Lethal and non-lethal effects of multiple indigenous predators on the invasive golden apple snail (Pomacea canaliculata)

1. We investigated the individual and combined effects of two predators (the climbing perch, Anabas testudineus, and the wetland crab, Esanthelphusa nimoafi) indigenous to wetlands in Laos, on the behaviour and survival of the invasive South American golden apple snail (Pomacea canaliculata). The snail is considered a pest, consuming large amounts of rice and other aquatic vegetation in the region. 2. Snail avoidance reactions to released predator chemical cues were investigated in aquaria while the effects of predators on a mixed snail population were studied in field enclosures that contained native aquatic plants (Salvinia cucullata, Ludwigia adscendens and Ipomoea aquatica). 3. In the aquaria experiment, neonate (2-3 mm) and medium-sized snails (8-10 mm) responded to fish chemical cues by going to the surface, whereas adult snails (35-40 mm) went to the bottom. In contrast, no size class of snails reacted to chemical cues released by crabs. 4. In the field experiment, fish reduced the abundance of neonate snails, and crabs reduced the abundance of all size classes. The effect of the combined predators could not be predicted from the mortality rate observed in single predator treatments. The survival of neonate and medium-sized snails was greater and of adults less than expected. The presence of predators did not affect egg production. Snails consumed significant amounts of plants despite the presence of predators. 5. Our findings suggest that some indigenous Asian predators have lethal and sublethal effects on P. canaliculata that depend on snail size and predator type. When in the presence of several predators the response of snails to one predator may either increase or decrease the vulnerability of snails to the others

Is salinity an obstacle for biological invasions?

Invasions of freshwater habitats by marine and brackish species have become more frequent in recent years with many of those species originating from the Ponto-Caspian region. Populations of Ponto-Caspian species have successfully established in the North and Baltic Seas and their adjoining rivers, as well as in the Great Lakes-St. Lawrence River region. To determine if Ponto-Caspian taxa more readily acclimatize to and colonize diverse salinity habitats than taxa from other regions, we conducted laboratory experiments on 22 populations of eight gammarid species native to the Ponto-Caspian, Northern European and Great Lakes-St. Lawrence River regions. In addition, we conducted a literature search to survey salinity ranges of these species worldwide. Finally, to explore evolutionary relationships among examined species and their populations, we sequenced the mitochondrial cytochrome c oxidase subunit I gene (COI) from individuals used for our experiments. Our study revealed that all tested populations tolerate wide ranges of salinity, however, different patterns arose among species from different regions. Ponto-Caspian taxa showed lower mortality in fresh water, while Northern European taxa showed lower mortality in fully marine conditions. Genetic analyses showed evolutionary divergence among species from different regions. Due to the geological history of the two regions, as well as high tolerance of Ponto-Caspian species to fresh water, whereas Northern European species are more tolerant of fully marine conditions, we suggest that species originating from the Ponto-Caspian and Northern European regions may be adapted to freshwater and marine environments, respectively. Consequently, the perception that Ponto-Caspian species are more successful colonizers might be biased by the fact that areas with highest introduction frequency of NIS (i.e., shipping ports) are environmentally variable habitats which often include freshwater conditions that cannot be tolerated by euryhaline taxa of marine origin

Remibar: Fria vandringsvägar och effekten på konnektiviteten : Utvärdering av åtgärder inom Remibar

Syftet med projektet Remibar (Remediation of Migratory Barriers in Streams) har varit att åtgärda 304 vandringshinder i fem projektområden i lika många avrinningsområden i Norrbottens och Västerbottens län. De fem avrinningsområdena är Natura 2000-områden och skyddade enligt Habitatdirektivet. I Norrbotten ingick följande projektområden: Ängesån (del av Kalixälvens avrinningsområde), Råneälven (större delen av Råneälvens avrinningsområde) och Varjisån (del av Piteälvens avrinningsområde). I Västerbotten ingick Sävarån och Lögdeälvens avrinningsområden. Remibar startade 2011 och avslutades 2016. Det finansierades av EUkommissionen genom Life+ programmet som är EUs miljöfond.EC LIFE+ programme LIFE10 NAT/SE/045Remiba

Remibar: The Impact of Migration Barrier Removal on Connectivity : Evaluation of Remibar

The objective of the Remibar (Remediation of Migratory Barriers in Streams) project has been to remove 304 migration barriers in five project areas in as many river systems in the counties of Norrbotten and Västerbotten in northern Sweden. The five river systems are protected under the Natura 2000 Habitats Directive. In Norrbotten, the project areas were: Ängesån (part of the Kalix River system), Råneälven (most of the Råne River system), and Varjisån (part of the Pite River system). In Västerbotten, the two project areas Sävarån and Lögdeälven each encompassed one river system, i.e., the Sävar River and Lögde River systems. The Remibar project started in 2011 and was completed in 2016. It was financed by the EU Commission through the Life+ programme, which is an EU environmental fund.Remiba

Remibar: After LIFE-plan

The objective of the Remibar LIFE project (Remediation of Migratory Barriers in Streams) was to increase the connectivity in five river systems in the very north of Sweden, in the counties of Norrbotten and VästerbottenRemiba

The effects of interspecific interactions and environmental heterogeneity on the dominance of an invasive crustacean

The success and impact of an introduced exotic species may be highly variable across sites, owing to the influence of local abiotic and biotic factors. The upper St. Lawrence River is a physically heterogeneous ecosystem that has been invaded by several Ponto-Caspian species, including an amphipod crustacean (Echinogammarus ischnus), a benthic fish (the round goby Neogobius melanostomus), and two dreissenid mussels (Dreissena polymorpha and D. bugensis). Echinogammarus is replacing the native amphipod Gammarus fasciatus on rocky substrates in the lower Great Lakes, but in the St. Lawrence River the native species remains dominant at many sites ten years after invasion.While Gammarus is a strictly freshwater species, Echinogammarus is adapted to ion-rich waters. A series of field and laboratory experiments tested the hypothesis that their relative dominance is dependent on local physicochemical conditions. These experiments revealed that both species are mutual predators whose differing physiological tolerances influence the magnitude and direction of predation, such that a dominant predator can reverse to an inferior predator along a conductivity gradient. Additional experiments compared the survival, growth and fecundity of both species across a range of conductivities. At low conductivity, growth of both species is reduced and Echinogammarus also suffers higher mortality. A further study examined predation by adults on the juveniles of opposing species at different conductivities. Contrary to expectations, Gammarus had a higher type II functional response than Echinogammarus in both levels of conductivity. This finding indicates the importance of considering different life stages when assessing the overall effects of intraguild predation. A final series of experiments revealed that amphipod species replacement is not influenced by their respective ability to compete for refugia. Competition for microhabitat on dreissenid mussel-covered substrates does not increase the native amphipod's vulnerability to goby predation. Echinogammarus is more vulnerable to native predators, but the round goby does not have a differential impact on the native amphipod. Thus, the outcome of antagonistic interactions involving these amphipods is mediated more by abiotic factors than by shared evolutionary history with co-occurring exotic species.Le succès et l'impact d'une espèce introduite exotique peuvent être hautement variables à travers des sites à cause des influences des facteurs abiotiques et biotiques locaux. Le Haut-Saint-Laurent est physiquement un écosystème fluviale hétérogène qui a été envahi par plusieurs espèces Ponto-Caspiennes, incluant un crustacé amphipode (Echinogammarus ischnus), un poisson benthique (la gobie à tache noire Neogobius melanostomus), et deux moules dreissenidae (Dreissena polymorpha et D. bugensis). Echinogammarus est en train de remplacer l'amphipode indigène Gammarus fasciatus sur les substrats rocheux des Grands Lacs inférieurs, mais demeure dominant dans le fleuve St-Laurent dans plusieurs sites dix ans après l'invasion. frAlors que Gammarus est une espèce strictement dulcicole, Echinogammarus est adaptée aux eaux riches en ions. Une série d'expériences en laboratoire et sur le terrain ont testé l'hypothèse que leur dominance relative est dépendante des conditions physico-chimiques. Ces expériences ont démontré que les deux espèces sont des prédateurs mutuels dont la différence de leurs tolérances physiologiques influence la magnitude et la direction de prédation, de manière à ce qu'un prédateur dominant puisse changer vers un prédateur inférieur au long d'un gradient de conductivité. Des expériences supplémentaires ont comparé la survie, la croissance et la fécondité des deux espèces à travers une gamme de conductivités. En basse conductivité, la croissance des deux espèces est réduite, et Echinogammarus subit également une mortalité élevée. Une étude supplémentaire a examiné la prédation des adultes sur les juvéniles de l'espèce opposée à des conductivités différentes. Contrairement aux attentes, Gammarus avait une réponse de type II fonctionnel supérieur à celui de Echinogammarus dans les deux niveaux de conductivité. Cette découverte indique l'importance de prendre en compte les différentes étapes de vie lors de l'évaluation des effets totaux de la prédation au sein de la guilde. Une série finale d'expériences a démontré que le remplacement des espèces d'amphipode n'est pas influencé par leur capacité respective de compétitionner pour les refuges; la compétition pour les microhabitats sur les substrats couverts par les moules dreissenidae n'augmente pas la vulnérabilité de l'amphipode indigène envers la prédation du gobie. Echinogammarus est plus vulnérable aux prédateurs indigènes, mais le gobie à tache noire n'a pas d'impact différentiel sur l'amphipode indigène. Donc, les résultats des interactions antagonistes impliquant ces amphipodes sont déterminés plus par les facteurs abiotiques que par l'hi

Uden for tema: Privatisering for enhver pris? Drivkræfter og barrierer i privatiseringen af DONG 2001-2018

Siden 1980 har den danske stat helt eller delvist frasolgt selskaber for et samlet provenu på over 80 mia. kr. (2017-priser). Privatiseringen af offentlige selskaber har blandt andet været drevet frem af ønsket om markedseffektivitet, politisk ideologi og EU-direktiver møntet på at fremme konkurrencen i det indre marked. På den baggrund undersøges det, hvorfor det tog over ti år at gennemføre en delvis privatisering af det statslige energi- og forsyningsselskab DONG (nu Ørsted). John Kingdons multiple streams-tilgang anvendes i et omfattende dokumentstudie til at indfange de kræfter, der i perioden 2001 til 2018 satte privatiseringen af DONG på den politiske dagsorden og bidrog til at forsinke og forandre beslutningen om at privatisere. Den drypvise privatisering af DONG blev dels formet af eksogene faktorer som international konkurrence, finanskrise og investeringsbanken Goldman Sachs, dels af den indsats, som skiftende regeringer, centraladministration og ledelsen i DONG lagde i at realisere privatiseringen