Celtic Seas ecoregion – Aquaculture Overview

Aquaculture policy differs between the five countries within the Celtic Seas ecoregion; within the UK, aquaculture policy is a devolved matter with each of the separate administrations of Wales, England, Northern Ireland, and Scotland being responsible for oversight. Aquaculture production within the Celtic Seas ecoregion requires licences and is regulated.

Total aquaculture production in the ecoregion in 2018 represents 21% of the overall aquaculture production in Europe by volume and 34% by value. Total production increased from 1950 up to 2004 but has since then stabilized by fluctuating around 240 000 tonnes. Marine aquaculture production within the ecoregion is currently strongly dominated by Atlantic salmon (> 80% of the total production by volume), largely produced in Scotland. Shellfish aquaculture predominates in terms of the number of licensed sites and enterprises. Production volumes of other invertebrates and seaweeds are relatively small.

Major changes have occurred in the average price per tonne for some important cultured taxa in the last decade: mussel prices have decreased by approximately 49% while Pacific oyster prices have increased by approximately 31%. Small production units (fewer than five employees) predominate in all jurisdictions although larger, more capital-intensive operations characterize the finfish sector and are also increasing in the mussel sector. Employment status is more stable for the finfish sector than the shellfish sector. The aquaculture sector has a high socio-economic importance in rural coastal communities. 

The primary environmental interactions relate to habitats and species. Sea lice and genetic introgression from farmed salmon are considered as the main threats to wild salmon populations. Other important environmental interactions considered include disease transmissions, emissions of dissolved nutrients, particulate organic matter, pollutants, and therapeutants. Increased species richness, diversity, and abundance of sessile and mobile organisms relative to ambient conditions have been observed nearby some mussel farms. The introduction of several non‑indigenous invertebrate species has also been directly linked to shellfish aquaculture. Impacts on overwintering shore-birds has been described in relation to intertidal culture operations of oysters and clams. 

Sustainable aquaculture growth in the ecoregion requires innovative production technologies to reduce the environmental impacts. These include the diversification of existing culture systems in response to changing environmental or biological drivers, application of diverse and innovative delousing techniques, expansion of seaweed aquaculture, diversification of fish culture species other than salmonids, and development of offshore aquaculture.

Future aquaculture development and management should increasingly consider interactions with other human activities, such as wild capture fisheries, recreation/tourism, offshore renewables, and the designation of marine protected areas. Climate change can further hamper sustainable growth and existing capacity for aquaculture in the ecoregion and alter interactions with other sectors.