Jncc coastal Directories Project Region 11 The Western Approaches

It has been suggested that the Isles of Scilly are
important for marine species.  The Isles of Scilly are the only
Lusitanian, semi-oceanic archipelago in Europe (Anon.
1995).  Added to this the waters around the Isles of Scilly
have an unusual temperature regime, varying annually by
only about 5°C - a factor that may be responsible for its rich
and varied algal communities, for example (Maggs & Guiry
1987b).  Many nationally rare and scarce species discussed
here are found in the Isles of Scilly and Lundy.  This may be
to some extent a result of geographically localised survey
effort.  However, many small offshore islands are often
habitat-rich when compared to similar areas of open coast,
because they contain, within a small area, both areas
exposed to and others sheltered from wave action and
currents.  If rarities occur in a wide range of habitat types,
the likelihood that rarities will be found in a habitat-rich
area may be higher.  Furthermore, extreme south-western
shores in the British Isles tend to bear species-rich floras and
faunas (e.g. Price et al. 1980; Connor et al. 1995; Anon. 1995),
probably because of varied topography and geology
combined with position (in the path of the North Atlantic
Drift) (Turk 1983).  In biogeographic terms Cornwall has
sometimes been regarded as more akin to northern France
than to the rest of the British Isles (Turk 1983).
None of the species from this region is known to be a
common deep-water species, and so it is unlikely that any
appear rare simply because their distribution only just
includes the generally shallower near-shore sea area that is
the focus of this study.  Some of the listed species, however,
are likely to occur to some extent in the waters of Great
Britain beyond the scope of this study.
5.4.3  Information sources used
The sites of intertidal and subtidal benthic survey data
utilised in this analysis are mapped in 
section 4.2
.  In Region
11 some of the available data come from MNCR survey
work and earlier NCC-funded surveys.  There is a history of
collecting associated with the Marine Biological Association
in Plymouth (Marine Biological Association 1957).  Data are
also available from environmental impact assessments and
Environment Agency (formerly the National Rivers
Authority) surveys as well as from publications arising from
the extensive collections of local marine biological recorders
and staff at the Cornish Biological Records Centre and the
Universities of Exeter and Plymouth.  Additional records
have been considered following personal communications
with experts in many taxonomic fields.  It has not been
possible in this chapter to list all the available literature on
which this analysis has been based, but the information
reviews and recent papers listed in 
sections 5.4.5
and 
4.2.6
should allow access to the majority of the available
information.
The availability of suitable information in the subtidal
zone of Region 11 shows concentrations.  Coverage is
generally good but some areas are more heavily surveyed.
Intertidal surveys in Region 11 also show a patchy
distribution, with some concentrations in estuaries and
sounds.
In Region 11 records go back over many years; for
example, marine molluscs were first recorded in the area as
early as the mid 1700s (Turk 1983).  Whereas every effort has
been made to obtain biogeographic data for rarity
assessment in the present study, data have not been used
from reports prior to 1965.  There are also, however, old
records from the Isles of Scilly, the Helford River and other
parts of south Cornwall and Devon of, for example, the
rarely recorded sea anemone Anemonactis mazeli, the crabs
Bathynectes longipes and Eurynome spinosa, the shrimp
Alpheus macrocheles, the snails Gibbula pennanti, Jordaniella
truncatula, Ocinebrina aciculata and Paludinella littorina and
the bryozoan Diporula verrucosa.  The warty cockle
Plagiocardium papillosum is no longer thought to exist at its
former sites of occurrence in the Helford and the Isles of
Scilly, and the hermit crab Clibanarius erythropus has
apparently disappeared from most of its known sites in
south Cornwall, following either natural environmental
changes or human environmental impact (Southward &
Southward 1988).  It would be valuable to attempt to re-
confirm old records.  Species that are likely to be very
under-recorded or overlooked on a national scale have been
avoided in the present work.
MNCR survey work uses a consistent methodology to
record conspicuous species (Hiscock 1996).  Not all the data
available from surveys in this region are as broad in scope
as MNCR surveys and they may not include less common
species or those less familiar to a specialist worker.
Inconsistent recording has, however, not substantially
reduced the quantity of available information for rarity
assessment in this region.  The MNCR of Great Britain is at
present incomplete but in future will substantially increase
the quality and evenness of distribution of the available
data.  This combined with other surveys will almost
certainly expand our knowledge of the ‘nationally rare’ and
‘scarce’ species in Region 11.  Consequently the nationally
rare and scarce status of the organisms presented here may
require re-evaluation, and in future further species may be
added to the list for this region.  Populations of species with
short life histories, such as ephemeral algae and sea slugs,
may require more regular re-evaluation of their occurrence
than others.  Longer-term trends in the English Channel
may cause range extensions and even the loss of certain
species from the extreme south-west of the British Isles (see
Southward & Crisp 1954; Turk 1983).
5.4.4  Acknowledgements
The author is grateful for the assistance of the JNCC Marine
Conservation and Coastal Conservation Branches as well as
the expert advice of Dr R.N. Bamber, Dr J.M. Baxter,
Dr J. Brodie, P.F. Clark, D.W. Connor, Dr M.J. Costello,
Dr R.L. Fletcher, Dr J.D. Fish, Dr P.R. Garwood, Dr J.M. Hall-
Spencer, Dr T. Harris, Dr P.J. Hayward, Dr K. Hiscock,
J.M. Light, I.J. Killeen, Dr G. Könnecker, Dr C.A. Maggs,
Dr J.D. McKenzie, Prof. P.G. Moore, J.J. Moore, D. Moss,
Prof. T.A. Norton, Dr J.D. Nunn, B.E. Picton, D.R. Seaward,
Dr E.C. Southward, I. Tittley, S.M. Turk and
Dr R.B. Williams.  The regional expertise of M. Camplin,
Dr P. Gainey and especially S.M. Turk has also been of great
value, as has the general assistance and comments on drafts
by Dr R.S.K Barnes, Dr J.D. George, Dr T.O. Hill and Dr
A. Rogers.  Access to the JNCC’s Marine Nature
Conservation Review Database, the NIBESRC Database at
the Ulster Museum and the ERICA database run by the
Cornish Biological Records Unit has been invaluable for the
overall analysis.
5.4  Rare sea-bed species
105

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