Population dynamics of the invasive Pacific oyster Crassostrea gigas during the early stages of an outbreak in the Wadden Sea (Germany)

Abstract

Since the late 1990s, the Pacific oyster (Crassostrea gigas) has spread into the East Frisian Wadden Sea (Germany). This invasion provided an opportunity to study the population dynamics and the patterns of spread during the initial bioinvasion process. With its source area in The Netherlands, the bioinvasion continues in an eastward direction, as documented by a gradient of high abundances in the west and low abundances in the east during the first study year. One year later, abundances of the Pacific oyster were more heterogenic and differed between adjacent tidal basins. The increase in population sizes at all study sites was very high, reaching levels similar to native occurrence populations. The growth constant (K) varied between 0.300 and 0.990 year -1 . The mussel bed with the highest densities had a mean abundance of [300 ind. m -2 , and a maximum of 1,460 ind. m -2 . Furthermore, the bioinvasion was facilitated by a low mortality (Z) found for populations between 0.5 and 1.5 years old (Z = 0.03-0.13 year -1 ). At present, Pacific oysters are well established at several locations in the East Frisian Wadden Sea and may become with these reproductive potential self-sustaining populations.

Development and distribution of the non-indigenous Pacific oyster (Crassostrea gigas) in the Dutch Wadden Sea

“…From these results it can be concluded that the Pacific oyster increased explosively between 2003 and 2005, but it seems to have stabilised since then. A comparably fast increase has also been found in the German Wadden Sea Brandt et al 2008;Schmidt et al 2008). (Fig.…”

“…Oysters seem to grow up to 4 cm in the first year (this study ;Cadée 2000;Reise 1998;Wehrmann et al 2000;Schmidt et al 2008). Cadée (2000) also measured growth of second year oysters in the Mokbaai (Texel).…”

L’huître, un coquillage nomade sans tête ni jambe mais avec un pied

“…Ainsi, en France, la rade de Brest et d'autres secteurs de Bretagne Sud et Vendée, qui ne connaissaient qu'un captage limité les années favorables sont maintenant en état de soutenir l'ostréiculture bretonne par la fourniture de naissains. La Wadden See (néerlandaise et allemande) a été colonisée dès 1980 (Diederich et al 2005, Schmidt et al 2008. En 2010, le Danemark, la Suède et la Norvège (Wrange et al 2010) voient des populations de Crassostrea gigas s'installer.…”

Invasion dynamics of a non-indigenous bivalve clam; Venerupis aurea (Gmelin, 1791), in Lake Qarun, Egypt.

“…Biological invasions consist of human induced species translocation such as global shipping and aquaculture or of natural range expansions (Schmidt et al, 2008). Venerupis aurea (Gmelin, 1791) is endemic to the Mediterranean Sea and have penetrated through the Suez Canal and successfully colonized Lake Timsah (Fouda and Abou Zied, 1990).…”