Pink sea fan survey
of our specialist projects since 2001 has been to collect more data
on sea fans in SW Britain. To date there have been a number of reports
arising from this work all of which can be downloaded from this
website. They are:
Sea Fan Surveys 2001-2002
sea fan surveys 2005
sea fan surveys 2005
Sea Fan Surveys 2004-2006
Bay Surveys June 2007
extract of the pink sea fan data is also available to use on the
National Biodiveristy Network website. This includes all of the
records of pinks sea fans, sea fan anemones, sea fan nudibranchs
and sea fan false cowries, except for those from the Channel Islands
which the NBN cannot yet display. It does not include the size,
condition and fouling species data.
now know that pink sea fans occur from Poole Bay in Dorset and around
the whole of the south-west peninsula as far as Ilfracombe as well
as in the Channel Islands, Pembrokeshire and southern and western
Ireland as far north as Donegal.
know that the densest 'forests' of sea fans occur in deeper water,
below 25m and generally on flattish rocks and wreckage.
know that in most areas the populations are in generally good condition
but in some there have been significant levels of disease leading
to mortality and overgrowth by other animals.
know that sea fans are easily damaged by trawling and gill netting.
know that white sea fans are healthy, but rare, that sea fan anemones
are very rare indeed and that up to 20% of sea fans in some areas
have sea fan nudibranchs resident on them.
what else is there to discover?
continue to have a number of targets for sea fan recording. These
to look for sea fan forests, including those on deeper wrecks
identified a new dense sea fan forest south of The Manacles in Cornwall
in 2007 and want to continue to identify dense populations so they
can be recorded and recommended for protection. Some of the densest
sea fan forests can be found on wrecks.
to look at outlying populations
are especially interested in sea fans at the present extent of their
range to see if there is any spreading taking place in places like
Dorset, North Pembrokeshire and Donegal. Look out for small sea
fan 'sticks' as well as mature colonies. The range in North Pembrokeshire
was extended slightly in 2008 with a sighting close to Strumble
monitoring the condition of sea fan populations around Lundy
fans on Lundy suffered extensive damage from disease in the early
2000s and we are cntinuing to monitor their gradual recovery.
to locate the extent of sea fan forests and sunset cup-corals on
The Drop Off south of Plymouth
is one of the densest areas for sea fans in the whole of the UK.
We are gradually recording its extent and the site has now been
included in a Special Area of Conservation.
the presence of sea fan nudibranchs throughout the range
on about 20% of sea fans there was a dramatic drop in numbers in
2006 but by 2008 they seemed to be on the increase again.
the presence of sea fan anemones throughout the range
of sea fan anemones remain very small and have a more restricted
distribution than pink sea fans as a whole.
the presence of false cowries, Simnia hiscocki, on sea
fans. False cowries have been recoreded more often in recent years
and we are interested in finding out more about their numbers and
whilst records from any site will be welcome, those from all the
areas above will be particularly helpful.
you can take part
some cases we are arranging special sea fan recording dives but
we hope that most of the information will come from divers who are
diving these areas as a part of their dive plan for the year. All
you need are copies of the forms and guidance notes, which can be
downloaded below, a slate and means of measuring underwater (the
Seasearch slates already have a scale printed on them so are ideal).
sea fan recording form
Nudibranchs and False Cowries
of the things we are looking out for in the general sea fan surveys
is the presence of these three animals that live on sea fans.
fan anemone, Amphianthus dohrnii
thought to be quite common these little anemones now seem to be
extremely rare. We have seen them in the Scilly Isles, near Lands
End, The Manacles, off Plymouth and in Bigbury Bay, but nowhere
else. Even here less than 1% of sea fans have them on them!
two pictures show what you are looking for. The top one is a close
up showing a single anemone. It is around 1cm across and, as you
can see, is wrapped around one stem of the sea fan.
bottom picture shows how you often get a number of anemones on a
single sea fan. This is because of their reproductive strategy which
uses basal laceration - basically tearing a new anemone from the
base of the old one.
presence of a number of anemones seems to encourage the settlement
of other life, here a silty turf, in areas where the living skin
of the sea fan has been damged by the base of the anemone.
have carried out a survey of sea fan anemones on the wreck of the
Rosehill in Whitsand Bay over a six-year period and the results
can be viewed here: Rosehill
Sea Fan Anemones 2006-12.
fan nudibranch, Tritonia nilsodneri
sea fan nudibranch is much more common, at least in some areas.
In the Manacles, Cornwall 26% of sea fans have sea fan nudibranchs
or their eggs on them. On the other hand noe were seen in our previous
survey at all in Pembrokeshire and they were rare in Lyme Bay and
adult is an amazing mimic of the sea fan polyps both in colour and
shape and very difficult to spot.
egg sprials, though small, do stand out better since they are quite
different shape to anything else on the sea fan. The picture shows
a spiral of eggs around the tip of one of the sea fan branches.
Cowrie, Simina hiscocki
False Cowrie that lives on sea fans has recently been shown to be
a separate species to the one which lives on soft corals. Like the
species, above it feeds on the sea fan polyps, but numbers are low
and it does not seem to do any permanent damage.
are interested in records of this species to establish its distribution
eyes are required to spot it!