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This review considers the energy flow through a tidal flat ecosystem in the western Wadden Sea. Based on available estimates of primary production, input of allochthonous organic matter, a s well as on consumption and production a t different trophic levels, a modified concept of energy flow is advanced. In the traditional concept the secondary level has mainly been quantified in terms of herbivorous macrobenthos with a n apparently excessive primary food supply, and with the higher trophic levels being food-limited. In our opinion, the importance of small a n d very small zoobenthos with a negligible biomass, but with a relatively high production, has hitherto been underestimated. This complex -in this review referred to a s 'small food web' -consists, in addition to bacteria, of microfauna, meiofauna, temporary meiofauna and small macrofauna. In our opinion these groups contr~bute far more to the consumption of primary food and to the production of food for small carnivores than is generally assumed i n food-chain studies conducted in the western Wadden Sea.

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In order to evaluate the impact of the lesser weever on the ecosystem of the southern North Sea, geographical distribution, density, growth, production and food requirements have been estimated. High densities were found on and around the Brown Ridge, an area with high tidal current velocities, medium grain‐size of the sediment and a poor benthic fauna. Growth is restricted to the months of June October. During the winter cessation of growth a considerable loss of weight (about 20%) takes place. Mortality has been estimated by using the average size frequency distribution of all catches made from 1972 to 1984. The resulting convex type of survival curve indicates a high survival rate of the II to IV‐group fishes. The production (estimated with Allen's graphical method) of a population of 100 individuals including all age groups (0‐VI) amounts to 123.7 g AFDW‐year‘. In areas with highest densities, consequently, production amounts to 0.018–0.078 g AFDW‐m2 ‐year‐1. With an assumed transfer efficiency of 10% through the year, food requirements amounts to 0.18–0.78 g AFDW‐m 2 ‐year ‐1. Since the lesser weever feeds mainly on fish (85.6%), almost exclusively on gobies (Pomatoschistus sp.), and with an assumed transfer efficiency of approximately 10%, the indirect predatory pressure exerted by it may amount to 1.6 6.7g AFDW‐m 2.year ‐1. A possible feeding by gobies on pelagic organisms (calanoids, mysids) is discussed.

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