more monitoring and assessment data become available, the threshold criteria for favourable condition for each species should be improved, and uncertainty in the procedures reduced.

Copyright © 2008 John Wiley & Sons, Ltd.     

黑水河鱼类优先保护次序的定量分析

在金沙江下游干流大规模水电开发的背景下,干流开发与支流保护是生态环境保护的有效措施;黑水河是白鹤滩库区鱼类的优先保护支流,确定其鱼类优先保护次序和保护物种是进行鱼类栖息地修复和保护工作的首要任务和前提基础。在野外调查和查阅相关文献资料的基础上,运用濒危系数、遗传价值系数和物种价值系数对黑水河35种鱼类进行优先保护次序的定量分析,并结合黑水河栖息地实际情况,确定保护目标鱼类。结果显示,达到黑水河一级保护的鱼类只有1种,为长江上游特有鱼类长薄鳅（Leptobotia elongata）;达到二级保护的种类有12种,其中昆明裂腹鱼（Schizothorax grahami）、黄石爬鮡（Euchiloglanis kishinouyei）、短须裂腹鱼（Schizothorax wangchiachii）和长鳍吻鮈（Rhinogobio ventralis）为长江上游特有鱼类;处于三级保护的鱼类有17种,其中钝吻棒花鱼（Abbottina obtusirostris）和张氏?（Hemiculter tchangi）是长江上游特有鱼类;四级保护鱼类有5种,其中短体副鳅（Paracobitis potanini）为长江上游特有鱼类,评价结果基本反映了黑水河鱼类的实际情况。结合白鹤滩水库蓄水后黑水河栖息地生境改变的情况,最终确定昆明裂腹鱼、黄石爬鮡、短须裂腹鱼为黑水河栖息地修复和保护的目标鱼类,长薄鳅和长鳍吻鮈为备选保护鱼类。     

Cumulative impacts of fisheries in the California Current

Ecosystem‐based fisheries management calls for the consideration of the indirect and cumulative effects of fishing, in addition to estimating direct fishing mortality. Here, we quantify such effects of fishing fleets, and their interactions, using a spatially explicit Atlantis simulation model of the food web and fisheries in the California Current. Simulations testing the effects of single fleets suggested that bottom trawl, fixed gear, and hake (Merluccius productus) trawl primarily have direct impacts on their target and bycatch species. Few indirect effects from these three fleets extended through predator–prey links to other parts of the food web. In contrast, effects of the purse seine fleet extended beyond the three groups it harvested, strongly altering the abundance of predators, planktonic prey, and benthos. In terms of nine ecosystem attributes, our experiments involving single fleets identified six fleets that caused the bulk of negative impacts. Specific fleets impacted different aspects of the ecosystem, for instance with groundfish gears causing reductions in piscivore abundance, and hake trawl and purse seine increasing krill through reducing abundance of planktivores. In terms of interactions among fleets' effects, the vast majority of effects were simply additive – the combined effect of two fleets was simply the sum of the individual fleets' effects. The analyses offer one way to sharpen the focus of ecosystem‐based fisheries management in the California Current, emphasizing impacts and interactions of particular stressors.     

Predicting the vertical profiles of anchovy (Engraulis mordax) and sardine (Sardinops sagax) eggs in the California Current System

Several published models exist for simulating vertical profiles of pelagic fish eggs, but no one has rigorously assessed their capacity to explain observed variability. In this study, we applied a steady‐state model, with four different formulations for vertical diffusivity, to northern anchovy (Engraulis mordax) and Pacific sardine (Sardinops sagax) eggs in the California Current region. Vertical mixing profiles, based on wind speed and hydrography, were combined with estimated terminal ascent velocities of the eggs based on measurements of egg buoyancy and size, to simulate the vertical profiles of the eggs. We evaluated model performance with two data sets: (1) vertically stratified tows for both species and (2) paired samples for sardine eggs from 3‐m depth and in vertically integrated tows. We used two criteria: whether the model predicted individual observed vertical profiles (1) as well as the observed mean and (2) better than the observed mean. Model predictions made with the formulation producing the most gradual profile of vertical diffusivity provided the best match to observations from both data sets and for both species. Addition of a random error term to the terminal ascent velocity further improved prediction for anchovy eggs, but not sardine. For the paired data, model prediction of integrated abundance from abundance at 3‐m depth had significantly lower mean square error than prediction based on a linear regression of 3 m on integrated abundance. Our results support the feasibility of using data from the Continuous Underway Fish Egg Sampler quantitatively as well as qualitatively in stock assessments.     

Oceanographic drivers of sablefish recruitment in the California Current

Oceanographic processes and ecological interactions can strongly influence recruitment success in marine fishes. Here, we develop an environmental index of sablefish recruitment with the goal of elucidating recruitment‐environment relationships and informing stock assessment. We start with a conceptual life‐history model for sablefish Anoplopoma fimbria on the US west coast to generate stage‐ and spatio‐temporally‐specific hypotheses regarding the oceanographic and biological variables likely influencing sablefish recruitment. Our model includes seven stages from pre‐spawn female condition through benthic recruitment (age‐0 fish) for the northern portion of the west coast U.S. sablefish stock (40°N–50°N). We then fit linear models and use model comparison to select predictors. We use residuals from the stock‐recruitment relationship in the 2015 sablefish assessment as the dependent variable (thus removing the effect of spawning stock biomass). Predictor variables were drawn primarily from ROMS model outputs for the California Current Ecosystem. We also include indices of prey and predator abundance and freshwater input. Five variables explained 57% of the variation in recruitment not accounted for by the stock‐recruitment relationship in the sablefish assessment. Recruitment deviations were positively correlated with (i) colder conditions during the spawner preconditioning period, (ii) warmer water temperatures during the egg stage, (iii) stronger cross‐shelf transport to near‐shore nursery habitats during the egg stage, (iv) stronger long‐shore transport to the north during the yolk‐sac stage, and (v) cold surface water temperatures during the larval stage. This result suggests that multiple mechanisms likely affect sablefish recruitment at different points in their life history.     

Global Advances in Conservation and Management of Marine Ornamental Resources

Currently, as many as 30 million coral reef fish belonging to 1,000 species are collected annually to supply private and public aquaria around the world. In addition, over 100 species of invertebrate are used, involving hundreds of thousands or even millions of individuals. The majority of these specimens come from coral reefs and associated habitats, with about 45 countries supplying the ornamental market. Considering the many pressures currently faced by reefs it is vital that ornamental fisheries are investigated and monitored, and management strategies formulated to ensure they are sustainable. This requires research, monitoring, training, use of non-damaging collecting methods and adoption of conservation strategies for controlling catch, such as reserves, quotas and closed seasons. There are also a number of possibilities for enhancing the fishery, such as mariculture and construction of artificial reefs. This paper concentrates on some of the conservation measures that can be taken and discusses their application and effectiveness. Such measures include limiting collecting effort, establishment of species-based or overall quotas, restrictions on rare and/or endemic species, temporary closures and establishment of fisherybreak reserves.     

Occurrence of demersal fishes in relation to near‐bottom oxygen levels within the California Current large marine ecosystem

Various ocean‐climate models driven by increased greenhouse gases and higher temperatures predict a decline in oceanic dissolved oxygen (DO) as a result of greater stratification, reduced ventilation below the thermocline, and decreased solubility at higher temperatures. Since spreading of low oxygen waters is underway and predicted to increase, understanding impacts on higher trophic levels is essential. Within the California Current System, shoaling of the oxygen minimum zone (OMZ) is expected to produce complex changes. Onshore movement of the OMZ could lead to habitat compression for species with higher oxygen requirements while allowing expansion of species tolerant of low bottom DO. As part of annual groundfish surveys, we sampled catch across a range of conditions from the upper to the lower limit of the OMZ and shoreward across the continental shelf of the US west coast. DO ranged from 0.02 to 4.25 mL L^?1 with 642 stations (of 1020 sampled) experiencing hypoxic conditions in 2008–2010. Catch and species richness exhibited significant and positive relationships with near‐bottom oxygen concentration. The probability of occurrence was estimated for four species (spotted ratfish, petrale sole, greenstriped rockfish and Dover sole) using a binomial Generalized Additive Model. The models for each species included terms for position, day of the year, salinity, near‐bottom temperature and the interaction term between depth and near‐bottom DO. Spotted ratfish and petrale sole were sensitive to changes in near‐bottom oxygen, while greenstriped rockfish and Dover sole show no changes in probability of occurrence in relation to changes in oxygen concentration.     

Conservation implications of establishment success of the Critically Endangered Twee River redfin ‘Pseudobarbus’ erubescens (Skelton, ) in an artificial impoundment in South Africa

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Freshwater mussels in Mediterranean-climate regions: Species richness,conservation status,threats, and Conservation Actions Needed

1. The five global Mediterranean-climate regions are experiencing alarming rates of freshwater biodiversity loss. Although freshwater mussels are recognized as important functional components in aquatic ecosystems, and are among the most threatened faunal groups globally, there has been no synthesis of the plight of this group within these regions.
2. Data from the International Union for Conservation of Nature (IUCN) Red List were reviewed to compare the conservation status, threats, and conservation actions needed for freshwater mussel species occurring in Mediterranean-climate regions (med-mussels) with those of other freshwater mussel species globally. The first comprehensive catalogue of med-mussel species was compiled using existing taxonomic literature.
3. There are 41 med-mussel species, 30 of which occur in the Mediterranean basin. Many regions have just a single species, and regions where multiple species occur generally only have between one and four species per river basin. Med-mussel species are almost twice as likely to be ‘Imperilled’, are affected by 2.4 times more threats, and require 3.5 times more conservation actions than non-med mussels. In many cases, the exact threats have not been identified.
4. In combination with low species richness, this level of imperilment means that Mediterranean-climate regions are at risk of losing the benefits that mussels provide to broader ecosystem functioning. The conservation of med-mussels can be improved by increasing our knowledge of species distributions, including the identification of cryptic species and significant management units, through population genetic work. In addition, recognizing the potential of ‘novel’ habitats and refuge areas could augment the management of this important functional group.