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This paper presents data on the length distribution and age composition of male and female dab Limanda limanda L, as observed in the German Bight in March 1990 during the Bremerhaven Workshop. Further data on distribution and seasonal movements from tagging experiments are reviewed with regard to the interpretation of the results of the studies carried out during the workshop. It is shown that highest densities of dab coincided with the main centre of egg production in the inner German Bight. Within the spawning period the spatial distribution changed significantly in a period of 2 wk between mid and late March: the abundance of dab increased in the inner German Bight and decreased at the offshore stations. The dab population was dominated by 4 and 5 yr old fish. Growth of dab was higher at the inner stations and on the Dogger Bank compared with the intermediate stations. The results of the tagging experiments suggest that the dab population at one sampling site is a temporary aggregation of fish originating from a large area. The significant change in the spatial distribution between mid-March and late March implies that even within a period of 3 wk substantial movements of dab occur. The results of the biological effects studies during the workshop, therefore, can only be interpreted In very general terms, especially when dealing with responses that are slowly induced, such as gross pathology (liver tumors) and the tissue residue data.

Changes in the somatic growth of female plaice Pleuronectes platessa L. between 1930 and 1985 is studied by back-calculation of otoliths. It is shown that in the period 1940-49 growth rate was reduced, which coincided with a 3-fold increase in the plaice stock due to the closure of the fishery during the second world war. The growth reduction was largest in large fish (>45 cm) as compared to medium sized fish (30-40 cm), but could not be detected in the size classes c 20 cm. In large plaice the growth reduction occurred later in time as compared to the medium sized fish. Growth in the immediate pre-and post-war years appeared to be sim~lar. At some time in the 1950s and 1960s a growth acceleration started in the size classes up to 30 cm, levelling off in the 1970s. This growth acceleration was largest in the smallest size classes. Within the period of growth acceleration, the 1963 year class. whlch was about 3 times the average year class strength, showed a slight but significant reduction in growth. The reduction in growth was restricted to size classes c 3 0 cm and was 1a.rgest in smaller fish. It is concluded that growth rate in plaice is reduced at high density both in the juvenile phase (pre-war period and year class 1963) and in the adult phase (period 1940-49). The increase in growth of juven~le plaice starting in the 1950s appears to be related to an increase in the availability of food in the coastal waters of the southern North Sea.

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