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Flanders Marine Institute and its consortium of experts on non-indigenous species conduct an ongoing effort to collect and maintain a list of alien species with documented established populations in the Belgian part of the North Sea and its adjacent estuaries. The list strives to include all currently known non-indigenous and cryptogenic species registered in salt and brackish environments in the Belgian part of the North Sea, the Belgian coastal zone and adjacent estuaries (Yser, Scheldt, Ostend Sluicedock). The discovery of America (1492) marked by a strong increase in trans-Atlantic shipping is set as the historical baseline of this assessment. This effort scrutinizes intentional and unintentional introductions by man or other vectors. Alien species for which there is no evidence of resident populations are not included in the list, nor are species that are limited to the fresh water environment. Newly registered species as a consequence of (expected) naturally induced migrations are also excluded. This initiative aims at providing a freely available online source of information on non-indigenous species and its associated network of experts for this study area. This includes definitions, information sheets and background literature, by species, and further links to European and international initiatives. Each information sheet describes the life cycle and ecology of the species, the introduction pathways and distribution, the possible effects or impacts of the species on its environment and potential mitigation measures. Pictures and a fully documented reference list - all available at the VLIZ library - represent an important added-value.http://www.vliz.be/NL/Cijfers_Beleid/Niet_inheemse (Dutch)

Our study about the biotope of the ostreiculture, the ‘Bassin de Chasse d'Ostende’, has shown us that: 1. (1) the phyto- and zooplanktonic population extraordinary abundant let suppose us that the available food is enormous. 2. (2) The harmful organisms (Polydora ciliata) and the competitors of food for the oyster (Mytilus edulis, Balanus, Mya arenaria) have fixed them by a clumsy manner on the ostrea. 3. (3) The abundance of the competitors did not restrain the growth of the mussels and the oysters. On the contrary, their growth appear to be one of the greatests of Europe.

The Sluice-dock of Ostend, a shallow (1.5 m) marine biotope of 86 ha stays closed during some 6-7 months of the year and is not influenced by the tides. During 24 h cycles the nycthemeral migrations of the zooplankton at 5 depths in a watercolumn of 1 meter were studied in relation to several environmental factors: water temperature, dissolved oxygen, pH and chlorophyll content. The photosynthesis shows a minimum during the night and shows a maximum during the late afternoon, at which time the water-temperature is also maximal. Holo- and meroplanktonic organisms migrate towards the surface around 3-5 o'clock a.m., at which time the chlorophyll content is minimal, hence our hypothesis of nocturnal grazing, this phenomenon perhaps combined with a nocturnal division of phytoplankton cells. Each observed species has its own characteristic behaviour in relation to its negative diurnal phototropism and its own diurnal bottomward migration speed.

Nursery rearing of bivalve molluscs as the intermediate step between the controlled production of larvae in hatcheries and non-controlled growing-out in the wild, is a practice in modern shellfishery management which receives more and more attention. A major bottle-neck in the culturing process of the postlarval bivalves is, however, the production of large quantities of marine microalgae suitable as food for the growing spat. Experience was gained by the authors in small 1 m2 outdoor units with induced blooms of natural phytoplankton. The cultures were run either as a turbidostat or as a chemostat with discontinuous or continuous harvesting.Natural seawater (25-32°) was enriched with inorganic (commercial), or organic fertilizers (manure), solely or in combination. The influence of environmental factors such as light, temperature, detention time, nutrients and turbulence on yield and species composition are reviewed briefly. As a next step, a semi-industrial pilot plant for the controlled nursery growing of edible shellfish was designed and built at the Belgian coast. This pilot-scale plant should provide bio-technical guidelines, and aims at assessing the cost-benefit of an industrial bivalve nursery.

Electron microscopic observations on the demanian system of female Metoncholaimus denticaudatus Schuurmans Stekhoven and Adam, 1931 from the Sluice Dock of Ostend lead to following conclusions: 1) there is no ductus uterinus; 2) the system is not a seminal receptacle; 3) it should be interpreted as an elaborate cascade system of glands, the secretion of which serves some important purpose related to reproduction.

The life-cycle of the harpacticoid copepod Tisbe furcata (Baird, 1837) at 18 C was studied quantitatively. Stage durations were determined by two different methods, using synchronous cohorts. Combined nauplius stages last for 80·4 h; the successive copepodite stages take 23·0, 23·2, 28·0 (♀) to 23·2 (♂), 33·4 (♀) to 24·2 (♂) and 48·8 (♀) to 34·7 (♂) h, respectively. Females develop more slowly but more synchronously than males. Age-specific survival and fertility rates were used to calculate the stable stage distribution in an exponentially growing population. From life-table data the following demographic parameters were computed: intrinsic rate of natural increase rm = 0·233 day−1; net reproductive rate Ro = 94; minimum generation time Tmin = 14·9 days; parameters related to ‘generation time’: T = 19·5 days, = 16·4 days, Tc = 25·4 days.

Primary production parameters (numbers and identifications , pigments, photosynthesis, respiration, excretion) have been measured or estimated in a marine lagoon during 4 years. On the seasonal scale, the succession pattern shows a spring bloom in April-May, a depression in May and a summer bloom from June to August. Various nannoplanktonic flagellates are responsible for these fluctuations, which are well paralleled by photosynthetic capacity variations. Primary production was computed using a light-photosynthesis function. Photosynthetic capacities and function parameters have been determined and discussed. On the diel scale, a strong periodicity involving natural mortality was observed and taken into account. Uptake and regeneration rates of inorganic N as well as liberation and consumption of dissolved O2 matched this periodicity well. Turn-over times are very short and according recycling is intense.

In a series of bi-mensual samplings in 1966, the method of direct counting on membrane filters has been used to determine the quantity of bacteria present in the water of the Sluice-dock in Ostend (Belgium) as a possible important food-stock for oysters which are reared there.

The difference of phototropism and phototaxis of both molluscs influenced their fixation. The orientation of both molluscs is towards the incoming light-direction, less pronounced when the light-density to the center of the tile is decreasing. The density of the populations of oysters is increasing towards the center of the tiles by decreasing light-intensity, the density of the Crepidula-population decreasing towards the center of the collector. The competition of both organisms in relation to space, is, under the opposed influence of the light, less than described in the literature. Theoretically it is possible to separate Crepidula and oyster-fixation, using this property. Statistical analysis corroborated our observations.