长江河口潮间带盐沼植被分布区及邻近光滩鱼类组成特征

研究鱼类群落在不同生境中的差异或者变化,是评价与预测生境丧失、环境退化等对湿地生物多样性与生态系统功能影响的重要基础。2006年4—11月,在长江河口崇明东滩盐沼植被分布区(简称草滩)和邻近的光滩区域分别设置采样站位,每月大潮期采用定制插网对鱼类群落进行了取样调查。分析研究了长江河口潮间带盐沼植被分布区和邻近光滩区域的鱼类组成及其月际变化,并对影响鱼类分布的主要因子进行了探讨。调查期间共采集鱼类标本1638尾,分属9目14科22种;其中,淡水鱼类2种,定居性河口鱼类12种,海洋鱼类5种,洄游鱼类3种。植被分布区和光滩区域鱼类组成及优势种特征存在明显差异。调查期间,植被分布区记录鱼类13种,主要优势种为斑尾刺虾虎鱼(Acanthogobius ommaturus)、鲻(Mugil cephalus)和棱鮻(Liza carinatus)(IRI>20),其他种类基本不具有优势度特征(IRI<0.05);光滩区域记录鱼类20种,主要优势种鲻(IRI>20),其他包括斑尾刺虾虎鱼、狼牙鳗虾虎鱼(Taenioides rubicundus)、棱鮻和棘头梅童鱼(Collichthys lucidus)也具有一定的优势特征(20>IRI>10);两个区域共有种为11种,部分种类只出现在光滩或植被分布区,但主要优势种均为定居性河口鱼类。与世界其他河口盐沼湿地鱼类研究结果不同的是,光滩区域记录的鱼类物种数、个体数、生物量和整体物种多样性水平均高于植被分布区;光滩和植被分布区鱼类相应的量比关系存在明显的月际变化,但两种生境鱼类组成间的关联性和差异性均不显著。通过比较两种生境共有的优势种体长发现,长江河口盐沼植被分布区鱼类优势种的平均体长大于光滩区域,而且植被分布区部分优势种体长的上、下限范围也大于光滩区域。长江河口盐沼植被分布区,除了育幼场外,还是许多鱼类成鱼的重要栖息地。影响河口潮间带盐沼湿地鱼类组成与分布的主要因素包括鱼类自身的生物学与生活史特征、饵料生物的组成与分布、植被出现与表形特征等生物因素和水温、盐度、淡水径流、潮汐特性等非生物因素,其对长江河口潮间带盐沼湿地中鱼类群落的组成与分布的综合作用机理有待进一步研究。     

闽南-台湾浅滩渔场二长棘鲷群体景观多样性

根据1998年7月到2000年6月闽南-台湾浅滩渔场开展二长棘鲷资源的专项调查资料,以各个渔区CPUE(Catch Per Unit Effort)及其到渔场重心距离为参数,构建基于渔场重心动能的景观要素,运用景观多样性,并结合因子分析,分析了二长棘鲷群体景观多样性的空间格局及其与海洋环境因子之间的关系,探究了种群空间分布格局与生态过程之间的相互作用关系,旨在揭示闽南-台湾浅滩渔场二长棘鲷的生态境况及空间变异特征,为从生态水平上合理综合利用二长棘鲷渔业资源提供新的依据。结果表明:(1)不同月份鱼群的分布特征差别明显,8月鱼群分布范围最广,11月鱼群分布最为均匀,2月和12月鱼群分布最集中,而9月鱼群占据渔场空间能力最强;(2)不同群体之间具有不同分布特征,生殖群体分布范围最小,且最集中,其占据渔场空间能力最弱,幼鱼群体分布范围小,且相对均匀,其占据渔场空间能力强,索饵群体分布范围最广,且较均匀,鱼群分散索饵,其占据渔场空间能力最强,而9—11月群体平均分布范围较广,且最均匀,其占据渔场空间能力较弱;(3)鱼群综合景观指数是具空间结构的CPUE指数,从生态水平上反映了鱼群CPUE,其排名依次为8月、6月、7月、9月、10月、11月、5月、1月、4月、3月、2月、12月;(4)多样性指数、均匀度指数和优势度指数指示的生态学意义分别为鱼群的分布范围、均匀程度和鱼群空间竞争能力,其中多样性指数和均匀度指数呈正相关;(5)水温是影响鱼群景观均匀度的主要因子,索饵是增加鱼群景观多样性和优势度的主要因子,而生殖因子则降低鱼群景观多样性和优势度,水温、索饵和生殖是二长棘鲷群体景观格局变化的主要驱动因素。     

Molecular Characterization and Functional Commonality of Nucleophosmin/Nucleoplasmin in Two Cyprinid Fish

Nucleophosmin/nucleoplasmin has been studied mostly in mammals and amphibians. To clarify the characteristics and function of nucleophosmin/nucleoplasmin in teleost fish, we cloned a full-length cDNA sequence from two cyprinid fish, Carassius auratus gibelio and Carassius auratus. Molecular characterization and multiple sequence alignments suggested that they are the homologs of nucleophosmin. RT-PCR and Western blot detected a specific expression in gonads, and immunofluorescence localization revealed their distribution in oogenic and spermatogenic cells. Furthermore, a sperm decondensation function was demonstrated by immunodepletion and in vitro sperm decondensation experiments. The data suggest that the cloned nucleophosmin should share expressional and functional characterization with nucleoplasmin and therefore provide novel evidence for a functional commonality of nucleophosmin and nucleoplasmin in fish.     

The ethology of Labroides dimidiatus (cuv. & val.) (Labridae,Pisces) on Aldabra

A small group of Labroides dimidiatus were studied over a period of 4 months in the shallow reef environment of Aldabra. It was found necessary to redefine the concept of a cleaning station. Different sizes of Labroides occupied different types of area and it was found the smallest individuals do not have fixed ranges, but move about beneath available crevices. Larger individuals occupied more open situations and the adults usually lived in pairs. The areas occupied appeared to reflect the fishes' ability to maintain position against strong water movements and tidal currents. Labroides dimidiatus shows territorial, intraspecific aggression and model presentation experiments indicate that body pigmentation acts as the releaser for this aggression. This aggression serves as a dispersal mechanism for young fish. Interspecific aggression occurred against fish with similar body markings to Labroides or which constituted a threat. The cleaning behaviour was studied and it was found that different species of host fish are cleaned in a highly specific manner, and certain hosts are preferred to others. There is evidence that this may be learned as a result of early experience with the host fish. Measurements are made of the cleaning intensity in the area. Some host fish were shown to be attracted to the cleaning range and may adopt invitation postures in the absence of the cleaner. The results are discussed in relation to the recent literature on Labroides dimidiatus and their importance to reef fish populations.     

Electric Imaging through Evolution,a Modeling Study of Commonalities and Differences

Modeling the electric field and images in electric fish contributes to a better understanding of the pre-receptor conditioning of electric images. Although the boundary element method has been very successful for calculating images and fields, complex electric organ discharges pose a challenge for active electroreception modeling. We have previously developed a direct method for calculating electric images which takes into account the structure and physiology of the electric organ as well as the geometry and resistivity of fish tissues. The present article reports a general application of our simulator for studying electric images in electric fish with heterogeneous, extended electric organs. We studied three species of Gymnotiformes, including both wave-type (Apteronotus albifrons) and pulse-type (Gymnotus obscurus and Gymnotus coropinae) fish, with electric organs of different complexity. The results are compared with the African (Gnathonemus petersii) and American (Gymnotus omarorum) electric fish studied previously. We address the following issues: 1) how to calculate equivalent source distributions based on experimental measurements, 2) how the complexity of the electric organ discharge determines the features of the electric field and 3) how the basal field determines the characteristics of electric images. Our findings allow us to generalize the hypothesis (previously posed for G. omarorum) in which the perioral region and the rest of the body play different sensory roles. While the “electrosensory fovea” appears suitable for exploring objects in detail, the rest of the body is likened to a “peripheral retina” for detecting the presence and movement of surrounding objects. We discuss the commonalities and differences between species. Compared to African species, American electric fish show a weaker field. This feature, derived from the complexity of distributed electric organs, may endow Gymnotiformes with the ability to emit site-specific signals to be detected in the short range by a conspecific and the possibility to evolve predator avoidance strategies.     

The Influence of Infective Dose on the Virulence of a Generalist Pathogen in Rainbow Trout (Oncorhynchus mykiss) and Zebra Fish (Danio rerio)

Pathogen density and genetic diversity fluctuate in the outside-host environment during and between epidemics, affecting disease emergence and the severity and probability of infections. Although the importance of these factors for pathogen virulence and infection probability has been acknowledged, their interactive effects are not well understood. We studied how an infective dose in an environmentally transmitted opportunistic fish pathogen, Flavobacterium columnare, affects its virulence both in rainbow trout, which are frequently infected at fish farms, and in zebra fish, a host that is not naturally infected by F. columnare. We used previously isolated strains of confirmed high and low virulence in a single infection and in a co-infection. Infection success (measured as host morbidity) correlated positively with dose when the hosts were exposed to the high-virulence strain, but no response for the dose increase was found when the hosts were exposed to the low-virulence strain. Interestingly, the co-infection resulted in poorer infection success than the single infection with the high-virulence strain. The rainbow trout were more susceptible to the infection than the zebra fish but, in both species, the effects of the doses and the strains were qualitatively similar. We suggest that as an increase in dose can lead to increased host morbidity, both the interstrain interactions and differences in infectivity in different hosts may influence the severity and consequently the evolution of disease. Our results also confirm that the zebra fish is a good laboratory model to study F. columnare infection.     

Characteristics of Bacterial Isolates from the Gut of Freshwater Fish, Labeo rohita that May be Useful as Potential Probiotic Bacteria

In this study, we aimed to evaluate the in vitro probiotic characteristics of three bacteria, Lactobacillus plantarum VSG3, Pseudomonas aeruginosa VSG2, and Bacillus subtilis VSG1, isolated from the gut of Labeo rohita. The bacterial isolates tolerated low pH and high bile concentrations in the fish well. The bacterial adhesion capacity to fish intestinal mucosa revealed that the three potential probiotic isolates had a significantly higher adhesion capacity compared to the pathogenic strains tested. L. plantarum VSG3 exhibited the best adhesion capacity (19.1?%) to the intestinal mucosa. Among the isolates, L. plantarum VSG3 and P. aeruginosa VSG2 showed strong antibacterial activities against fish pathogens as measured in spent culture liquids. Moreover, all the isolates were susceptible to each tested antibiotic, which ensured their inability to exhibit antibiotic-resistance properties. Considering these promising results, selected strains should be further studied to determine their probiotic effects in vivo in fish.     

Orosensory food testing in fish: Chronology of behavior

The orosensory food testing behavior in fish was studied using the nine-spined stickleback Pungitius pungitius as an example. The patterns of the chronology of manipulations performed by fish in testing food objects were identified. The existence of two stereotypical patterns of feeding behavior was confirmed, and their new characteristics were obtained. The relationship between the responsiveness to food and the predisposition of fish to feeding was revealed.     

Divergence in reproductive ecology of the three-spined stickleback,Gasterosteus aculeatus

An anadromous population (trachurus form) and three freshwater populations (leiurus form) of the three-spined stickleback,Gasterosteus aculeatus, in central Japan were compared with one another in the reproductive traits: body length at maturity, egg size, clutch size, the swell of abdomen and the number of eggs per nest. The anadromous fish which become larger in body size at maturity spawn eggs smaller in size and greater in number than the freshwater fish. The abdomen swell of gravid females expressed by the proportion of abdomen width to body length was greater in the freshwater fish. The anadromous male fish collected a mean of 2,638 eggs with a range of 1,119 to 4,052 eggs from about 6–7 females. In the three freshwater (the Yamayoke, the Tsuya and the Jizo) populations, males must have mated with about 9–22, 7–18 and 4–7 females respectively. It seems that theleiurus form increases its reproductive success by its much more mating opportunities and the parental efforts of nesting males as well as by spawning large eggs. Furthermore, among the freshwater populations, the Jizo one inhabiting the upper stream was clearly larger in body size, in egg size and in clutch size than the Yamayoke and the Tsuya ones which inhabit stable waterbodies with springs. It is possible that the Jizo population adopted the strategy of spawning a few large eggs as an adaptation to its habitat. The causal and functional explanations in reproductive characteristics among the four populations are discussed in regard to differences in the environmental conditions.     

The Response of Blood Biomarkers of the Round Goby <Emphasis Type="Italic">Neogobius melanostomus</Emphasis> (Pallas, 1814) (Perciformes: Gobiidae) to Chronic Coastal Pollution in the Sea of Azov

The long-term variations in blood biomarkers and weight–size characteristics of the round goby, Neogobius melanostomus (Pallas, 1814), have been studied in specimens collected from two sites of the southwestern Sea of Azov. The fish from catches of 2011–2012 showed a decrease in the size and weight parameters and an increase in the antioxidant enzyme activities and the level of oxidized serum proteins compared to the values in the fish caught in 2003. The ecological causes of the observed differences and the possibility of using the studied fish blood biomarkers in programs of monitoring the marine coastal waters are discussed.     

Philomena oncorhynchi: Effect of hormones on maturation in anadromous sockeye, Oncorhynchus nerka

Adult sockeye salmon, Oncorhynchus nerka (Walbaum), treated with salmon pituitary extract in July survived for up to 47 days and developed nuptial colours in both male and female fish during this period, whereas no such characteristics appeared in untreated control fish. Furthermore, results showed that 20 of 50 adult female Philomena oncorhynchi recovered from the 15 treated fish contained fully developed tailed larvae in the uterus as compared with only one of 44 female P. oncorhynchi from 31 untreated control fish. None of 51 worms from 13 stilboestrol treated adult sockeye showed development in utero beyond an elongated embryo, nor did the host fish develop nuptial colours. P. oncorhynchi and its immature sockeye host (approx. 1 year prior to spawning) remained unaffected by any of three separate hormone treatment experiments using injection of salmon pituitary extract, injection of 17-β-estradiol, and stilboestrol mixed in the food.     

Small-scale environmental variation influences whether coral-dwelling fish promote or impede coral growth

Mutualistic symbioses are ubiquitous in nature and facilitate high biodiversity and productivity of ecosystems by enhancing the efficiency of energy and nutrient use within ecological communities. For example, small groups of fish that inhabit coral colonies in reef ecosystems potentially enhance coral growth through defense from coral predators, aeration of coral tissue and nutrient provisioning. This study examines whether the prevalence and consequences of fish-coral interactions vary among sites with different environmental conditions in a coral reef lagoon, using the humbug damselfish Dascyllus aruanus and its preferred coral host Pocillopora damicornis as a study system. Using a field experiment, we tested the site-specific effects of D. aruanus on coral growth, and show that the cost-benefit ratio for corals hosting fish varies with local environmental variation. Results of this study also demonstrate that fish prefer to inhabit coral colonies with particular branch-spacing characteristics, and that the local abundance of D. aruanus influences the proportion of coral colonies within a site that are occupied by fish rather than increasing the number of fish per colony. We also show that corals consistently benefit from hosting D. aruanus via defense from predation by corallivorous butterflyfish, regardless of local environmental conditions. These findings highlight the need to consider the potential for multiple scale- and state-dependent interaction effects when examining the ecology of fish-coral associations. We suggest that fluctuating cost-benefit ratios for species interactions may contribute to the maintenance of different colony phenotypes within coral populations.     

Dynamics and the state of fishery resources in the Rybinsk Reservoir from 1950–2010

Data on dynamics of the main commercial fish populations in the Rybinsk Reservoir over the period of 1950–2010 have been generalized. Fishing intensity is the main factor that determines the state of fish resources. It affects not only the abundance of commercial fish but also determines changes in population characteristics, i.e., changes in age and size structure and increase in the portion of young individuals. The effect of fishing on populations of some species depends on their commercial value. Commercial fishing affects notably such species as bream Abramis brama, zander Sander lucioperca, and pike Esox lucius. Commercial fishing affects, to a lesser extent, populational characteristics of such mass fish species as roach Rutilus rutilus and blue bream Abramis ballerus whose commercial value is lower.     

Formation and development of the Black Sea-Caspian kilka Clupeonella cultriventris (Clupeidae) in the Rybinsk reservoir

We studied the state and development of the population of the Black Sea-Caspian kilka Clupeonella cultriventris in the Rybinsk reservoir from 1994 to 2010. The population dynamics, the rate of growth of the kilka, as well as its food relationships with other fish species of the pelagial community, were analyzed. It was found that the period of exponential increase in the numbers was replaced by the period of interannual fluctuations. With the development of the population, tendencies for a decrease in the rate of growth of the kilka and aggravation of its food relationships with other species are revealed, which is determined by changes in the structure of pelagic aggregations of fish. One of the most significant environmental factors determining dynamics of the numbers and state of the kilka population in the northernmost part of its modern range is water temperature.     

Study on the toxic effects of pharmaceutical drugs – Norfloxacin using Pangasius Sp. fish model and its mitigation using Artemisia pallens

In the present times, international environmental regulations are earnest on the risk caused by the release of toxins into the aquatic biome; predominantly the water bodies. The discharge of active pharmaceutical compounds in the environment is found to have fatal effects on the biota of the oceanic ecosystem. The key objective of the study is to scrutinize the toxicological reprecussion of norfloxacin, an antibiotic used to treat bacterial infections which being prescribed as human medicine was found to have the possibility to pollute the water resource and sediments via input from sewage treatment plants. To explicate this study, Pangasius sp. The fish model was tested with the drug and its effects were studied thereby. This study focuses on the oxidative stress parameters which can be probed by virtue of biological markers, hormonal changes after acclimatizing the fish at suitable LC₅₀ concentration of norfloxacin and the tissue damage assessed using histopathological analysis. The oxidative stress parameters were procured by analysis of biological markers such as Lipid peroxides, Conjugated diene, Protein sulfhydryl, Protein Carbonyl, Inorganic phosphorus, Superoxide dismutase and Catalase. The hormonal changes were studied concerning the changes in cortisol levels, which are influenced by oxidative stress. The mitigation effect and hepato-protective activity of Artemisia pallens were also studied with Norfloxacin treated fish, to imbibe the bioremediation as a strategic upfront for remediation.     

Dioxins and polychlorinated biphenyls in the muscles of fish from rivers of the Chechen Republic

Pollution with toxic polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, and polychlorinated biphenyls has been studied in rivers of the Chechen Republic using several fish species. The pollution of the river network of the republic with dioxin-like xenobiotics is assessed as relatively low. A tendency towards the isomer-specific bioaccumulation of toxicants has been revealed in different freshwater fish species. The Terek River is shown to be more strongly polluted than its tributary, the Sunzha River. Possible sources of pollution and the routes by which it spreads in the ecosystem of the region are analyzed.     

Aphanomyces invadans,the causal agent of Epizootic Ulcerative Syndrome,is a global threat to wild and farmed fish

Aphanomyces invadans is a eukaryotic pathogen and the causative agent of Epizootic Ulcerative Syndrome (EUS) in fish and is responsible for mortalities of up to 100% in aquaculture. A. invadans was first discovered in Japan in 1971, and since then it has been found in Australia, North America, Southern African countries and Asia. Methods for the correct identification of A. invadans are well established now and involve PCR-based detection and microscopy. However, the pathogenesis of A. invadans is poorly understood. Environmental stress (mainly temperature) and the associated immunocompromised fish seem to induce infections of A. invadans and outbreaks of EUS. Understanding the process of infection in more depth is fundamental for the discovery of novel effective treatments to combat the disease. In this review, we discuss morphological characteristics of A. invadans and its pathogenicity as well as various approaches of treatment.     

Parasite-induced change in host behaviour and susceptibility to predation in an eye fluke-fish interaction

Trophically transmitted parasites may increase their transmission efficiency by altering the behaviour of infected hosts to increase their susceptibility to predation by target hosts (the next host in the life cycle). The parasite Diplostomum spathaceum (Trematoda) reduces the vision of its fish intermediate hosts: its metacercariae lodge themselves in the eyes of fish and induce cataract formation, which gives them the opportunity to affect fish behaviour. We examined whether D. spathaceum eye flukes change the preference of fish for the surface layers of the water column or their escape behaviour, which could make the fish more vulnerable to predation by bird hosts. We also studied the influence of parasites on the susceptibility of fish to artificial aerial predators that were able to catch fish from the water surface. Infected and control fish did not differ in their preference for the surface layers but infected fish showed less escape behaviour when a black plate was drawn over the water surface. They were also more easily caught by human ‘predators’ dipping a net into the tank. Thus, infected fish should be easier prey for gulls and terns, implying that the ability of D. spathaceum eye flukes to alter fish behaviour may be a parasite strategy evolved to enhance transmission.     

Genetic diversity and population structure of bocachico Prochilodus magdalenae (Pisces,Prochilodontidae) in the Magdalena River basin and its tributaries,Colombia

Prochilodus magdalenae is an endemic freshwater fish that occurs in the Magdalena, Sinú and Atrato hydrographic basins. It has an important economic role and is a food resource for the artisanal fishing communities. Its socioeconomic importance contrasts with the current status of its fisheries, where stocks are being depleted. Considering its importance and lack of information on its genetic structure, we used seven microsatellite markers to assess the genetic structure of wild populations of P. magdalenae. The genetic diversity was assessed and the population genetic structure was estimated through Fst, analysis of molecular variance and Bayesian analysis. A total of 290 alleles were found in all loci throughout all population. The high polymorphism contrasts with the levels of observed heterozygosity (Ho = 0.276), which are the lowest values recorded for the family. We found three populations of bocachico coexisting throughout the studied system, contradicting the hypothesis that freshwater migratory fish form panmictic populations. These results on the genetic structure of P. magdalenae constitute tools for a better understanding of the behavior and biology of this species, contributing to fish management and conservation programs.     

Specific features of feeding and trophic status of mass species of the family Macrouridae in the northwestern part of the Pacific Ocean

Based on materials of expeditions of TINRO-Center into the northwestern part of the Pacific Ocean, we analyze data on feeding of mass species of Macrouridae. Grenadiers Albatrossia pectoralis and Caryphaenoides longifilis are consumers (in order of importance) of cephalopods, fish, and crustaceans and C. acrolepis and C. cinereus are consumers of crustaceans, cephalopods, and fish. All grenadiers demonstrate age-related variability of food composition from polychaetes and small crustaceans to fish, squids, and large crustaceans. The change in dominant prey of A. pectoralis occurs upon its reaching a length of 50?C60 cm, and that in C. cinereus occurs upon its reaching a length of approximately 50 cm. Changes in the feeding spectra from prey of in- and epifauna to macroplanktonic and nektonic organisms indicate the widening of trophic niches of grenadiers in ontogenesis. The spatial position of each species of grenadiers correlates with its size: the smaller the species, the less it is separated from the ground trophically. According to the type of feeding, C. cinereus is a bentho-planktonic feeder, A. pectoralis is a nekto-benthonic feeder, and C. acrolepis occupies an intermediate position between them. According to the calculated values of trophic levels, the studied species are (in order of decrease) A. pectoralis, C. acrolepis, and C. cinereus; the trophic level of C. longfilis can be preliminarily assessed as close to that of A. pectoralis.