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(i) Variability in North Sea plaice recruitment seems to be generated mainly during the egg stage. (ii) Density-dependent mortality processes, if they apply, are likely to operate in the early post-larval stage in the nurseries. However, the data do not exclude the possiblity that such processes are lacking or insignificant in juvenile plaice. (iii) An inverse relationship between length and abundance, observed in O-group plaice, appears to be generated by temperature-dependent processes in the egg stage, affecting the rate of egg development and egg mortality. (iv) Recruitment fluctuations in North Sea plaice are probably mainly generated by between-year temperature differences experienced during the egg stage. Variations in egg production by the adult stock might also affect recruitment, but in the range of stock sizes considered the effect seems less important.

Con~position, abundance and distribution of the meiofauna of a well-studied tidal flat in the western part of the Wadden Sea, The Netherlands, was determined by sampling with 2-monthly intervals at 12 stations during a year. The meiofauna was strongly dominated by nematodes (85 %) and largely restricted to the top 10 cm of the sediment. Clear seasonal variation was observed in harpacticoids and annelids, but not in nematodes. Harpacticolds and annelids were most numerous in the lower parts of the tidal flat, near the main gullies, in areas with coarser sediment, whereas nematodes showed a maximum at intermediate tidal level with average mean particle-size conditions. Low meiofaunal abundances were observed on the high tidal flats with fine sediment and a high organic carbon content. Arguments are given that the role of the meiofauna as consumers of primary organic matter is very restricted in the area and probably much lower than that of the macrofauna. This situation differs from that in most other areas and is largely determined by the relat~vely small biomass of the meiofauna (f 0.45 g C m-') as compared to that of the macrofauna (k 10 g C m-2). It seems therefore unlikely that the rneiofauna of the tidal flat consumes a large part of the primary organic matter, postulated to be left over by the macrofauna (Kuipers et al., 1981). In fact, evidence is given that the primary food supply to the benthic system of the tidal flat might be much lower than formerly assumed.

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