LARVAE OF UNCOMMON CARIDEAN DECAPODS IN THE GERMAN BIGHT - SPECIES COMPOSITION, DISTRIBUTION AND ABUNDANCE

Typically, the most abundant group of shrimp larvae in the German Eigh t is formed by representatives of the family Crangonidae. Larvae of th e remaining species have been largely ignored, and only scarce informa tion concerning their ecology is available. Thus, the purpose of the p resent study was to determine the species composition, distribution an d abundance of noncrangonid shrimp larvae in the German Eight in July 1990, after the mildest winter of the century. The material is based u pon plankton samples collected at 77 stations, covering the entire Ger man Eight. Eight species were identified, as well as larvae of Palaemo nidae and Processa-juveniles. Processa nouveli holthuisi (53.0 %) and P. modica (31.3 %) were predominant in the collection. The distributio n of the two species was clearly separated: the main concentration of P. nouveli holthuisi (peak concentration of 1.94 larvae per m(3)) was confined to the northwest corner of the German Eight, while a majority of P. modica larvae (peak concentration of 0.54 larvae per m(3)) occu rred at the southwesterly stations. The spatial distribution of Caridi on steveni and Eualus occultus around Helgoland indicates the presence of an adult population at the only rocky island in the study area. Ot her taxa, such as larvae of Palaemonidae and juvenile Pandalina brevir ostris were collected exclusively in estuarine habitats. Based upon bo th the results of the present study and comparable data, we conclude t hat developmental stages of ten non-crangonid species, as well as repr esentatives of Palaemonidae, can be expected to occur in the plankton of the German Eight. The extremely mild temperatures of the preceding winter may have been, in part, responsible for the relatively high den sities of some taxa encountered during our plankton survey. We assume that warm winter temperatures favour the immigration, reproduction and survival of cold-sensitive species.