Early postlarval fish in the hyperbenthos of the Dutch Delta (south-west Netherlands)

Early (post)larval fish constitute a significant part of the temporary hype rbenthos, i.e. of the fauna living in the lower reaches of the water column close to the substratum. Information on the densities and spatial and temp oral variations of these stages, as well as on their lengths at the moment of occurrence, can be an important contribution to the knowledge of their d ispersion, migrations and to the identification of possible bottlenecks in their recruitment. Therefore the hyperbenthos of the Voordelta, a shallow c oastal zone in front of the Dutch Delta, as well as that of the subtidal ch annels and the intertidal brackish marsh creeks of the Westerschelde Estuar y, was sampled monthly during one year by means of a sledge and a stow net. A total of 37 taxa were recorded from 410 samples. Densities often exceede d 400 ind 1000 m(-2) in the Voordelta and 300 ind 1000 m(-2) in the Westers chelde, including the tidal marshes of Waarde and Saeftinghe. The dominant taxa were clupeid larvae (predominantly herring Clupea harengus and sprat S prattus sprattus), Pomatoschistus spp. (a mixture of sand goby P. minutus a nd Lozano's goby P. lozanoi), common goby Pomatoschistus microps, Syngnathu s spp, (probably almost exclusively Nilsson's pipe fish S. rostellatus), pl aice Pleuronectes platessa; sole Solea solea and flounder Pleuronectes fles us. Most species were found at a larger size in the Westerschelde (and in t he tidal marshes) suggesting migration from the shallow coastal area into t he estuary. Several species utilize the tidal marshes in the brackish reach es of the Westerschelde. The nursery value of these areas however, is restr icted to specific early life history stages of a few species, especially fl ounder, bass Dicentrarchus labrax and the common goby. The estuary itself s eems to function as a nursery for other species like sole and plaice. The h yperbenthic sledge was found to sample specific Life history stages of post larval flatfish (early settlement stages at the onset of asymmetry), which are not easy to sample with other types of sampling gear.