6 research outputs found
Biodiversity monitoring of offshore structures in the Danish North Sea using environmental DNA (eDNA)
No full textEnvironmental DNA (eDNA) is a cheap and accurate method for biodiversity monitoring based on sampling and analyzing the DNA that all living organisms shed to the environment. To investigate biodiversity at sites of interest in the sea, such as at and around platforms and natural reefs, it is necessary to understand the spatial and temporal variation of eDNA observations to accurately interpret and evaluate the results. Here, we used a metabarcoding approach to analyze top and bottom water samples collected along a transect from the DanF platform to Esbjerg harbor, which included both natural reefs and control stations. Temporal samples collected across 3 days using an onsite robotic sampler (ESP) were also analyzed to investigate short-term temporal variations. While general data analysis was performed using Illumina sequencing, a subset of data was further re-sequenced on the transportable ‘MinION’ sequencer from Oxford Nanopore to assess the suitability of this new technology for future on- site data generation
Sea lice (<i>Lepeophtherius salmonis</i>) detection and quantification around aquaculture installations using environmental DNA
No full textThe naturally occurring ectoparasite salmon lice (Lepeophtherirus salmonis) poses a great challenge for the salmon farming industry, as well as for wild salmonids in the Northern hemisphere. To better control the infestation pressure and protect the production, there is a need to provide fish farmers with sensitive and efficient tools for rapid early detection and monitoring of the parasitic load. This can be achieved by targeting L. salmonis DNA in environmental samples. Here, we developed and tested a new L. salmonis specific DNA-based assay (qPCR assay) for detection and quantification from seawater samples using an analytical pipeline compatible with the Environmental Sample Processor (ESP) for autonomous water sample analysis of gene targets. Specificity of the L. salmonis qPCR assay was demonstrated through in-silico DNA analyses covering sequences of different L. salmonis isolates. Seawater was spiked with known numbers of nauplii and copepodite free-swimming (planktonic) stages of L. salmonis to investigate the relationship with the number of marker gene copies (MGC). Finally, field samples collected at different times of the year in the vicinity of a salmon production farm in Western Norway were analyzed for L. salmonis detection and quantification. The assay specificity was high and a high correlation between MGC and planktonic stages of L. salmonis was established in the laboratory conditions. In the field, L. salmonis DNA was consequently detected, but with MGC number below that expected for one copepodite or nauplii. We concluded that only L. salmonis tissue or eDNA residues were detected. This novel study opens for a fully automatized L. salmonis DNA quantification using ESP robotic to monitor the parasitic load, but challenges remain to exactly transfer information about eDNA quantities to decisions by the farmers and possible interventions
DNA based monitoring of sharks, skates and rays, and risk-based evaluation of bycatch in Danish fisheries
No full textSharks and rays are important components of marine biodiversity. This together with their life history with slow growth, late maturation and large asymptotic size makes them candidates for biodiversity indicators under descriptor 1 of the Marine Strategy Framework Directive. However, the assessment of their abundance and occurrence in the fishery is complicated by expected poor species identification. Further, landings of skates and rays (Rajidae) have historically often been reported as “wings” in commercial landings, rendering the catches by species unknown. For sharks, many species are easier to identify visually, but some, such as Mustelus asterias (starry smoothhound) and Mustelus mustelus (common smoothhound) can be difficult to distinguish from each other. These difficulties mean that the Danish monitoring undertaken prior to the previous MSFD assessments could not support the evaluation of the impacts of fishing on individual species.This report aims to ensure that the species composition of sharks and rays in the Danish commercial fishery can be assessed going forward, and that Denmark can fulfil the obligations of the common fisheries policy and the marine strategy directive. This was approached through developing and testing DNA-based monitoring of by-catch of sharks and rays in the Danish commercial fishery and providing a knowledge base for risk-based management in relation to unintentional by-catch of sharks and rays. The project is divided into two components, mapping of the species composition of rays and selected sharks in the Danish fishery and an analysis of the catches of skates and rays in the Danish fishery. The mapping of species composition is confirmed by tissue samples from rays and selected shark species during observer trips on commercial fishing vessels and samples at landing sites. A risk-based analysis combines results from the genetic analysis with the observer and landing data to rank fisheries and gear in relation to the extent of unintentional by-catch.Species identification performed by trained scientific staff (i.e., scientific surveys and observer trips) was more accurate than that performed by fishers. Misidentification rates were highest for the spotted ray species (Raja brachyura, Raja montagui and Leucoraja naevus), and thornback ray (Raja clavata). The unspecified categories of ray and skate wings consisted of a relatively large number of species and these categories should therefore be avoided. Misidentification levels were similar for samples collected in Sweden and Holland, regardless of the country of origin of the fishers. Hence, there is a general challenge of misidentification across European countries. Shark species caught as part of scientific surveys were in general identified correctly. However, all specimens originally identified as M. mustelus were genetically identified to be M. asterias. This finding is in line with earlier published research and supports that M. mustelus is a more southern species, while M. asterias is likely the only one of the two species occurring in Danish waters.Danish landings of rays and skates have more than doubled over the last ten years. Historically, rays and skates were landed mainly as a mix of species (Raja spp), or as common skate (Dipturus batis), but since 2021 almost all landings have been recorded by species. The genetic samples confirmed the species identification of most landed species and their distribution. R. clavata was generally identified correctly, while it seems more difficult to distinguish R. brachyura from R. montagui. Rajella lintea (sailray) was the dominant species landed in recent years. The species first occurred in the landing statistics in 2018 even though a previous investigation showed considerable landings twenty years ago. A small amount of Dipturus oxyrinchus (longnose skate) has been recorded in the landings statistics since 2021. The genetic samples confirm the species ID of D. oxyrinchus even though some specimens were landed as R. lintea. Species ID of Rajidae from surveys and discard sampling was, in general, correct with a few misclassifications of R. brachyura and R. montagui. The quality of species recording from landings in Denmark has improved considerably since 2021, but misclassification still occurs. Ideally, all catches of rays and skates should be identified to species level, and landings of especially the protected species (complex) Dipturus batis/intermedia need to be confirmed by tissue samples. The development in species identification means that the relative importance of species cannot be evaluated historically, but in 2022, 60% of the landings were R. lintea, while R. clavata was the second most important species with 19% of landings.The use of genetic identification meant that the wider distribution of the species in landings than from surveys could be used to indicate actual species distribution rather than be disregarded as expected misidentifications. This allowed documentation of the distribution of R. lintea and D. oxyrinchus, which were previously poorly known in the North Sea. It was also documented that protected species such as D. batis are at present rare but not completely absent from Danish catches. While the original intention of the study was to identify high abundance areas for the species and use these both to aid in species ID and in risk assessments, the distribution of the rarer species examined turned out to be much wider than indicated by scientific surveys in both sampled depths and at deeper waters. Though high abundance areas could not be identified, deeper waters generally had higher occurrences of the larger Dipturus and Rajella species. These deeper waters have in later years exhibited an increase in landing value, indicating that they may experience increased fishing pressure and hence increased risk in later years. Among the remaining species, all but Amblyraja radiata (starry ray) and Raja undulata (undulate ray) have increased in the past 20 years, presumably as a result of the general decline in demersal fishing since 2000. A. radiata is widespread in the central and northern North Sea and northern part of the inner Danish waters and it was not possible to identify areas with greater risk of bycatch for this species.The analyses provide the basis for assessing the mortality as a result of accidental bycatch for sharks and rays per species for assessments from 2021 onwards under the Marine Strategy Framework Directive. The knowledge about the fisheries, gear type and areas with a significant risk of accidental bycatch can on a longer time scale potentially be used during the preparation of action programs under the auspices of Denmark's marine strategy to ensure a reduction in catch where necessary and the achievement of good environmental status
Development of species-specific eDNA-based test systems for monitoring of non-indigenous species in Danish marine waters
No full textProject manager Jesper H. Andersen.The MONIS 3 project reports the development of 22 species-specific eDNA-based test systems for monitoring and mapping of the occurrence of non-indigenous species in Danish marine waters. The development has been undertaken by the MONIS partnership and the species have been selected based on the outcome of the MONIS 2 project. It should be noted that the test systems are considered operational cf. the MONIS definition (see Chapter 1). It should also be noted that the 22 test systems have been applied in the MONIS 4 project, where monitoring of 16 Danish harbours have been carried out to map occurrence of nonindigenous marine species using both conventional methods and molecular methods (eDNA). Development of additional test systems is being planned and expected to be carried out in 2019 pending funding. The MONIS partnership encourages interested institutions, especially in neighbouring countries (Germany, Norway, Poland and Sweden) to make use of the test systems.publishedVersio
A baseline study of the occurrence of non-indigenous species in Danish harbours
No full textProject Manager/Main Author Jesper H. AndersenWe report the first ever nation-wide study of the occurrence of non-indigenous species in Danish harbours. The sampling was car-ried out using both conventional and biomolecular methods (eDNA). In total, 16 harbours were covered – Esbjerg and Aarhus, the two largest harbours in Denmark, with intensive sampling and 14 harbours with a reduced programme. 26 non-indigenous species were recorded using conventional sampling and 13 species were recorded using eDNA-based methods. Excluding overlapping rec-ords, we have recorded a total of 34 non-indigenous species in the 16 harbours studied. Based on the results, we conclude the following: 1) more non-indigenous species are found in the western parts of Denmark (North Sea region) then in the eastern parts (Baltic Sea), and 2) a few species previously unseen in Danish marine waters were recorded, i.e. the two bristle worms Eteone het-eropoda (fam. Phyllodocidae) and Streblospio benedicti (fam. Spionidae). Further, we provide a proof-of-concept regarding the overarching objectives of the MONIS 1-3 projects and the eDNA-based test systems developed. The results constitute a baseline for future studies in Danish ports and other hotspot areas.publishedVersio
Danmarkshistorier: National Imagination and Novel in Late Twentieth Century Denmark
No full textDanmarkshistorier: National Imagination and Novel in Late Twentieth-Century Denmark C.C.Thomson, University of Edinburgh, 2003 This thesis centres on the contemporary Danish novel as a conduit for national imagining. Chapter one begins with a discussion of Benedict Anderson's account of the ability of novels to facilitate an imagining of the national community in time and space. Critical responses to Anderson's hypothesis are then situated in the context of late twentieth-century debates on the 'postnational' and 'posthistorical'. Recent Danish historiography attempts to negotiate national histories that recognise not only the contingency of established historical accounts but also their narrative nature, employing textual strategies such as resisting linear chronology and causality, historicising space and place, and fusing (individual) memory and (collective) history. Such texts, hybrid narratives between histories and stories of Denmark (or Danmarkshistorier), implicate a Danish national model reader who is alive both to the homogenising contemporary discourse of danskhed (Danishness) and to its self-ironising subversion. Contemporary Danish literature, it is argued, shares this concern with what Bhabha identifies as the symbiosis of nationalist historical pedagogy and narrative performance. Chapters two to four focus on three novels which map out the Danish experience of the twentieth century and sit at the intersection of the genres which have marked Danish literature in the 1990s: the punktroman and the encyclopedic novel. Thus all three texts explore temporalities alternative to Anderson's interpretation of Benjamin's 'homogenous empty time', and they construct shifting textual communities of national subjects predicated on the liminalities of cultural identities, on the boundaries between historical fact and fiction, and on the tension between privileged and marginal forms of narrative. In chapter two, Peter Høeg's Forestilling om det tyvende århundrede (1988) is discussed as an anthropological novel which pastiches postcolonial and magical realist writing to critique the longing for order inherent in national historiography and fiction. Peer Hultberg's Byen og verden (1992) is read, in chapter three, as a spatial history of a community in which local, national and global places and times of belonging can coalesce. Chapter four examines the configurations of individual and collective memory, trauma and event, the epochal and the everyday in Vibeke Grønfeldt's I dag (1998). The thesis concludes with a discussion of the novels in question as sites of textual memory, in which 'postnational' spacetimes, including the term of the millennium and the glocal, can be negotiated
