Fisheries & Conservation Science Group
The Northern Menai Strait mussel fishery is run by Bangor Mussel Producers Ltd.. This is an association of four businesses; Myti Mussels Ltd., Extramussel Ltd., Ogwen Mussel Ltd., and Deep Dock Ltd. The fishery has been certified by the Marine Stewardship Council (MSC). Mussel seed is fished from Morecambe Bay and Caernarfon Bay (areas without invasive species such as the Slipper limpet, Crepidula fornicata) with a proposed area in the River Dee. The mussel seed is then laid in the Straits on “lays”. These are areas of the seabed leased to each company. It takes three years of growth before they can be harvested. Over this time they are moved from shallow intertidal waters (year one) to deeper sub tidal waters (year three) Once harvested, using a mussel dredge, they are left for 42 hours in clean water before being exported to Holland, Ireland and France. Discussions are currently underway to meet the growing demand for locally produced seafood by keeping more of these mussels in the Welsh marketplace.
The Blue mussel is a common marine bivalve that varies in colour from purple/blue to brown, with a pearl white interior. The shell is roughly triangular but varies depending on the environmental conditions. The shell is smooth but has concentric lines running down each valve from the umbones. Their size varies from 2-20cm, but is usually 5-10cm.
The Blue mussel is found from the high intertidal zone to the shallow sub tidal. They attach to the substrate using byssal threads (strong, silky fibres) and often occur in high densities forming large ‘biogenic’ reefs, binding to each other and forming layers. They are found on exposed open coasts on rocks as well as in sheltered estuarine environments and are common all over the British Isles. They range from the White Sea in the North to Southern France in the NE Atlantic as well as from the Canadian Maritimes down to North Carolina in the W Atlantic. They also occur off the coasts of Chile, Argentina, The Falkland Islands, There are also several large commercial beds, for example in the Menai Straits and the Wash.
Spawning occurs over a long time period in some populations with a peak in Spring and Summer. Reproduction timings vary with environmental conditions. Fertilisation is external with an individual female releasing from 7-40 million eggs depending on environmental factors and size. This can occur over a broad range of temperatures (5-22°C) and salinities (15-40psu). The eggs are released into the water column and usually take around 1 month to develop. The juvenile mussels (pediveligers) test the substrate with their sensory foot before settling, preferring uneven ground without adults. They first settle on filamentous substrate, for example ground rich in algae, bryozoan or hydroids, at a size of around 260µm. When they reach a size of 1-2mm they move to grounds where the adult mussels lie, drifting using their byssal threads. These newly settled mussels are called ‘Spat’. As a result of drifting with currents in the water column and then again to re-settle mussels can be dispersed over wide areas.
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Morris, E.S., Goudge, H., & Duce, C. (2007). An introductory review of the biology and population dynamics of the green shore crab, Carcinus maenas, in the UK, with special reference to the Menai Strait. CCW Policy Research Report 07/18
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