Recruitment variability in dab (Limanda limanda) in the southeastern NorthSea

Data from three annual surveys, covering inshore and offshore waters of the southeastern North Sea, were analysed to study recruitment variability in dab (Limanda limanda) over the period 1978-1997. Geometric mean abundance o f 0- to 5-group dab was estimated using general linear models. Juvenile dab (0- and 1-group) were found over the entire area, from inside the estuarie s to 50 m depth offshore. Environmental conditions (water temperature, wind stress, turbidity) affected the catch rates. The potential errors in the e stimates of year-class strength, caused by differences in catchability, are discussed. The inter-annual pattern of year-class strength appeared to be established between ages 1 and 2, suggesting that factors determining recru itment are not restricted to the pelagic early life phase only, but also op erate during the demersal juvenile phase. Recruitment variability at age 2 was in the order of 50-60% and appears to be equal to, or lower than, recru itment variability in plaice and sole. These results contradict expectation s based on the concentration hypothesis, which states that the degree of va riation in recruitment is inversely related to the degree of concentration during early life phases. (C) 2001 Elsevier Science B.V. All rights reserve d.