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Jan H Sundet - One of the best experts on this subject based on the ideXlab platform.
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the norwegian management of an introduced species the arctic red King Crab fishery
Marine Policy, 2016Co-Authors: Jan H Sundet, Alf Hakon HoelAbstract:Abstract Introduced into the Barents Sea in the 1960s, the red King Crab ( Paralithodes camtschaticus ) has been fished commercially in Norway since 2002. Because it is an introduced species, its management raises a number of concerns. Minimising the threats posed by non-native species that cannot be eradicated is a challenge facing nature management authorities worldwide. High concentrations of Crab on fishing grounds in eastern Finnmark in North Norway have interfered with traditional gillnet and longline fisheries, prompting fishermen to demand compensation for lost income. Difficult trade-offs were posed by the dual management objectives, which included (i) preventing the geographical expansion of the Crab and (ii) exploiting the resource to provide income to coastal communities. The Norwegian government, with the consent of Parliament, has developed a management regime that addresses both objectives: an open-access fishery west of 26°E to prevent further west- and southward expansion of the Crab population, and a regular commercial fishery east of that longitude. This management regime commands wider consideration, owing to its handling of the dilemmas inherent in the management of introduced species.
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dispersal of the introduced red King Crab paralithodes camtschaticus in norwegian waters a tag recapture study
Ices Journal of Marine Science, 2014Co-Authors: Kristin Windsland, Carsten Hvingel, Einar M Nilssen, Jan H SundetAbstract:The aim of this study was to explore the effect of sex, size, region, and density on dispersal rate of the introduced red King Crab (Paralithodes camtschaticus) in Norwegian waters. We examined the effect of these factors using logistic regression analysis. Tag-recapture data corrected for fishing effort enabled us to estimate dispersal rates from four main regions along the Norwegian coast: Varangerfjorden, Tanafjorden, Laksefjorden, and Porsangerfjorden. The probability of dispersal was independent of sex and size, but both the logistic regression and the evaluation of corrected tag-recapture data revealed differences in dispersal between region and with increasing duration. The recapture data indicated a relationship between population density and dispersal within research regions but not between population density and dispersal between research regions. Our main conclusion is that there are large individual differences in dispersal ability and the range expansion of red King Crab is a result of (i) the presence of long-distance dispersers and (ii) time-dependent slow migration by short distance dispersers. We also conclude that there appears less dispersal in Norwegian waters than in native waters, which might be caused by differences in geographical complexity.
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Contribution to the Themed Section: ‘Marine Harvesting in the Arctic’ Original Article Dispersal of the introduced red King Crab (Paralithodes camtschaticus) in Norwegian waters: a tag-recapture study
2014Co-Authors: Kristin Windsl, Carsten Hvingel, Einar M Nilssen, Jan H SundetAbstract:The aim of this studywas to explore the effect of sex, size, region, and density on dispersal rate of the introduced red King Crab (Paralithodes camtschaticus) inNorwegianwaters.Weexamined the effect of these factors using logistic regression analysis. Tag-recapture data corrected for fishing effort enabled us to estimate dispersal rates from four main regions along the Norwegian coast: Varangerfjorden, Tanafjorden, Laksefjorden, and Porsangerfjorden. The probability of dispersal was independent of sex and size, but both the logistic regression and the evaluation of corrected tag-recapture data revealed differences in dispersal between region and with increasing duration. The recapture data indicated a relationship between population density and dispersal within research regions but not between population density and dispersal between research regions. Our main conclusion is that there are large individual differences in dispersal ability and the range expansion of red King Crab is a result of (i) the presence of long-distance dispersers and (ii) time-dependent slow migration by short distance dispersers. We also conclude that there appears less dispersal in Norwegian waters than in native waters, which might be caused by differences in geographical complexity
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evaluation of von bertalanffy growth curves for the introduced red King Crab paralithodes camtschaticus in norwegian waters
Fisheries Research, 2013Co-Authors: Kristin Windsland, Carsten Hvingel, Einar M Nilssen, Jan H SundetAbstract:Abstract The introduced red King Crab ( Paralithodes camtschaticus ) is abundant in the coastal waters off northern Norway. We developed Bayesian hierarchical models to estimate growth parameters of a von Bertalanffy growth function using tag–recapture data. Individual variability in L ∞ (asymptotic length) was incorporated in the analysis. The models successfully estimate female red King Crab lengths at intervals where data were sufficient. The length of small males was overestimated. The results indicate a difference in growth rate of male and female juvenile red King Crab. The importance of including individual variability was confirmed: Variability in L ∞ for individuals was high compared to population variability in L ∞ . The model that incorporated individual variation resulted in more plausible values for the growth parameters and increased the precision of length estimates compared to the model that estimate a common L ∞ .
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reduced size composition and fecundity related to fishery and invasion history in the introduced red King Crab paralithodes camtschaticus in norwegian waters
Fisheries Research, 2012Co-Authors: Ann Merete Hjelset, Einar M Nilssen, Jan H SundetAbstract:Abstract The introduced red King Crab (Paralithodes camtschaticus) in the Barents Sea is abundant in the coastal waters of eastern Finnmark and supports a valuable fishery. In this paper we look at the development in size span among ovigerous females in the period between 1995 and 2010. We identify variations in individual fecundity in three fjords in Finnmark from 2000 to 2007. All the analyses were performed using regression and general linear models. We found that the size range decreased during this period. A decline in individual fecundity was observed. Individual egg weight (IEW) varied among fjords and years, and displayed a tendency to decline during the period of investigation, but the IEW was not affected by Crab size. Increased fishing pressure on large males may have caused both a decline in size range of ovigerous females as well as a decline in fecundity. Reduced IEW however is likely to be due to limited available food. We attempted to compare individual fecundity in the invasive Crab with fecundity results from populations in native areas. This comparison was inconclusive, due to differences in sampling season, size range and the methods employed.
Thomassen, Marte Renate - One of the best experts on this subject based on the ideXlab platform.
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Occupational exposure, respiratory health and sensitisation among Crab processing workers. A study among processors of King Crab (Paralithodes camtschaticus) and edible Crab (Cancer pagurus) in Norwegian land based Crab processing plants.
UiT Norges arktiske universitet, 2017Co-Authors: Thomassen, Marte RenateAbstract:The papers II and IV of this thesis are not available in Munin. Paper II: Thomassen, M. R., Kamath, S. D., Lopata, A. L., Madsen, A. M., Eduard, W., Bang, B. E., Aasmoe, L.: “Occupational Exposure to Bioaerosols in Norwegian Crab Processing Plants”. Available in Ann Occup Hyg 2016, 60(7):781-94. Paper IV: Thomassen, M. R., Kamath, S. D., Bang, B. E., Lopata, A. L., Aasmoe, L.: “Allergic sensitisation among Norwegian King Crab (Paralithodes camtschaticus) and edible Crab (Cancer pagurus) processing workers and identification of major allergenic proteins”. (Manuscript).Occupational asthma and allergy are health problems found in the seafood processing industry. The aim of this thesis was to investigate the exposure to central components in bioaerosols collected in the breathing zone of Crab processing workers, and explore the workers’ prevalence of respiratory symptoms and sensitisation to crustacean allergens. This thesis describes the exposure levels of total protein, tropomyosin, trypsin, NAGase and endotoxin in King Crab and edible Crab processing plants. This work establishes that both King Crab and edible Crab processing workers are exposed to bioaerosols containing these components. When comparing King Crab and edible Crab processing, King Crab processing results in highest levels of endotoxin while edible Crab processing has the highest levels of tropomyosin and total protein. Differences in exposure levels between the King Crab processing plants suggesting a plant effect where local differences in production, ventilation and plant layout is important for the exposure to bioaerosols. This work also describes the increased prevalence of respiratory symptoms among Crab processing workers compared to a non-exposed control group. However, there is little difference between exposed workers and controls in lung function parameters. The control group has an increased prevalence of self-reported asthma and allergy compared to the Crab processing workers. Furthermore, this work demonstrates elevated IgE and positive skin prick test results among both King Crab and edible Crab workers. Immunoblots also show that workers are sensitised to several allergens, including tropomyosin, arginine kinase, enolase and hemocyanin. The low prevalence of asthma and allergy despite the presence of respiratory symptoms and sensitisation suggests a healthy worker effect where unhealthy individuals are excluded from the workforce. It causes an underestimation of the health effects of worKing in the plant
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Occupational exposure, respiratory health and sensitisation among Crab processing workers. A study among processors of King Crab (Paralithodes camtschaticus) and edible Crab (Cancer pagurus) in Norwegian land based Crab processing plants.
'UiT The Arctic University of Norway', 2017Co-Authors: Thomassen, Marte RenateAbstract:Occupational asthma and allergy are health problems found in the seafood processing industry. The aim of this thesis was to investigate the exposure to central components in bioaerosols collected in the breathing zone of Crab processing workers, and explore the workers’ prevalence of respiratory symptoms and sensitisation to crustacean allergens. This thesis describes the exposure levels of total protein, tropomyosin, trypsin, NAGase and endotoxin in King Crab and edible Crab processing plants. This work establishes that both King Crab and edible Crab processing workers are exposed to bioaerosols containing these components. When comparing King Crab and edible Crab processing, King Crab processing results in highest levels of endotoxin while edible Crab processing has the highest levels of tropomyosin and total protein. Differences in exposure levels between the King Crab processing plants suggesting a plant effect where local differences in production, ventilation and plant layout is important for the exposure to bioaerosols. This work also describes the increased prevalence of respiratory symptoms among Crab processing workers compared to a non-exposed control group. However, there is little difference between exposed workers and controls in lung function parameters. The control group has an increased prevalence of self-reported asthma and allergy compared to the Crab processing workers. Furthermore, this work demonstrates elevated IgE and positive skin prick test results among both King Crab and edible Crab workers. Immunoblots also show that workers are sensitised to several allergens, including tropomyosin, arginine kinase, enolase and hemocyanin. The low prevalence of asthma and allergy despite the presence of respiratory symptoms and sensitisation suggests a healthy worker effect where unhealthy individuals are excluded from the workforce. It causes an underestimation of the health effects of worKing in the plant
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Occupational Exposure to Bioaerosols in Norwegian Crab Processing Plants
'Oxford University Press (OUP)', 2016Co-Authors: Thomassen, Marte Renate, Kamath, Sandip D., Lopata, Andreas L., Madsen, Anne Mette, Eduard Wijnand, Bang Berit, Aasmoe LisbethAbstract:Introduction: Aerosolisation of components when processing King Crab (Paralithodes camtschaticus) and edible Crab (Cancer pagurus) may cause occupational health problems when inhaled by workers. Methods: A cross-sectional study was carried out in three King Crab plants and one edible Crab plant. Personal exposure measurements were performed throughout work shifts. Air was collected for measurement of tropomyosin, total protein, endotoxin, trypsin and N-acetyl-β-D-glucosaminidase (NAGase). T-tests and ANOVAs were used to compare the levels of exposure in the different plants and areas in the plants. Results: Total protein and tropomyosin levels were highest in the edible Crab plant, endotoxin levels were highest in King Crab plants. King Crab exposure levels were highest during raw processing. Tropomyosin levels were highest during raw King Crab processing with geometric mean (GM) 9.6 ng/m3 vs 2.5 ng/m3 during cooked processing. Conversely, edible Crab tropomyosin levels were highest during cooked processing with GM 45.4 ng/m3 vs 8.7 ng/m3 during raw processing. Endotoxin levels were higher in King Crab plants than in the edible Crab plant with GM=6285.5 endotoxin units (EU)/m3 vs 72 EU/m3. In the edible Crab plant, NAGase levels were highest during raw processing with GM=853 pmol4- methylumbelliferone (MU)/m3 vs 422 pmol4-MU/m3 during cooked processing. Trypsin activity was found in both King Crab and edible Crab plants and levels were higher in raw than cooked processing. Differences in exposure levels between plants and worker groups (raw and cooked processing) were identified Conclusions: Norwegian Crab processing workers are exposed to airborne proteins, tropomyosin, endotoxins, trypsin and NAGase in their breathing zone. Levels vary between worker groups and factories
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Occupational Exposure to Bioaerosols in Norwegian Crab Processing Plants
'Oxford University Press (OUP)', 2016Co-Authors: Thomassen, Marte Renate, Kamath, Sandip D., Lopata, Andreas L., Madsen, Anne Mette, Eduard Wijnand, Bang Berit, Aasmoe LisbethAbstract:Source at https://doi.org/10.1093/annhyg/mew030 Introduction: Aerosolisation of components when processing King Crab (Paralithodes camtschaticus) and edible Crab (Cancer pagurus) may cause occupational health problems when inhaled by workers. Methods: A cross-sectional study was carried out in three King Crab plants and one edible Crab plant. Personal exposure measurements were performed throughout work shifts. Air was collected for measurement of tropomyosin, total protein, endotoxin, trypsin and N-acetyl-β-D-glucosaminidase (NAGase). T-tests and ANOVAs were used to compare the levels of exposure in the different plants and areas in the plants. Results: Total protein and tropomyosin levels were highest in the edible Crab plant, endotoxin levels were highest in King Crab plants. King Crab exposure levels were highest during raw processing. Tropomyosin levels were highest during raw King Crab processing with geometric mean (GM) 9.6 ng/m3 vs 2.5 ng/m3 during cooked processing. Conversely, edible Crab tropomyosin levels were highest during cooked processing with GM 45.4 ng/m3 vs 8.7 ng/m3 during raw processing. Endotoxin levels were higher in King Crab plants than in the edible Crab plant with GM=6285.5 endotoxin units (EU)/m3 vs 72 EU/m3. In the edible Crab plant, NAGase levels were highest during raw processing with GM=853 pmol4- methylumbelliferone (MU)/m3 vs 422 pmol4-MU/m3 during cooked processing. Trypsin activity was found in both King Crab and edible Crab plants and levels were higher in raw than cooked processing. Differences in exposure levels between plants and worker groups (raw and cooked processing) were identified Conclusions: Norwegian Crab processing workers are exposed to airborne proteins, tropomyosin, endotoxins, trypsin and NAGase in their breathing zone. Levels vary between worker groups and factories
Einar M Nilssen - One of the best experts on this subject based on the ideXlab platform.
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dispersal of the introduced red King Crab paralithodes camtschaticus in norwegian waters a tag recapture study
Ices Journal of Marine Science, 2014Co-Authors: Kristin Windsland, Carsten Hvingel, Einar M Nilssen, Jan H SundetAbstract:The aim of this study was to explore the effect of sex, size, region, and density on dispersal rate of the introduced red King Crab (Paralithodes camtschaticus) in Norwegian waters. We examined the effect of these factors using logistic regression analysis. Tag-recapture data corrected for fishing effort enabled us to estimate dispersal rates from four main regions along the Norwegian coast: Varangerfjorden, Tanafjorden, Laksefjorden, and Porsangerfjorden. The probability of dispersal was independent of sex and size, but both the logistic regression and the evaluation of corrected tag-recapture data revealed differences in dispersal between region and with increasing duration. The recapture data indicated a relationship between population density and dispersal within research regions but not between population density and dispersal between research regions. Our main conclusion is that there are large individual differences in dispersal ability and the range expansion of red King Crab is a result of (i) the presence of long-distance dispersers and (ii) time-dependent slow migration by short distance dispersers. We also conclude that there appears less dispersal in Norwegian waters than in native waters, which might be caused by differences in geographical complexity.
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Contribution to the Themed Section: ‘Marine Harvesting in the Arctic’ Original Article Dispersal of the introduced red King Crab (Paralithodes camtschaticus) in Norwegian waters: a tag-recapture study
2014Co-Authors: Kristin Windsl, Carsten Hvingel, Einar M Nilssen, Jan H SundetAbstract:The aim of this studywas to explore the effect of sex, size, region, and density on dispersal rate of the introduced red King Crab (Paralithodes camtschaticus) inNorwegianwaters.Weexamined the effect of these factors using logistic regression analysis. Tag-recapture data corrected for fishing effort enabled us to estimate dispersal rates from four main regions along the Norwegian coast: Varangerfjorden, Tanafjorden, Laksefjorden, and Porsangerfjorden. The probability of dispersal was independent of sex and size, but both the logistic regression and the evaluation of corrected tag-recapture data revealed differences in dispersal between region and with increasing duration. The recapture data indicated a relationship between population density and dispersal within research regions but not between population density and dispersal between research regions. Our main conclusion is that there are large individual differences in dispersal ability and the range expansion of red King Crab is a result of (i) the presence of long-distance dispersers and (ii) time-dependent slow migration by short distance dispersers. We also conclude that there appears less dispersal in Norwegian waters than in native waters, which might be caused by differences in geographical complexity
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evaluation of von bertalanffy growth curves for the introduced red King Crab paralithodes camtschaticus in norwegian waters
Fisheries Research, 2013Co-Authors: Kristin Windsland, Carsten Hvingel, Einar M Nilssen, Jan H SundetAbstract:Abstract The introduced red King Crab ( Paralithodes camtschaticus ) is abundant in the coastal waters off northern Norway. We developed Bayesian hierarchical models to estimate growth parameters of a von Bertalanffy growth function using tag–recapture data. Individual variability in L ∞ (asymptotic length) was incorporated in the analysis. The models successfully estimate female red King Crab lengths at intervals where data were sufficient. The length of small males was overestimated. The results indicate a difference in growth rate of male and female juvenile red King Crab. The importance of including individual variability was confirmed: Variability in L ∞ for individuals was high compared to population variability in L ∞ . The model that incorporated individual variation resulted in more plausible values for the growth parameters and increased the precision of length estimates compared to the model that estimate a common L ∞ .
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reduced size composition and fecundity related to fishery and invasion history in the introduced red King Crab paralithodes camtschaticus in norwegian waters
Fisheries Research, 2012Co-Authors: Ann Merete Hjelset, Einar M Nilssen, Jan H SundetAbstract:Abstract The introduced red King Crab (Paralithodes camtschaticus) in the Barents Sea is abundant in the coastal waters of eastern Finnmark and supports a valuable fishery. In this paper we look at the development in size span among ovigerous females in the period between 1995 and 2010. We identify variations in individual fecundity in three fjords in Finnmark from 2000 to 2007. All the analyses were performed using regression and general linear models. We found that the size range decreased during this period. A decline in individual fecundity was observed. Individual egg weight (IEW) varied among fjords and years, and displayed a tendency to decline during the period of investigation, but the IEW was not affected by Crab size. Increased fishing pressure on large males may have caused both a decline in size range of ovigerous females as well as a decline in fecundity. Reduced IEW however is likely to be due to limited available food. We attempted to compare individual fecundity in the invasive Crab with fecundity results from populations in native areas. This comparison was inconclusive, due to differences in sampling season, size range and the methods employed.
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the introduced species red King Crab paralithodes camtschaticus in the barents sea ii growth increments and moulting probability
Fisheries Research, 2006Co-Authors: Einar M Nilssen, Jan H SundetAbstract:Russian scientists introduced the red King Crab (Paralithodes camtschaticus) to the Barents Sea during the 1960s and 1970s, and the Crab has now become abundant in the coastal waters of Finnmark, North Norway. The growing stock size of this introduced species raises increasing demands for management of the stock. Therefore, basic knowledge of general biology and ecology is required. This paper presents analyses of the moulting increment and moulting frequency results based on tag and recapture experiments. The mean increments in carapace length per moult of males (immature and mature) are estimated to be 17.0 mm for all premoult carapace lengths between 67 and 172 mm, while the increment decreased from 14.4 to 5.1 mm for females as they became ovigerous. The results show that the growth increments of the red King Crab in Varanger are within the ranges reported in the eastern Bering Sea. A model relating probability of moulting as a function of carapace length is developed based on tag-recapture and qualitative carapace age judgement.
Kristin Windsland - One of the best experts on this subject based on the ideXlab platform.
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total and natural mortality of red King Crab paralithodes camtschaticus in norwegian waters catch curve analysis and indirect estimation methods
Ices Journal of Marine Science, 2015Co-Authors: Kristin WindslandAbstract:The red King Crab (Paralithodes camtschaticus) is native to the Bering Sea, butwas deliberately introduced to the Barents Sea during the 1960s. Since then, the redKing Crabhas spread toNorwegianwaters, and Crabdensities have increased sufficiently to support a coastal fishery. Information about total and natural mortality, which is important to ensure adequatemanagement, is lacKing. Estimates of annual total mortality (Z) were calculated using length-converted catch curves in three periods of different levels of exploitation. Separate analyses were run on trap and trawl data as well as on original and catch per unit effort-corrected data. Natural mortality was estimated using a linear regression of total mortality and exploitation level and by using indirect methods based on life history parameters. There was a significant increase in Z throughout the consecutive periods in both sexes. In males, the increase coincided with the increase in exploitation level. The increase in female mortality, which was not explained by exploitation level, is probably an effect of the increase inmalemortality. Naturalmortality (M ), estimated using indirectmethods, averaged 0.23 for both sexes. The estimatedM using linear regression was 0.37/0.44, which may be an overestimate.
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dispersal of the introduced red King Crab paralithodes camtschaticus in norwegian waters a tag recapture study
Ices Journal of Marine Science, 2014Co-Authors: Kristin Windsland, Carsten Hvingel, Einar M Nilssen, Jan H SundetAbstract:The aim of this study was to explore the effect of sex, size, region, and density on dispersal rate of the introduced red King Crab (Paralithodes camtschaticus) in Norwegian waters. We examined the effect of these factors using logistic regression analysis. Tag-recapture data corrected for fishing effort enabled us to estimate dispersal rates from four main regions along the Norwegian coast: Varangerfjorden, Tanafjorden, Laksefjorden, and Porsangerfjorden. The probability of dispersal was independent of sex and size, but both the logistic regression and the evaluation of corrected tag-recapture data revealed differences in dispersal between region and with increasing duration. The recapture data indicated a relationship between population density and dispersal within research regions but not between population density and dispersal between research regions. Our main conclusion is that there are large individual differences in dispersal ability and the range expansion of red King Crab is a result of (i) the presence of long-distance dispersers and (ii) time-dependent slow migration by short distance dispersers. We also conclude that there appears less dispersal in Norwegian waters than in native waters, which might be caused by differences in geographical complexity.
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evaluation of von bertalanffy growth curves for the introduced red King Crab paralithodes camtschaticus in norwegian waters
Fisheries Research, 2013Co-Authors: Kristin Windsland, Carsten Hvingel, Einar M Nilssen, Jan H SundetAbstract:Abstract The introduced red King Crab ( Paralithodes camtschaticus ) is abundant in the coastal waters off northern Norway. We developed Bayesian hierarchical models to estimate growth parameters of a von Bertalanffy growth function using tag–recapture data. Individual variability in L ∞ (asymptotic length) was incorporated in the analysis. The models successfully estimate female red King Crab lengths at intervals where data were sufficient. The length of small males was overestimated. The results indicate a difference in growth rate of male and female juvenile red King Crab. The importance of including individual variability was confirmed: Variability in L ∞ for individuals was high compared to population variability in L ∞ . The model that incorporated individual variation resulted in more plausible values for the growth parameters and increased the precision of length estimates compared to the model that estimate a common L ∞ .
Raul Primicerio - One of the best experts on this subject based on the ideXlab platform.
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impact scenario for the invasive red King Crab paralithodes camtschaticus tilesius 1815 reptantia lithodidae on norwegian native epibenthic prey
Hydrobiologia, 2007Co-Authors: Lis Lindal Jørgensen, Raul PrimicerioAbstract:Large invasive predators like the King Crab, Paralithodes camtschaticus, deserve particular attention due to their potential for catastrophic ecological impact on recipient communities. Conspicuous, epibenthic prey species, such as the slow growing commercial scallop Chlamys islandica, are particularly exposed to the risk of local extinction. A research program integrating experiments and field monitoring is attempting to predict and track the impact of invasive King Crab on scallop beds and associated fauna along the north Norwegian coast. The claw gape of the Crab shows no limitations in handling the flat-bodied scallop. However, the potential impact of the Crab on scallop may depend on the availability of other calcified prey associated with scallop beds, such as the sea star, sea urchin, and blue mussel, all species recorded in the diet of P. camtschaticus. To address this issue, a laboratory experiment on foraging behaviour of P. camtschaticus was conducted. The experimental results show that all size classes of red King Crab prefer scallops, but small juveniles and medium sized Crabs demonstrate active selection for starfish (Asterias rubens) that equals or surpasses the electivity of the large Crab. The selection of sea urchin (Strongylocentrotus droebachiensis) and blue mussel (Mytilus edulis) is slightly positive or neutral for the three Crab size classes. These results suggest that scallop beds with a rich associated fauna are less vulnerable to red King Crabs predation and possibly more resilient than beds with few associated species. Also, Crab size distribution is likely relevant for invasion impact, with increasing abundance of small and medium sized Crabs being detrimental for alternative calcified prey associated with scallop beds. Successive stages of Crab invasion will see an acceleration of scallop mortality rates associated with (i) decreasing availability of alternative prey, due to protracted predation pressure intensified by recruitment of juvenile Crabs, and (ii) increased number of large Crabs. Estimates of Crab density and intake rates suggest that the accelerated loss rates will eventually endanger scallop beds persistence.
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impact scenario for the invasive red King Crab paralithodes camtschaticus tilesius 1815 reptantia lithodidae on norwegian native epibenthic prey
Hydrobiologia, 2007Co-Authors: Lis Lindal Jørgensen, Raul PrimicerioAbstract:Large invasive predators like the King Crab, Paralithodes camtschaticus, deserve particular attention due to their potential for catastrophic ecological impact on recipient communities. Conspicuous, epibenthic prey species, such as the slow growing commercial scallop Chlamys islandica, are particularly exposed to the risk of local extinction. A research program integrating experiments and field monitoring is attempting to predict and track the impact of invasive King Crab on scallop beds and associated fauna along the north Norwegian coast. The claw gape of the Crab shows no limitations in handling the flat-bodied scallop. However, the potential impact of the Crab on scallop may depend on the availability of other calcified prey associated with scallop beds, such as the sea star, sea urchin, and blue mussel, all species recorded in the diet of P. camtschaticus. To address this issue, a laboratory experiment on foraging behaviour of P. camtschaticus was conducted. The experimental results show that all size classes of red King Crab prefer scallops, but small juveniles and medium sized Crabs demonstrate active selection for starfish (Asterias rubens) that equals or surpasses the electivity of the large Crab. The selection of sea urchin (Strongylocentrotus droebachiensis) and blue mussel (Mytilus edulis) is slightly positive or neutral for the three Crab size classes. These results suggest that scallop beds with a rich associated fauna are less vulnerable to red King Crabs predation and possibly more resilient than beds with few associated species. Also, Crab size distribution is likely relevant for invasion impact, with increasing abundance of small and medium sized Crabs being detrimental for alternative calcified prey associated with scallop beds. Successive stages of Crab invasion will see an acceleration of scallop mortality rates associated with (i) decreasing availability of alternative prey, due to protracted predation pressure intensified by recruitment of juvenile Crabs, and (ii) increased number of large Crabs. Estimates of Crab density and intake rates suggest that the accelerated loss rates will eventually endanger scallop beds persistence.
