The Pacific oyster, Crassostrea gigas, has been present in Europe since it was introduced in 1964 for aquacultural purposes in the Netherlands, from where it has since spread extensively. This study revisits eight locations in the western part of the Limfjord, Denmark, that were examined for the presence of C. gigas in 2006, to determine how the population of Pacific oysters has developed in the five intervening years. Densities where found to have declined at all but two locations on Mors. No systematic differences where found between locations or years on average shell lengths, condition indices or DW. No clear pattern of change is seen in the number or distribution of shell size classes. The similarities between locations on shell sizes, age distributions, dry weights and condition indices point towards one coherent population instead of several distinct populations. Although a survey shows that the population has not moved further eastwards to Fur, the Pacific oyster is still present in the eastern Limfjord. The decrease in densities at most locations may be due to two harsh preceding winters in 2009/10 and 2010/11. Reproduction in the population appears continuous, however the optimal environmental conditions for settlement and growth do not seem to be met. The present study found no results that indicate that the Pacific oyster is a cause for concern to the Limfjord ecosystem. This is liable to change, though, if rising temperatures and several mild winters make the physical conditions ideal for a rapid population expansion.