Report: Ecosystem Research Wadden Sea: Development of mussel benches – Niedersächsische Watten (1996)»
Description
Within the framework of this sub-project, two mussel benches (Mytilus edulis) located in the East Frisian Wadden Area (Mytilus edulis) were examined from 1992 to 1994. A mapping of the mussel deposits in the Spiekerooger and a part in the Langeooger back cotton was carried out in August and September 1993. The mussel stock of the entire Lower Saxony Watten was mapped from May to mid-July 1994 in cooperation with the NLÖ Coast Research Centre.
According to the above-mentioned studies, stock developments continued to decline. In the range of medium size classes (for shell lengths of approx. 20 to approx. 55 mm), there were no mussels in almost all ripe occurrences in 1994. The direct cause of this is primarily to be regarded as feeding pressure from birds. The observed decline was also largely due to the effects of the winter 1992/93. The storm vulnerability of the banks had probably increased due to their altered age structure.
The decline affected both fished and unfished mussel benches. Mussel advertising does not always lead to a longer-term decline in the area of a fished occurrence. The sites of mature deposits are also fished for stocking mussel production. Mussel fishing is in direct competition with the stocks of mussel-eating seabirds through the preferential use of young bivalve molluscs to occupy the cultivated areas.’
Two intertidal mussel beds (Mytilus edulis) were examined at the coast of East Frisia from 1992 until 1994. A survey of the mussel beds at the Spiekerooger and parts of the Langerooger intertidal flats was carried out in August and September 1993. The mussel stock of the whole Lower Saxonian intertidal area was mapped from May to mid-July 1994 in cooperation with the NLÖ-Forschungstelle Küste. According to the above-mentioned investigations the development of the blue mussel stock still was declining. Mussels with a shell-length between c. 20 and c. 55 mm were missing in almost all mature beds. This gab in the size-frequency distribution was probably mainly caused by predation of birds. Furthermore, the observed decrease of the mussel stock resulted mainly from the winter 1992/93. Presumably the susceptibility of the mussel beds to storm impacts increased during the last years because of the described change of the population structure. Both fished and not fished mussel beds decreased in biomass and area. Mussel Fishery doesn't account for a longer-term decrease of fished mussel beds in general. Positions of mature mussel beds are used by the fishermen to obtain seed mussels for their culture plots, too. The mussel fishery competes directly with increased populations of mussel-eating birds for the same size-classes of young mussels.
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Tags
- miesmuschel-mytilus-edulis-populationsaufbau-ökosystemforschung-miesmuschelfischerei-bestandsentwicklung-ecosystem-research-mussel-fishery-population-structure-stock-development-mytilus-edulis-nlwkn
- spiekeroog-langeoog-wadden-sea-of-lower-saxony