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Basking
Sharks in the Isle of Man 2007
Written by Jackie
Hall MSc (Coordinator for Manx Basking Shark Watch)
Graphs and maps by
Dr Philippa Tomlinson (DAFF)
It has been an amazing year. We counted basking sharks, we
watched them, we tagged them and we filmed them. The following report gives you
maps, graphs and photographs to give you an overview of the 2007 Manx basking
shark season: enjoy!
Thank you all so much for sharing your basking shark sightings
with Manx Basking Shark Watch and hence with the public at large. We could not
do it without you.
YOUR 2007 REPORTS
Overall results
You have sent in 685 basking shark sightings reports this year
compared to 257 sighting reports in 2005 and 522 in 2006. The graph below shows
this increase in reporting quite clearly.
2007 was a very good basking shark year, no doubt about that
but we must not forget that the new website has made it much easier for people
to report their sightings.
If you look at the map ‘Basking Shark Sightings 2007”
you can see that as usual most of the sightings are on the extreme south and
the southwest of the Islands coast. Most of these sightings are for single
sharks but some of them were for very large groups of sharks. For example there
was one report was for 32 sharks (off The Ayres Visitor Centre), two reports
were for 36 sharks (4km and 7 km NW of Peel), and a fisherman reported seeing
‘sharks as far as the eye could see’ (off Lynague). He stopped counting when he
got to 45. It is important to remember that this does not mean that there were
not necessarily 1000s of sharks in Manx waters in 2007 as the same shark may
have been reported many times.
The first shark sighting was in March this year. If you look
at the graph below called ‘Number of sightings in ‘07’ you can see that the
pattern was much the same as any year, a couple of basking sharks in March and
April, a few in May, more in June and numbers peaking in July. August saw
a lot more sharks than usual. September saw only a few, with the last one
seen on September 12th.
This pattern of sightings is what we would expect except the
we had a big surprise when John Galpin of Manx Whale and Dolphin Watch
www.mwdw.net saw a 7 foot long basking shark off Laxey Head on November
4th! It was, as they say, the exception that proves the rule.
Results Month by Month
The maps that follow show the basking shark sightings for each month as red
dots.
March saw just one basking shark sighting off the coast near
Douglas. Early sightings are often off this bit of coastline whereas you hardly
ever see them there later in the season.
As you can see, the same pattern in April, just one sighting
off the coast just south of Douglas.
May sees the real start of the Manx basking shark season. You
will notice that there are quite a few sightings off the southern tip of the
Island as well as the normal spread up the south and west coast.
June. The Manx basking shark season is in full swing. You will
notice that there are still quite a few sightings in the south, especially
around Langness.
July sees basking shark numbers at their highest. Most of the
sightings are on the west coast.
By August the sightings numbers are well down. A lot of the
sightings are around Peel.
By September the season is virtually over.
But as you can see, November gave us a little surprise off
Laxey Head!
Basking Shark Sizes in 2007
As you can see from the graph below ‘Number of Basking Sharks
in Each Size Category’ small sharks are uncommon and the most common shark size
is 6-8m.
Look at the graph of ‘Sizes of Basking Sharks May to August
2007’. It shows you when you are most likely to see basking sharks of the
different size categories. It is quite difficult to estimate the size of a
shark but we are very fortunate that 70% of our sighting reports have size
estimates for the sharks. The mid-blue bars are for very small basking
sharks, ‘new borns’ of just 1.5 to 2 m length. There are relatively few of them
and they occur in June, July and August. It is amazing that we get so
many of these as it is very rare to see them. We had 29 sightings of
newborns on the Isle of Man this year. I suspect that this might be more than
the rest of the British sightings but the Marine Conservation Society does not
have its results published for 2007 yet. As you can see looking at the mauve
columns for the 2-4m long, young-of-the-year, sharks we also had a lot of them, 177,
most of them in July. Medium-sized sharks of 4-6m were seen in all months
but were most common in July and August. 6-8m sharks were also seen in
all months but again they were most common in July. Very big sharks of over 8m
length (dark purple) were present in every month.
Your Reports of Courtship Behaviour
or ‘Social Swimming’.
In the summer months we get many reports about the interesting
behaviour of basking sharks. It is thought that many of these interesting
behaviours are examples of basking shark courtship behaviour. Scientists are
always sceptical about labelling this as courtship and the scientific papers
refer to these behaviours as “putative’ courtship behaviour. For simplicity we
will omit this word for the rest of this account and just call it courtship.
In 2007 you have sent us reports of many basking shark
courtship events such as nose – to – tail following, parallel swimming,
‘jousting’ and breaching. We are very lucky on the Isle of Man because a lot of
this behaviour is seen and now that the MBSW reporting scheme has been going
for 3 years many of our reporters are looking at this behaviour with an
informed eye. We hope to publish this invaluable data in a scientific paper in
2008. Thank you all for contributing to this data collection. Here is a brief
summary of what you found this year. There is much more detail but we will keep
it simple here.
Courtship Behaviour Reports
If you look at the graph below, of basking shark courtship,
you will see that basking shark courtship behaviour was most common in June and
July. This is what we normally see; we were just very lucky to witness rather a
lot of it in 2007.
Looking at the map below “Basking Shark Courtship behaviour
2007’ you will see that all of these behaviours have been seen along the West
coast with clusters off the Calf, Fleshwick Bay and off Peel. These clusters
may occur because it is relatively easy for people to observe basking sharks
there. Boats take people out to watch sharks in these areas and it is possible
to see these behaviours from the shore at the Sound and Fleshwick.
Formation Swimming as Courtship
Behaviour.
You may be lucky enough to see basking sharks swimming very
close together. By this I mean that 2 or more sharks are swimming less than
half a shark body length apart for a minute or more. Sometimes they swim one
behind the other in a nose – to-tail fashion. They can be so close doing this
that they almost touch one another. At other times they swim parallel to
one another, usually about a quarter shark body length apart. I have observed
sharks swapping from one pattern to the other and back again. Several of the
‘courtship’ reports for this year are of 3 sharks together. As a picture is
worth a thousand word look at these two photographs-
Graham Hall took this photo on 07/07/07. It shows 2 sharks
‘close following’. This is thought to be a form of courtship. You can see two
shark’s dorsal fins and the rear sharks tail fin. These sharks are almost
touching nose - to - tail but we count it as nose to tail even if they
are up to half a shark body length apart. They need to be doing it for at least
30 seconds for us to think that it might be courtship. Sometimes they do it for
hours. These sharks were alternating between this and another form of courtship
called parallel swimming (see photo below).
Graham Hall took this photo on 07/07/07. This is the same
group of sharks as the nose to tail behaviour. These two basking sharks
are ‘parallel swimming’. This is also thought to be a form of courtship.
You can see the two sharks dorsal fins. They are normally about a quarter of a
shark body length apart when they do this.
Breaching.
Basking sharks sometimes breach. This is very spectacular, you
do not really expect to see something the size of a bus leap clear out of the
water. It is thought that this is a behaviour associated with courtship.
There is some question about whether breaching is associated
with courtship behaviour but it is normally done by sexually mature sharks of
more than 6m length and it tends to be seen on days when other courtship
behaviours such very close formation swimming is reported.
The graph below shows how many breaching events were
reported to MBSW in 2007. As you can see most of the breaching occurred in July
so look out for this in 2008. IF any breaching behaviour is reported I suggest
you keep well away as you don’t want a shark the size of a bus to land on your
boat! This does seem to have happened once in a Scottish town called Carradale
in the 1930s. Let’s not have it happen here.
SATELLITE TAGGING WORK
We successfully tagged 2 basking sharks with satellite tags.
Dr Mauvis Gore from Marine Conservation International came over from Scotland
to show us how to do it. Dr David Rowat from the Seychelles whale - tagging
project is analysing the tag data as I write this. These tags were £3000 each.
We are VERY grateful to Tower Insurance, Dennis Drummond and DAFF for funding 3
tags. The Gough Richie Foundation gave us £2000 towards our boat costs. We used
Bob Taylors boat ‘Gemini’ for the tagging work. Very nice bacon sandwiches Bob,
thank you! The tagging findings are ground – breaking. More of that later when
the scientific papers have been published! Hopefully at least one paper will be
published in Nature early in 2008.
This is a satellite tag. As you can see it is quite small,
that is a sheet of A4 paper behind it. This wonderful instrument can measure
the position of the shark, the water temperature and the depth. We programmed
the tags to stay on for 100 days. We don’t get any information until they pop
off and start to send us their data. Waiting can be a bit frustrating.
There are two levels of information that we can get from the
tag once it pops up. When they do pop off they beam their information to the
Argos satellite, which then emails the information down to us. IF we are lucky
enough to retrieve the actual tag we can have much more data by removing the
information chip from it. We have retrieved one of the tags so far and another
has popped up and given us its information by satellite only.
FILMING
As if that wasn’t enough our Manx basking sharks became famous
when they were featured in BBCs ‘COAST” series. 2007 saw 3 film companies
filming our Manx basking sharks. Tigress Productions filmed the tagging for
‘The One Show’ on BBC1, also Border TV and a Belgian Film company.
Miranda Krestiovnikoff off Port St Mary during the filming of Manx basking
sharks for BBC ‘COAST”
SOME GREAT SHARK PHOTOS
We have received 100s of great photos from you this year.
These include some great video footage. You will find some of these
video clips on the website. I will put more on in 2008. It’s a question of
getting around to it and the video format being compatible with the websites
requirements. Paul Steer, our software expert, has done a fantastic job of
putting these on for us. You will also find some truly excellent basking shark
photographs attached to the individual sighting reports, including some very
small sharks and some courtship events.
I apologize for the dearth of still photos in the photo
section. They WILL be put on eventually. We have had some technical problems
but these will be sorted for 2008 and the very best of the 2007 photos will be
put on then as well.
In the meantime I leave you with a great example of the 2007
photos. This great photo anchors the basking shark so firmly in the Manx
landscape.
Ian Judd: Basking shark and rainbow in Peel Bay 2007
Acknowledgements and MANY thanks
The sighting reports
As I said at the beginning of this report, we could not have
done all this without every one of you being kind enough to share your
sightings, photos and video with Manx Basking Shark Watch.
The website
The new website has been a complete success. We are planning
to improve it still further with automatic mapping and graphing for 2008. Paul
Steer www.deltait.co.uk,
our software expert, has done the most fantastic work for us. Thank you so very
much. The website costs have been funded by DAFF. We could not have afforded it
without this funding. We hope to get more funding from DAFF for the new phase
of the website.
The Tagging
The tagging work would not have been possible without Dr
Mauvis Gore, David Rowat, Bob Taylor, Dr Fiona Gell and my long suffering
husband Graham Hall. Most importantly we could not have done any of it
without our financial sponsors.
Tower Insurance, DAFF and Dennis Drummond of Canada each paid
for one £3000 tag. Their generosity is about to reap GREAT results. Well done
and thank you for your generosity. DAFF paid for Dr Gore to come across for the
tagging. The Gough Richie Foundation sponsored us generously for the boat hire.
David Stacey of Tower Insurance and Dennis Drummond have both offered to
sponsor another tag next year.
Dr Gore actually put the tags on and she is analysing
the data as it comes back. We could not have done it without her expertise. We
certainly couldn’t have done it without Graham Halls improved ‘pole tagger’.
David Rowat has been responsible for downloading and interpreting the data from
the Argos satellite. How he has fitted it in with his own work on whale shark
tagging in the Seychelles is not quite clear!
We used Bob Taylors boat “Gemini’ for the filming and tagging
work. Bob Taylor and his crew, John Paynton and Dave Ogden handled Gemini with
expertise and precision. This allowed us to get close enough to these huge
beasts without harming the sharks or risking our lives and limbs by being in a
small boat. The hospitality, especially the cake and bacon sandwiches, was much
appreciated. Bob let us hire Gemini for half his normal commercial rate so,
effectively, he was sponsoring us as well as letting us hire his boat.
Data Analysis.
So now we come to one of the most important acknowledgements
of all. If you look at the recent sightings page for 2007 you will see a long
list of sightings. Each sighting is interesting, the photographs and stories
bring each sighting to life BUT it is almost impossible to get an overall
impression of the patterns of sightings. It is hard to see WHERE most of the
shark sightings are and when basking sharks are seen at different locations
around the Island. You cannot really pick out WHEN the best times are to look
for sharks. The different SIZES of sharks are not obvious either. To do this
the data needs to be analysed and interpreted. For this we need PICTURES, maps
and graphs. All the maps and graphs you see in this report have been made
possible by the huge amount of work done by Dr Philippa Tomlinson of DAFF. With
686 individual sightings reports and no mapping program I would have been
completely unable to process all the 2007 sightings without her extensive help.
Many, many thanks!
More to Come!
I have lots more to add to this 2007 report but it will have
to wait until the New Year.
Jackie Hall
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