majority was in China, which produced 84% of the global production. Japan, France and the Republic of Korea also contributed, producing 261 000, 238 000 and 115 000 tonnes, respectively. The other two major producers are the United States (43 000 tonnes) and Taiwan (23 000 tonnes). In 2003, global Pacific oyster production was worth $ 3.69 billion. Current issues Virus management Pacific oysters are nonspecific filter feeders, which means they ingest any particulate matter in the water column. This presents major issues for virus management of open-water shellfish farms, as shellfish like the Pacific oyster have been found to contain norovirus strains which can be harmful to humans. Globally, noroviruses are the most common cause of nonbacterial gastroenteritis, and are introduced into the water column by faecal matter, either from sewage discharge or land runoff from nearby farmland. Heavy metal pollution Pacific oysters, like other shellfish, are able to remove heavy metals, such as zinc and copper, as well as biotoxins (microscopic toxic phytoplankton), from the surrounding water. These can accumulate in the tissues of the animal and leave it unharmed (bioaccumulation). However, when the concentrations of the metals or biotoxins are high enough, shellfish poisoning can result when they are consumed by humans. Most countries have strict water regulations and legislation to minimise the occurrence of such poisoning cases. Diseases Various diseases are known to affect Pacific oyster: Predators Numerous predators are known to damage Pacific oyster stocks. Several crab species (Metacarcinus magister, Cancer productus, Metacarcinus gracilis), oyster drills, and starfish species (Pisater ochraceus, Pisater brevispinus, Evasterias troschelii, and Pycnopodia helianthoides) can cause severe impacts to oyster culture. Competition with other uses of the seashore Increasing numbers of frames for oysters to grow on has led to claims that the character of the beach is changed and that other users may be endangered. In the preparations for the Tokyo 2020/2021 Summer Olympics, equipment for the canoeing and rowing was found to be contaminated with of M. gigas, necessitating US$1,280,000/£930,000 in removal expenditures. Ocean acidification Ocean acidification due to increasing atmospheric carbon dioxide impacts shellfish such as oysters. The increasing acidity of the ocean reduces oyster reproduction, lowers the survival rate of juvenile oysters, and causes delayed sexual maturation. Overall, these effects combine to lower recruitment to oyster populations, reduce the maximum sustainable yield that can be harvested, and reduce the profitability of oyster farms. It is unknown if