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Genetic Identification of Corkwing Wrasse Cleaner Fish Escaping from Norwegian Aquaculture
Get PDFThe genetic impact of farmed fish escaping aquaculture is a highly debated issue. However,
non-target species, such as cleaner fish that are used in fish farms to remove parasitic sea lice,
are rarely considered. Here, we report that wild corkwing wrasse (Symphodus melops), which
are transported long distances to be used as cleaner fish in salmon farms, escape and
hybridize with local wrasse populations. Recently, increasing numbers of corkwing wrasse
have been reported north of its described distribution range, in Flatanger in Trøndelag in
Norway, an area heavily relying on the import of cleaner fish from Skagerrak. Using a high
number of nuclear genetic markers identified with 2bRAD sequencing, we show that,
although the Flatanger population is largely a result of a northward range expansion, there is
also evidence of considerable gene flow from southern populations in Skagerrak. Of the 40
corkwing wrasses first sampled in Flatanger, we discovered two individuals with clear
southern genotypes, one first-generation hybrid, and 12 potential second-generation hybrids.
Thus, we found clear evidence of gene flow from source populations of translocated cleaner
fish at the edge of an ongoing northwards range expansion.
To better understand the extent of gene flow we then greatly expanded our sampling. Based
on patterns of genetic divergence and homogeneity, we identified a smaller battery of 84
SNPs which is able to detect escapees with a Skagerrak origin as well as first and secondgeneration hybrids with high accuracy and power. We then used these SNPs to investigate the
magnitude and geographic extent of escaping and hybridizing cleaner fish along the
Norwegian coast. We found that escapees and hybrids may constitute up to 20 % of the local
populations at the northern edge of the species distribution. In other parts of the Norwegian
coast where salmon farming is also common, we found surprisingly few escapees and
hybrids. Possible causes for few escapees and hybrids found in these areas are difficult to
evaluate with the current lack of reporting of translocations by aquaculture operators.
Overall, these findings provide critical information both for aquaculture management and
conservation of wild populations of non-target species, and have implications for the
increasing use of cleaner fish as parasite control in fish farms, that is both poorly documented
and regulated. Moving genetic material between isolated populations could drastically alter
the genetic composition and erode population structure, potentially resulting in loss of local
adaptation and hampering natural range expansion. Although the ecological and evolutionary
significance of escapees warrant further investigation, these results should be taken into
consideration in the use of translocated cleaner fish
Crossing barriers: Genetic consequences of translocating wild cleaner fish for aquaculture
No full textSeveral species of fish show a symbiotic cleaning behaviour, where they assist other species by feeding and removing dead skin or ectoparasites. Some of these cleaner fish species are used as a low-cost parasite control in salmon aquaculture, often considered to be more environmentally friendly than other delousing methods. Approximately 54 million cleaner fish are annually used in Norwegian salmon farms. This has resulted in an increasing fishing pressure on wild cleaner fish populations. Together with long-distance translocation, this raises concerns of potential overfishing, anthropogenic introductions, and hybridisation. Recently, increasing numbers of corkwing wrasse (Symphodus melops), have been reported in mid Norway, north of its described distribution range. This is an area heavily relying on the import and translocation of cleaner fish from Skagerrak-Kattegat, more than 1000 km away. Using genetic markers, I show that the new population is both a result of a northward range expansion, as well as a translocation of individuals from southern populations. Further investigation revealed that escapees and hybrids may constitute up to 20 % of the populations at the northern edge of the species distribution. In contrast, escapees and hybrids are rare in other parts along the Norwegian west coast, where salmon farming is also common. The set of genetic markers has a high power to detect escapees and hybrids, and can be applied to monitoring of wild populations. Investigations of corkwing wrasse in Skagerrak-Kattegat revealed reduced genetic diversity, a weak pattern of isolation by distance, and surprisingly little population structure. This suggests a very recent colonisation and high connectivity among sites in this region. Along the Swedish west coast, I evaluate the potential effects of the newly established wrasse fishery on local ecosystems and populations, and provide a baseline to support ecosystem-based management for wrasse fisheries in Sweden. I also investigate the genetic population structure of lumpfish (Cyclopterus lumpus) across the Atlantic, which is the most commonly used cleaner fish species. I show that there is a lot more structure than previously known, and identify eight genetically divergent regions. Hierarchical analysis of these regions demonstrates additional local and cryptic substructure. The genetic markers used her can also be applied for management of wild lumpfish populations and the identification of population origin. Overall, these findings provide important information both for aquaculture management and conservation of wild populations, and have implications for the increasing use and translocation of cleaner fish for parasite control in aquaculture. Moving genetic material between isolated populations could drastically alter the genetic composition and erode population structure, potentially resulting in loss of local adaptation and hampering natural range expansion. Although the ecological and evolutionary significance of escapees warrants further investigation, these results should be taken into consideration in the use of translocated cleaner fish
Genetic Identification of Corkwing Wrasse Cleaner Fish Escaping from Norwegian Aquaculture
No full textThe genetic impact of farmed fish escaping aquaculture is a highly debated issue. However, non-target species, such as cleaner fish that are used in fish farms to remove parasitic sea lice, are rarely considered. Here, we report that wild corkwing wrasse (Symphodus melops), which are transported long distances to be used as cleaner fish in salmon farms, escape and hybridize with local wrasse populations. Recently, increasing numbers of corkwing wrasse have been reported north of its described distribution range, in Flatanger in Trøndelag in Norway, an area heavily relying on the import of cleaner fish from Skagerrak. Using a high number of nuclear genetic markers identified with 2bRAD sequencing, we show that, although the Flatanger population is largely a result of a northward range expansion, there is also evidence of considerable gene flow from southern populations in Skagerrak. Of the 40 corkwing wrasses first sampled in Flatanger, we discovered two individuals with clear southern genotypes, one first-generation hybrid, and 12 potential second-generation hybrids. Thus, we found clear evidence of gene flow from source populations of translocated cleaner fish at the edge of an ongoing northwards range expansion. To better understand the extent of gene flow we then greatly expanded our sampling. Based on patterns of genetic divergence and homogeneity, we identified a smaller battery of 84 SNPs which is able to detect escapees with a Skagerrak origin as well as first and secondgeneration hybrids with high accuracy and power. We then used these SNPs to investigate the magnitude and geographic extent of escaping and hybridizing cleaner fish along the Norwegian coast. We found that escapees and hybrids may constitute up to 20 % of the local populations at the northern edge of the species distribution. In other parts of the Norwegian coast where salmon farming is also common, we found surprisingly few escapees and hybrids. Possible causes for few escapees and hybrids found in these areas are difficult to evaluate with the current lack of reporting of translocations by aquaculture operators. Overall, these findings provide critical information both for aquaculture management and conservation of wild populations of non-target species, and have implications for the increasing use of cleaner fish as parasite control in fish farms, that is both poorly documented and regulated. Moving genetic material between isolated populations could drastically alter the genetic composition and erode population structure, potentially resulting in loss of local adaptation and hampering natural range expansion. Although the ecological and evolutionary significance of escapees warrant further investigation, these results should be taken into consideration in the use of translocated cleaner fish
Crossing barriers: Genetic consequences of translocating wild cleaner fish for aquaculture
Get PDFSeveral species of fish show a symbiotic cleaning behaviour, where they assist other species by feeding and removing dead skin or ectoparasites. Some of these cleaner fish species are used as a low-cost parasite control in salmon aquaculture, often considered to be more environmentally friendly than other delousing methods. Approximately 54 million cleaner fish are annually used in Norwegian salmon farms. This has resulted in an increasing fishing pressure on wild cleaner fish populations. Together with long-distance translocation, this raises concerns of potential overfishing, anthropogenic introductions, and hybridisation.
Recently, increasing numbers of corkwing wrasse (Symphodus melops), have been reported in mid Norway, north of its described distribution range. This is an area heavily relying on the import and translocation of cleaner fish from Skagerrak-Kattegat, more than 1000 km away. Using genetic markers, I show that the new population is both a result of a northward range expansion, as well as a translocation of individuals from southern populations. Further investigation revealed that escapees and hybrids may constitute up to 20 % of the populations at the northern edge of the species distribution. In contrast, escapees and hybrids are rare in other parts along the Norwegian west coast, where salmon farming is also common. The set of genetic markers has a high power to detect escapees and hybrids, and can be applied to monitoring of wild populations.
Investigations of corkwing wrasse in Skagerrak-Kattegat revealed reduced genetic diversity, a weak pattern of isolation by distance, and surprisingly little population structure. This suggests a very recent colonisation and high connectivity among sites in this region. Along the Swedish west coast, I evaluate the potential effects of the newly established wrasse fishery on local ecosystems and populations, and provide a baseline to support ecosystem-based management for wrasse fisheries in Sweden. I also investigate the genetic population structure of lumpfish (Cyclopterus lumpus) across the Atlantic, which is the most commonly used cleaner fish species. I show that there is a lot more structure than previously known, and identify eight genetically divergent regions. Hierarchical analysis of these regions demonstrates additional local and cryptic substructure. The genetic markers used her can also be applied for management of wild lumpfish populations and the identification of population origin.
Overall, these findings provide important information both for aquaculture management and conservation of wild populations, and have implications for the increasing use and translocation of cleaner fish for parasite control in aquaculture. Moving genetic material between isolated populations could drastically alter the genetic composition and erode population structure, potentially resulting in loss of local adaptation and hampering natural range expansion. Although the ecological and evolutionary significance of escapees warrants further investigation, these results should be taken into consideration in the use of translocated cleaner fish
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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