Offshore Overfalls MCZ

Offshore Overfalls Marine Conservation Zone is one of the seven MCZs designated within Sussex coastal waters. Identified as the second largest area of mixed sediment in the region,  the site supports a diverse mixture of habitats and animals. Formed during the last glaciation, the English Channel Outburst is also an additional protected geological feature in the MCZ, characterised as a large ancient valley.


Offshore Overfalls was designated within the second tranche of MCZ sites in January 2016. This is an offshore site located roughly 18km east of the southern part of the Isle of Wight, crossing both the inshore and offshore boundaries and covering an area of 594 km². A small section of the site falls within the 6 mile limit to the northwest corner of the boundary. The rest is outside of 6nm and therefore the Marine Management Organisation is leading on its management.

DEFRA information, including MCZ factsheet and designation order with site boundary coordinates.


The Overfalls within the MCZ is of high scientific value due to its unusual seabed composition of glacial deposits. This comprises mixed sediment, sand and gravel, that supports a diverse mixture of animals. Sandwaves formed within the sediment provide a particularly important habitat for bony fish and elasmobranchs, with the site being designated for protection of the endangered (IUCN threatened species list) undulated ray. Bass, cod, tope, Molgula sea squirts and sandeels are amongst some of the fish species present in the MCZ. To see more information on the habitats and video clips of seabed surveys click here for our interactive map.

Worms, bivalves, starfish and urchins, anemones, sea firs and sea mats are found in and on the sediment. Ross worm beds and the invasive American slipper limpet are present at several locations across the MCZ, while blue mussel beds are also thought to occur here.

The site has four designated features, including:

Sediment: Subtidal coarse sediment, subtidal mixed sediments and subtidal sand
Geological: English Channel outburst flood features

There is more information about these habitat classifications on the EUNIS website.


Fishing activity and effort in Offshore Overfalls

There is evidence of mobile demersal, mobile pelagic and static gear effort within the site, with UK and non-UK registered vessels notably active in the area. More information on fishing vessel effort within the Sussex IFCA District can be found inthis report

Management Options 

The steer from government is that management measures for second tranche MCZ sites should be developed within 2 years of designation.

Links to further information 

Joint Nature Conservation Committee (JNCC) Offshore Overfalls MPA page 

DEFRA’s Offshore Overfalls MCZ factsheet and designation order

Marine Conservation Society Offshore Overfalls MCZ page 

The Wildlife Trusts Offshore Overfalls Fact File

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