The spawning of plaice Pleuronectes platessa in the Kattegat

Cruises were carried out in the entire Kattegat in early March of 1998 and 2000 to investigate the spawning of plaice Pleuronectes platessa. The data showed that plaice still spawn in the Kattegat, with a main spawning area in the southern Kattegat and an area of less, but variable importance in the northern coastal Kattegat. The results indicate that spawning in the southern part of Kattegat occurs earlier than in the northern Kattegat. The preferred spawning depth was found to be around 30–40 m. Juvenile recruitment in the nursery areas along the Danish east coast derives mainly from the southern stock in the southern Kattegat with low and variable input of Skagerrak plaice. Maturity ogives for both sexes were obtained and both A 50 and L 50 were lower than those estimated 10 years previous to this study and for plaice in the North Sea. The shift towards earlier maturity and the absence of the larger age groups in the catches indicate that the Kattegat plaice stock is under severe pressure today.