Blue mussel

Farmed mussels do not require any commercial feed sources as they get all of their nutrient requirements from the surrounding water.Mussels feed by filtering mainly microscopic algae (phytoplankton), but also some organic detritus in sea water.

Overall, UK mussel aquaculture performs well on environmental impacts, as they require no chemical inputs, disease risk is low and naturally settling spat are used for ongrowing.Mussels used in aquaculture can be found naturally in marine and brackish areas and therefore culture is entirely sea based. Habitat concerns resulting from the physical infrastructure associated with suspended mussel culture are minimal and include the alteration of hydrodynamics, current velocities, and reduced flow rates. A variety of shellfish predators exist among mussel farms, including oyster drills, sea stars, crabs, benthic fishes, seabirds, and mammals. Methods used to harvest mussels in suspended rope culture generally do not result in direct impacts to predators. Passive and benign barrier netting can be used to prohibit any type of predator and is usually species specific. Duck deterrents are also used, with varying results.Recent mussel culture generally does not involve the application of chemicals (e.g. antibiotics, pesticides, herbicides, fertilizers) to control fouling and predators or to prevent disease. The amount of chemicals used in mussel culture is thought to be minute, if at all. In addition, the water in which chemicals would be used is generally not released into the marine environment and therefore, there is no threat of chemical contamination to adjacent waters or organisms. As farmed mussels are not provided external feed and there is no nutrient fertilisation, there is no concern about the impact of effluents. However, there can be a concern over changes in the sedimentary environment around mussel farms due to bio deposition and sediment trapping. These changes are limited to the farm site and are not considered to extend beyond the immediate vicinity of the farm. Furthermore, mussel farming has been shown to increase water quality at the farm site through removal of excess nutrients and phytoplankton.Mussel juveniles or 'spat' used for suspension farming settle naturally on purpose made collectors. Research into and the development of a mussel hatchery is currently ongoing in Scotland in order to address the issues of reliability and quality of Scottish spat. At present, the cultivation of mussels does not rely on hatchery production of seed as wild spatfalls are usually of sufficient quality and reliability. Aquaculture systems that are open to the environment tend to pose a risk for disease and parasite interaction with wild populations. However, there have been few mass mortality events described for adult blue mussels and good management practices ensure that the risk is low and does not threaten regional level populations.

Animal welfare is not applicable for shellfish as it is not covered by EU regulations on welfare. Humane slaughter has been carried out by RSPCA definitions.

Regulation of mussel farming in the UK is comprehensive, and appears to be fully effective in minimising negative impacts. This assessment covers uncertified mussels from the UK and Ireland, the score is respective of both countries.Aquaculture policy in the UK is a devolved matter, with the separate administrations of Wales, England, Scotland and Northern Ireland responsible for its collective oversight. In England, the Marine Management Organisation is preparing marine plans for 11 predefined areas in England. The first of these plans were published in 2014 and all plans are due to be in place by 2021. Aquaculture production in Scotland is covered in the 2015 Scottish National Marine Plan and in Wales by the 2019 Welsh National Marine Plan. The Northern Ireland Marine Plan will come into effect by 2021. Aquaculture production in Ireland is covered by the National Marine Planning Framework (NMPF) which was adopted in 2020.In the UK and Ireland, the regulations regarding the environmental impacts of aquaculture are either not applicable or are in place and are fully effective. This includes the Habitats Directive 92/43/EEC and the Birds Directive 2009/147/EC, which form the cornerstones of the EU s nature conservation policy and protect valuable habitats and species. There is also regulation in place to cover the use of land and water resources, discharges including effluents and their impacts, biosecurity and disease management.