Eutrigla Research Articles

Feeding of grey gurnard Eutrigla gurnardus (Triglidae) in the area of the Rockall Seamount

Specific features of feeding of grey gurnard Eutrigla gurnardus depending on vertical distribution and habitat conditions in the area of the Rockall Seamount in 2000 were considered. The intensity of feeding of grey gurnard from April to September decreased by several times. The main food of this species in spring are euphausiids and that in autumn are fish. Males feed slightly more intensively than females. The intensity of feeding, distribution, and behavior of grey gurnard in different seasons and at different depths near bottom and in the pelagial noticeably differ and depend on the composition of distribution and numbers of dominant food items (euphausiids, sand eel Ammodytes marinus, fish juveniles).

Anisakis simplex (s.l.) in Grey gurnard (Eutrigla gurnardus) from the North Sea: Food safety considerations in relation to fishing ground and distribution in the flesh

Previous studies have shown that Grey gurnard from the North Sea is comparatively heavily infected with the larvae of the parasitic and potentially consumer hazardous nematode Anisakis simplex (s.l.). Especially the high abundance of Anisakis larvae in the fish flesh is of concern regarding the possible intensified utilisation of Grey Gurnard as a food resource. To gain better knowledge of the nematode burden with emphasis on abundance and distribution in the fish flesh, various Grey gurnards from 6 localities across the North Sea, each representing either western, northern or eastern fishing grounds, were examined for anisakid nematodes during summer of 2010 and 2012. The overall prevalence of A. simplex (s.l.) larvae in the gurnards from all localities (n = 188) was nearly total, i.e. only a single fish from the northernmost locality (Viking Bank) was apparently not infected. GLM-analyses revealed that catching locality had by far the strongest effect on larval infection probability, both in total (flesh + viscera) and in the fish flesh, while body size (weight) was a weak but still significant predictor of overall A. simplex (s.l.) abundance, but not in the flesh. Thus, the overall larval abundance in the gurnards from the two western localities off the east-coast of British mainland was significantly higher compared to the other catching localities. In the former localities, the overall mean abundance of A. simplex (s.l.) larvae was 35.0 ± 23.9 and 92.2 ± 87.4, and ranged from 14 to 114 and 9 to 397, respectively. It was further shown that 93.8% of the larvae infecting the fish flesh were situated in the belly flaps, i.e. the ventral portion of each flesh side or fillet, independent of catching locality and fish size. However, trimming of the fillets by removing the belly flaps may reduce the abundance in the fillets to, on an average, 0.3 larvae.

An early footprint of fisheries: Changes for a demersal fish assemblage in the German Bight from 1902–1932 to 1991–2009

Groundfish survey data from the German Bight from 1902–08, 1919–23, and 1930–1932 and ICES International Bottom Trawl Survey (IBTS) quarter 3 data from 1991 to 2009 were analysed with respect to species frequencies, maximum length, trends in catch-per-unit-effort, species richness parameters (SNR) and presence of large fish (Φ40), the latter defined as average presence of species per haul with specimens larger than 40cm given. Four different periods are distinguished: (a) before 1914 with medium commercial CPUE and low landings, Φ40≈2, high abundance in elasmobranchs and SNR conditions indicating highly diverse assemblages, (b) conditions immediately after 1918 with higher commercial CPUE, recovering landings, Φ40 at >4 in 1919, and SNR conditions indicating highly diverse assemblages, (c) conditions from 1920 to the early 1930's with decreasing commercial CPUE, increased landings, decreasing Φ40, SNR conditions similar to later years indicating less diverse assemblages, and a decrease in elasmobranchs. In the IBTS series (d), Φ40 remains low indicating an increased rarity of large specimens, and SNR characteristics are similar to the third period. Dab, whiting and grey gurnard have increased considerably in the IBTS series as compared to the historic data. Φ40 is suggested an alternative indicator reflecting community functional diversity when weight based indicators cannot be applied.

Metals and other elements in tissues of wild fish from fish farms and comparison with farmed species in sites with oxic and anoxic sediments

Farmed fish and wild fish aggregating in the vicinity of four Mediterranean fish farms with different environmental conditions were sampled. Levels of metals (including As and Se) were measured in the muscle, liver, gills, bone and intestine. The wild fish from sites with anoxic substrata accumulate metals (including As and Se) from the ambient habitat in their gills whereas those from sites with oxic substrata concentrate these elements through their diet in their intestine. Tissues of wild fish aggregating around farm cages accumulate a greater number of these elements and with higher concentrations than farmed fish. Habitat, diet, ecological needs, fat content of fish, and protein expression may play an important role in these element differences between fish species. Fe in flathead grey mullet, As in surmullet, rainbow wrasse, grey gurnard and picarel and Hg in bogue may pose a risk for human health. Farmed and wild fish are good sources of P, K, Cr and Se while flathead grey mullet, picarel and comber are excellent sources of Ca and Se.

Correlations between benthic habitats and demersal fish assemblages — A case study on the Dogger Bank (North Sea)

The interdependence between groundfish assemblages and habitat properties was investigated on the Dogger Bank in the North Sea. Abiotic habitat parameters considered included topography, hydrographic conditions, sediment composition, and the biotic habitat variable the prevailing benthic invertebrates. Distinct epi- and infauna communities occurred at different locations on the Dogger Bank. Fish assemblages were clearly linked to both the biotic and abiotic habitat characteristics.Overall, fish and benthic communities revealed similar spatial distribution, represented in the respective clusters of characteristic and abundant species. Distribution patterns corresponded with the prevailing abiotic conditions such as depth and sediment composition, which appear to relate to autecological preferences of individual species.The apparently most generalist species, grey gurnard (Eutrigla gurnardus) and dab (Limanda limanda) occurred at all stations and dominated in terms of biomass in most cases. The absolute numbers of grey gurnards were related to the abundance of suitable prey, invertebrate and fish species, which stomach analyses revealed as part of the diet in an independent study during the same research cruise. Haddock (Melanogrammus aeglefinus) and whiting (Merlangius merlangus) were only abundant at deep stations along the flanks of the bank. The occurrence of lemon sole (Microstomus kitt), American plaice (Hippoglossoides platessoides) and cod (Gadus morhua) was also positively correlated with depth, whereas especially lesser weever (Echiichthys vipera), sandeel species and solenette (Buglossidium luteum) occurred predominantly at the shallower sites. At the same time, individual fish species such as solenette and lesser weever were associated with high densities of selected epi- or infauna species.

Spatial assessment of predator–prey relationships in the North Sea: the influence of abiotic habitat properties on the spatial overlap between 0‐group cod and grey gurnard

AbstractThe understanding of spatio‐temporal dynamics of marine ecosystems is crucial for ecosystem‐based fisheries management and climate change impact assessments. We quantified temporal changes in the distribution of 0‐group cod (Gadus morhua) and grey gurnard (Eutriglia gurnardus), a primary predator of 0‐group cod, with the help of regression kriging and assessed the temporal dynamics of the related spatial predator–prey overlap of these two species at different spatial scales. We analysed the robustness of relationships among abiotic habitat properties (temperature, salinity and depth) and abundance. Small cod was mainly found in low salinity areas of the Skagerrak but larger year classes were able to expand their distribution area towards the central and northern North Sea. In contrast, grey gurnard was mainly found in waters with salinities above 33 and temperatures above 14°C. This species has expanded its high density areas in the central North Sea northward over the last two decades. Recruitment success of cod was negatively correlated to a Moran's I cross‐correlation index, a proxy for the degree of spatial overlap between both species. Strong cod year classes overlapped less with grey gurnard at the large and medium spatial scale. In general, the relationships between abiotic habitat properties and abundance showed an increased inter‐annual variability, which was likely caused by underlying factors not taken into account in the distribution models. Thus assemblage modeling approaches combining the strength of different model types should be considered in the future to predict potential distribution patterns under climate change scenarios.

Morphological and molecular characterization of Ceratomyxa gurnardi sp. n. (Myxozoa: Ceratomyxidae) infecting the gallbladder of the grey gurnard Eutrigla gurnardus (L.) (Scorpaeniformes, Triglidae)

The myxosporean specimens were noted in grey gurnard Eutrigla gurnardus (L.) from the area near the Shetland Islands. The structure and dimensions of its vegetative stage differ from earlier descriptions. A sequence of small subunit ribosomal RNA gene obtained during the current study differs from other Ceratomyxa spp. available in GenBank. A phylogenetic position of parasite based on the 18S rDNA fragment was estimated. The proposed name for this myxosporean is Ceratomyxa gurnardi sp. n.

Body condition of predatory fishes linked to the availability of sandeels

Lesser sandeels Ammodytes marinus are eaten by a range of predatory fishes including commercially fished species, but are also exploited at large scale by industrial fisheries. Is availability of sandeels, as key prey source, linked to the body condition of predatory fishes? In the North Sea, the largest sandeel biomass is concentrated in the Dogger Bank region. Here we studied predator–sandeel interactions at two sites differing widely in sandeel abundance and local sandeel fishing effort. Surveys took place in 2004, 2005, and 2006, years when local sandeel densities observed at these sites were low, intermediate, and high, respectively. Five predator species––whiting, lesser weever, grey gurnard, plaice, and haddock––showed better body condition indices in either the years or study area (or both) characterised by higher local sandeel densities, when compared to sandeel-poorer conditions. Moreover, whiting, weever, and gurnard condition was better for those individuals actually observed to have eaten sandeels (based on stomach contents) than for those that had not. As body condition relates to growth, reproduction, and survival, predators in sandeel-rich conditions may be inferred to have a higher fitness. These links between sandeel availability, sandeel consumption, and predator condition hint that, if large-scale localised depletions of sandeels were to occur, negative indirect effects on predatory fish might become apparent, underlining the importance of considering the sandeel fishery in an ecosystem context.

Molecular detection of plaice remains in the stomachs of potential predators on a flatfish nursery ground

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 444:223-238 (2012) - DOI: https://doi.org/10.3354/meps09439 Molecular detection of plaice remains in the ­stomachs of potential predators on a flatfish ­nursery ground Aitor Albaina1,3,*, Martin I. Taylor1, Clive J. Fox2 1Molecular Ecology and Fisheries Genetics Laboratory, School of Biological Sciences, ECW Building, Bangor University, Bangor LL57 2UW, UK 2Scottish Association for Marine Science, Scottish Marine Institute, Oban, Argyll PA37 1QA, UK 3Present address: Laboratory of Genetics, Department of Genetics, Physical Anthropology & Animal Physiology, University of the Basque Country, Leioa 48940, Spain *Email: aitoralbaina@hotmail.com ABSTRACT: Stomach contents of potential predators from a flatfish nursery ground on the Scottish west coast were examined visually and probed using a TaqMan real-time PCR based assay designed to detect plaice Pleuronectes platessa DNA. Stomachs from 1137 brown shrimp Crangon crangon, along with a lesser number of shore crab Carcinus maenas, grey gurnard Eutrigla gurnardus and Gobiidae were analysed. Overall 45% of shrimp tested positive for plaice DNA, a proportion considerably higher than in stomachs containing visually identifiable flatfish remains. When scaled to the population level, predation by shrimp generated an estimated mortality of ~9% d–1, which compares with a decline in plaice abundance from mid-May to mid-June of ~4.4% d−1. The discrepancy between mortality estimates based on molecular and catch-curve analysis might be due to sampling being conducted at low water between dusk and dawn, which would concentrate predators and prey at times coincident with peaks of shrimp feeding. In addition, the sensitivity of the TaqMan assay could have led to some over-estimation because non-fatal interactions may also have been detected, e.g. shrimp are known to nibble the fins of flatfish, that might result in a positive TaqMan result but not necessarily in mortality for the fish. The percentage of shrimp testing positive for presence of plaice DNA in their stomachs was also related to plaice density in a positive, linear manner. For less abundant predators, stomachs of 6% of shore crabs, 40% of gurnards and 11% of large gobies also tested positive. KEY WORDS: Stomach contents · TaqMan real-time PCR assay · Pleuronectes platessa · Crangon crangon · Carcinus maenas · Predator−prey interactions · Nursery ground · Tralee Beach Full text in pdf format PreviousNextCite this article as: Albaina A, Taylor MI, Fox CJ (2012) Molecular detection of plaice remains in the ­stomachs of potential predators on a flatfish ­nursery ground. Mar Ecol Prog Ser 444:223-238. https://doi.org/10.3354/meps09439 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 444. Online publication date: January 10, 2012 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2012 Inter-Research.

Collarinema eutriglae n. sp. (Nematoda: Cystidicolidae), a new gastric parasite of the scorpaeniform fish Eutrigla gurnardus (Osteichthyes: Triglidae) in the North Sea, with remarks on the systematic status of Collarinema Sey, 1970

A new species of parasitic nematode, Collarinema eutriglae n. sp. (Cystidicolidae), is described from the stomach of the marine scorpaeniform fish Eutrigla gurnardus (Linnaeus), the grey gurnard (Triglidae), collected in the North Sea in the vicinity of the Shetland Islands (61°12'N, 00°30'E) during March, 2011. The new species, studied using both light and scanning electron microscopy, is characterised mainly by the structure of the mouth (small pseudolabia with terminal projections, submedian labia and well-developed sublabia not exceeding the labia externally), very small simple deirids, the length of the spicules (405-423 and 117-135 μm) and non-filamented eggs. Collarinema Sey, 1970 is considered a valid genus and an amended diagnosis is provided. Ascarophis collaris Petter, 1970 is transferred to Collarinema as C. collaris (Petter, 1970) n. comb.

A method of detecting patterns in mean lengths of samples of discarded fish, applied to the self-sampling programme of the Dutch bottom-trawl fishery

Abstract Uhlmann, S. S., Bierman, S. M., and van Helmond, A. T. M. 2011. A method of detecting patterns in mean lengths of samples of discarded fish, applied to the self-sampling programme of the Dutch bottom-trawl fishery. – ICES Journal of Marine Science, 68: 1712–1718. In 2009, a self-sampling programme was organized in the Netherlands, fishers sampling ca. 80 kg of discards from randomly selected bottom trawls in the North Sea. A statistical procedure is proposed to highlight samples, trips (with multiple samples), or vessels (which may have multiple trips within a year) where extreme mean lengths of discarded fish were observed. Randomization methods were used to test for evidence of non-randomness in patterns of highlighted discard samples, e.g. repeated observations of extreme mean lengths for consecutive discard samples across trips from the same vessel. European plaice (Pleuronectes platessa), common dab (Limanda limanda), grey gurnard (Eutrigla gurnardus), and whiting (Merlangius merlangus) were considered because these were the most abundant species in most of the discard samples. A linear mixed model was used to estimate random-sample effects on the estimated mean lengths by species. These random effects were incorporated into uni- and bivariate procedures to identify extreme samples that were summed for each vessel, and the probability of observing such numbers was estimated. Excluding these samples from the dataset had marginal effects on estimated size distributions of fish.

Resource partitioning amongst five coexisting species of gurnards (Scorpaeniforme: Triglidae): Role of trophic and habitat segregation

Feeding habits and habitat preferences of five related species ( Aspitrigla cuculus, Chelidonichthys lucerna, Chelidonichthys obscurus, Eutrigla gurnardus and Trigla lyra) (Scorpaeniformes: Triglidae) were studied in the southern Bay of Biscay. Specimens were collected during annual bottom trawl surveys carried out every autumn between 1990 and 2008 on soft bottoms of the Galician and Cantabrian Sea continental shelf between 30 and 800 m depth. All species were found to display a different depth distribution, despite co-occurring in many of the hauls (co-occurrence percentage ranged between 4.45 and 34.77%). Although depth was the main variable explaining the triglid distribution, latitude, temperature and sediment type were also important driving factors. Regarding feeding habits all triglids fed mainly on crustaceans, their main prey being Alpheus glaber, Polybius henslowii, Scyllarus arctus, Chlorotocus crassicornis and Pagurus prideaux. However, fish accounted for a considerable proportion of the diet with Gadiculus argenteus, Callionymus spp., and Cepola rubescens being the most common fish prey. Ontogenetic changes in diet were evident in all species but C. obscurus. Dietary overlap, determined by the Schoener Index greatly differed amongst species pairs ranging between 0.10 and 0.63. Considering all ontogenetic groups in the triglid assemblage, either diet or habitat segregation occurred between most of them. This fact suggests that any of these strategies on their own would suffice in order to avoid inter and intra specific competitions. Nevertheless, habitat partitioning occurred mainly at the inter-specific level and trophic segregation at the intra-specific level. A. cuculus and E. gurnardus showed the poorest resource partitioning in the assemblage, possibly as a consequence of the increasing abundance of the population of the first during the last decades.

Occurrence and distribution of anisakid nematodes in Grey gurnard (Eutrigla gurnardus L.) from the North Sea

Grey gurnard (Eutrigla gurnardus L.) is an abundant and widely distributed demersal fish in the North Sea. It is currently considered a sustainable stock, thus permitting future increased utilisation as a food resource. In order to address both consumer safety and aesthetical product quality, the occurrence and distribution of anisakid nematode larvae in Grey gurnard from two localities in the North Sea were investigated. Two anisakid species were recorded, i.e. Hysterothylacium aduncum in the viscera, and Anisakis simplex in both the viscera and flesh of the fish. Virtually all gurnards were infected with nematode larvae. However, H. aduncum was significantly less abundant than A. simplex in the fish from both localities. Only for the gurnards from the northernmost sampling locality there was a significantly positive correlation between host body weight and total A. simplex abundance. No such correlation was found for H. aduncum in either locality. Separate analyses of the Anisakis infection data in gurnards of marketable size (≥250g) and pooled for both localities, revealed 83% prevalence of A. simplex larvae in the fish flesh, ranging 1–16 in intensity. The relative larval distribution between the viscera and flesh was 89 and 11%, respectively. Moreover, a significantly positive correlation was found between A. simplex occurring in the viscera and the flesh of this particular host size group, i.e. the number of larvae in the flesh appeared to increase with increasing infection level in the viscera. In general, Grey gurnard from the North Sea can be considered as heavily infected with nematode larvae. Especially the comparatively high abundance of A. simplex larvae in the flesh is of concern regarding the possible intensified utilization of Grey gurnard as a food resource.

The role of prey composition for the condition of grey gurnard (Eutrigla gurnardus)

During a fisheries research cruise on the Dogger Bank in the central North Sea, we studied the role of diet for the condition of grey gurnard (Eutrigla gurnardus). Seventeen stations across the Dogger Bank were sampled with the GOV otter trawl in April/May 2006. Each fish sampled was categorised according to three feeding types: a predator specialised on fish, on invertebrates or having a mixed diet, depending on the percentage of fish and/or invertebrates in the stomach. These predator-prey categories were compared by means of three condition indices: Fulton’s condition factor, a hepatosomatic index (HSI) and a gonadosomatic index (GSI). Fulton’s condition factor provided evidence that a specialisation on fish prey increases the condition of grey gurnards in terms of the length-specific individual weight. In contrast, the HSI scored highest for predators feeding on a mixed diet. The GSI showed a tendency to be highest with a diet dominated by invertebrate prey, but differences between the three predator-prey categories were not significant. Based on the topography of the Dogger Bank, stations were allocated in shallow and deep regions. At shallow stations, the brown shrimp Crangon allmani and sandeels, combining basically the taxa Ammodytidae, Ammodytes juv. and Ammodytes marinus, were typically observed in stomach contents of gurnards whereas the amphipod Hyperia galba was predominantly found in gurnards sampled in deep regions.

PBB levels in fish from the Baltic and North seas and in selected food products from Poland

Recently, a significant amount of attention has been devoted to the determination of polybrominated biphenyls in food and the environment. In this study, PBB contamination of fish from the North and Baltic Seas, with a special focus on samples from Poland and France, was investigated. North Sea fish like salmon, herring, scarp, gilthead seabream and grey gurnard were collected from a French fish market. Baltic Sea fish like salmon, tunny, trout, herring, and freshwater fish such as carp were purchased from a Polish fish market. Cod livers in oil were also analyzed in this study. As additional food samples, butter, pork fat and beef fat were tested. Concentrations of PBBs in North Sea fish (except herring) were higher than in fish from the Baltic Sea. The highest total PBB concentration was measured in scarp muscle tissue (635 ± 107 pg g −1 wet weight), and the lowest was in carp samples (0.567 ± 0.245 pg g −1 wet weight). The PBB content in tunny oil samples was below the detection limits (0.45–1.05 pg g −1 fat). Our study also demonstrated that PBBs may bioaccumulate in the liver, where PBB concentrations were 2116 ± 351 pg g −1 wet weight and 841 ± 147 pg g −1 wet weight. In fish species from Poland, the most dominant congeners were tetrabromobiphenyls, followed by pentabromobiphenyls and hexabromobiphenyls. In some species of fish from the North Sea, the most dominant groups were hexabromobiphenyls and tetrabromobiphenyls. Although the relative abundances of structurally known and unknown isomers varied from species to species, all fish (except tunny) were contaminated with PBBs.

Length-weight relationships for the family Triglidae in the Adriatic Sea, northeastern Mediterranean

Summary Length–weight relationships were estimated for the first time for seven species of gurnards (Triglidae) based on data collected over the past 27 years in the Adriatic Sea (northeast Mediterranean). Results show significantly different relationships between juveniles and adults (females and males combined) for Aspitrigla cuculus, Eutrigla gurnardus, Chelidonichthys lucerna and Lepidotrigla cavillone. Isometric growth of juveniles is indicated for four species, allometric growth of adults for all species.

Linking spatial pattern of bottom fish assemblages with water masses in the North Sea

AbstractUnderstanding the links between large scale spatial structuring of fish assemblages and shaping factors is essential to develop comprehensive ecosystem‐based fisheries management. In this study, we investigated spatial patterns of bottom fish assemblages in the North Sea in relation to prevailing water masses in the region. We based our analysis on catch data from the German Small‐Scale Bottom Trawl Survey conducted between 1987 and 2005 and used both ordination techniques and Mantel tests. Spatial variability of bottom fish assemblages was larger than inter‐annual variability. Five significantly different bottom fish assemblages were associated with the following prevailing hydrographical regimes: i) the English Channel, ii) Continental Coastal, iii) central North Sea, iv) northern North Sea, and v) northern Atlantic water masses. Associations were generated by gradients in relative proportions of abundant species such as grey gurnard (Eutrigla gurnardus), dab (Limanda limanda), whiting (Merlangius merlangus), haddock (Melanogrammus aeglefinus) and Norway pout (Trisopterus esmarki). Taking into account large scale spatial structuring of catch data Mantel tests confirmed significant correlation between the fish assemblages and hydrographical variables. In summary, our results strongly support the hypotheses that hydrographical features such as water masses, fronts, and residual currents could shape bottom fish associations in the North Sea. Spatial demarcations of bottom fish assemblages indicated by this study can be used to support ecosystem‐based fisheries management strategies.

Ichthyoplankton of Rockall-Hutton seamounts

Species composition and quantitative distribution of ichthyoplankton in areas of the Rockall-Hutton seamounts are considered in a comparative aspect, and the spawning biomass of the blue whiting Micromesistius poutassou, the main commercial item of this region, is calculated. Maximal catches of eggs and larvae were recorded in spring 2006 and minimal catches were recorded in spring 2003. The highest number of species was recorded in March–April 2006 and the lowest number was recorded in March–April 2003. In the seasons under consideration, M. poutassou had the most mass of the commercial fish in the plankton; haddock Melanogrammus aeglefinus and gurnard Eutrigla gurnardus were less numerous. Of the noncommercial species, the larvae of myctophids (fam. Myctophidae) and of other mesopelagic fish occurred more frequently in the ichthyoplankton. The species and quantitative composition of ichthyoplankton was considerably more numerous at the Rockall Seamount than at the Hutton Seamount, which is explained by specific oceanographic features of the region and the more southern location of this seamount. According to the data of the ichthyoplanktonic method, the spawning biomass of M. poutassou exhibited a tendency for an increase in the period of 2002 to 2006.

Occurrence of acanthocephalans in Teleost fishes of Gemlik Bay, Sea of Marmara, Turkey

Abstract The fish acanthocephalan fauna of Turkish waters is poorly known. In this study 8 fish species (Merluccius merluccius, Trachurus trachurus, Uranoscopus scaber, Gobius niger, G. cobitis, Scorpaena scrofa, Eutrigla gurnardus, Solea vulgaris) were collected from Gemlik Bay and examined for their acanthocephalan fauna. Four species not previously recorded in fish of Turkish waters were found: Solearhynchus soleae (Echinorhynchidae), Acanthhocephaloides propinquus, Paracanthocephaloides kostylewi (Arhythmacanthidae), and Longicollum pagrosomi (Pomphorhynchidae). The most common species was A. propinquus, a parasite that infects mostly gobiids (G. niger, G. cobitis). Longicollum pagrosomi was a new record for the Mediterranean basin.

Grey gurnard (Eutrigla gurnadus) in the North Sea: an emerging key predator?

Grey gurnard (Eutrigla gurnadus) is a widely distributed demersal species in the North Sea that has been ranked frequently among the 10 dominant species. Since the late 1980s, grey gurnard catch rates in the international bottom trawl surveys showed a pronounced increase and it was included as an "other predator" in the North Sea multispecies virtual population analysis (MSVPA) in 1997. The MSVPA results estimated grey gurnard to be responsible for approximately 60% of the total predation mortality on age-0 Atlantic cod (Gadus morhua). Long-term MSVPA predictions led to the extinction of North Sea cod. As a possible technical reason, the Holling type II functional response implemented in the model was discussed. In the current analysis, it was demonstrated that the Holling type II functional response was not responsible for the extinction of cod in the model, which was rather a true effect of high grey gurnard predation. Further, it was shown that grey gurnard predation had a significant top-down effect on whiting (Merlangius merlangus) and potentially also on cod recruitment, which was linked to the spatial distribution of the three species. Eventually, the implications of the results for North Sea cod stock recovery plans were discussed.