Report: ‘Muscles: Influence of stocking shell removal on the development of eulitorial resettlement (1994-1995)»
Description
The present study was carried out within the framework of the research project “Inquiries on the development of mussel banks of the Lower Saxony Wadden Sea – taking into account mussel fishing” of the Lower Saxony Wadden Sea Ecosystem Research (ÖSF) (HERLYN & MICHAELIS 1996) and in the research project “Recovery and documentation of the mussel stock of the Lower Saxony Wadden Sea as well as analysis and evaluation of alternative methods for the production of stocking mussels” of the Lower Saxony Wadden Sea Foundation. [...]
Mussel fishing is in direct competition with the growing stocks of shellfish, such as eider duck, silver gull and oyster fisherman, thereby reducing one of its most important food resources (NEHLS et al. 1997) in the Eulitoral. [...]
Due to a severe incubation of Mytilus edulis in the spring and early summer of 1994, the stock situation as described above changed: Older deposits were repopulated and there were also pure resettlements. In the previous years, however, neither the comparable breeding case of 1991 (MICHAELIS et al. 1995) The increase in the settlement of young bivalve molluscs in existing banks changed the development of the stock sustainably in 1993 and 1994 (HERLYN & MICHAELIS 1996). According to these observations, one major cause of the decline in populations in the post-establishment phase is to be sought: What prevents a truly sustainable recruitment despite strong breeding cases and despite successful settlement? In this context, it was of interest to investigate the development of resettlements of the breeding case in 1994. Special consideration was given to the production of stocking shells: What is the relevance of fishing a young mussel deposit for its further development? [...]
The influence of stocking mussel extraction on the development of young mussel deposits was investigated by comparing eight fished and twelve unfished mussel banks/areas in the Wadden Sea of Lower Saxony. Seven of these occurrences/areas, three of which were fished, were sampled over a longer period (from autumn 1994 to autumn 1995).
The main results: Out of 12 unfished banks/banking areas, none is extinct in the year after settlement, while out of eight fished banks, seven are almost extinct or no longer present. The seven banks/banks examined several times shows: Without fishing, there was a gradual decline that did not lead to a state of care or complete extinction. Fishing, on the other hand, led to rapid population decline to complete extinction. The losses resulting from fishing shall not be limited to the quantities of stocking mussels taken directly (as indicated by the fishermen). Losses due to side effects seem to outperform the quantities taken many times over. As a rule, repopulation of fishing traces from unfished areas does not take place. Since fishing alone is directly controllable of all factors reducing stocks, catch reduction and conservation are the only measures for the restoration of stable, eulitoral mussel benches.’
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Tags
- niedersächsisches-küstengebiet
- miesmuschelbestände-miesmuschelbänke-mytilus-edulis-besatzmuschelentnahme-nlwkn