Use of environmental DNA to detect the myxozoan endoparasite Tetracapsuloides bryosalmonae in large Norwegian lakes

Understanding the underlying causes behind human–elephant conflict (HEC)-driven mortality of humans and Environmental DNA (eDNA) is an increasingly used noninvasive and cost-effective method for species detections in surveillance studies. The myxozoan endoparasite Tetracapsuloides bryosalmonae is the causative agent of proliferative kidney disease (PKD) in salmonid fish. PKD is a potentially lethal disease of freshwater salmonids when water temperatures exceed 12–14°C for prolonged periods. Periodically, high mortality and decline in farmed and wild salmonid populations in Europe and North America have been reported in the last decades. The aim of this study was to use eDNA as a method to detect Tetracapsuloides bryosalmonae from large, deep, dimictic Norwegian lakes. Such habitats are expected to become increasingly important for cold-water salmonids with global warming. Samples were collected from five lakes in southeastern Norway, and parasite DNA was detected by qPCR. eDNA from T. bryosalmonae was detected in four of the five lakes surveyed. These findings corresponded with the detection of T. bryosalmonae DNA in salmonid kidneys in four of the lakes in a previous survey. The detection of parasites from eDNA varied between years and stations within the same lake, revealing a changing and apparently stochastic spatial distribution of parasite DNA from year to year. Nonetheless, by sampling multiple sites throughout the lakes, we were able to detect T. bryosalmonae at the lake level in both survey years. Strategies for eDNA sampling in deep, dimictic lakes are discussed. deep lakes, dimictic, eDNA, sampling strategy, Tetracapsuloides bryosalmonaepublishedVersio

Genetic population structure of the monogenean parasite Gyrodactylus thymalli and its host European grayling (Thymallus thymallus) in a large Norwegian lake

Understanding how populations are structured in space and time is a central question in evolutionary biology. Parasites and their hosts are assumed to evolve together, however, detailed understanding of mechanisms leading to genetic structuring of parasites and their hosts are lacking. As a parasite depends on its host, studying the genetic structure of both parasite and host can reveal important insights into these mechanisms. Here, genetic structure of the monogenean parasite Gyrodactylus thymalli and its host the European grayling (Thymallus thymallus) was investigated in 10 tributaries draining into the large Lake Mjøsa in Norway. The population genetic structure of spawning grayling was studied using microsatellite genotyping, while G. thymalli was studied by sequencing a mitochondrial DNA gene (dehydrogenase subunit 5). Two main genetic clusters were revealed in grayling, one cluster comprising grayling from the largest spawning population, while the remaining tributaries formed the second cluster. For both taxa, some genetic differentiation was observed among tributaries, but there was no clear isolation-by-distance signature. The structuring was stronger for the host than for the parasite. These results imply that moderate to high levels of gene flow occur among the sub-populations of both taxa. The high parasite exchange among tributaries could result from a lack of strong homing behavior in grayling as well as interactions among individual fish outside of the spawning season, leading to frequent mixing of both host and parasite.publishedVersio

Regnbueørret (Onchorhynchus mykiss); produksjon og interaksjoner med stedegne arter

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Environmental risk assessment of genetically modified sterile VIRGIN® Atlantic salmon for use in research trials in aquaculture sea-cages

One of the substantial environmental challenges posed by the aquaculture industry is the escape of farmed Atlantic salmon (Salmo salar), which can mate with wild Atlantic salmon and alter the genetic composition of the wild populations. One potential solution to mitigate this issue is the cultivation of sterile salmon in aquaculture. Atlantic salmon can be made sterile by pressure or temperature treatment of newly fertilized eggs to produce triploids, which are functionally sterile due to their unpaired chromosomes. However, these triploids often perform poorly on commercial fish farms and the production of triploid salmon in Norway is put on hold due to welfare issues of the fish. In this application, the Institute of Marine Research (IMR), Bergen, seeks to rear genetically modified sterile Atlantic salmon (VIRGIN® salmon) in a marine aquaculture environment from the post-smolt stage until harvest. The research trials are to take place in small, open sea cages (net pens) at the IMR Matre Aquaculture Research Station from autumn 2023 until February 2025. The Norwegian Environment Agency has asked VKM to assess the environmental risks associated with this field trial according to the Gene Technology Act and using risk assessment guidance from the European Food Safety Authority, EFSA.Environmental risk assessment of genetically modified sterile VIRGIN® Atlantic salmon for use in research trials in aquaculture sea-cagespublishedVersionpublishedVersio

Environmental risk assessment of genetically modified sterile VIRGIN® Atlantic salmon for use in research trials in aquaculture sea-cages

One of the substantial environmental challenges posed by the aquaculture industry is the escape of farmed Atlantic salmon (Salmo salar), which can mate with wild Atlantic salmon and alter the genetic composition of the wild populations. One potential solution to mitigate this issue is the cultivation of sterile salmon in aquaculture. Atlantic salmon can be made sterile by pressure or temperature treatment of newly fertilized eggs to produce triploids, which are functionally sterile due to their unpaired chromosomes. However, these triploids often perform poorly on commercial fish farms and the production of triploid salmon in Norway is put on hold due to welfare issues of the fish. In this application, the Institute of Marine Research (IMR), Bergen, seeks to rear genetically modified sterile Atlantic salmon (VIRGIN® salmon) in a marine aquaculture environment from the post-smolt stage until harvest. The research trials are to take place in small, open sea cages (net pens) at the IMR Matre Aquaculture Research Station from autumn 2023 until February 2025. The Norwegian Environment Agency has asked VKM to assess the environmental risks associated with this field trial according to the Gene Technology Act and using risk assessment guidance from the European Food Safety Authority, EFSA.Environmental risk assessment of genetically modified sterile VIRGIN® Atlantic salmon for use in research trials in aquaculture sea-cagespublishedVersionpublishedVersio

Environmental risk assessment of genetically modified sterile VIRGIN® Atlantic salmon for use in research trials in aquaculture sea-cages

One of the substantial environmental challenges posed by the aquaculture industry is the escape of farmed Atlantic salmon (Salmo salar), which can mate with wild Atlantic salmon and alter the genetic composition of the wild populations. One potential solution to mitigate this issue is the cultivation of sterile salmon in aquaculture. Atlantic salmon can be made sterile by pressure or temperature treatment of newly fertilized eggs to produce triploids, which are functionally sterile due to their unpaired chromosomes. However, these triploids often perform poorly on commercial fish farms and the production of triploid salmon in Norway is put on hold due to welfare issues of the fish. In this application, the Institute of Marine Research (IMR), Bergen, seeks to rear genetically modified sterile Atlantic salmon (VIRGIN® salmon) in a marine aquaculture environment from the post-smolt stage until harvest. The research trials are to take place in small, open sea cages (net pens) at the IMR Matre Aquaculture Research Station from autumn 2023 until February 2025. The Norwegian Environment Agency has asked VKM to assess the environmental risks associated with this field trial according to the Gene Technology Act and using risk assessment guidance from the European Food Safety Authority, EFSA.Environmental risk assessment of genetically modified sterile VIRGIN® Atlantic salmon for use in research trials in aquaculture sea-cagespublishedVersio

Assessment of the risk of negative impact on biodiversity from import and release of eggs or live fish from landlocked Atlantic salmon from Klarälven in Sweden to Trysilelva in Norway. Scientific Opinion of the Panel on Alien Organisms and Trade in Endangered Species of the Norwegian Scientific Committee for Food and Environment

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Forsøksbehandling med monokloramin mot Gyrodactylus salaris i elva Glitra

Prosjektleder Anders Gjørwad HagenLaboratorieforsøk ved Veterinærinstituttet har vist at hypokloritt tilsatt i svært lave konsentrasjoner (18-50 μg/l) til vannet kan fjerne G. salaris fra laksunger i løpet av 2-6 dager uten å ha vesentlige negative effekter på fisken. Senere forsøk har i tillegg vist at tilsetting av 30-50 μg monokloramin/l også fjernet G. salaris fra laksunger i løpet av 2-6 dager i vann fra Drammenselva. Resultatene fra disse forsøkene legger grunnlag for å utrede monokloramin som et potensielt kjemikalium til bekjempelse av G. salaris i norske laksevassdrag. I denne rapporten presenteres et feltforsøk der målet har vært å utrede om monokloramin kan brukes i fullskala behandling mot G. salaris. Tilnærmingen er basert på forskningsbehov som har fremkommet etter laboratorieforsøkene nevnt over og i et fagseminar arrangert i mars 2016 der aktuelle problemstillinger ble diskutert. Problemstillingene omfatter doseringsteknologi, eventuelle akutte effekter på biota og det avgjørende spørsmålet om hvorvidt effekten av klor mot parasitten reduseres når kjemikaliet tilsettes til en elv og transporteres med vannmassene i et naturlig vassdrag. Spørsmålene er besvart gjennom et klordoseringsforsøk i elva Glitra, øverst i Lierelva i Buskerud. Forsøkslokaliteten ble benyttet til å gjennomføre flere undersøkelser for å belyse de aktuelle problemstillingene. Forsøkene viste at monokloramin har god behandlende effekt mot G. salaris når kjemikaliet tilsettes og ransporteres med vannmassene i et naturlig vassdrag, og at effekten fra ett doseringspunkt vedvarte i minimum 80 minutter. I tillegg ble det ikke observert vesentlige negative effekter på laks og bunndyrsamfunnet i vassdraget under kloraminbehandlingen. Doseringsteknologien og metodikken for produksjon av monokloramin i felt fungerte tilfredsstillende og sikret en stabil konsentrasjon av kjemikaliet i elvevannet gjennom forsøket. Det kreves svært lave konsentrasjoner av klor for å fjerne G. salaris, noe som gjør klor godt egnet til behandling i vassdrag med høy vannføring. Monokloramin fremstår således som en god kandidat for videre utvikling av en behandlingsmetode mot G. salaris.MiljødirektoratetpublishedVersio