135 research outputs found
Introduced Pathogens and Native Freshwater Biodiversity: A Case Study of Sphaerothecum destruens
No full textA recent threat to European fish diversity was attributed to the association between an intracellular parasite, Sphaerothecum destruens, and a healthy freshwater fish carrier, the invasive Pseudorasbora parva originating from China. The pathogen was found to be responsible for the decline and local extinction of the European endangered cyprinid Leucaspius delineatus and high mortalities in stocks of Chinook and Atlantic salmon in the USA. Here, we show that the emerging S. destruens is also a threat to a wider range of freshwater fish than originally suspected such as bream, common carp, and roach. This is a true generalist as an analysis of susceptible hosts shows that S. destruens is not limited to a phylogenetically narrow host spectrum. This disease agent is a threat to fish biodiversity as it can amplify within multiple hosts and cause high mortalities
Initial Impact of the Gabíkovo Hydroelectric Scheme on the Species Richness and Composition of 0+ Fish Assemblages in the Slovak Flood Plain, River Danube
No full textRelatively little information exists on the effects of hydroelectric schemes on 0+ fish composition in large European rivers because few or no pre-impact data exist. We compared 0+ fish species richness and composition, relative density, fish size as well as available and used habitat using data from 12 floodplain sites sampled just prior to (1992) and four years after (1996) the start of operations of the Gabíkovo hydropower station on the River Danube (Slovakia). We also used modelling techniques to assess the change in species richness and habitat use and to predict 1996 occurrences from the 1992 data set. The floodplain was greatly modified by the hydroscheme. Only 12 of 27 sites sampled in August 1992 were extant in August 1996. Therefore, all four channel types identified (flowing, abandoned, weir, wing-dam) were more lentic in 1996 than in 1992, with increased width, smaller-sized sediment (silt, clay) and greater amounts of macrophytes. After the operations of the hydroscheme, the overall relative density of fishes (individuals per surface area) of all ages decreased, with the exception of 0+ fishes, despite a slight reduction in 0+ fish density in all channel types except weirs. Species number increased from 25 to 28, although in all channel types there was a change in the composition of the 0+ fish assemblages, with rheophiles generally replaced by limnophiles and migrants from the lower Danube. The two most important microhabitat variables were the proportion of macrophytes and gravel, the latter being the factor distinguishing 0+ fish microhabitat use in 1992 (preferences) and 1996 (indifference or avoidance). Species richness and 0+ fish density in 1996 could be predicted from the 1992 data using simple log-linear models (density, richness, sample number). Species-specific occurrence in 1996 could not be predicted using environmental/fish data from 1992 with multiple regression or generalized additive models (GAM). However, the overall GAM from 1992 could predict overall fish occurrence in 1996
Understanding the threats posed by non-native species: public vs. conservation managers.
No full textPublic perception is a key factor influencing current conservation policy. Therefore, it is important to determine the influence of the public, end-users and scientists on the prioritisation of conservation issues and the direct implications for policy makers. Here, we assessed public attitudes and the perception of conservation managers to five non-native species in the UK, with these supplemented by those of an ecosystem user, freshwater anglers. We found that threat perception was not influenced by the volume of scientific research or by the actual threats posed by the specific non-native species. Media interest also reflected public perception and vice versa. Anglers were most concerned with perceived threats to their recreational activities but their concerns did not correspond to the greatest demonstrated ecological threat. The perception of conservation managers was an amalgamation of public and angler opinions but was mismatched to quantified ecological risks of the species. As this suggests that invasive species management in the UK is vulnerable to a knowledge gap, researchers must consider the intrinsic characteristics of their study species to determine whether raising public perception will be effective. The case study of the topmouth gudgeon Pseudorasbora parva reveals that media pressure and political debate has greater capacity to ignite policy changes and impact studies on non-native species than scientific evidence alone
Current ecological understanding of fungal-like pathogens of fish: what lies beneath?
No full textDespite increasingly sophisticated microbiological techniques, and long after the first discovery of microbes, basic knowledge is still lacking to fully appreciate the ecological importance of microbial parasites in fish. This is likely due to the nature of their habitats as many species of fish suffer from living beneath turbid water away from easy recording. However, fishes represent key ecosystem services for millions of people around the world and the absence of a functional ecological understanding of viruses, prokaryotes, and small eukaryotes in the maintenance of fish populations and of their diversity represents an inherent barrier to aquatic conservation and food security. Among recent emerging infectious diseases responsible for severe population declines in plant and animal taxa, fungal and fungal-like microbes have emerged as significant contributors. Here, we review the current knowledge gaps of fungal and fungal-like parasites and pathogens in fish and put them into an ecological perspective with direct implications for the monitoring of fungal fish pathogens in the wild, their phylogeography as well as their associated ecological impact on fish populations. With increasing fish movement around the world for farming, releases into the wild for sport fishing and human-driven habitat changes, it is expected, along with improved environmental monitoring of fungal and fungal-like infections, that the full extent of the impact of these pathogens on wild fish populations will soon emerge as a major threat to freshwater biodiversity
Social network properties within a fish assemblage invaded by non-native sunbleak Leucaspius delineatus
No full textNetwork theory is commonly applied to identify local and global properties of interconnected nodes, such as brain cells or websites on the internet (Newman, 2003a). Despite its potential to quantify disease spread (Newman, 2002) as well as the social interactions between individuals within and between groups, network theory has rarely been used to examine the social organisation of animal groups ([Lusseau, 2003], [Croft et al., 2004], [Croft et al., 2006] and [Godfrey et al., 2009]). The application of social network analysis to interactions in animal populations has great potential. For example, it may assist in the progress of research and analysis of co-operative behaviour, the transmission of information via social interactions and the mechanisms of disease and/or parasite transmission (Watts and Strogatz, 1998 D.J. Watts and S.H. Strogatz, Collective dynamics of small world networks, Nature 393 (1998), pp. 440–442. Full Text via CrossRef | View Record in Scopus | Cited By in Scopus (6835)[Watts and Strogatz, 1998], [Latora and Marchiori, 2001] and [Abramson and Kuperman, 2001]). It is also possible to predict a network's resistance to predation and the subsequent loss of individuals (Lusseau, 2003), as well as to examine social segregation (Newman, 2003b). Indeed, social network analysis may assist in the better understanding of the social integration of invasive species and the characteristics of a successful invasion. It may be particularly useful in uncovering new important social traits used in ecosystem colonisation.
Many organisms form groups with benefits that have traditionally been explained by performance in predator–prey interactions and locomotion efficiency ([Magurran, 1990] and [Pitcher and Parrish, 1993]). But more recently, studies have suggested that abilities that enable social group-living may rather reveal direct information about individual performance that may have evolved as amplifiers of individual quality (Barber and Folstad, 2000). The drivers of social organisation include responses to predation pressure and inter-specific competition that can determine the success or failure of entire populations. For group-living organisms, such as shoaling fishes, social structure may be particularly important following the introduction of a new species, which may compete within the shoal for positions normally occupied by native fishes (Witte et al., 1992).
In most organisms, early life is a crucial phase for growth and subsequent survival to recruitment. During their early life, fishes undergo a series of ontogenetic changes in morphology, behaviour, physiology, ecological interactions and thus in their performance-related capabilities ([Balon, 1975] and [Balon, 1990]). The aim of the present study was to apply the network approach to assess social network properties within a fish assemblage that has been invaded by non-native sunbleak Leucaspius delineatus (Heckel, 1843) during early life. A small cyprinid native to most of continental Europe, the sunbleak was introduced into the Stoneham Lakes (Southern England) in the mid-1980s via the aquaculture trade (Farr-Cox et al., 1996) and has since become well established in various canal systems, rivers and lakes of the South and South West of England. A few populations have also been discovered in the North West of the country ([Gozlan et al., 2003] and [Hickley and Chare, 2004]) and more recently in the Southeastern English counties of East Sussex and Kent (G. Zięba and G.H. Copp, unpubl. data, 2009).
Sunbleak naturally aggregate in shoals throughout their life ([Rüppell and Gößwein, 1972], [Siegmund and Wolff, 1973a], [Siegmund and Wolff, 1973b], [Andoerfer, 1980], [Arnold and Längert, 1995] and [Pinder and Gozlan, 2004]), which suggests strong social connections between individual fish. As a means of identifying one or more mechanisms that may facilitate the invasion process of sunbleak, our objectives were to: (1) determine whether sunbleak integrate into the native species social network during their early life, and (2) assess the properties of the social ties between the invading sunbleak and native species during their early development. This is the first study that utilises network analysis to examine the social properties of a native fish assemblage containing a non-native fish species
Densidad de los armadillos (dasypus spp.) mediante el uso de cámaras la densidad de armadillos trampa y densidad de madrigueras en la Guayana Francesa
No full textArmadillo density estimates are important for species knowledge, but they are unknown in the Guiana Shield. We aimed at estimating Dasypus density through burrow density and camera trapping. We surveyed and trapped burrows in three protected sites in French Guiana, on strip transects covering 4.8 ha in each site, and estimated Dasypus density taking into account burrow measures and occupancy. Population densities ranged between 7.6 and 48.6 animals/km2 for Dasypus sp. nov. and 10.3 and 34.7 animals/km2 for D. kappleri. Dasypus density estimates through burrow survey and exclusive burrow entrance camera trapping is relatively low-cost, non-invasive and reliable.La densidad de armadillos es desconocida en el Escudo guayanés. Nuestro objetivo fue estimar la densidad de Dasypus a través de la densidad de madrigueras y mediante cámaras trampa. Identificamos y monitoreamos madrigueras en tres sitios en Guayana Francesa, en transectos cubriendo 4.8 ha por sitio. Estimamos la densidad poblacional de Dasypus teniendo en cuenta las medidas y la ocupación de las madrigueras. Las densidades poblacionales variaron entre 7.6 y 48.6 animales/km2 para Dasypus sp. nov. y 10.3 y 34.7 animales/km2 para D. kappleri. Estimar la densidad de Dasypus mediante las madrigueras y cámaras trampas es relativamente de bajo costo, no invasivo y confiable.Fil: Schaub, Roxane. Université de Guyane; Guayana Francesa. Centre Hospitalier Andree Rosemon; Guayana FrancesaFil: Leclerc, Léo. Centre Hospitalier Andree Rosemon; Guayana FrancesaFil: Guilloton, Edith. Centre Hospitalier Andree Rosemon; Guayana FrancesaFil: Szpigel, Jean-François. Réserve Naturelle Régionale Trésor; Guayana FrancesaFil: Couppié, Pierre. Université de Guyane; Guayana Francesa. Centre Hospitalier Andree Rosemon; Guayana FrancesaFil: Gozlan, Rodolphe E.. Université de Montpellier; FranciaFil: Ackermann, Luc. Réserve Naturelle Nationale de La Trinite; Guayana FrancesaFil: Superina, Mariella. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Medicina y Biología Experimental de Cuyo; ArgentinaFil: Thoisy, Benoit de. Institut Pasteur de la Guyane; Guayana Francesa. Kwata Ngo; Guayana Frances
Le rôle du changement climatique et de la déforestation dans l'émergence des maladies infectieuses
No full textInternational audienc
Le rôle du changement climatique et de la déforestation dans l'émergence des maladies infectieuses
No full textInternational audienc
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