Impact of an icy winter on the Pacific oyster (Crassostrea gigas Thunberg, 1793) populations in Scandinavia

Abstract

Most species of bryozoans have short-lived larvae with limited dispersal potential, yet many of these species possess global distributions. In this study, we report the first occurrence from the western Atlantic Ocean of the widely distributed arborescent bryozoan Tricellaria inopinata d 'Hondt and Occhipinti-Ambrogi, 1985. This species was collected in Eel Pond, Woods Hole, Massachusetts, in September 2010. At that time, T. inopinata colonies had already formed dense conspecific aggregations at some collection sites, despite the presence of several other arborescent bryozoans. Sites were monitored throughout 2011 to track the success of this introduction, and to assess the reproductive timing of T. inopinata in Eel Pond. To determine the likelihood of T. inopinata persisting in Eel Pond and competing with previously established bryozoans, rates of metamorphic initiation, metamorphic completion, and overall offspring survivability were compared to one of the other dominant arborescent species. Finally, we provide taxonomic details to aid in identifying these animals, consider the potential mode of transport, and discuss the potential ecological implications resulting from this introduction.

Population genomics shed light on the demographic and adaptive histories of European invasion in the Pacific oyster, Crassostrea gigas

“…Pacific oysters began to reproduce in Brittany (France) and now form large reefs in soft sediments and on rocks in this area (Lejart and Hily 2011). A northward range expansion was then observed in the Netherlands (Nehring 2006), throughout the Wadden Sea (Bruins 1983;Reise 1998;Nehring 1999;Dankers et al 2004), and as far north as Sweden, where dense populations of recently settled oyster populations have been observed in several shallow-water sites (Strand et al 2012). In Norway, populations can now be found in the shallow waters of the southern and western coasts (Wrange et al 2010).…”

“…), and as far north as Sweden, where dense populations of recently settled oyster populations have been observed in several shallow‐water sites (Strand et al. ). In Norway, populations can now be found in the shallow waters of the southern and western coasts (Wrange et al.…”

Origin and route of establishment of the invasive Pacific oyster Crassostrea gigas in Scandinavia

“…In 2007, many independent observations of Pacific oyster settlement on the west coast of Sweden and Norway were reported, indicating a large recruitment in 2006. Since then, despite both high winter (Strand et al 2012) and summer mortalities (Mortensen et al 2016), the species has in creased in densities (Strand & Lindegarth 2014) and is now firmly established in Scandinavian waters (Laugen et al 2015). Thus, the complex colonization history of the oyster in Scandinavian waters may be used as a good case study to gain further knowledge on processes determining genetic diversity of marine organisms.…”

Pacific oysters, Crassostrea gigas, established in Scotland

“…In Scandinavia, feral populations have been recorded as far as 60°north (Wrange et al, 2010). Studies in Norway indicate that, although severe winters may kill a proportion of established feral C. gigas, sufficient individuals can survive to sustain the local population (Strand et al, 2012). Pacific oysters are thus colonizing some of the former grounds of the European flat oyster in northern Europe, which imposes an additional challenge for restoring populations of native oysters (Ruesink et al, 2005).…”