This is a static version of the conservation advice for this site, generated on 20/09/2019.
Please check the latest advice for this site at https://designatedsites.naturalengland.org.uk/

Isles of Scilly: Gilstone to Gorregan MCZ

Last updated: 15th September 2017

Supplementary advice

The Supplementary Advice on Conservation Objectives (SACOs) present attributes which are ecological characteristics or requirements of the designated species and habitats within a site. The listed attributes are considered to be those which best describe the site’s ecological integrity and which if safeguarded will enable achievement of the Conservation Objectives. These attributes have a target which is either quantified or qualified depending on the available evidence.

The target identifies as far as possible the desired state to be achieved for the attribute. In many cases, the attribute targets show if the current objective is to either ‘maintain’ or ‘recover’ the attribute.

Where there is no evidence to determine a marine feature’s condition, a vulnerability assessment, which includes sensitivity and exposure information for features and activities in a site, has been used as a proxy for condition. Evidence used in preparing the SACO has been cited with hyperlinks included where possible. Where references have not been provided, Natural England has applied ecological knowledge and expert judgement.

Some, but not all, of these attributes can also be used for regular monitoring of the condition of the designated features. The attributes selected for monitoring the features, and the standards used to assess their condition, are listed in separate monitoring documents, which will be available from Natural England. As condition assessment information becomes available, the conservation advice package will be reviewed accordingly.

When to use

You should use this information, along with the conservation objectives and case-specific advice issued by Natural England when developing, proposing or assessing an activity, plan or project that may affect the site.

Any proposals or operations which may affect the site or its features should be designed so they do not adversely affect any of the attributes in the SACO or achievement of the conservation objectives.

Feature target

‘Maintain’ targets do not preclude the need for management, now or in the future, to avoid a significant risk of damage or deterioration to the feature. The supporting and/or explanatory notes in the SACOs set out why the target was chosen and any relevant site based supporting information. This is based on the best available information, including that gathered during monitoring of the feature’s current condition.
Feature/Subfeature nameAttributeTargetSeasonSupporting notes
High energy intertidal rockDistribution: presence and spatial distribution of biological communitiesMaintain the presence and spatial distribution of intertidal rock communities.N/AA variety of communities make up the habitat. Listed component communities reflect the habitat's overall character and conservation interest. Communities are described as biotopes using EUNIS or the Marine Habitat Classification. Communities include, but are not limited to, those that are notable or representative of the feature. Representative communities include, for example, those covering large areas and notable communities include those that are rare, scarce or particularly sensitive to pressure. Changes to the spatial distribution of communities across the feature could highlight changes to the overall feature (Joint Nature Conservation Committee (JNCC), 2004).
Site-specifics:


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Moderate energy intertidal rockDistribution: presence and spatial distribution of biological communitiesMaintain the presence and spatial distribution of intertidal rock communities.N/AA variety of communities make up the habitat. Listed component communities reflect the habitat's overall character and conservation interest. Communities are described as biotopes using EUNIS or the Marine Habitat Classification. Communities include, but are not limited to, those that are notable or representative of the feature. Representative communities include, for example, those covering large areas and notable communities include those that are rare, scarce or particularly sensitive to pressure. Changes to the spatial distribution of communities across the feature could highlight changes to the overall feature (Joint Nature Conservation Committee (JNCC), 2004).
Site-specifics:


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Moderate energy intertidal rockExtent and distributionMaintain the total extent and spatial distribution of intertidal rock subject to natural variation in sediment veneer.N/AThe extent describes the presence and area of the habitat. It’s the total area of the habitat across the site as a whole, even where it’s patchy. The distribution describes the more detailed location(s) and pattern of habitat across the site. The distribution will influence the component communities present, and also help increase the health and resilience of the feature. The extent of intertidal rock is unlikely to change over time, unless as a result of human activity. However, the reef boundaries may become indistinct if bedrock is covered by a thin layer of sediment. (Joint Nature Conservation Committee (JNCC), 2004), (Davies et al., 2001), (Ware and Kenny, 2011)
Site-specifics:

Intertidal rock is located around the shores of the small islands and rocky outcrops in this MCZ.


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

High energy intertidal rockExtent and distributionMaintain the total extent and spatial distribution of intertidal rock subject to natural variation in sediment veneer.N/AThe extent describes the presence and area of the habitat. It’s the total area of the habitat across the site as a whole, even where it’s patchy. The distribution describes the more detailed location(s) and pattern of habitat across the site. The distribution will influence the component communities present, and also help increase the health and resilience of the feature. The extent of intertidal rock is unlikely to change over time, unless as a result of human activity. However, the reef boundaries may become indistinct if bedrock is covered by a thin layer of sediment. (Joint Nature Conservation Committee (JNCC), 2004), (Davies et al., 2001), (Ware and Kenny, 2011)
Site-specifics:

Intertidal rock is located around the shores of the small islands and rocky outcrops in this MCZ.


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Spiny lobster (Palinurus elephas)Population: population sizeRecover the population size within the site.N/A

Population size is the number of individuals within a population that are able to contribute to the species viability at a local, national and bio-geographic scale. Population size relates to the abundance of a species. It should include all the populations of a species within the site. Abundance may vary spatially and temporally.

The sexual maturity of spiny lobster adults varies from site to site, allowing individuals to grow and become sexually mature helps to ensure the sustainability of the population (Goñi and Latrouite, 2005).


Site-specifics:

There is evidence (Goñi and Latrouite, 2005) that spiny lobster is in unfavourable condition in all South West England waters as stocks are depleted. Evidence also suggests a decline in size within the population (Joint Nature Conservation Committee (JNCC), 2010). The recruitment and reproductive capability of spiny lobster within Isles of Scilly MCZ is therefore judged to be reduced and in need of recovery.

Due to the mobile nature of the species and the lack of scientific understanding surrounding its migration and biology, it is thought that in order to recover populations of the species to favourable condition in South West England waters, a mechanism that covers areas larger than individual MCZ sites would be required, in addition to any measure introduced through MCZs (Joint Nature Conservation Committee (JNCC) and Natural England (NE), 2012).

The population size in the Isles of Scilly is not known. A small fishery exists for spiny lobster, targeting them with trammel or tangle nets and a peak in crawfish catch is seen in late summer and autumn in the Isles of Scilly (Holt and Kielly-Fletcher, 2016). Evidence suggests a decline in average body length in the south west in populations which have been targeted by fisheries (Goñi and Latrouite, 2005).


This target is based on evidence the spiny lobster population in South West England has severely declined

Spiny lobster (Palinurus elephas)Population: recruitment and reproductive capabilityRecover the reproductive and recruitment capability of the species.N/A

Recruitment and reproductive capability reflect the health and success of the population in terms of maintaining and / or restoring numbers. A reduction in the availability of individuals able to successfully reproduce, and survival rates, may impact the overall size and age-structure of the population.

The spiny lobster usually reaches sexual maturity at 4-5 years (Goñi and Latrouite, 2005), (Joint Nature Conservation Committee (JNCC), 2010). Human pressure on this species has reduced the number of large individuals. Where females are returned to the sea survival rates are likely to be high, however, egg loss through capture is possible and this may particularly be the case for tangle net fisheries where the action of the net could remove eggs (Leslie and Shelmerdine, 2012).

A balanced sex ratio, or at least more females to males, may increase the reproductive capability of spiny lobster stock and improve recruitment. It's estimated, from laboratory rearing, that the planktonic life stage for spiny lobster is about 4 months. Eggs are released between July and September. Berried females occur from September onwards. In Wales, sexually mature females have been found with a carapace length of 121 mm.


Site-specifics:

There is evidence (Goñi and Latrouite, 2005) that spiny lobster is in unfavourable condition in all South West England waters as stocks are depleted. Evidence also suggests a decline in size within the population (Joint Nature Conservation Committee (JNCC), 2010). The recruitment and reproductive capability of spiny lobster within Isles of Scilly MCZ is therefore judged to be reduced and in need of recovery.

Due to the mobile nature of the species and the lack of scientific understanding surrounding its migration and biology, it is thought that in order to recover populations of the species to favourable condition in South West England waters, a mechanism that covers areas larger than individual MCZ sites would be required, in addition to any measure introduced through MCZs (Joint Nature Conservation Committee (JNCC) and Natural England (NE), 2012).

Relatively low numbers of juvenile crawfish were caught in the Isles of Scilly fishery between 2013 and 2015, despite the fishing gear not being size selective. Whether this indicates recruitment problems within the population, or different habitat use by sub-adults when compared to adults is unclear. Over 70% of egg carrying females caught were landed. Two thirds of spiny lobster catches were male (Holt and Kielly-Fletcher, 2016).


This target is based on evidence the spiny lobster population in South West England has severely declined

Spiny lobster (Palinurus elephas)Presence and spatial distribution of the speciesRecover the presence and spatial distribution of the species and their ability to undertake key life cycle stages and behaviours.N/A

The presence describes the species occurrence, with the spatial distribution providing a more detailed overview of the location(s) and pattern of occurrence within a site. It’s important to consider the various life stages of a species as this may influence its distribution. Disturbance caused by human activities should not adversely affect the species.

Historically, the spiny lobster has been observed in south-west coastal regions. However, sightings have not been made in many of these locations since the 1970s. The species is considered to be rare in the eastern English Channel and the North Sea (Joint Nature Conservation Committee (JNCC), 2010).


Site-specifics:

There is evidence (Goñi and Latrouite, 2005) that spiny lobster is in unfavourable condition in all South West England waters as stocks are depleted. Evidence also suggests a decline in size within the population (Joint Nature Conservation Committee (JNCC), 2010). The recruitment and reproductive capability of spiny lobster within Isles of Scilly MCZ is therefore judged to be reduced and in need of recovery.

Due to the mobile nature of the species and the lack of scientific understanding surrounding its migration and biology, it is thought that in order to recover populations of the species to favourable condition in South West England waters, a mechanism that covers areas larger than individual MCZ sites would be required, in addition to any measure introduced through MCZs (Joint Nature Conservation Committee (JNCC) and Natural England (NE), 2012).

Fishing for spiny lobster in the islands is broadly targeted towards the south west of the main archipelago, the area where this MCZ lies (Holt and Kielly-Fletcher, 2016). This suggests that the deeper, more exposed rocky habitat here may be some of the most suitable for spiny lobster in the archipelago. However, there may well be other factors affecting the location of the fisheries. Data from the Isles of Scilly lobster and crawfish tagging project confirms that spiny lobster in the archipelago undertake the seasonal migration onshore to breed, moving offshore again by late Autumn (Holt and Kielly-Fletcher, 2016).


This target is based on evidence the spiny lobster population in South West England has severely declined

Spiny lobster (Palinurus elephas)Structure and function: biological connectivityMaintain connectivity of the habitat within sites and the wider environment to ensure larval dispersal and recruitment, and / or to allow movement of migratory species.N/A

Connectivity is the extent to which populations in different parts of a species’ range are linked by the movement of eggs, larvae or other propagules, juveniles or adults (Palumbi, 2003).

Adult spiny lobster undertake an offshore migration, and this activity has been suggested as the defining characteristic of the adult stage (Díaz et al., 2001). Migration occurs after egg laying (September onwards), with a return to shallower waters in the spring for mating (Ansell and Robb, 1977), (Goñi and Latrouite, 2005), (Hunter, 1999). The migration is highly temperature-dependent (Hunter, 1999).


Site-specifics:

Although the GMA for this feature is 'recover', Natural England's expert opinion is that this particular attribute has not been impacted. The target has therefore been set at 'maintain'.

Due to their mobile nature spiny lobster in the Isles of Scilly are likely to be connected to stocks in the south west of England and Brittany (Palero et al., 2008). Management and conservation measures, including minimum landing size, should therefore be co-ordinated beyond the Isles of Scilly and throughout these wider regions (Holt and Kielly-Fletcher, 2016).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Moderate energy intertidal rockStructure and function: presence and abundance of key structural and influential species[Maintain OR Recover OR Restore] the abundance of listed species*, to enable each of them to be a viable component of the habitat.N/A

Natural England has included an attribute for the abundance of key structural and influential species for habitat features.

Structural species are those that form part of the habitat structure or help to define a key biotope.

Influential species are those that are likely to have a key role affecting the structure and function of the habitat (such as bioturbators (mixers of sediment), grazers, surface borers, predators or other species with a significant functional role linked to the habitat).

These will be identified at a national level in accordance with the criteria defined in the key structural and influential species paper (Covey et al., 2016). *For each species listed the reason for its inclusion as structural or influential and the information supporting its presence within the community of this site will be provided.


Site-specifics:


High energy intertidal rockStructure and function: presence and abundance of key structural and influential species[Maintain OR Recover OR Restore] the abundance of listed species*, to enable each of them to be a viable component of the habitat.N/A

Natural England has included an attribute for the abundance of key structural and influential species for habitat features.

Structural species are those that form part of the habitat structure or help to define a key biotope.

Influential species are those that are likely to have a key role affecting the structure and function of the habitat (such as bioturbators (mixers of sediment), grazers, surface borers, predators or other species with a significant functional role linked to the habitat).

These will be identified at a national level in accordance with the criteria defined in the key structural and influential species paper (Covey et al., 2016). *For each species listed the reason for its inclusion as structural or influential and the information supporting its presence within the community of this site will be provided.


Site-specifics:


High energy intertidal rockStructure: non-native species and pathogensRestrict the introduction and spread of non-native species and pathogens, and their impacts.N/ANon-native species may become invasive and displace native organisms by preying on them or out-competing them for resources such as food, space or both. In some cases this has led to the loss of indigenous species from certain areas (Joint Nature Conservation Committee (JNCC), 2004). A pathogen causes disease or illness to its host. Pathogens include bacteria, viruses, protozoa and fungi (Biology-Online, 2008).
Site-specifics:

Non-natives recorded in the Isles of Scilly SAC include numerous algal species; Harpoon weed (Asparagopsis armata), Wireweed (Sargassum muticum), Devil’s Tongue Weed (Grateloupia turuturu), Captain Pike’s weed (Pikea californica) which is not recorded in mainland GB and Polysiphonia harveyi. Neither Sargassum muticum and Grateloupia turuturu were present on the isles of Scilly shores in 1983, but both were observed to be well established during 2010 surveys (Juliet Brodie in (Gall, 2011)). Other non-natives include Chinaman’s hat (Calyptraea chinensis) and the crustaceans (Corophium sextonae and Solidobalanus fallax).

This MCZ site is outside of the main archipelago in deeper water, where these species are unlikely to be found. However, new non-natives have the potential to establish in the Isles of Scilly MCZs.


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Spiny lobster (Palinurus elephas)Structure: Non-native species and pathogensRestrict the introduction and spread of non-native species and pathogens, and their impacts.N/A

Non-native species may become invasive and displace native organisms by preying on them or out-competing them for resources such as food, space or both. In some cases this has led to the loss of indigenous species from certain areas (Joint Nature Conservation Committee (JNCC), 2004). A pathogen causes disease or illness to its host. Pathogens include bacteria, viruses, protozoa and fungi (Biology-Online, 2008).


Site-specifics:

Although the GMA for this feature is 'recover', Natural England's expert opinion is that this particular attribute has not been impacted. The target has therefore been set at 'restrict'.

Non-natives recorded in the Isles of Scilly SAC include numerous algal species; Harpoon weed (Asparagopsis armata), Wireweed (Sargassum muticum), Devil’s Tongue Weed (Grateloupia turuturu), Captain Pike’s weed (Pikea californica) which is not recorded in mainland GB and Polysiphonia harveyi. Other non-natives include Chinaman’s hat (Calyptraea chinensis) and the crustaceans (Corophium sextonae and Solidobalanus fallax).

None of the recorded species are known to have a detrimental effect on spiny lobster, and this MCZ site is outside of the main archipelago in deeper water, where the non-natives are unlikely to be found. However, new non-natives have the potential to establish in the Isles of Scilly MCZs.


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Moderate energy intertidal rockStructure: non-native species and pathogensRestrict the introduction and spread of non-native species and pathogens, and their impacts.N/ANon-native species may become invasive and displace native organisms by preying on them or out-competing them for resources such as food, space or both. In some cases this has led to the loss of indigenous species from certain areas (Joint Nature Conservation Committee (JNCC), 2004). A pathogen causes disease or illness to its host. Pathogens include bacteria, viruses, protozoa and fungi (Biology-Online, 2008).
Site-specifics:

Non-natives recorded in the Isles of Scilly SAC include numerous algal species; Harpoon weed (Asparagopsis armata), Wireweed (Sargassum muticum), Devil’s Tongue Weed (Grateloupia turuturu), Captain Pike’s weed (Pikea californica) which is not recorded in mainland GB and Polysiphonia harveyi. Neither Sargassum muticum and Grateloupia turuturu were present on the isles of Scilly shores in 1983, but both were observed to be well established during 2010 surveys (Juliet Brodie in (Gall, 2011)). Other non-natives include Chinaman’s hat (Calyptraea chinensis) and the crustaceans (Corophium sextonae and Solidobalanus fallax).

This MCZ site is outside of the main archipelago in deeper water, where these species are unlikely to be found. However, new non-natives have the potential to establish in the Isles of Scilly MCZs.


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Moderate energy intertidal rockStructure: physical structure of rocky substrateMaintain the surface and structural complexity, and the stability of the rock structure.N/AThe physical structure of the rock will influence the marine life that's likely to be present within a site. Structural and surface complexity, the spaces between rocks, fissures and crevices are all examples of aspects that should be considered (Hiscock et al., 2006).
Site-specifics:


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

High energy intertidal rockStructure: physical structure of rocky substrateMaintain the surface and structural complexity, and the stability of the rock structure.N/AThe physical structure of the rock will influence the marine life that's likely to be present within a site. Structural and surface complexity, the spaces between rocks, fissures and crevices are all examples of aspects that should be considered (Hiscock et al., 2006).
Site-specifics:


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

High energy intertidal rockStructure: species composition of component communitiesMaintain the species composition of component communities.N/A

Species composition of communities includes a consideration of both the overall range of species present within the community, as well as their relative abundance. Species considered need not be restricted to sessile benthic species but could include mobile species associated with the benthos. Species composition could be altered by human activities without changing the overall community type. Within each component community, species composition and population structure should be taken into consideration to avoid diminishing biodiversity and affecting ecosystem functioning within the habitat (Joint Nature Conservation Committee (JNCC), 2004).


Site-specifics:


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Moderate energy intertidal rockStructure: species composition of component communitiesMaintain the species composition of component communities.N/A

Species composition of communities includes a consideration of both the overall range of species present within the community, as well as their relative abundance. Species considered need not be restricted to sessile benthic species but could include mobile species associated with the benthos. Species composition could be altered by human activities without changing the overall community type. Within each component community, species composition and population structure should be taken into consideration to avoid diminishing biodiversity and affecting ecosystem functioning within the habitat (Joint Nature Conservation Committee (JNCC), 2004).


Site-specifics:


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Spiny lobster (Palinurus elephas)Supporting habitat: extent and distributionMaintain the extent and spatial distribution of the following supporting habitats: reef; subtidal rock.N/A

The extent of supporting habitats captures the presence and area of the habitats that the species relies on. The distribution of supporting habitat will partially govern the distribution of the species, and maintaining or recovering the distribution of supporting habitats will help ensure the stability of this species. Supporting habitats may not be limited to those described in the target.

The spiny lobster is found on rock ledges, in amongst boulders and hollows, usually in the circalittoral on open, often exposed, coasts. Some individuals may stay in the same location for several years while others may actively migrate. Moulting occurs in specific areas at specific points in the lobster lifecycle and is a time of higher vulnerability. Moulting usually occurs in areas of increased current and takes 10-15 minutes.


Site-specifics:

Although the GMA for this feature is 'recover', Natural England's expert opinion is that this particular attribute has not been impacted. The target has therefore been set at 'maintain'.

Spiny lobster are distributed throughout this site on areas of subtidal rock. Data from the Isles of Scilly lobster and crawfish tagging project confirms that spiny lobster in the archipelago undertake the seasonal migration onshore to breed, moving offshore again by late Autumn (Holt and Kielly-Fletcher, 2016).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Spiny lobster (Palinurus elephas)Supporting habitat: food availabilityMaintain the cover / abundance of preferred food items required by the species.N/A

The availability of an abundant food supply is critically important for successful breeding, adult fitness and survival and the overall sustainability of the population. Inappropriate management and direct or indirect impacts that may affect the distribution, abundance and availability of food items could adversely affect the population.

Adult spiny lobsters preferentially feed on echinoderms and bivalve molluscs (mussel, Mytilus edulis) and occasionally fish (horse mackerel, Trachurus trachurus) (Goñi and Latrouite, 2005).


Site-specifics:

Although the GMA for this feature is 'recover', Natural England's expert opinion is that this particular attribute has not been impacted. The target has therefore been set at 'maintain'.


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Moderate energy intertidal rockSupporting processes: energy / exposureMaintain the natural physical energy resulting from waves, tides and other water flows, so that the exposure does not cause alteration to the biotopes and stability, across the habitat.N/AThe amount of energy received across the site significantly affects the communities present. Physical energy can be received through wave energy and / or tidal flow, and can be altered through human activity. Any such alterations to energy should be avoided (Hiscock et al., 2006).
Site-specifics:

The Isles of Scilly are in an exposed location, with prevailing westerly winds across the Atlantic creating large waves. Wave heights in the winter exceed 4m for 10% of the time. The steep seafloor gradient around the islands means that large waves have lost little of their energy before reaching the coastline (Barne et al., 1996). Tidal currents are not particularly strong in the Isles of Scilly, but are fastest where water is forced into channels between islands and around headlands (Gall, 2011). Tidal range during spring tides is between 4 and 5 m, when maximum tidal currents can exceed 3 knots (Barne et al., 1996).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

High energy intertidal rockSupporting processes: energy / exposureMaintain the natural physical energy resulting from waves, tides and other water flows, so that the exposure does not cause alteration to the biotopes and stability, across the habitat.N/AThe amount of energy received across the site significantly affects the communities present. Physical energy can be received through wave energy and / or tidal flow, and can be altered through human activity. Any such alterations to energy should be avoided (Hiscock et al., 2006).
Site-specifics:

The Isles of Scilly are in an exposed location, with prevailing westerly winds across the Atlantic creating large waves. Wave heights in the winter exceed 4m for 10% of the time. The steep seafloor gradient around the islands means that large waves have lost little of their energy before reaching the coastline (Barne et al., 1996). Tidal currents are not particularly strong in the Isles of Scilly, but are fastest where water is forced into channels between islands and around headlands (Gall, 2011). Tidal range during spring tides is between 4 and 5 m, when maximum tidal currents can exceed 3 knots (Barne et al., 1996).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

High energy intertidal rockSupporting processes: physico-chemical propertiesMaintain the natural physico-chemical properties of the water.N/AThe physico-chemical properties that influence habitats include salinity, pH and temperature. They can act alone or in combination to affect habitats and their communities in different ways, depending on species-specific tolerances. In coastal habitats they can vary widely and can influence the abundance, distribution and composition of communities at relatively local scales. Changes in any of these properties, as a result of human activities, may impact habitats and the communities they support (Joint Nature Conservation Committee (JNCC), 2004).
Site-specifics:

The waters around the Isles of Scilly are full salinity and subject to natural fluctuations in temperature (Barne et al., 1996). Sea temperatures vary from the mainland, with slightly higher temperatures in Scilly in the winter and slightly colder temperatures in the summer. This is because the sea water does not completely stratify around the islands, allowing cold water from depths to mix with warmer surface water (Gall, 2011).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Moderate energy intertidal rockSupporting processes: physico-chemical propertiesMaintain the natural physico-chemical properties of the water.N/AThe physico-chemical properties that influence habitats include salinity, pH and temperature. They can act alone or in combination to affect habitats and their communities in different ways, depending on species-specific tolerances. In coastal habitats they can vary widely and can influence the abundance, distribution and composition of communities at relatively local scales. Changes in any of these properties, as a result of human activities, may impact habitats and the communities they support (Joint Nature Conservation Committee (JNCC), 2004).
Site-specifics:

The waters around the Isles of Scilly are full salinity and subject to natural fluctuations in temperature (Barne et al., 1996). Sea temperatures vary from the mainland, with slightly higher temperatures in Scilly in the winter and slightly colder temperatures in the summer. This is because the sea water does not completely stratify around the islands, allowing cold water from depths to mix with warmer surface water (Gall, 2011).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Spiny lobster (Palinurus elephas)Supporting processes: physico-chemical propertiesMaintain the natural physico-chemical properties of the water.N/A

The physico-chemical properties that influence the species include salinity, pH and temperature. These abiotic factors can affect the species in different ways depending on species-specific tolerances. Temperature and salinity are closely linked and can act either alone or in combination and can ultimately determine the success of a population, most notably in coastal habitats. Changes in any of these properties, as a result of human activity, may also impact the supporting habitats and the food favoured by the species.

The spiny lobster inhabits water at full salinity, which is considered to be between 30-40 psu. Water temperature is known to affect the growth rate and moult cycles of this species. In the Adriatic Sea, the temperature range of the moult cycle is between 12-16 ⁰C. Populations in colder waters grow at a slower rate and take longer to reach sexual maturity than those in warmer waters (Joint Nature Conservation Committee (JNCC), 2010), (Hunter, 1999).


Site-specifics:

Although the GMA for this feature is 'recover', there is a lack of evidence that this attribute has been impacted by anthropogenic activities. The target has therefore been set at 'maintain'.

The waters around the Isles of Scilly are full salinity and subject to natural fluctuations in temperature (Barne et al., 1996). Sea temperatures vary from the mainland, with slightly higher temperatures in Scilly in the winter and slightly colder temperatures in the summer. This is because the sea water does not completely stratify around the islands, allowing cold water from depths to mix with warmer surface water (Gall, 2011).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Spiny lobster (Palinurus elephas)Supporting processes: sediment movement and hydrodynamic regimeMaintain all hydrodynamic and physical conditions such that natural water flow and sediment movement is not significantly altered or constrained.N/A

Sediment movement is influenced by tide and wave driven water flow. Natural movement of water and sediment should not be hindered. Hydrodynamic conditions include the speed and direction of wave and tidal currents, seabed shear stress and wave exposure. Alterations to these processes could affect species presences and distribution.

The spiny lobster inhabits wave-exposed areas of the upper and lower circalittoral and lower infralittoral zones (Joint Nature Conservation Committee (JNCC), 2010).


Site-specifics:

Although the GMA for this feature is 'recover', there is a lack of evidence that this attribute has been impacted by anthropogenic activities. The target has therefore been set at 'maintain'.

The Isles of Scilly are in an exposed location, with prevailing westerly winds across the Atlantic creating large waves. Wave heights in the winter exceed 4m for 10% of the time. The steep seafloor gradient around the islands means that large waves have lost little of their energy before reaching the coastline (Barne et al., 1996). Tidal currents are not particularly strong in the Isles of Scilly, but are fastest where water is forced into channels between islands and around headlands (Gall, 2011). Tidal range during spring tides is between 4 and 5 m, when maximum tidal currents can exceed 3 knots (Barne et al., 1996).

Sedimentation rate around the islands is low, as water arrives from across the Atlantic and contains minimal land based sediment (Barne et al., 1996). There are no rivers running from the islands into the sea and the land area itself is small, reducing run off (Gall, 2011).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Moderate energy intertidal rockSupporting processes: sedimentation rateMaintain the natural rate of sediment deposition.N/AThe rate at which sediment is deposited is known to influence the status of reef habitats and / or their associated communities. Sedimentation on reef habitats can influence community composition, alter species growth rates and potentially affect reproductive success, reducing larval recruitment. This target has been included to minimise the risk of smothering to the habitat (Joint Nature Conservation Committee (JNCC), 2004).
Site-specifics:

Sedimentation rate around the islands is low, as water arrives from across the Atlantic and contains minimal land based sediment (Barne et al., 1996). There are no rivers running from the islands into the sea and the land area itself is small, reducing run off (Gall, 2011).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

High energy intertidal rockSupporting processes: sedimentation rateMaintain the natural rate of sediment deposition.N/AThe rate at which sediment is deposited is known to influence the status of reef habitats and / or their associated communities. Sedimentation on reef habitats can influence community composition, alter species growth rates and potentially affect reproductive success, reducing larval recruitment. This target has been included to minimise the risk of smothering to the habitat (Joint Nature Conservation Committee (JNCC), 2004).
Site-specifics:

Sedimentation rate around the islands is low, as water arrives from across the Atlantic and contains minimal land based sediment (Barne et al., 1996). There are no rivers running from the islands into the sea and the land area itself is small, reducing run off (Gall, 2011).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

High energy intertidal rockSupporting processes: water quality - contaminantsRestrict aqueous contaminants to levels equating to High Status according to Annex VIII and Good Status according to Annex X of the Water Framework Directive, avoiding deterioration from existing levels.N/AContaminants may impact the ecology of the Marine Protected Area by having a range of biological effects on different species within the habitat, depending on the nature of the contaminant. (Joint Nature Conservation Committee (JNCC), 2004), (UK Technical Advisory Group on the Water Framework Directive (UKTAG), 2008), (Environment Agency, 2014)
Site-specifics:

Due to the remote location of the Isles of Scilly and the prevailing currents, we would expect water quality in this MCZ to be high. Run off from the islands is low, although untreated sewage effluent is discharged into the ocean in a few places. However, due to high water movement around the islands these discharges are thought to disperse quickly (Gall, 2011).

Water sampling in St Mary's harbour found polyaromatic hydrocarbons (PAHs), total petroleum hydrocarbons (TPHs) and polychlorinated biphenyls (PCBs) to be below detectable levels, whilst metal and trace metal contamination was below harmful levels (O’Dell et al., 2014). Additionally, water quality in the harbour is likely to show higher contamination levels than in this MCZ site, due to shipping.


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Moderate energy intertidal rockSupporting processes: water quality - contaminantsRestrict aqueous contaminants to levels equating to High Status according to Annex VIII and Good Status according to Annex X of the Water Framework Directive, avoiding deterioration from existing levels.N/AContaminants may impact the ecology of the Marine Protected Area by having a range of biological effects on different species within the habitat, depending on the nature of the contaminant. (Joint Nature Conservation Committee (JNCC), 2004), (UK Technical Advisory Group on the Water Framework Directive (UKTAG), 2008), (Environment Agency, 2014)
Site-specifics:

Due to the remote location of the Isles of Scilly and the prevailing currents, we would expect water quality in this MCZ to be high. Run off from the islands is low, although untreated sewage effluent is discharged into the ocean in a few places. However, due to high water movement around the islands these discharges are thought to disperse quickly (Gall, 2011).

Water sampling in St Mary's harbour found polyaromatic hydrocarbons (PAHs), total petroleum hydrocarbons (TPHs) and polychlorinated biphenyls (PCBs) to be below detectable levels, whilst metal and trace metal contamination was below harmful levels (O’Dell et al., 2014). Additionally, water quality in the harbour is likely to show higher contamination levels than in this MCZ site, due to shipping.


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Spiny lobster (Palinurus elephas)Supporting processes: water quality - contaminantsRestrict aqueous contaminants to levels equating to High Status according to Annex VIII and Good Status according to Annex X of the Water Framework Directive, avoiding deterioration from existing levels.N/A

Contaminants may have a range of biological effects on the species, depending on the nature of the contaminant (Joint Nature Conservation Committee (JNCC), 2004), (UK Technical Advisory Group on the Water Framework Directive (UKTAG), 2008), (Environment Agency, 2014).


Site-specifics:

Although the GMA for this feature is 'recover', there is a lack of evidence that this attribute has been impacted by anthropogenic activities. The target has therefore been set at 'maintain'.

Due to the remote location of the Isles of Scilly and the prevailing currents, we would expect water quality in this MCZ to be high. Run off from the islands is low, although untreated sewage effluent is discharged into the ocean in a few places. However, due to high water movement around the islands these discharges are thought to disperse quickly (Gall, 2011).

Water sampling in St Mary's harbour found polyaromatic hydrocarbons (PAHs), total petroleum hydrocarbons (TPHs) and polychlorinated biphenyls (PCBs) to be below detectable levels, whilst metal and trace metal contamination was below harmful levels (O’Dell et al., 2014). Additionally, water quality in the harbour is likely to show higher contamination levels than in this MCZ site, due to shipping.


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Spiny lobster (Palinurus elephas)Supporting processes: water quality - dissolved oxygenMaintain the dissolved oxygen (DO) concentration at levels equating to High Ecological Status (specifically ≥ 5.7 mg per litre (at 35 salinity) for 95 % of the year), avoiding deterioration from existing levels.N/A

Dissolved Oxygen (DO) levels affect the condition and health of species. Excessive nutrient load and / or high turbidity can lead to a drop in DO, especially in warmer months. Low DO can have sub-lethal and lethal effects on fish, and infauna and epifauna communities. However, there's a significant amount of natural variation that needs to be considered (Best et al., 2007), (Environment Agency Marine Monitoring Service, 2014).


Site-specifics:

Although the GMA for this feature is 'recover', there is a lack of evidence that this attribute has been impacted by anthropogenic activities. The target has therefore been set at 'maintain'. Low run off (and therefore nutrient enrichment) from the land, in addition to the mixing of deep and surface water (Gall, 2011) mean the waters around the Isles of Scilly are not at high risk of oxygen depletion.


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Moderate energy intertidal rockSupporting processes: water quality - dissolved oxygenMaintain the dissolved oxygen (DO) concentration at levels equating to High Ecological Status (specifically ≥ 5.7 mg per litre (at 35 salinity) for 95 % of the year), avoiding deterioration from existing levels.N/ADissolved Oxygen (DO) levels affect the condition and health of features. Excessive nutrients and / or high turbidity can lead to a drop in DO, especially in warmer months. Low DO can have sub-lethal and lethal impacts on fish and infauna and epifauna communities (Best et al., 2007). However, there’s a significant amount of natural variation that needs to be considered (Environment Agency Marine Monitoring Service, 2014).
Site-specifics:

Low run off (and therefore nutrient enrichment) from the land, in addition to the mixing of deep and surface water (Gall, 2011) mean the waters around the Isles of Scilly are not at high risk of oxygen depletion.


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

High energy intertidal rockSupporting processes: water quality - dissolved oxygenMaintain the dissolved oxygen (DO) concentration at levels equating to High Ecological Status (specifically ≥ 5.7 mg per litre (at 35 salinity) for 95 % of the year), avoiding deterioration from existing levels.N/ADissolved Oxygen (DO) levels affect the condition and health of features. Excessive nutrients and / or high turbidity can lead to a drop in DO, especially in warmer months. Low DO can have sub-lethal and lethal impacts on fish and infauna and epifauna communities (Best et al., 2007). However, there’s a significant amount of natural variation that needs to be considered (Environment Agency Marine Monitoring Service, 2014).
Site-specifics:

Low run off (and therefore nutrient enrichment) from the land, in addition to the mixing of deep and surface water (Gall, 2011) mean the waters around the Isles of Scilly are not at high risk of oxygen depletion.


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

High energy intertidal rockSupporting processes: water quality - nutrientsMaintain water quality and specifically mean winter dissolved inorganic nitrogen (DIN) at a concentration equating to High Ecological Status (specifically mean winter DIN is < 12 µM for coastal waters), avoiding deterioration from existing levels.N/AHigh concentrations of nutrients in the water column can cause phytoplankton and opportunistic macroalgae blooms, leading to reduced dissolved oxygen availability. These seaweeds can smother the sediment, preventing aeration and causing anoxia (lack of oxygen). This can impact sensitive fish, epifauna and infauna communities. The aim is to seek no further deterioration or improve water quality (Devlin et al., 2007), (Best, 2014).
Site-specifics:

Minimal run off from the land in Scilly and high water movement and mixing (Gall, 2011) reduces the risk of phytoplankton and algal blooms.


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Moderate energy intertidal rockSupporting processes: water quality - nutrientsMaintain water quality and specifically mean winter dissolved inorganic nitrogen (DIN) at a concentration equating to High Ecological Status (specifically mean winter DIN is < 12 µM for coastal waters), avoiding deterioration from existing levels.N/AHigh concentrations of nutrients in the water column can cause phytoplankton and opportunistic macroalgae blooms, leading to reduced dissolved oxygen availability. These seaweeds can smother the sediment, preventing aeration and causing anoxia (lack of oxygen). This can impact sensitive fish, epifauna and infauna communities. The aim is to seek no further deterioration or improve water quality (Devlin et al., 2007), (Best, 2014).
Site-specifics:

Minimal run off from the land in Scilly and high water movement and mixing (Gall, 2011) reduces the risk of phytoplankton and algal blooms.


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Spiny lobster (Palinurus elephas)Supporting processes: water quality - nutrientsMaintain water quality and specifically mean winter dissolved inorganic nitrogen (DIN) at a concentration equating to High Ecological Status (specifically mean winter DIN is < 12 µM for coastal waters), avoiding deterioration from existing levels.N/A

High concentrations of nutrients in the water column can cause phytoplankton and opportunistic macroalgae blooms, leading to reduced dissolved oxygen availability. These seaweeds can smother the sediment, preventing aeration and causing anoxia (lack of oxygen). This can impact sensitive fish, epifauna and infauna communities. The aim is to seek no further deterioration or improve water quality (Devlin et al., 2007), (Best, 2014).


Site-specifics:

Although the GMA for this feature is 'recover', there is a lack of evidence that this attribute has been impacted by anthropogenic activities. The target has therefore been set at 'maintain'. Minimal run off from the land in Scilly and high water movement and mixing (Gall, 2011) reduces the risk of phytoplankton and algal blooms.


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Moderate energy intertidal rockSupporting processes: water quality - turbidityMaintain natural levels of turbidity (eg concentrations of suspended sediment, plankton and other material) across the habitat.N/AWater turbidity is a result of material suspended in the water, including sediment, plankton, pollution or other matter washed into the sea from land sources. In coastal environments turbidity levels can rise and fall rapidly as a result of biological (eg plankton blooms), physical (eg storm events) or human (eg coastal development) factors. Prolonged changes in turbidity may influence the amount of light reaching the seabed, affecting the primary production and nutrient levels of the habitat’s associated communities. Changes in turbidity may also have a range of biological effects on different species within the habitat, eg affecting their abilities to feed or breathe (Joint Nature Conservation Committee (JNCC), 2004).
Site-specifics:

Water clarity in the Isles of Scilly is normally very good, with visibility usually over 5m (Gall, 2011).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

High energy intertidal rockSupporting processes: water quality - turbidityMaintain natural levels of turbidity (eg concentrations of suspended sediment, plankton and other material) across the habitat.N/AWater turbidity is a result of material suspended in the water, including sediment, plankton, pollution or other matter washed into the sea from land sources. In coastal environments turbidity levels can rise and fall rapidly as a result of biological (eg plankton blooms), physical (eg storm events) or human (eg coastal development) factors. Prolonged changes in turbidity may influence the amount of light reaching the seabed, affecting the primary production and nutrient levels of the habitat’s associated communities. Changes in turbidity may also have a range of biological effects on different species within the habitat, eg affecting their abilities to feed or breathe (Joint Nature Conservation Committee (JNCC), 2004).
Site-specifics:

Water clarity in the Isles of Scilly is normally very good, with visibility usually over 5m (Gall, 2011).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

Spiny lobster (Palinurus elephas)Supporting processes: water quality - turbidityMaintain natural levels of turbidity (eg concentrations of suspended sediment, plankton and other material) in areas where this species is, or could be, present.N/A

Water turbidity is a result of material suspended in the water, including sediment, plankton, pollution or other matter washed into the sea from land sources. In coastal environments turbidity levels can rise and fall rapidly as a result of biological (eg plankton blooms), physical (eg storm events) or human (eg coastal development) factors. Prolonged increases in turbidity could affect the ability of the species to feed and respire.


Site-specifics:

Although the GMA for this feature is 'recover', there is a lack of evidence that this attribute has been impacted by anthropogenic activities. The target has therefore been set at 'maintain'. Water clarity in the Isles of Scilly is normally very good, with visibility usually over 5m (Gall, 2011).


The target has been set in accordance with the MCZ General Management Approach, based on application of the vulnerability assessment, from the time of designation. The GMA has been tailored to specific attributes according to the likely impacts.

The targets given for each attribute do not represent thresholds to assess the significance of any given impact in MCZ assessments. You will need to assess this on a case-by-case basis using the most current information available. See further guidance on how to undertake an assessment of implications of a proposal on a MCZ is given in Marine Conservation Zones and Marine Licensing.

These tables bring together the findings of the best available scientific evidence which may be updated or supplemented in further publications from Natural England and other sources. You may decide to use other additional sources of information.

These tables do not give advice about other legally protected species which may also be present within the MCZ.