| Summary: | The distribution of the sand eel stretches in the Northeast Atlantic from 490 N to 730 N (Reay, 1970) with a tendency to inhabit in well-defined areas on shallow banks (Macer, 1966). The substrate must be conductive to burrowing (Meyer et al., 1979) with the choice of habitat probably determined by the type of sediment and the hydrodynamic processes affecting the sediment (Pinto et al., 1984). Wright et al., 1998 found that the sand eel was absent from sediment with a silt content less than 10% which together with depth and tide influenced habitat choice. The depth maximum for sand eel abundance is about 100m (Pedersen et al., 1999), and the water flow must be above 0.6 ms-1 (Wright et al., 1998). These constraints leads to a very restricted distribution of sand eels, i.e. they are found in sandy areas where tides and wave action is expected to scour the bottom giving rise to coarse sand and well-aerated substrate. These areas appear to coincide with the areas of the North Sea influenced by tidal front activity. The distribution of fishing areas clearly matches the san eel preferred habitat (figure 1). Due to the stationary habit of post-settled sand eels, a patchy distribution of the sand eel habitat, and a limited interchange of the planktonic stages between the spawning areas the sand eel stock in IV consist of a number of sub-populations (Proctor et al. 1998, Pedersen et al. 1999). Due to a to coarse spatial aggregation level of the fisheries data that is used in the sand eel assessment and a lack of biological information for defining the limits of each of the reproductively isolated population units, it is presently not possible to make an assessment that take account of the sub-population structure of sand eels (ICES 2006). The catches of sand eels in area IV consist mainly of the lesser sand eel Ammodytes marinus. However, other species of sand eels is also caught. At some of the grounds in the Dogger Bank area the smooth sand eel Gymnammodytes semisquamatus can be important, and in the catches from more ...
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