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The spatio-temporal distribution and population dynamics of the non-indigenous ctenophore Mnemiopsis leidyi A. Agassiz 1865 were investigated through monthly and quarterly surveys in 2011–2012 at several locations in the Belgian part of the North Sea, the main coastal ports and the adjacent Westerschelde estuary. M. leidyi occurred from August to December, but was never found more than 30 km offshore. Densities were generally low (average 0.8 ± SD 2.8 ind m-3) compared to other invaded European systems. Highest densities of M. leidyi were found in the semi-enclosed basin (port of Oostende; 18.4 ind m-3) and Westerschelde estuary (1.9 ind m-3). The presence of larvae and sudden appearance of high numbers across the size distribution in August indicated that ports and estuaries may act as sources, populating the adjacent coastal area. The zero-inflated logistic regression model showed that there is a higher chance of finding M. leidyi (presence) when temperature declines from late summer onwards. Combined with a negative binomial regression, our model suggests that increasing M. leidyi densities are associated with decreasing autumn temperatures, low wave height (low energetic systems) and low dissolved oxygen concentrations Although densities remained relatively low since its first appearance in 2007, a permanent population seems to be established in Belgian waters. As population outbursts may occur with only a small change in environmental parameters, further monitoring of this notorious invasive species is recommended.

The realignment of the international river Scheldt into a flood control area in Kruibeke, Bazel and Rupelmonde in Flanders (Belgium) took over 35 years. It evolved from a technocratic engi- neering concept towards a sophisticated example of an integrated flood risk measure to enhance the adaptive capacity of the international river Scheldt. Connecting the functional domains of flood control, nature restoration (as compensation for the environmental impact of the expan- sion of the Port of Antwerp) and agriculture in this flood control area and finding an appropriate frame proved to be a difficult task. In this article, we focus our analysis on two important aspects of creating space for the river Scheldt near the towns of Kruibeke, Bazel and Rupelmonde. To begin with, we present how the problem definition and the proposed space for the river solution evolved over time in interaction between the main involved actors. In addition to that, we look at the frames of proponents and opponents of the creation of a space for controlled flood storage. Finally, in light of and partially explained by aforementioned governance aspects we look at the evolution of the fit of the proposed solution within stakeholder boundary judgments.

The Belgian coastal zone hosts a complex of space-use and resource-use activities with a myriad of pressures. Specifically at the beaches, predictions on sea-level rise, storms and flood risk from the North Sea have led to several big coastal defence projects. Management of sandy beaches is a multi-faceted and complex endeavor, where the interests of several stakeholders need to be combined.In this paper, we used the marine biological valuation (BV) method in order to (1) analyse the spatial structure of the intertidal and shallow subtidal Belgian coastal zone; and (2) explore the applications of BV for an ecosystem-based approach to marine spatial planning of two space-use conflicts at the Belgian coast, being flood protection, by means of beach nourishment, and nature conservation.The biological value was assessed with a focus on a detailed and integrated dataset (1995 – 2011), gathering all available ecological information on macrobenthos, epibenthos, hyperbenthos and birds. The 67 km Belgian coastline was divided into an across-shore intertidal and shallow subtidal subzone while the width of the along-shore subzones comprises 250 m for benthic components and wider distances of 3 km for the birds. The intrinsic biological value of each subzone was calculated using the BV method and the pertained score, ranging from very low to very high, was plotted accordingly in order to obtain a marine biological valuation map (BVM).Following trends in BV along the Belgian coastline were detected: (1) a strong mosaic pattern of BV along the coastline; (2) a clear lack of (benthic) data at the eastern part of the Belgian coast; (3) a rather high biological value score for around 70 % of the shallow part of the subzones, compared with the intertidal part; (4) a high/very high biological values found in intertidal zones located immediately to the east of the harbours Nieuwpoort, Oostende and Zeebrugge.A detailed analysis of protected areas and areas under coastal flood risk indicates that the use of BVMs is very promising in order to differentiate between several impact values. BV can therefore be used as a management tool by local decision makers and can allow for the integration of ‘natural/ecological values’ at an early stage of policy implementation.

The growing development of offshore wind energy installations across the North Sea is producing new hard anthropogenic structures in the natural soft sediments, causing changes to the surrounding macrobenthos. The extent of modification in permeable sediments around a gravity based wind turbine in the Belgian part of the North Sea was investigated in the period 2011 – 2012, along four gradients (south-west, north-east, south-east, north-west). Sediment grain size significantly reduced from 427 µm at 200 m to 312 ± 3 µm at 15 m from the foundation along the south-west and north-west gradients. The organic matter content increased from 0.4 ± 0.01% at 100 m to 2.5 ± 0.9% at 15 m from the foundation. The observed changes in environmental characteristics triggered an increase in the macrobenthic density from 1390 ± 129 ind m-2 at 200 m to 18 583 ± 6713 ind m-2 at 15 m together with an enhanced diversity from 10 ± 2 at 200 m to 30 ± 5 species per sample at 15 m. Shifts in species dominance were also detected with a greater dominance of the ecosystem-engineer Lanice conchilega (16–25%) close to the foundation. This study suggests a viable prediction of the effects offshore wind farms could create to the naturally occurring macrobenthos on a large-scale.

In de context van het ‘Vlaams Integraal Actieplan Marien Zwerfvuil’ van OVAM werd VLIZ gevraagd de wetenschappelijke onderbouwing te voorzien op basis van de beschikbare wetenschappelijke studies over marien zwerfvuil en microplastics in Vlaanderen. In Vlaanderen wordt al meer dan 10 jaar onderzoek gedaan naar de aanwezigheid en mogelijke effecten van zwerfvuil in de Noordzee en op het strand. Momenteel bestaan een veertigtal A1 publicaties inzake zwerfvuil of microplastics waarvan ten minste één onderzoeker verbonden is aan een Belgische universitaire associatie of wetenschappelijke instelling. Daarnaast werd ook een kritische reflectie gevraagd vanuit de mariene onderzoekswereld naar hiaten en onderzoeksnoden. De aanwezigheid van marien zwerfvuil is een mondiaal probleem dat blijft toenemen in alle zeeën en oceanen. Op de zeebodem van het Belgisch deel van de Noordzee kunnen tot 20 000 items zwerfvuil per km² aangetroffen worden, waarvan 90 tot 96% uit plastic afval bestaat. Ook op het strand bestaat 95,5% van het afval uit plastic. Het microscopisch plastic afval (microplastics) is eveneens abundant aanwezig in het Belgisch deel van de Noordzee. Plastic afval kan, o.a. door verstikking of verstrikking, leiden tot de dood van talrijke zeedieren zoals walvissen en zeehonden. Microplastics worden opgenomen door een zeer brede waaier aan organismen en kunnen ook bij deze dieren leiden tot ongewenste negatieve effecten. De aanwezigheid van microplastics in zeevoedsel en andere voedingswaren kan een bedreiging vormen voor onze voedselveiligheid. Momenteel bestaat nog geen voedingsnormen voor microplastics, en zijn niet genoeg wetenschappelijke gegevens beschikbaar om de risico’s voor de volksgezondheid in te schatten. Zowel op het vlak van fundamenteel en toegepast wetenschappelijk onderzoek als in de context van het (overheids-) beleid zijn er duidelijke noden om de problematiek van zwerfvuil en microplastics in Vlaamse aquatische milieus te bestuderen en aan te pakken.

In September 2011, two harbour porpoises (Phocoena phocoena) presenting extensive traumatic lesions washed ashore in Belgium. Similar lesions, with large parts of skin and blubber missing, had not been recorded before on harbour porpoises in Belgium but were recently observed in a number of cases in neighbouring countries. We compared the lesions with the mouth and teeth structure of possible predators. The circumstances of the strandings, the observations during the necropsies, and the results of seal skull investigations pointed towards seals, presumably grey seals (Halichoerus grypus), as the prime suspects for having caused the death of both harbour porpoises. Although purely aggressive behaviour cannot be completely excluded, predation is considered most likely as part of the skin and blubber tissue of the harbour porpoises was missing. The grey seal is an opportunistic predator, feeding on a variety of fish and cephalopods, and occasionally even on crustaceans and seabirds, but predation on harbour porpoises, or any other marine mammal, had to our knowledge never been described. This finding might shed a new light on the cause of death of some of the other mutilated harbour porpoises recently stranded on southern North Sea beaches, and it presents a case of a change in the feeding strategy of a top predator.

This study examines the heterogeneity of the Belgian fishing fleet based on “strategic groups”, a concept borrowed from the field of strategic management. Its objectives are: (1) to define strategic groups within the Belgian fishing fleet; (2) to examine the performance differences among these strategic groups; (3) to examine whether firms (i.e., vessels) move between strategic groups over time; and (4) to examine if firm-movement (i.e., vessel-movement) differs across strategic groups. In this study, strategic groups are derived through clustering firms based on their state of resources, built up through the collection of their past competitive strategic decisions, which are perceived as the main sources of mobility barriers (i.e. competitive advantages) in the fishing industry, namely: (1) technology, (2) product range and (3) geographic reach. Highly valid cluster solutions are obtained through use of excessive within- and between-method triangulation. Following this method, five strategic groups are identified that have distinct performance outcomes: (1) the large beam trawler fleet; (2) the small beam trawler fleet; (3) the shrimp beam trawler fleet; (4) the otter trawler fleet; and (5) the trammel netter fleet. Furthermore, in terms of firm movement and group loyalty, this study finds that once a vessel has decided on its strategic position in the fishing industry (i.e., the strategic group), in 80% of the cases, it stays in that position for a significant amount of time (in this case 10 years). However, not every strategic group enjoys this high level of group loyalty, since firm-movement differs significantly between the strategic groups. Although this is definitely a topic for further research, a possible interpretation for this phenomenon is the theory of “asymmetric mobility barriers” in combination with a firm's “isolating mechanisms”. The value of this study lies in its practical relevance to both policymakers and ship owners. Strategic group theory gives insight into the strategic differences and the patterns of rivalry between firms within the same industry. Such insights are crucial when managing fisheries and could result in regulations which are more focused on (1) affecting strategic groups’ competitive advantages (i.e., mobility barriers), (2) affecting “isolating mechanisms” of firms, and (3) managing rivalry between strategic groups. Ship owners and skippers can use the results of this study on the different performance potentials for the different competitive strategies in the current industry to determine if they are still satisfied with their current strategic direction. It allows them to reflect on current business and change strategic course based on the various performance indicators included in this research.

In Belgium, centralized reporting on landings of sea fisheries at the species level started in 1929. This paper summarizes the process and the results of integrating time-series, based on fragmented and disperse data sources for the period 1929–1999. The resulting database contains data by species (41), by port of landing in Belgium (4) and in ‘foreign ports,’ and by fishing area of origin (31). After quality control, total reported landings over the period 1929–2008 amounted to 3,320,518 tonnes, of which 90% was landed in the Belgian ports. After a maximum of 75,370 tonnes in 1947, annual landings declined steadily to only 26% of this peak by 2008. Currently, landings are below those achieved in 1929. The most important species in terms of landings (1929–1999) were cod (17% of all landings) and herring (16%). In terms of economic value, sole (31%) and cod (15%) were the most valuable. Close to 73% of all landings originated from 5 of the 31 fishing areas. Twenty percent of all landings (1929–1999) originated from the ‘coastal waters’, while these waters contributed nearly 60% of all landed pelagic species and 55% of all landed ‘molluscs and crustaceans’. Compared to the currently available ICES data, this local database offers advantages in temporal coverage (data from 1929 onwards), temporal scale (monthly values), and at the taxonomic level. It also provides more detailed information at the spatial scale of the southern and central North Sea, and it is the only source of historical information on landings originating from the coastal waters. Given the importance of the shallow and productive ‘Flemish banks’ as a local source of food in historical and recent times, this data is valuable for further research on the productivity of the coastal ecosystem and the local impact of fisheries. The database broadens the historical view on fisheries, underlines the decline in landings since reporting started, and serves as a basis for further (fisheries) research and policy-making in Belgium.

article i nfo Article history: The structural distribution of juvenile flatfish in nursery areas is generally studied on a larger scale on which the effects of abiotic factors such as sediment characteristics, beach profile, tides, and turbidity dominate. The biotic structuring factor has never before been investigated from a very small scale-perspective. The latter is the subject of the present study. In an in situ experimental sampling design, the structuring effect of biogenic reefs on the distribution of Pleuronectes platessa (Plaice) in an intertidal nursery area is investigated. The density distribution of this flatfish species is significantly (pb0.0001) explained by the presence of reefs built up by the polychaete Lanice conchilega. The importance of this reef builder has been highlighted before in other studies but present study demonstrates that not only the benthic biodiversity is affected by L. conchilega reefs, but that the distribution pattern of P. platessa is structured by them as well. This structuring impact of small-scale benthic reefs creating a patchy environment in nursery areas potentially plays an important role in other marine environments and indicates the need for further research on the ecological function of benthic reef environments for several flatfish species. Further modification of these biogenic habitats may lead to a loss of one or more ecosystem functions which flatfish species depend on. © 2009 Elsevier B.V. All rights reserved.

In order to disentangle the contribution of host and parasite biology to host specificity, we compared the structure and population dynamics of the Gyrodactylus (von Nordmann, 1832) flatworm community living oil sympatric three-spined Gasterosteus aculeatus L. and nine-spined Pungitins pungitius (L.) stickleback. Between April 2002 and March 2003, a small lowland creek was sampled monthly. Species identity of about 75% of the worms per host was determined with a genetic nuclear marker (ITSI). Each stickleback species hosted a characteristic gill- and in-parasitic Gyrodactylus: G. arcuatus Bychowsky, 1933 and G. gasterostei Glaser, 1974 respectively infecting the three-spined stickleback, with G. rarus Wegener, 1910 and G. pungitii Malmberg, 1964 infecting the nine-spined stickleback. Host size and seasonal dynamics were strong determinants of parasite abundance. A strong interaction between host and parasite species determined infection levels and affected three levels of parasite organisation: community structure, population structure and topographical specialisation. Community and population structure were shaped by asymmetric cross-infections, resulting in a net transmission of the Gyrodactylus species typical of the nine-spined stickleback towards the three-spined stickleback. I-lost density was not a major determinant of parasite exchange. Aggregation and topographical specialisation of the Gyrodactylus species of the three-spined stickleback were more pronounced than that of the nine-spined stickleback. ispartof: Folia parasitologica vol:55 issue:3 pages:187-196 ispartof: location:Czech Republic status: published

Although the waters of Belgium only form a minor part of the North Sea, they contain some of the busiest shipping routes in the world with the Dover Strait and some of the biggest European ports in the immediate vicinity. It is therefore recognized as a key maritime risk area, also in terms of ship-source oil pollution. This chapter first discusses the significant, stepwise decrease of illegal oil discharges from ships in and around the waters of Belgium based on national aerial surveillance data since 1991 but also gives indications as to why the ecological quality objectives have not yet been met despite this decline. It further gives an overview of the accidental oil pollution incidents in this key risk area over the last 30 years and reflects on the high level of accidental marine pollution risk. Finally, the various measures are discussed that have been and will be undertaken in terms of oil pollution prevention, enforcement, preparedness and response with the aim to (further) reduce the oil pollution pressure in this environmentally sensitive area.

The cosmopolitan sandy beach polychaete Scolelepis squamata constitutes an important food resource for juvenile flatfish and wading birds in the northeastern Atlantic, thus playing an important role in sandy beach ecosystem functioning. However, its population dynamics and life history in this part of the world have gone widely uninvestigated. Eight beach transects on Belgian sandy beaches were sampled monthly from October 2003 until October 2004, in order to investigate seasonal trends in the species' abundance, biomass, secondary production, and patterns in reproduction and zonation.Average density, modal density and modal biomass (ash-free dry weight) (mean average density = 169 ± 9 SE ind/m2; mean modal density = 505 ± 38 SE ind/m2; mean modal biomass = 0.25 ± 0.02 SE g/m2) did not exhibit major seasonal changes, whereas average biomass (0.081 ± 0.005 SE g/m2) and individuals and biomass per strip transect (IST = 16286 ± 1330 SE ind/m; BMST = 7.8 + 0.7 SE g/m) did, peaking in May 2004. Production was calculated at 1.9 g/(m2*year) (size-frequency method, SFM) and 0.88 g/(m2*year) (mass specific growth rate method, MSGR) and mean annual biomass was 0.797 g/m2; resulting in a P/B ratio of 2.40/year (SFM) and 1.11/year (MSGR), which is intermediate to moderately low compared to other polychaete species. Gravid individuals were found from February until August and a single recruitment period was observed from July until September. An average sex ratio of 1.41 ± 0.08 SE was calculated, with a female predominance. Highest densities (>200 ind/m2) were mostly found above 3 m above MLLWS and at a median grain size from 190 to 320 µm. Average modal or peak density along each transect was situated from 3.95 m up to 4.40 m above MLLWS, in contrast to some other studies where the species was restricted to mid-tidal levels. Significant differences in elevation of peak density were found between non-gravid (411 ± 4 SE cm) and gravid (402 ± 5 SE cm) animals, but none between gravid males and females. The portion of the tidal range that was occupied by the species in the vertical dimension, just failed to differ significantly between non-gravid and gravid individuals, while gravid males (48.2 ± 5.6 SE cm) occupied a significantly wider range than gravid females (36.8 ± 4.7 SE cm), corresponding with a horizontal range difference of 6–9 m cross-shore. The observed zonation pattern, together with a trend in the difference of peak abundance elevation between males and females, are hypothesised to be a result of a strategy of gravid animals to ensure co-occurrence in a narrower zone during reproduction. Observed differences between Brazilian, Moroccan and Belgian populations (e.g. density, biomass, productivity, P/B, life span, body width, period of presence of gravid individuals and recruitment) do not seem to concur with differences in morphodynamics and might be attributed to latitude-associated gradients like climate. Furthermore, the fact that Scolelepis squamata, as defined today, might be a superspecies, cannot be ruled out.

The distribution patterns and genetic structure of the Pellioditis marina species complex in Belgium and The Netherlands were compared between four consecutive seasons. Different types of habitats (coast, estuary, semi-estuary and lake) with different degrees of connectivity were sampled. In addition, each habitat type was characterised by either temporal or permanent algal deposits. We screened 426 bp of the mitochondrial cytochrome oxidase c (COI) gene with the single-strand conformation polymorphism (SSCP) method in 1615 individuals of Pellioditis marina. The 51 haplotypes were divided into four (sympatric) lineages, with divergences ranging from 0.25 to 10.6%. Our results show that the lineages have different temporal dynamics, which may be linked to abiotic factors. Analysis of Molecular Variance (AMOVA) indicated a significant structuring in the PmI lineage, which correlated with habitat characteristics and which changed over time (Mantel, r = 0.51; p = 0.126). Intrapopulational diversity was similar in all locations, and temporal changes in haplotype frequencies were not higher in temporary than in permanent algal deposits. Instead, the results of the temporal survey indicated that (some) P. marina populations are characterised by a metapopulation structure. It is emphasized that a complete and correct interpretation of processes causing genetic structuring within species and of the genetic structure itself can only be done when analyses are performed at several time points.

Sandy intertidal zones were analysed for the presence of meiofauna. The material was collected on six macro-tidal sandy beaches along the North Sea (The Netherlands, France, Belgium), in order to analyse the vertical and horizontal meiofaunal distribution patterns. Eleven higher meiofauna taxa (one represented by larval stage—Copepoda nauplii) were recorded. The maximum total meiofauna abundance was observed on the Dutch beach (4,295±911 ind. 10 cm-2) in the Westerschelde estuary, while the lowest values (361±128 ind. 10 cm-2) were recorded in France at the Audresselles beach. Meiofauna of the different localities consisted mainly of nematodes, harpacticoids and turbellarians. Nematodes numerically dominated all sampled stations, comprising more than 45% of the total meiofauna density. Meiofauna was mainly concentrated at the sand surface with about 70% present in the uppermost 5 cm. Meiofauna occurred across the entire intertidal zone. A clear zonation pattern in the distribution of meiofauna taxa across the beaches was observed. The present work suggests that designation of exposed sandy beaches as physically controlled (McLachlan 1988) does not explain their biological variability.

The Suspended sediment processes and the mudfields found in the Belgian/Dutch coastal area (Southern North Sea) are discussed by presenting an integrated data-modelling approach of the suspended sediment transport along the Belgian-Dutch coast, using, a fine-grid coupled 2D hydrodynamic and sediment transport model and existing field and literature data. These mudfields and turbidity maxima are situated in a well-mixed, highly energetic hydrodynamic environment. In the past the occurrence of this high turbidity zone (more than a few hundreds mg/l of suspended matter) was ascribed to a closed hydrodynamic system (gyre) in front of the coast. This study shows that the SPM input through the Strait of Dover, the shallowness of the considered area, the decreasing magnitude of the residual transport vectors from the French/Belgian border towards Zeebrugge and the specific hydrodynamic features are the main processes responsible for the presence of the turbidity maximum. The origin and the formation of these mud deposits in front of the coast are explained by the neap-spring tidal cycles and the presence of SPM Sources (import Of SPM through the Strait of Dover and through erosion of clay layers). (C) 2003 Elsevier Science Ltd. All rights reserved.

The hyperbenthos of the Belgian continental shelf, the Dutch continental shelf off Zeeland and the Westerschelde estuary was sampled. Seven biotic communities were identified and the distribution was correlated with the presence of isolated sandbanks. A community in the Westerschelde estuary was different from the shelf hyperbenthos and was characterised by the highest density and biomass and lowest diversity. Two gradients in community structure were detected on the continental shelf: the principal onshore-offshore gradient perpendicular to the coastline and a less pronounced east-west gradient parallel to the coastline. The first gradient mainly indicated differences in density and biomass, while the second reflected species richness and diversity. The holohyperbenthos reached highest densities onshore and consisted nearly exclusively of mysids; Schistomysis spiritus and S. kervillei were the most common species. The high levels of suspended matter and mud in this area probably advantage this motile fauna in terms of food. Community composition altered with distance from the shore and planktonic species increased in abundance. Estuarine influence may have caused a decline of species richness eastward. The merohyperbenthos was most abundant at a certain distance from the coast and was mainly composed of a variety of larval decapods. Biomass peaked onshore with a dominance of postlarval gobies. A strong diversity gradient was found for the merohyperbenthos with a richer fauna off the Belgian coast than in the waters off Zeeland. Current direction and habitat heterogeneity are believed to be the most important structuring factors.

1. Diatom assemblages of man-made coastal dune wetlands between Blankenberge and Heist (Belgium), dating from 1852 to 1929 and sampled from herbarium specimens of macrophytes, were compared with more recent samples collected in the remaining calcareous dune marshes and pools in this area. 2. Overall, nutrient conditions inferred from the reference assemblages were fairly eutrophic for phosphorus. Only a minority of the historical assemblages pointed to presumably nitrogen-limited conditions. 3. Significant alterations in general assemblage composition were observed, including a marked decline of epiphytic species, and a decrease in the compositional variation in sediment diatom assemblages. These changes can be attributed mainly to an increased availability of nutrients and degradable organic matter since the mid 1970s. No changes in the salinity range seem to have occurred, suggesting fairly stable hydrological conditions. 4. Possible causes for eutrophication include increased atmospheric deposition of nutrients, but also more site-related phenomena such as guanotrophication, angling and, perhaps, effects of nature management on soil–nutrient cycling. Their relative importance needs to be established and further monitoring is necessary. 5. Measures are required to reduce nutrient levels of both permanently and periodically inundated sites and to promote small-scale habitat differentiation. Due to physical constraints, the latter will be possible only by mimicking the processes that act upon more natural dune systems in management practice. Copyright © 2003 John Wiley & Sons, Ltd.