WET-tests with sea bass (Dicentrarchus labrax) eggs with discharge water of the MICROFADE II system : addendum to IMARES report C079/16
Kaag, N.H.B.G. - \ 2016
IJmuiden : Wageningen Marine Research (Wageningen Marine Research rapport C088/16) - 14
dicentrarchus - fish eggs - saline water - fresh water - embryonic development - dicentrarchus - visseneieren - zout water - zoet water - embryonale ontwikkeling
Atlantic mackerel and Horse mackerel egg survey 2016: Dutch participation on board FV Atlantic Lady: May
Damme, C.J.G. van - \ 2016
IMARES (Report / IMARES C077/16) - 30
mackerels - trachurus trachurus - scomber scombrus - fish eggs - censuses - surveys - makrelen - trachurus trachurus - scomber scombrus - visseneieren - tellingen - karteringen
From 10 till 25 May 2016 IMARES carried out a mackerel and horse mackerel egg survey on board the FV Atlantic Lady. This survey was part of the international mackerel and horse mackerel egg survey coordinated by ICES. The Redersvereniging voor de Zeevisserij (RVZ) asked IMARES to carry out this survey. Numbers of mackerel eggs in the samples were low, lower compared to previous surveys. Most mackerel eggs were found along the 200m depth contour of the continental slope. Most of the adult mackerel had running or newly developing (in between batches) gonads. Few mackerel had gonads which were spent. Numbers of horse mackerel eggs were extremely low. A few horse mackerel eggs were found along the 200m depth contour on the most southern transects. Adult horse mackerel caught had running or newly developing gonads.
The fish egg microbiome : diversity and activity against the oomycete pathogen Saprolegnia
Liu, Y. - \ 2016
Wageningen University. Promotor(en): Francine Govers; Jos Raaijmakers, co-promotor(en): Irene de Bruijn. - Wageningen : Wageningen University - ISBN 9789462577671 - 169
salmon - fish eggs - marine microorganisms - microbial diversity - bioinformatics - genomics - saprolegnia - oomycota - fish diseases - suppression - fungal antagonists - zalm - visseneieren - mariene micro-organismen - microbiële diversiteit - bio-informatica - genomica - saprolegnia - oömycota - visziekten - onderdrukking - schimmelantagonisten
Prof. dr. F. Govers (promotor); Prof. dr. J.M. Raaijmakers (promotor); Dr. I. de Bruijn (co-promotor); Wageningen University, 13 June 2016, 170 pp.
The fish egg microbiome: diversity and activity against the oomycete pathogen Saprolegnia
Emerging oomycete pathogens increasingly threaten biodiversity and food security. This thesis describes the study of the microbiome of Atlantic salmon (Salmo salar L.) eggs and analyses of the effects of infections by the oomycete pathogen Saprolegnia on the microbial architecture. A low incidence of Saprolegniosis was correlated with a relatively high abundance and richness of specific commensal Actinobacteria. Among the bacterial community, the isolates Frondihabitans sp. 762G35 (Microbacteriaceae) and Pseudomonas sp. H6 significantly inhibited hyphal attachment of Saprolegnia diclina to live salmon eggs. Chemical profiling showed that these two isolates produce furancarboxylic acid-derived metabolites and a lipopeptide viscosin-like biosurfactant, respectively, which inhibited hyphal growth of S. diclina in vitro. Among the fungal community, the fungal isolates obtained from salmon eggs were closely related to Microdochium lycopodinum/Microdochium phragmitis and Trichoderma viride. Both a quantitative and qualitative difference in the Trichoderma population between Saprolegnia-infected and healthy salmon eggs was observed, which suggested that mycoparasitic Trichoderma species could play a role in Saprolegnia suppression in aquaculture. This research provides a scientific framework for studying the diversity and dynamics of microbial communities to mitigate emerging diseases. The Frondihabitans, Pseudomonas and Trichoderma isolates, and/or their bioactive metabolites, are proposed as effective candidates to control Saprolegniosis.
North Sea mackerel egg survey in May and June 2015
Damme, C.J.G. van - \ 2015
IJmuiden : IMARES (Report / Centrum voor Visserijonderzoek (CVO) 15.010) - 39
makrelen - visseneieren - kuitschieten - distributie - visbestand - noordzee - mackerels - fish eggs - spawning - distribution - fishery resources - north sea
After technical problems prevented the North Sea mackerel egg survey to be carried out in 2014, a successful survey was carried out in May-June 2015. The survey was carried out on board ‘RV Tridens’. The expected mackerel spawning area was covered in each of four periods in east-west transects, separated by 1 degree. In total 260 valid plankton hauls with a Gulf VII plankton sampler were performed, as well as 3 fish hauls and 4 sets of flowmeter calibrations hauls.
Feasibility study combining North Sea and Atlantic mackerel egg surveys
Damme, C.J.G. van; Thorsen, A. ; Brunel, T.P.A. ; Nash, R.D.M. - \ 2015
IJmuiden : IMARES (Report / IMARES Wageningen UR C124/15) - 23
scomber scombrus - makrelen - kuitschieten - visseneieren - visserij - noordzee - scomber scombrus - mackerels - spawning - fish eggs - fisheries - north sea
Mackerel Scomber scombrus is a widely distributed species with a high economic and ecological importance. The North East Atlantic mackerel comprises three different spawning components. The Spawning Stock Biomass (SSB) index from the mackerel egg surveys is used as a fisheries independent tuning index for the mackerel assessment. The North Sea mackerel triennial egg survey is carried out in the year after the egg survey of the Western and Southern spawning components. Due to this time lag currently the North Sea egg survey SSB index is not used directly in the mackerel assessment. However, the egg survey is the only available information on the mackerel spawning component in the North Sea. Can the North Sea mackerel egg survey index be incorporated in the mackerel assessment and what is the impact of the incorporation of this index? Could the North Sea and Atlantic egg surveys be carried out in the same sampling year?
Atlantic mackerel and horse mackerel egg survey 2013: Dutch participation
Damme, C.J.G. van - \ 2014
IJmuiden : IMARES (Report / IMARES Wageningen UR C0100/14) - 35
trachurus trachurus - makrelen - visseneieren - kuitschieten - bemonsteren - eierproductie - tellingen - visbestand - trachurus trachurus - mackerels - fish eggs - spawning - sampling - egg production - censuses - fishery resources
In 2013 the international Atlantic mackerel and horse mackerel egg survey was performed. This year the entire spawning area was sampled by 10 institutes from 9 different countries: Faeröer Islands, Germany, Iceland, Ireland, Norway, Portugal, Scotland, Spain and The Netherlands. Sampling started in February along the Portuguese coast and continued until July west of Scotland. The Dutch institute IMARES participated in the survey in May and June on board ‘RV Tridens’. IMARES covered the area of the Northern Bay of Biscay and Southern Celtic Sea once each month.
Bacterie beschermt zalmeitje tegen schimmel (interview met I. de Bruijn en Y. Liu)
Ramaker, R. ; Bruijn, I. de; Liu, Y. - \ 2014
Resource: weekblad voor Wageningen UR 8 (2014)16. - ISSN 1874-3625 - p. 9 - 9.
aquacultuur - zalmteelt - gastheer parasiet relaties - saprolegnia - oömyceten - visseneieren - actinobacteria - wetenschappelijk onderzoek - aquaculture - salmon culture - host parasite relationships - saprolegnia - oomycetes - fish eggs - actinobacteria - scientific research
Een bacterie die leeft op zalmeitjes, beschermt zijn gastheer tegen een schadelijke schimmelsoort. Dit ontdekten ecologen van Wageningen Universiteit en het NIOO. De vinding moet ervoor zorgen dat minder eitjes sterven tijdens de zalmkweek.
Eggsposed : impact of maternally transferred POPs on fish early life development
Foekema, E.M. - \ 2013
Wageningen University. Promotor(en): Tinka Murk. - S.l. : s.n. - ISBN 9789461736659 - 208
vissen - persistente organische verontreinigende stoffen - maternale effecten - visseneieren - larven - biologische ontwikkeling - overleving - marien milieu - verontreiniging - ecotoxicologie - fishes - persistent organic pollutants - maternal effects - fish eggs - larvae - biological development - survival - marine environment - pollution - ecotoxicology
Persistent organic pollutants (POP), with well-known representatives as polychlorinated biphenyls (PCBs), dioxins, and brominated flame retardants as polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecanes (HBCD), are still globally present in the marine environment, This despite the substantial reduction of application and emission that was achieved during the last decades. Apart from their persistency these compounds share low water solubility and a high lipophilicity which make that the highest concentrations in the aquatic environment are found in the organic matrix of sediments and in biota. Dissolved water concentrations are low. Hence, intake of contaminated food items forms the major source for POPs exposure of aquatic organisms, and through biomagnification the highest concentrations can be found in the tissue of top predators. POPs have the potency to cause a variety of toxic effects, among which endocrine disruption and teratogenic effects that especially apply to early life stages. As the early life stages of most fish species develop suspended in the water column, exposure to POPs may be considered relatively low, at least until the larvae start feeding after yolk absorption. However, POPs accumulated in the tissue of the mother are transferred to the eggs. The research presented in this thesis aims at the determination of the impact of such maternally transferred POPs on development and survival of fish early life stages, in order to assess if this exposure route can significantly impact the development of a fish population at current environmental concentrations, especially in combination with high fishing pressure.
For this purpose a bioassay was developed with the common sole (Solea solea). The advantages for this research of this new bioassay above standard fish early life stage (ELS) tests are that sole is a native West European species that as all flatfishes undergoes an obvious metamorphosis. The test set-up includes this metamorphosis that is thyroid hormone mediated and therefore expected to be easily disrupted by POPs, based on research with amphibians. The prolonged Early Life Stage test (p-ELS) with sole is presented in chapter 2. Early life stages were exposed to a concentration series of the dioxin-like PCB 126 (3,3',4,4',5-pentachlorobiphenyl) in seawater until 4, 8,10 and 15 days post fertilisation (dpf). Subsequently the development of the larvae was registered under further unexposed conditions. The LC50s at the start of the free-feeding stage (12 dpf) ranged between 39 and 83 ng PCB 126/l depending on exposure duration. After the fish had completed the metamorphosis, the LC50 values ranged between 1.7 and 3.7 ng PCB 126/l for the groups exposed for 4, 8 and 10 dpf respectively. Thus exposure for only 4 days, covering only the egg stage, was sufficient to cause adverse effects during a critical developmental phase two weeks later. This study indicates that ELS fish tests that are terminated shortly after the fish becomes free-feeding underestimate the toxic potential of compounds with low acute toxicity such as PCBs. The internal dosages of these larvae at the end of the exposure, determined by means of an in-vitro gene reporter assays as dioxin-equivalent values (TEQ), revealed an internal lethal concentration, ILC50 of 1 ng TEQ/g lipid, which is within the same order of magnitude as TEQ levels found in fish from highly polluted areas. This suggests that larval survival of fish populations at contaminated sites can be affected by persistent compounds that are accumulated by the female fish and passed on to the eggs.
Based on these first results the p-ELS test procedure was improved to reach a better control performance. The exposure period was terminated when all larvae had hatched (6 dpf), this in order to mimic exposure through maternal transfer as good as possible without exposing parent fish or manipulation the eggs. In a second test (Chapter 3) the eggs were exposed to a concentration series of methyltriclosan (MTCS), a metabolite of triclosan (TCS) that is commonly used as bactericide in a wide variety of human care products. MTCS and TCS are discharged with waste water, bioaccumulate in fish tissue, and are known to have the potency to disrupt the thyroid hormone system. Mortality occurred in the higher treatment levels until 20 dpf. Indications for thyroid hormone disruption were not observed; all surviving larvae completed metamorphoses without problems. Internal effect concentrations, reached in larvae at the end of the exposure (6 dpf), were 5.8 mg/g lipid weight (lw) and 2.1 mg/g lw for ILC50 and ILC10 respectively. These internal effect concentrations are at least 200 times higher than concentrations that due to maternally transfer can be expected in the eggs of highly exposed fish in a field situation. Our results thus do not indicate a high risk from maternally transferred MTCS for fish at the current field concentrations.
In order to get more insight in the fate of the POPs in the larvae, in Chapter 4 the existing bioaccumulation model OMEGA was adjusted for sole early life stages and validated with experimental data with PCBs. This study revealed, that tissue concentrations of compounds with log Kow>6, peak in the tissues of developing sole at the end of the yolk-sac stage, when lipid reserves are depleted. As a result, just before the larvae become free feeding, the peak tissue concentrations of the pollutants in the larvae exceed that of the adult fish. This also explains at least partly, the delayed effects that were observed in Chapter 2 (and 5).
Chapter 5 assesses the likelihood that early life development of fish from contaminated areas is affected by maternally transferred POPs. Following the p-ELS test protocol, effects on sole larvae were determined for the dioxin-like PCB 126, the technical PCB-mixture Arochlor 1254, PBDEs and HBCDs, for an artificial mixture of PCBs and PBDEs, and for ‘field mixtures’ extracted from sole collected from the North Sea and in the contaminated Western Scheldt estuary. As was earlier observed with PCB126 and MTCS, exposure to PCBs, PBDEs and the artificial and field mixtures caused mortality that started to occur shortly after the larvae became free-feeding and continued to increase until the onset of metamorphoses. The effects induced by the field mixtures correlated well with the ∑PCB concentrations in the tissue of the exposed larvae. No indications were found for synergistic effects or for substantial contribution of other (unknown) substances in the field mixtures. HBCD did not induce toxic effects. POP levels in sole from Western Scheldt estuary are about 20 times lower than the ILC50, the larval tissue concentration that produced 50% early life stage mortality. Levels in North Sea sole are an order of a magnitude lower.
Chapter 6 describes a risk assessment for toxicant induced larval survival for European eel (Anguilla anguilla). Eels are considered sensitive for the effect of POPs that can accumulate to high levels in their lipid rich tissue. During spawning migration without feeding high lipophilic dioxin-like POPs in the eel’s tissue were estimated to increase 1.33 or 2 fold, due to weight loss. As no toxicity data are available for eel larvae, the critical egg concentrations for larval survival was estimated from a sensitivity distribution based on literature data of other species. It was assumed that eel larvae belong to the 5% or 1% most sensitive teleost fish species. Given concentrations of dioxin-like pollutants as reported for European eel, and following the worst case scenarios with respect to sensitivity of the larvae and bio amplification during migration, it can be expected that larvae of eel from highly contaminated locations in The Netherlands and Belgium will experience more than 50% mortality due to maternally transferred dioxin-like toxicants.
Chapter 7 explores the potential impact of (toxicant induced) early life stage mortality on the population development of sole by application of a simple age structured matrix model. The model is used to explore the population response to a combination of (toxicant induced) larval mortality and fishing-related mortality of mature fish. The results indicate that the impact of larval mortality that occurs before metamorphosis is very low, even in population subject to high fishing pressure. This is the result of the combination of a high fecundity and the fact that the larval mortality occurs before the moment when the number of recruits is limited by the carrying capacity of the nursery areas. When colonising the nursery areas the, until than pelagic sole larvae metamorphose into flatfishes with a benthic life style. The individuals hence concentrate from the three dimensional pelagic environment to a two dimensional benthic environment, which caused density dependent mortality. This concentration of early life stages is typical for flatfish. Mortality that occurs after the nursery areas are populated will have a more pronounced impact on population development. The results further imply that population development of pelagic fish species that do not concentrate in nursery areas, and species with low fecundity is more vulnerable for disturbance through mortality of early life stages.
Chapter 8 synthesises and discusses the outcome of the research. It is stressed that short term fish tests, often covering only the embryonic development, will underestimate the real risk of lipophilic substances. Toxicity of these substances will peak after yolk sac absorption when these tests have already been ended. When the characteristics of the test substance are known this risk is predictable with for instance the ELS-OMEGA model. However, especially when mixtures of unknown composition (effluents, sediment extracts) are being tested one must realise that the contribution of lipophilic substances may be underestimated in test that are terminated before, or too soon after the fish larvae are free feeding.
The absence of effects on metamorphosis in our P-ELS test is explained by the prediction of the ELS-OMEGA model that the POPs concentrations in the larvae, had reached too low concentrations at the moment of metamorphoses to disrupt the thyroid hormone system. This was due to passive excretion (for substances with log Kow<6) and growth dilution.
It must be realised that the experimental set-up that was followed to mimic the effects of maternally transferred POPs does not include potential effects of maternally transferred metabolites of these POPs that can be formed by the parent fish and that are often more toxic than the mother compounds. Also effects of the mother’s condition on the quality of the eggs and epigenetic effects were not included. This implies that the results of the tests as performed in some cases might underestimate the actual effects of these substances.
The species most vulnerable to the effects of maternally transferred POPs share a high exposure, low fecundity and the absence of density dependent mortality of early life stages. According to these criteria sharks and especially the Greenland shark (Somniosus microcephalus) that is highly exposed to POPs can be considered as highly vulnerable. It is therefore recommended to investigate the actual sensitivity of this species, in order to get more insight in the potential vulnerability of the populations.
Dietary overlap between the potential competitors herring, sprat and anchovy in the North Sea
Raab, K.E. ; Nagelkerke, L.A.J. ; Boeree, C. ; Rijnsdorp, A.D. ; Temming, A. ; Dickey-Collas, M. - \ 2012
Marine Ecology Progress Series 470 (2012). - ISSN 0171-8630 - p. 101 - 111.
engraulis-encrasicolus l. - central baltic sea - clupea-harengus - feeding-behavior - intraguild predation - trophic interactions - population-dynamics - mediterranean sea - fish eggs - irish sea
European anchovy Engraulis encrasicolus increased its abundance and distribution in the North Sea during the mid-1990s and may consume similar zooplankton to and/or compete with other occupants of the North Sea like herring Clupea harengus and sprat Sprattus sprattus. The diets of adult anchovy, sprat and juvenile herring of comparable sizes, sampled close in time and space, were compared to understand how the 3 species prey on zooplankton and establish whether their diets overlap or not. Anchovy was found to be more generalist, consuming a higher diversity of prey items. Herring was more specialized, with low diversity of food items. Sprat was intermediate between anchovy and herring. The dietary overlap between anchovy and sprat was highest, followed by herring and sprat before anchovy and herring. The mean weight of stomach contents did not differ between species. We conclude that of the 3 species, anchovy is likely to be the least affected by changing plankton communities.
North Sea mackerel egg survey: dutch participation may and June 2011
Damme, C.J.G. van - \ 2012
IJmuiden : IMARES (Report / IMARES Wageningen UR no. C026/12) - 32
makrelen - distributie - monitoring - kuitschieten - visseneieren - noordzee - mackerels - distribution - monitoring - spawning - fish eggs - north sea
Every three years an international North Sea survey is carried out by two European institutes, Institute for Marine Research (IMR) from Norway and Institute for Marine Resources and Ecosystem Studies (IMARES) from the Netherlands, to monitor the spatial and seasonal distribution of North Sea mackerel. In 2011 the North Sea mackerel egg survey was performed. The entire spawning area was sampled by IMR, Norway and IMARES, The Netherlands. The whole spawning area was sampled three times. IMARES covered the complete sampling area in the first period, in the second period IMR covered the northern part and IMARES the southern part of the spawning area. The third period the whole spawning area was covered by IMR. In total 190 ichthyoplankton samples were taken with a Gulf VII plankton torpedo with a Seabird CTD mounted on top. Additionally, adult fish samples for the estimation of fecundity and atresia were taken using a pelagic trawl. The survey was successful and IMARES managed to sample all but 3 of the planned stations. Numbers of mackerel eggs found in the samples were comparable to 2008. Total mackerel egg production in 2011 was 116*1012 and Spawning Stock Biomass (SSB) was estimated at 165*103 tons, which is slightly higher compared to 2008. Highest egg production was found in the first sampling week and it is possible that the beginning of mackerel spawning is missed.
Shorlist Masterplan Wind. Evaluation of the sampling grid of the year-round ichthyoplankton survey
Bolle, L.J. ; Beek, J.K.L. van - \ 2011
IJmuiden : IMARES (Report / IMARES Wageningen UR C026/11) - 34
zoöplankton - kuitschieten - bemonsteren - monitoring - methodologie - visseneieren - larven - vissen - het kanaal (english channel) - noordzee - zooplankton - spawning - sampling - monitoring - methodology - fish eggs - larvae - fishes - english channel - north sea
Within the research programme 'Shortlist Masterplan Wind' a year-round ichthyoplankton survey is being carried out. The sampling area is based on known spawning concentrations and prevailing currents.
Shortlist Master plan Wind Monitoring fish eggs and larvae in the southern North Sea: final report Part A en B
Damme, C.J.G. van; Hoek, R. ; Beare, D.J. ; Bolle, L.J. ; Bakker, C. ; Barneveld, E. van; Lohman, M. ; Os-Koomen, E. van; Nijssen, P.J.M. ; Pennock, I. ; Tribuhl, S.V. - \ 2011
IJmuiden : IMARES (Report / IMARES Wageningen UR C098/11) - 433
visseneieren - larven - distributie - monitoring - noordzee - fish eggs - larvae - distribution - monitoring - north sea
This report presents the results of twelve monthly ichthyoplankton surveys carried out from April 2010 until March 2011 in the southern North Sea. The aim of this study was to collect data on the temporal and spatial distribution of fish eggs and larvae on the Dutch Continental Shelf (NCP). However, since fish eggs and larvae are transported with the currents onto the NCP a larger area covering the majority of the southern North Sea was sampled during the surveys. Despite technical problems or bad weather conditions preventing the sampling of all planned stations during each survey, the coverage was good and the general trends in ichthyoplankton abundance became apparent. Fish eggs were found in all months but species and numbers varied per month across the southern North Sea. The highest abundance of fish eggs was found from January until May with fish eggs being found at all stations from April until July. Very few eggs were found between August and November. From December onwards abundance of eggs increased again. The pattern was the same on the NCP. In total 35 different species of fish eggs were found. Fish larvae were found in all months but species and numbers varied in a similar pattern to the fish eggs, except the highest abundance of larvae was found in December and January in the English Channel (mostly herring). Numbers of larvae in the southern North Sea increased from April until June and afterwards then gradually declined until November. After this the abundances increased again. Larvae were found at almost all stations from May until September. In October and November larvae were found at half of all the stations both in the whole sampling area and on the NCP. The patterns was the same on the NCP. In total 74 different species of fish larvae were found. Based on the results of a modelling study, a mitigating measure was issued by the Dutch authorities forbidding pile driving of offshore wind farm foundations from January to June, in order to ensure that negative effects on prey availability for birds and marine mammals within Natura 2000 areas are minimised. The results of the year-round monthly surveys show that from April until September fish larvae were found throughout the survey area, including the NCP, in varying numbers and varying species. Still in October and November larvae were found at half of the stations although at lower abundances. Even in December larvae were still found at a quarter of the stations on the NCP. Whilst the abundance of larvae was low in October and November, there are a few species with larvae present that are absent at other times of the year. These results on ichthyoplankton abundance and results of the experimental study on the effect of pile driving on fish larvae need to be combined. Ideally they should also be assessed with subsequent studies of ichthyoplankton transport and impact on the Natura 2000 sites. This unique study is the first to comprehensively sample and analyse the ichthyoplankton with monthly resolution in the southern North Sea. These data on spatial and temporal distribution of fish eggs and larvae can be used in modelling studies to assess the effects of human activities in the southern North Sea, on different fish stocks.
Shortlist Masterplan Wind. Fish eggs and larvae in the southern North Sea: May 2010 cruise
Bolle, L.J. ; Hoek, R. ; Bakker, C. ; Os-Koomen, E. van - \ 2010
IJmuiden : IMARES (Report / IMARES Wageningen UR C063/10) - 16
visseneieren - larven - monitoring - distributie - noordzee - fish eggs - larvae - monitoring - distribution - north sea
Atlantic mackerel and horse mackerel egg survey: Dutch participation May and June 2010
Damme, C.J.G. van; Bakker, C. - \ 2010
IJmuiden : IMARES (Report / IMARES Wageningen UR no. C078/10) - 33
visserij - visserijbeheer - trachurus trachurus - monitoring - visseneieren - kuitschieten - periode van kuitschieten - voortplantingsgedrag - fisheries - fishery management - trachurus trachurus - monitoring - fish eggs - spawning - spawning season - reproductive behaviour
Every three years an international Atlantic survey is carried out by different European institutes to monitor the spatial and seasonal distribution of Atlantic mackerel and horse mackerel. During this survey mackerel and horse mackerel eggs are sampled using a plankton torpedo or bongo nets. The survey covers the whole spawning area and season. It starts along the Portuguese coast in February and continues until July when the waters west of Scotland are sampled. The mackerel and horse mackerel egg survey is coordinated by the ICES working group for mackerel and horse mackerel egg surveys (WGMEGS). England and France started the egg survey in the western area in 1977. The Netherlands participates since 1983. Nowadays participating countries and sampling area have expanded. In 2010 the following countries participated in this survey: Faeröer Islands, Germany, Iceland, Ireland, Norway, Portugal, Scotland, Spain and The Netherlands.