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Odd Aksel Bergstad - One of the best experts on this subject based on the ideXlab platform.
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Intermittent recruitment and exploitation pulse underlying temporal variability in a demersal deep-water fish population
Ices Journal of Marine Science, 2013Co-Authors: Odd Aksel Bergstad, Hege Overbo Hansen, Terje JørgensenAbstract:Recent temporal variability in abundance, size and age structure, distribution, and recruitment of the Skagerrak population of the commercially exploited long-lived deep-water demersal macrourid roundnose grenadier (Coryphaenoides rupestris) appeared strongly influenced by a combined effect of a single pronounced recruitment incident in the early 1990s and a subsequent pulse in targeted exploitation a decade later. Fishery-independent annual survey data showed that probably only one strong year class occurred across an almost three-decade period, 1985–present. Recruitment studies in deep-water fish remain few, yet rarity of successful recruitment events may have to be added to life-history characteristics already recognized as limiting the potential for sustainable harvesting of deep-water demersal fish, i.e. extended lifespan, slow growth, high age at first maturity, and low fecundity.
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population genetic structure in a deepwater fish Coryphaenoides rupestris patterns and processes
Marine Ecology Progress Series, 2012Co-Authors: Halvor Knutsen, Odd Aksel Bergstad, Per Erik Jorde, Morten D SkogenAbstract:We observed significant genetic structure in a widely distributed North Atlantic demersal deepwater fish, the roundnose grenadier Coryphaenoides rupestris (Pisces: Macro - uridae). The overall estimate of genetic differentiation, based on 6 microsatellite loci (FST = 0.0152; p < 0.0001), was elevated by samples from the periphery of the species' range, off Norway and Canada. Samples from the central area of distribution showed less pronounced genetic structure, indicating more extensive dispersal and gene flow. Simulations were run to assess expected pat- terns of genetic differentiation under 2 major hypotheses of gene flow: passive larval drift and demographic diffusion. In spite of the relatively long duration of the pelagic egg and juvenile phases, no correlation was found between observed pairwise FST values and those predicted under the hypothesis of drift of progeny by ocean currents. The observed pattern may instead arise from a combination of bathymetric barriers limiting deep pelagic mixing and advection, early life ontogenetic changes in vertical distribution, and limited migration once a benthopelagic life style has been established.
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feeding ecology of Coryphaenoides rupestris from the mid atlantic ridge
PLOS ONE, 2010Co-Authors: Odd Aksel Bergstad, Guro Gjelsvik, Christoffer Schander, Age S HoinesAbstract:The Macrourid fish roundnose grenadier, Coryphaenoides rupestris, is one of the most common benthopelagic fishes on the northern mid-Atlantic Ridge. The ecology of the species is comparatively well studied in continental slope waters of the North Atlantic, but not on the mid-Atlantic Ridge, which is a central mid-ocean area of its distribution. In total, 166 specimens from the RV G.O. Sars cruise in July 2004 were examined. The diet mainly comprised cephalopods, pelagic shrimps and fish. Pelagic and benthopelagic copepods were the most numerous prey, but did not contribute much on a weight basis. Cephalopods were by far the most important prey of the small grenadiers, while shrimps and fish became increasingly significant with increasing size. Previous studies from other areas have also found pelagic prey to be important, but in contrast to this study, cephalopods were generally of less importance. The study was an element of more wide-ranging food-web studies of the mid-Atlantic Ridge macro- and megafauna communities within the international MAR-ECO project.
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the food of juvenile Coryphaenoides rupestris gunnerus 1765 pisces macrouridae in the skagerrak
Sarsia, 1994Co-Authors: John Mauchline, Odd Aksel Bergstad, John D M Gordon, Torleiv BrattegardAbstract:Abstract The food of 8–10 cm juvenile Coryphaenoides rupestris which had recently become benthpelagic, is described. Benthopelagic and hyperbenthic mysids were the most important prey, while ostracods were numerous in some stomachs.
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deep water ichthyoplankton of the skagerrak with special reference to Coryphaenoides rupestris gunnerus 1765 pisces macrouridae and argentina silus ascanius 1775 pisces argentinidae
Sarsia, 1994Co-Authors: Odd Aksel Bergstad, John D M GordonAbstract:Abstract Two species, Coryphaenoides rupestris and Argentina silus, were abundant in the ichthyoplankton of the 150–550 m depth zone of the Skagerrak in 1992. Eggs of C. rupestris occurred only in October and December and a single yolk sac larva was caught in December. Postlarvae and juveniles occurred in all months (Feb, Apr, Jun, Oct, Dec) and showed a continuous increase in length through the year. This confirms earlier indications of a single late autumn spawning period. By October the juveniles had attained a demersal mode of life. Argentina silus eggs and larvae occurred year-round, but eggs were most abundant in the spring. Most of the other fish eggs and larvae were probably caught incidentally in surface layers. Exceptions may be four postlarval Atlantic halibut Hippoglossus hippoglossus L.
O. A. Bergstad - One of the best experts on this subject based on the ideXlab platform.
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North Atlantic demersal deep‐water fish distribution and biology: present knowledge and challenges for the future
Journal of Fish Biology, 2013Co-Authors: O. A. BergstadAbstract:: This paper summarizes knowledge and knowledge gaps on benthic and benthopelagic deep-water fishes of the North Atlantic Ocean, i.e. species inhabiting deep continental shelf areas, continental and island slopes, seamounts and the Mid-Atlantic Ridge. While several studies demonstrate that distribution patterns are species specific, several also show that assemblages of species can be defined and such assemblages are associated with circulatory features and water mass distributions. In many subareas, sampling has, however, been scattered, restricted to shallow areas or soft substrata, and results from different studies tend to be difficult to compare quantitatively because of sampler differences. Particularly, few studies have been conducted on isolated deep oceanic seamounts and in Arctic deep-water areas. Time series of data are very few and most series are short. Recent studies of population structure of widely distributed demersal species show less than expected present connectivity and considerable spatial genetic heterogeneity and complexity for some species. In other species, genetic homogeneity across wide ranges was discovered. Mechanisms underlying the observed patterns have been proposed, but to test emerging hypotheses more species should be investigated across their entire distribution ranges. Studies of population biology reveal greater diversity in life-history strategies than often assumed, even between co-occurring species of the same family. Some slope and ridge-associated species are rather short-lived, others very long-lived, and growth patterns also show considerable variation. Recent comparative studies suggest variation in life-history strategies along a continuum correlated with depth, ranging from shelf waters to the deep sea where comparatively more species have extended lifetimes, and slow rates of growth and reproduction. Reproductive biology remains too poorly known for most deep-water species, and temporal variation in recruitment has only been studied for few deep-water species. A time series of roundnose grenadier Coryphaenoides rupestris recruitment spanning three decades of fisheries-independent data suggests that abundant year classes occur rarely and may influence size structure and abundance even for this long-lived species.
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Age Determination of Deep-Water Fishes: Experiences, Status and Challenges for the Future
Deep-Water Fisheries of the North Atlantic Oceanic Slope, 1995Co-Authors: O. A. BergstadAbstract:A review is presented of the literature on aging of deep water fishes and of experiences from studies of Coryphaenoides rupestris, Argentina silus, Molva molva, Molva dipterygia, Brosme brosme, and Glyptocephalus cynoglossus of the Skagerrak.
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Distribution, population structure, growth and reproduction of the roundnose grenadierCoryphaenoides rupestris (Pisces: Macrouridae) in the deep waters of the Skagerrak
Marine Biology, 1990Co-Authors: O. A. BergstadAbstract:The roundnose grenadier Coryphaenoides rupestris Gunnerus, 1765 occurs benthopelagically in the deepest parts of the Norwegian Deep, i.e., at depths >300 m in the Skagerrak. Based on studies of distribution carried out in the years 1984 to 1987, it appears that the concentrations contitute a largely self-sustaining population. From age-readings using transverse otolith sections, the population appears to consist of at least 50 to 60 age-groups and to include a very high proportion of old fish. Population growth-curves in terms of length and weight revealed that females grow comparatively fast for a longer time and attain greater asymptotic sizes than males. Maximum lengths appear however to be lower in the Skagerrak than in waters to the west of Scotland, and the length/weight data indicate that the weight at a given length (weight at length) of large individuals is less than reported from other areas. The major spawning season is in late autumn, probably extending into early winter. Fifty per-cent of females and males become mature for the first time at Age 10 and 8 yr, respectively. Corresponding pre-anal lengths are 11 and 8.5 cm.
John D M Gordon - One of the best experts on this subject based on the ideXlab platform.
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Putative fishery-induced changes in biomass and population size structures of demersal deep-sea fishes in ICES Sub-area VII, Northeast Atlantic Ocean
Biogeosciences, 2012Co-Authors: Jasmin A. Godbold, John D M Gordon, Martin A Collins, David M Bailey, Waldemar Spallek, Imants G. PriedeAbstract:A time series from 1977–1989 and 2000–2002 of scientific trawl surveys in the Porcupine Seabight and adjacent abyssal plain of the NE Atlantic was analysed to assess changes in demersal fish biomass and length frequency. These two periods coincide with the onset of the commercial deep-water fishery in the late 1970s and the onset of the regulation of the fishery in the early 2000's, which allowed us to investigate changes in the relationship between total demersal fish biomass and depth between the pre- and post commercial fishing periods, as well as changes in the biomass (kg km −2 ) depth distribution and length frequency distribution of the most dominant fish species. Our results show a decline in total demersal fish biomass of 36% within the depth range of the commercial fishery ( Coryphaenoides rupestris decreased by 57%) and non-target (e.g. C. guentheri and Antimora rostrata ) species, not all species declined significantly. Changes in the overall length-frequency distribution were detected for 5 out of the 8 dominant species occupying depth ranges both within and outside the maximum depth for commercial trawling. This suggests that whilst there is evidence for likely fishery impacts on the biomass distribution of the demersal fish population as a whole, species-specific impacts are highly variable. It is clear that changes in population structure can extend beyond the depth at which fishing takes place, highlighting the importance for also considering the indirect effects on deep-sea fish populations.
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A review of the spatial extent of fishery effects and species vulnerability of the deep-sea demersal fish assemblage of the Porcupine Seabight, Northeast Atlantic Ocean (ICES Subarea VII)
Ices Journal of Marine Science, 2010Co-Authors: Imants G. Priede, John D M Gordon, Martin A Collins, David M Bailey, Jasmin A. Godbold, Tomasz Niedzielski, Alain F. ZuurAbstract:We review information from scientific trawl surveys carried out between 1977 and 2002 in the Porcupine Seabight and Abyssal Plain area of the Northeast Atlantic (240-4865 m water depth). Since the late 1980s, commercial bottom-trawl fisheries targeting mainly roundnose grenadier (Coryphaenoides rupestris), black scabbardfish (Aphanopus carbo), and orange roughy (Hoplostethus atlanticus) have been operating at depths of 500-1500 m, intersecting the depth ranges of 77 demersal fish species that would therefore be vulnerable to fishery effects. Comparisons of trawls pre-1989 and post-1997 indicate a significant decrease in total abundance of demersal fish down to 2500 m. Detailed analyses of the 15 most-abundant species showed that nine species with depth ranges within the commercial fishing depth have decreased in abundance. Other species were either not affected (Bathypterois dubius) or only affected at the shallow end of their range (Coryphaenoides guentheri). Species with a minimum depth of occurrence >1500 m (Coryphaenoides armatus and Coryphaenoides leptolepis) increased in abundance over part of their depth range. Decreases in abundance are probably caused by commercial fishing activities, an effect that is transmitted downslope by removal of fish at the shallow end of their depth range, resulting in declines at the deeper end of the depth range. The estimated fishery area is ca. 52 000 km(2), but the potential impact probably extends to ca. 142 000 km(2) and to many non-target species.
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Effects of handling and storage methods on the concentrations of elements in deep-water fish otoliths
Journal of Fish Biology, 2006Co-Authors: Sarah Swan, John D M Gordon, Audrey J. Geffen, Beatriz Morales-nin, Tracy M ShimmieldAbstract:Sagittal otoliths of Coryphaenoides rupestris (roundnose grenadier), Helicolenus dactylopterus (bluemouth) and Merluccius merluccius (European hake) were collected using a variety of handling and storage treatments and their elemental composition was examined using inductively coupled plasma mass spectrometry. Some differences between element concentrations were identified between the control and treatment groups, most notably for the element Li. For H. dactylopterus and M. merluccius, Li concentrations were significantly higher in the otoliths extracted with metal forceps and stored in paper envelopes (treatment), compared to those from the same fishes that had been extracted using plastic forceps and stored in polyethylene vials (control). Lower concentrations of Ba and Cr were found in M. merluccius otoliths extracted from fish that had been stored frozen. The presence or absence of elemental concentrations above the instrumental limits of detection was noted, but no significant differences were identified between otolith pairs for any of the treatments. The differences between otolith pairs attributable to storage and handling effects are small compared to between-area differences.
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A review of age estimation in macrourid fishes with new data on age validation of juveniles
2001Co-Authors: Sarah Swan, John D M GordonAbstract:Abstract It was a long held belief that the constancy of the deep-water environment would result in continuous growth and all year round reproduction in deep-water fish. However, rings on scales and otoliths of deep-water fishes similar to those found in shallow-water fish species have been reported since the beginning of the 20th century. The development of a fishery for Coryphaenoides rupestris in the 1960s led to the use of scales and otoliths for age estimation without any attempt to validate the annual nature of the growth zones. This paper reviews the literature on age estimation in macrourid fishes. New data on the validation of age estimates of juvenile macrourids are presented. The species studied are all from the eastern North Atlantic and span a depth range from about 250 to 5000 m. A common feature is the apparent delay in the onset of the growing season until the autumn and winter months, which is possibly linked to food availability in the deep sea.
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Deep-water fisheries at the Atlantic frontier
2001Co-Authors: John D M GordonAbstract:Abstract The deep sea is often thought of as a cold, dark and uniform environment with a low-fish biomass, much of which is highly adapted for life in a food-poor environment. While this might be true of the pelagic fish living in the water column, it is certainly not true of the demersal fish which live on or close to the bottom on the continental slopes around the British Isles (the Atlantic Frontier). These fish are currently being commercially exploited. There is growing evidence to support the view that success of the demersal fish assemblages depends on the pelagic or benthopelagic food sources that impinge both vertically and horizontally onto the slope. There are several quite separate and distinct deep-water fisheries on the Atlantic Frontier. It is a physical barrier, the Wyville-Thomson Ridge, which results in the most significant division of the fisheries. The Ridge, which has a minimum depth of about 500 m, separates the warmer deep Atlantic waters from the much colder Norwegian Sea water and as a result, the deep-water fisheries to the west of the Hebrides and around the offshore banks are quite different from those of the Faroe-Shetland Channel (West of Shetland). The fisheries to the West of the Hebrides can be further divided by the fishing method used into bottom trawl, semipelagic trawl and longline. The bottom-trawl fisheries extend from the shelf-slope break down to about 1700 m and the target species varies with depth. The smallest vessels in the fleet fish on the upper slope, where an important target species is the anglerfish or monkfish ( Lophius spp.). On the mid-slope the main target species are blue ling ( Molva dypterygia ) and roundnose grenadier ( Coryphaenoides rupestris ), with bycatches of black scabbardfish ( Aphanopus carbo ) and deep-water sharks. On the lower slope orange roughy ( Hoplostethus atlanticus ) is an important target species. The major semipelagic trawl fishery is a seasonal fishery on spawning aggregations of blue whiting ( Micromesistius poutassou ). The other semipelagic fishery is on spawning aggregations of the greater silver smelt or argentine ( Argentina silus ). Spanish and UK vessels that target mainly hake ( Merluccius merluccius ) and a Norwegian fleet that targets ling ( Molva molva ), blue ling and tusk ( Brosme brosme ) dominate the upper slope longline fishery. West of Shetland, the fishery on the upper slope has some similarities with that of the Hebridean slope, with anglerfish and blue ling being important target species. A quite different fishery occurs in the transition zone between the Atlantic and Norwegian Sea waters. Here the main target species is Greenland halibut ( Reinhardtius hippoglossoides ). Below the transition zone biomass decreases rapidly and there is no fishery. It is generally agreed that many deep-water species have slow growth, a high age at first maturity and a low fecundity, which makes them vulnerable to over-exploitation. Other features of these fishes such as high mortality of discards and escapees will add to the problems. Despite this the only management procedures in place are general limitation of effort measures within the area of jurisdiction of the European Union.
Halvor Knutsen - One of the best experts on this subject based on the ideXlab platform.
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population genetic structure in a deepwater fish Coryphaenoides rupestris patterns and processes
Marine Ecology Progress Series, 2012Co-Authors: Halvor Knutsen, Odd Aksel Bergstad, Per Erik Jorde, Morten D SkogenAbstract:We observed significant genetic structure in a widely distributed North Atlantic demersal deepwater fish, the roundnose grenadier Coryphaenoides rupestris (Pisces: Macro - uridae). The overall estimate of genetic differentiation, based on 6 microsatellite loci (FST = 0.0152; p < 0.0001), was elevated by samples from the periphery of the species' range, off Norway and Canada. Samples from the central area of distribution showed less pronounced genetic structure, indicating more extensive dispersal and gene flow. Simulations were run to assess expected pat- terns of genetic differentiation under 2 major hypotheses of gene flow: passive larval drift and demographic diffusion. In spite of the relatively long duration of the pelagic egg and juvenile phases, no correlation was found between observed pairwise FST values and those predicted under the hypothesis of drift of progeny by ocean currents. The observed pattern may instead arise from a combination of bathymetric barriers limiting deep pelagic mixing and advection, early life ontogenetic changes in vertical distribution, and limited migration once a benthopelagic life style has been established.
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Isolation and characterisation of 11 microsatellite loci in the abyssal carapine grenadier Coryphaenoides carapinus (Actinoperygii, Macrouridae) and cross-amplification in two other deep-sea macrourid species
Conservation Genetics, 2009Co-Authors: Matthias Schneider, Per Erik Jorde, Hanne Sannæs, Halvor KnutsenAbstract:Microsatellites represent an important tool for characterising population structure, for attributing individuals to stocks, and for revealing ecological processes taking place on population and meta-population levels. A sound knowledge of population structure is essential for sustainable management of exploited fish stocks, and helps to understand population connectivity and speciation. We developed for the first time primers for microsatellite loci in the carapine grenadier, Coryphaenoides carapinus , inhabiting the abyssal Atlantic. Eleven microsatellites were obtained from partial genomic DNA libraries enriched for tetranucleotide repeats. The loci were characterised in three unrelated individuals and nine loci were found to be polymorphic. Cross-amplification in two commercially exploited deep-sea macrourid species ( Coryphaenoides rupestris and Macrourus berglax ) resolved two polymorphic loci in each species.
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isolation and characterization of microsatellite loci in the deep sea marine fish the roundnose grenadier Coryphaenoides rupestris
Molecular Ecology Resources, 2008Co-Authors: Halvor Knutsen, Marie Le Goffvitry, David Fiani, Rus A HoelzelAbstract:We developed polymerase chain reaction primers for eight dinucleotide microsatellite loci in the marine deep sea fish, roundnose grenadier (Coryphaenoides rupestris). All markers were obtained from a partial genomic DNA library, and characterized in 90 unrelated individuals from one putative population sampled on the Mid-Atlantic Ridge. The number of alleles ranged from two to 61 with an average of 21 per locus. The observed heterozygosity levels ranged from 0.301 to 0.987 with an average of 0.672. Several of the markers amplified multiple alleles from either the Atlantic cod (Gadus morhua) or the deep-sea fish roughhead grenadier (Macrourus berglax).
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Isolation and characterization of microsatellite loci in the deep‐sea marine fish, the roundnose grenadier (Coryphaenoides rupestris)
Molecular Ecology Resources, 2008Co-Authors: Halvor Knutsen, David Fiani, Marie Le Goff-vitry, A. Rus HoelzelAbstract:We developed polymerase chain reaction primers for eight dinucleotide microsatellite loci in the marine deep sea fish, roundnose grenadier (Coryphaenoides rupestris). All markers were obtained from a partial genomic DNA library, and characterized in 90 unrelated individuals from one putative population sampled on the Mid-Atlantic Ridge. The number of alleles ranged from two to 61 with an average of 21 per locus. The observed heterozygosity levels ranged from 0.301 to 0.987 with an average of 0.672. Several of the markers amplified multiple alleles from either the Atlantic cod (Gadus morhua) or the deep-sea fish roughhead grenadier (Macrourus berglax).
Lars Forlin - One of the best experts on this subject based on the ideXlab platform.
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histopathological and immunohistochemical studies in roundnose grenadier Coryphaenoides rupestris in the skagerrak north sea
Marine Environmental Research, 1996Co-Authors: Eric Lindesjoo, Astridmette Husoy, Inger Petterson, Lars ForlinAbstract:Abstract The aim of this study was to investigate whether the large-scale distribution of anthropogenic compounds in the Skagerrak deep sea gives rise to histopathological and immunohistochemical effects in fish. For this purpose, roundnose grenadier, Coryphaenoides rupestris , were examined from the Skagerrak (exposed site) and from a locality outside the Faroe Islands (reference site). The cytoplasm of hepatocytes offish from both areas was dominated by vacuoles, i.e. storage of either lipid or glycogen. Melanomacrophage centres (MMC) were also found. The major histological difference between the two groups was the increase of MMC in fish from the Skagerrak site. This finding was statistically confirmed by morphometry. Analysis of EROD showed that the enzyme was induced in the liver of fish from the Skagerrak. Immunohistochemical localization of cytochrome P450 1A in liver indicated positive staining of both vascular endothelial cells and hepatocytes. The induction of these parameters in fish from the Skagerrak cannot be excluded as being an effect of a large-scale contamination of anthropogenic compounds in the area.
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effects of contaminants in roundnose grenadier Coryphaenoides rupestris and norway lobster nephrops norvegicus and contaminant levels in mussels mytilus edulis in the skagerrak and kattegat compared to the faroe islands
Journal of Sea Research, 1996Co-Authors: Lars Forlin, Eric Lindesjoo, Susanne P Baden, Susanne P Eriksson, Ake Granmo, Kerstin Magnusson, Rolf Ekelund, Anders Esselin, Joachim SturveAbstract:Abstract In situ biomonitoring of roundnose grenadier (Coryphaenoides rupestris) and Norway lobster (Nephrops norvegicus) and measurements of pollutants levels in caged common mussel (Mytilus edulis) were used to assess the environmental impact of contaminants in the Skagerrak and Kattegat and near the Faroe Islands. By comparing the responses of a suite of established and potential biomarkers, i.e. different liver detoxification enzymes and histopathology in roundnose grenadier in the Skagerrak, and at a reference site off the Faroe Islands, evidence was found that the deeper parts of the Skagerrak are affected by anthropogenic contaminants. Levels of polycyclic aromatic hydrocarbons (PAH) and organochlorines in caged mussels were compared with those sediment. The Skagerrak/Kattegat area was found to be more polluted than the Faroe area and the caged mussels bioaccumulated the PAHs to a higher degree than the organochlorines. This seems to indicate that the PAHs in the sediments are more bioavailable than the organochlorines and that the induced ethoxyresorufin-O-deethylase activities observed in Skagerrak roundnouse grenadier may be due to PAH exposure. The Norway lobster accumulated manganese to various degrees in the different parts of the organism. The excretion rate of manganese could not cope with the uptake rate at higher exposure concentrations. Enhanced manganese concentrations, especially in the gills and haemolymph, seem to be a useful indication of increased manganese levels in the water. Hypoxia makes a sediment-bound manganese much more bioavailable. The elevated levels of manganese in Norway lobster from the Skagerrak/Kattegat area therefore seem to reflect the increasing occurrence of hypoxic conditions in the Kattegat and coastal areas of the Skagerrak. Accumulated manganese in Norway lobster may thus serve as a biomarker of hypoxia. In conclusion, the use of a suite of different biomarkers in ecotoxicological and ecophysiological studies and analyses of contaminant levels have provided evidence of a large-scale environmental impact of pollutants and nutrients in the Skagerrak/Kattegat area. This should lead to further efforts to decrease transport into and deposition of waste compounds in the sea.
