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Common dolphins, fastest mammal in the sea

Common dolphin (Delphinus delphis) swimming at high speed. Colin munro Photography
Common dolphin (Delphinus delphis) swimming at high speed. Colin munro Photography

Common dolphin (Delphinus delphis) swimming at high speed, just below the surface.

What is the fastest marine mammal? There are a number of pretty speedy guys in the water. It’s been calculated that when an orca, weighing up to five tonnes, breaches this requires an exit speed of around 40kph. That’s around the same as the maximum speed attained by Usain Bolt in a 100 metres race. Only he doesn’t weigh five tonnes…and he’s not doing it underwater. In 2009 french swimmer Frédérick Bousquet set a World record 50m freestyle sprint, with an avergae speed of 8.6kph. A lot faster than you or I, but never gonna outswim an orca; orcas can, in fact touch 50kph when they want to. Perhaps surprisingly, given that they weigh upwards of 150 tonnes, blue whales are also pretty zippy, also able to get the needle up to 50khp when in a hurry (why would blue whales be in a hurry?). However current data suggests that the fastest dude on the block is the common dolphin (Delphinus delphinus). These guys can reach 64kph (40mph). According to the Guiness Book of records that’s a whisker slower than the fastest racehorse (Winning Brew, 2008) over 400 metres (two furlongs). I’ve owned cars that struggle to do that on hills.

It is hard moving fast through water compared to air, so how do they do it? In 1936 zoologist Sir James Gray looked at this and concluded that dolphins simply shouldn’t be able to generate sufficient power to move them through the water as fast as they appeared able to do. This became known as Gray’s Paradox. It is now believed that the hydrodynamic shape of dolphins greatly reduces form drag, and thus the power required. There is also some evidence that the dolphin’s soft skin, which is continually shed, reduces friction drag. Even so, that a dolphin can travel as fast as a thoroughbred racehorse, through a medium almost 800 times more dense than air, is pretty impressive.

How many common dolphin species?
Until the 1960s all common dolphins were considered one single species. Genetic studies have indicated that there are probably at least two, possibly three distinct species. These are the short-beaked common dolphin (Delphinus delphis) which is the species most likely to be encountered in british waters; the long-beaked common dolphin (Delphnus capensis), and possibly a third species, the arabian common dolphin (Delphinus tropicalis) although many marine biologists consider this a subspecies of the long-beaked common dolphin.

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Colin Munro

Porbeagle populations in the N.E. Atlantic critically endangered.

Porbeagle shark, Lamna nasus, caught as bycatch, on the deck of a fishing vessel, Irish Sea, UK. Colin Munro Photography

Porbeagle shark, Lamna nasus, caught as bycatch, on the deck of a fishing vessel, Irish Sea, UK. Colin Munro Photography

Porbeagle shark, Lamna nasus, caught as bycatch, on the deck of a fishing vessel, Irish Sea, UK.


Porbeagle sharks (Lamna nasus) are a temperate water species of shark belong to the mackerel shark family (Lamnidae), the same family as salmon sharks, makos and great whites. Adults are around 2.5 metres long and and weigh about 140kg. They are considered vulnerable throughout their range. The population around UK shores (NE Atlantic) is considered critically endangered (IUCN). The International Committee for Exploration of the Seas (ICES) advises that the NE Atlantic stocks may be close to collapse. A quota system for porbeagles was introduced in 2008. The Total Allowable Catch (TAC) was reduced to 436 tonnes in 2009. In UK waters a total ban on targetted fishing by commercial fishermen has been in place since 2010, with release of accidental bycatch whenever possible. ICES has called for a zero TAC since 2006; there are now proposals to bring this in to effect throughout the EU.

There is a still a problem in that porbeagles, are fast swimming predators that feed on squid and fish. Freuqently the species that fishermen are also targetting. Porbeagles may end up as accidental bycatch in trawls or in set nets. Like other mackerel sharks, porbeagles’ gills work by obligate ram ventilation. This means they need a constant flow of water past their gills in order to oxygenate their blood. Trapped in nets they quickly drown. As set nets are often deployed on the seabed then hauled 12 or 24 hours later, even if the fishermen would like to release them alive it will be too late. The Centre for Environment, Fisheries and Aquaculture Science (CEFAS) is currently conducting a DEFRA commissioned study in to the threats posed by accidental bycatch to porbeagle in UK waters. Hopefully this will result in guidance for fishermen as to the best ways to minimise the risk of accidentally catching porbeagles.

Save our Seas is working with the Marine Institute in Ireland to satellite tag porbeagles. This should help us understand portbeagle migration and possibly identify nursey areas. This has so far shown that porbeagles tagged off northern coast of Ireland have resurfaced off Lisbon, Portugal. Details of the study can be seen here.

Interesting fact: All fish are cold blooded right? Not quite. Recent studies have found that most mackerel sharks (salmon sharks, great whites, shortfin mako and porbeagles) are able to maintain their body temperature above that of the surrounding water, as marine mammals do. They acheive this by passing deoxygenated blood, heated by muscle activity and biochemical reactions, past a network of cold, oxygenated blood travelling through a network of fine arteries (the rete mirable, literally ‘wonderful net’) thus transferring heat to the arterial blood rather than simly losing it to the external environment. Salmon sharks (Lamna ditropis) sharks have been found to maintain their core temperature up to 21 degrees C above that of the surrounding water (Goldman et al, 2004)

Update
Porbeagles are endangered throughout the Atlantic. The EU has now voted to ban commercial porbeagle fishing. Currently only Canada allows a commercial fishery, although the Canadian Government are coming under considerable pressure from conservationists within and outside Canada. More more information on this read the Friends of Hector article here.

References
Goldman, K.J., Anderson, S.D., Latour, R.J. and Musick, j.A., 2004. Homeothermy in adult salmon sharks, Lamna ditropis. Environmental Biology of Fishes 71 (4): 403–411.

Lyme Bay, what makes it special?

Lyme Bay, what makes it special?

I’ve published about Lyme Bay marine biological monitoring on my marine-bio-images blog   here and earlier on this blog here, looking at the monitoring of Lyme Bay Closed Area, a Marine protected Area success? Parts 1 and 2 describe the impacts mobile fishing gear, in particular scallop dredging, had been having on the reefs since at least the late 1980s. I describe the impacts of scallop dredging in detail here. I will look soon at the actual monitoring that has taken place since the closed area came in to being in 2008, but before doing so it is probably worth devoting a couple of blogs to describe why Lyme Bay is important and worth protecting; just what makes it special.

What Lyme Bay is not

In seeking to justify protection for the reefs and ‘sell’ the area to the wider public, the concepts of ‘coral gardens’ and ‘charismatic species’ has often been pushed.  Such poetic language may well raise the area’s profile and engender support in the short term, but it has lead to some fairly profound misunderstandings – including within NGOs and Government Agencies – about the bay and the reasons the reefs within are important.

A sediment covered limestone reef in Lyme Bay, Southwest England showing the profusion of sediment tolerant species that grow on such reefs. Colin Munro Photography.

A sediment covered limestone reef in Lyme Bay, Southwest England showing the profusion of sediment tolerant species that grow on such reefs. Image No. MBI001261.

Most of Lyme bay is not visually spectacular, there are few dramatic underwater rock cliffs painted with a riot of colour; nor is it beautiful clear water offering panoramic vistas across the seabed.  The reefs in Lyme bay are mostly low lying and the waters tend to be fairly gloomy and turbid.  As this is essentially a large, open, sandy bay exposed to the prevailing winds, then significant amounts of suspended sediment (at least near-shore, close to the seabed) are the norm.  Whilst winds may ease in summer, it is also prone to strong plankton blooms during May and June, with a second less pronounced bloom in late summer.  Thus underwater visibility rarely exceeds 10 metres (30ft) and frequently may be less than 3 metres (10ft).  The reefs in the bay, though numerous in the centre and east, are mostly discontinuous, forming a patchwork of low rocky outcrops surrounded by sediment.  This means that they tend to be covered by thin veneers of sediment as tide and wave action lifts and sweeps saltating sand across them.  The amount of sand will vary, depending on the size of the reef area, how high the reef rises above the surrounding sediment plain, the strength of tidal streams in that part of the bay and how strong the wind has been recently (and thus how big the waves).  This makes it a rather challenging environment both the underwater photographer and scientist attempting to record visual data.  Low light levels and high levels of suspended sediment producing lots of backscatter from lights making for tricky problems in producing good images.

An area of sediment covered boulder reef, Lyme Bay. The large white sea squirt Phallusia mammillata, and the blue-grey colonial sea squirt Diplosoma spongiforme, both characteristic of Lyme Bay, can be seen in this image. Image No. MBI001264. Colin Munro Photography

An area of sediment covered boulder reef, Lyme Bay. The large white sea squirt Phallusia mammillata, and the blue-grey colonial sea squirt Diplosoma spongiforme, both characteristic of Lyme Bay, can be seen in this image. Image No. MBI001264.

The species that make Lyme Bay different and the effects of the Closed Area

The flip side of this is that the communities on these reefs tend to be rather different from those inhabiting areas with perhaps more visually spectacular ‘clean’ reefs further west.  Species that tolerate a degree of sand and silt cover do well here.  A good example of this is the sponge Adreus fascicularis, a species found almost exclusively on silt-covered horizontal bedrock  Considered rare in UK waters, it is relatively common  on the reefs of Lyme Bay.  Similarly the large solitary sea squirt Phallusia mamillata.  A very distinctive species, the largest sea squirt found around British coasts its striking white colour stands out against the dull sediment.  More associated with silty, sheltered harbours and estuaries it is uncommon or rare on open coasts along the rest of its UK range, but quite abundant within Lyme Bay.  So the factors that make this a difficult environment in which to capture appealing images or gather data on the marine life in quite a significant contribute to Lyme Bay being an interesting and unusual environment. There are other species common here that we simply do not known enough about their ecology to say why they are more abundant in Lyme bay than elsewhere; a good example of this is the colonial sea squirt Diplosoma spongiforme. Though not rare elsewhere, it is abundant in Lyme Bay, forming mats, growing over rocks, seafans and other sponges. Similarly the tassled yellow sponge Iophon hyndmani/Iophonopsis nigricans (the two species are grouped together as very difficult to tell apart underwater) is particularly abundant in Lyme Bay. Indeed the sponge assemblages are frequently very rich and diverse on Lyme Bay reefs; for some reefs such as the boulder reefs (for example Lane’s Ground Reef in the central part of Lyme Bay) they are probably the most obvious characteristic of the reef and may well be the most diverse groups within the reef community there. Unfortunately they are still very poorly described (in part because sponge taxonomy is a difficult subject with field characteristics often not being sufficient for positive identification) and so are certainly under-reported and thus frequently undervalued in terms of the Bay’s conservation value. Yet sponges, being soft tissued and quite often slow-growing species, are amongst the most vulnerable to damage and eradication from areas of reef by mobile fishing gear. Indeed the sharp decline in sponge species occurring on Lane’s Ground Reef between 1995 and 2008 (clearly visible for video footage and still images taken by myself during this time period) was one of the most obvious and disturbing changes in the years before statutory protection from bottom-towed mobile fishing was established for central Lyme Bay.

Boulder reef, Lyme Bay.  The amount of suspended sediment in the water can be clearly seen.  The yellow tassled sponge Iophon hyndmani or Iophonopsis nigricans can be seen in the centre of the image, however the lack of sponges (and other attached life) compared to previous years is clear. Image No. MBI001267

Boulder reef, Lyme Bay. The amount of suspended sediment in the water can be clearly seen. The yellow tassled sponge Iophon hyndmani or Iophonopsis nigricans can be seen in the centre of the image, however it can be seen that many of the boulders are now (2010) bare of sponges and other attached life. Image No. MBI001267

Has there been a recovery of sponge species since the Closed Area was established in 2008? Our study (running from 2008-2010, when funding from Natural England ended) suggested that sponge recovery was beginning. Three years is too short a time in which to expect marked changes in such communities. It would also be foolish to read much in this data, three annual surveys (i.e. data being collected once a year for three years) represent only three data points. There will obviously be good years and bad years, plus a degree of error in any data collected, so a line drawn from three data points must come with huge caveats. Nevertheless, this slight improvement was noticeable. We are hopeful that we will be able to re-start our monitoring programme, albeit in a slightly reduced form, on a voluntary basis in 2013. It will be exciting to see what effects the Closed Area has had on the reef communities after five years.

More information about Lyme Bay, in particular the impacts of scallop dredging and the protected Closed Area, can be found on my marine biology blog www.marine-bio-images.com/blog, and on the marine-bio-images website where numerous reports on the research we have conducted here can be found.

All text and images in this blog copyright Colin Munro 2012.  All images are available to license.    Alternatively you can search all my online stock images at my www.colinmunroimages.com  site through the search box (top right) or on my main website here.

Flying crabs and flailing birdmen

Swimming crab, Liocarcinus depurator, swimming in mid-water. This crab is also known as the harbour crab, blue-legged swimming crab and sandy swimming crab. Colin Munro Photography.

All the images in this blog are available to license.  To view a gallery (license images or purchase prints of) these, and more of my North east Atlantic marine invertebrate images go here.  Alternatively you can search all my online stock images at my www.colinmunro.photoshelter.com  site through the search box (top right) here or on my main website here.  swimming crab images, Liocarcinus depurator images, necora puber images, stock images.

Flying crabs
A crab is neither the most graceful nor aerodynamic creature in the sea.  Okay you probably knew that already.  At first glance it does not appear to be designed for flight, its squat, angular body, entirely encased in a thick, heavy shell.  A crab attempting to fly would seem as sensible as attempting to run a marathon wearing a suit of armour.  But then, as anyone who has watched the London marathon will know, people do attempt – and succeeded  – in running marathons in suits of armour.  So why shouldn’t crabs fly?

I have been a little loose with the term ‘fly’; okay, they fly underwater.  They are collectively known as swimming crabs.  This group includes such species as the blue crab (Callinnectes sapidus) which is found around the coasts of North and South America, the red-eyed and fearless velvet swimming crab (Necora puber) that is common on shallow rocky reefs around the coast of UK and much of Europe, and the blue-legged swimming crab (Liocarcinus depurator) also common in shallow waters around UK and Europe but preferring sandier areas.

A velvet swimming crab, Necora puber (previously known as Liocarcinus puber) adopts a defensive posture as it moves across a maerl gravel seabed. Colin Munro Photography.

the distinctive wild red eyes and aggressive posture of a velver swimming crab (Necora puber). Note the broad swimmerets. Image No. MBI001256

A common feature of all these crabs is the adaptation of the fifth walking leg for propulsion through the water.  Crab legs are mostly fairly spindly affairs, ending in points on which they tippy-toe across the sea bed.  The final articulated segment of swimming crab legs is flattened and splayed into a paddle shape.  Additionally they are edged with long thick hairs, effectively widening the paddle blade.  These swimming legs are known as pleopods (from the Greek plein, to sail or to swim, and pods – legs) or swimmerets.

Swimming crab, Liocarcinus depurator, swimming in mid-water.  This crab is also known as the harbour crab, blue-legged swimming crab and sandy swimming crab. Colin Munro Photography.

Swimming crab, Liocarcinus depurator, swimming in mid-water. Image No. MBI001254.

I started this by stating that crabs were not really designed to fly (or swim for that matter).  This is true.  Swimming marine creatures conjures up images of graceful fluid movements.  That is not swimming crabs.  Generally swimming crabs swim when disturbed, as a means of escaping real or perceived danger.  They launch themselves off the seabed, flailing wildly as if convulsing through being wired up to high voltage electricity.  For seconds, or at most a few minutes, the crab will move erratically through the water.  As it tires its legs will slow; the crab will drift back down to the seabed, to scuttle away hopefully haven shaken off its pursuer.

Swimming crab, Liocarcinus depurator, swimming in mid-water.  This crab is also known as the harbour crab, blue-legged swimming crab and sandy swimming crab. Colin Munro Photography.

Close up of a swimming crab, Liocarcinus depurator, swimming in mid-water. Image No. MBI001254CP2

Watching a crab frantically waving its legs in an attempt to defy gravity, as it descends inexorably back to solid seabed I am always struck by the uncanny resemblance to another quirky British tradition (apart from wearing ridiculous costumes for marathons) that of the birdman competition.  This is an annual event held in several seaside towns, most notably Bognor Regis, where the great British eccentric emerges to don one-piece stripey swimsuits, circa 1900, batman masks, vinyl capes and wings that appear to be constructed from broom handles and ostrich feathers.  Suitably attired they launch themselves off the end of the town jetty.  Arms flaying wildly in an attempt to defy gravity (now you see where I’m coming from) they perform a graceless parabola and they too, descend inexorably to the sea below.

The first birdman competition (according to Wikipedia) occurred in Selsey, West Sussex, in 1971.  How long have crabs been launching themselves off the seabed, attempting to escape the limitations imposed by a million years of evolution, no-one knows.  Perhaps they have been sitting, half-buried, on the seabed, watching and pondering on ill-designed creatures in strange garb plunge in to the sea as they attempt to escape their own limitations.  Perhaps flying crabs are a recent phenomenon, the dreamers inspired by eccentrics in sleepy seaside towns.

Edible crabs, a little natural history.

Edible crab or brown crab, Cancer pagurus, close up, showing eyes. Colin Munro Photography

All the images in this blog are available to license.  To view a gallery (license images or purchase prints of) these, and more of my North east Atlantic marine invertebrate images go here.  Alternatively you can search all my online stock images at my www.colinmunro.photoshelter.com  site through the search box (top right) here or on my main website here.  Edible crab images, Cancer pagurus images, stock images.

Edible crabs
The pie-crust edged shell of the European edible crab, Cancer pagurus, is one of the most familiar sights in fishmongers windows and supermarket fish counters. Known by British fishermen as the brown crab, due to the deep reddish-brown colouration of its shell.  This is the crab we normally eat as ‘dressed crab’, with the crab meat served arranged in the open crab shell.  Juvenile edible crabs are often found under boulders by children rock pooling on the shore, their reddish-brown colour and much more chunky claws (chelipeds) easily distinuishing them from the more common shore crab (Carcinus maenus).

Edible crab or brown crab, Cancer pagurus, close up, showing eyes. Colin Munro Photography

Edible crab or brown crab, Cancer pagurus, close up, showing eyes. MBI000266

Adults generally live further offshore, down to about 200 metres depth.  Away from rocky areas edible crabs tend to bury themselves in ther sediment.  They’re pretty well camouflaged when they do this, one has to look pretty hard to make out the outline of their shell or see the two beady little eyes watching to see if you’ve spotted them.

An edible crab, Cancer pagurus, lying hidden in a shallow depression it has dug in the sediment. Colin Munro Photography

An edible crab, Cancer pagurus, lying hidden in a shallow depression it has dug in the sediment. Image No. MBI001178

Edible crabs are prodigious excavators of sandy or muddy seabeds.  During the course of a dive one can often observe numerous large shallow ‘craters’ created by edible crabs.

An edible crab, Cancer pagurus, digs in to algae covered sediment to create a depression in which to hide. Colin Munro Photography

An edible crab, Cancer pagurus, digs in to algae covered sediment to create a depression in which to hide. Image No. MBI001171

Migrations
Within the English Channel edible crabs undertake interesting migrations.  Females tend to move west or southwest; they can travel 2-3 kilometers a day, with some travelling up to 200 miles.  They larvae, which are planktonic for 60-90 days, tend to drift east, thus restocking the areas from which the adults migrated (Pawson, 1995).  Mating occurs in spring, shortly after the females have moulted, but the sperm is stored by the females and eggs are fertilised once they move offshore the following winter.

Lifespan and minimum landing sizes
Edible crabs generally live for 25-30 years.  There are various reports of them living up to 100 years but it’s hard to assess how reliable these reports are.  The minum landing size various regionally in UK waters between 130 and 140mm across the carapace.  In Devon, Cornwall and the Scilly Isles this is increased (for male crabs only) to 160mm.

Fun facts
The largest edible crab ever caught in British waters is believed to be one landed, not by a commercial fisherman, but by an amatuer diver.  Paul Worsley landed a 17lb crab with a 12 inch wide shell in July 2008.  This monster was caught on the wreck of the Empress of India, a British battleship dating from the 1890s that lies in deep water in Lyme Bay, Southwest England.

An edible crab, Cancer pagurus, raises its large heavy claws (chelipeds) adopting a defensive posture. Colin Munro Photography

An edible crab, Cancer pagurus, raises its large heavy claws (chelipeds) adopting a defensive posture. Image No. MBI001249

An edible crab, Cancer pagurus, attempting to hide in maerl gravel. Colin Munro Photography

An edible crab, Cancer pagurus, attempting to hide in maerl gravel. Image No. MBI001250

All images copyright Colin Munro
www.colinmunrophotography.com
www.colinmunro.photoshelter.com

All the images in this blog are available to license.  To view a gallery (license images or purchase prints of) these, and more of my North east Atlantic marine invertebrate images go here.  Alternatively you can search all my online stock images at my www.colinmunro.photoshelter.com  site through the search box (top right) here or on my main website here.

References
Pawson, M., G. 1995. Biogeographical identification of English Channel fish and shellfish stocks. Fisheries Research Technical Report (number 99), MAFF Direct Fisheries Research Lowestoft, England. Available from: http://www.cefas.co.uk/Publications/techrep/tech99.pdf

Diving the trawl 2: filming the trawl

Diving the trawl 2: filming the trawl

A couple of years ago I wrote a piece called lessons is stupidity: diving the trawl , describing the first time I dived on a trawler’s net.  I’ve done this a few times over the years, most recently a couple of days ago.  We re-did this because cameras improve and the quality of images improves, so we need to re-shoot.  We also wanted to get some slightly different images this time; in particular we wanted to get images as the trawl net was being hauled, when it was just below the surface.

As events transpired the weather conditions were against us. Strong winds prevailed through most of August and much of September.  It was not until the last week of September, with equinoxal gales just around the corner, that we finally found a brief window of opportunity.  Due to vessel availability and other logistical constraints we had only one day available that week in which everything came together.  The weather was marginal but we were now well into autumn with precious few opportunities remaining this year, so we decided to take a chance and go for it.

Trawl net close up as it is hauled to the surface, Lyme Bay, Southwest England, Colin Munro Photography

Trawl net close up as it is hauled to the surface, Lyme Bay, Southwest England,

We began to load the trawl net on to our vessel on a bright but chilly morning.  A stiff breeze was whipping whitecaps on the sea beyond the shelter of the harbour, but the latest forecast indicated this should die away during the morning.  By the time the net had been hauled aboard and rigged and all our gear on deck it was midday; Lynsey, John and I were hot, dirty and sweaty but pretty satisfied everything was as ready as it could be.  The wind had not abated.  But we were now committed, so warps were unhitched and we nosed out into the bay.  A 60 square mile exclusion area for bottom towed fishing gear (trawls and scallop dredges) has been established within the centre of Lyme Bay to protect the fragile reefs found there (this came about in part due to our earlier work looking at the impacts of bottom-fishing gear).  We therefore had a two hour steam to get to a suitable location beyond this closed area in which to set the trawl.  That gave us two hours for the wind to die down and the sea state to drop away.   If we were lucky the wind would not yet have stirred up the seabed enough to destroy the visibility.  The longer the wind continued the more our chances of success diminished.

Filming the trawl net being deployed

John does all the hard work while I film the trawl net being deployed

We reach a shallow bay outside the closed area, about 20 metres depth, shortly after 2.30p.m.  The wind was still fresh and we knew it was not looking good for getting workable conditions on the seabed.  We decided to have a test dip to check out visibility before deploying the trawl.

A bottom trawl, otter trawl. © Colin Munro

Diagram of the bottm trawl used (not to scale)

I wanted to stay dry in order to do some surface filming of the trawl being deployed, so this task fell to my dive buddy Lynsey.  A quick dip was enough to convince her it was no-go.  Seabed visibility was no more than one metre.  Quite apart from it being impossible to film the trawl operating in such conditions it would also have been too dangerous to be around heavy moving fishing gear.  Reluctantly I called the dive off and we reverted to plan B.

Setting up the Gates camera housing in the trawler’s tiny wheelhouse is always a bit of a challenge.

I also wanted to get footage of the trawl as it was being hauled, a little below the surface.  This we could do as the near-surface visibility, although far from perfect, was much better than that close to the seabed.  However, there were the added logistical problems that the trawl net had to be hauled with the boat steaming forward at a speed of several knots, way too fast to swim or hang on holding a large camera.  We had worked a method where I would be dropped off close to the net as it reached the surface, and drift back alongside it, filming as I went.  It sounded plausible – I mean what could possibly go wrong?  Before this we set up some surface and just below shots at speed, working from a small inflatable.

John and Lynsey in deep discussion as we trawl for a couple of hours.

John and Lynsey in deep discussion as we trawl for a couple of hours.

Poor Lyndsey had the unenviable task of heaving cameras across the tubes to me and hanging on to my legs as I dangled head-down in the water trying desperately to: a) get the vaguest impression of what I was filming through the spray and turbulence, and b) stop my camera from being ripped from my fingers.  From the surface I must have presented a highly comical sight, legs waving and coughing and spluttering to the surface every few seconds.  From a personal perspective it felt rather like what I imagine being waterboarded by a firehose while suspended upsidedown might feel like.   Having had my sinuses thoroughly irrigated at high pressure, it was now time to get into the water, before I had time to ponder the stupidity of my actions and change my mind.  At any rate, the sun was racing toward the horizon and light was fading rapidly, so it was either now or  call it off and wait ’til next year.    In the event the plan worked almost like clockwork; we were even able to repeat the operation so that I could run one haul taking stills and a second taking video footage.  Given the relatively poor visibility (~ 4 metres near the surface) I was quite pleased with the results.

The stupid grin you wear when it all works out.

Nothing got broken (apart from a torn shoulder muscle – my stupidity when the trying to work parallel to the waterflow) and everything worked pretty much as it should.  October gales have now set in so there will be no more dives on fishing gear this year.

Note:  As with my previous blog on this topic, this is NOT in any way designed to be a ‘how to’ guide to diving on trawl nets.  I have deliberately ommitted key elements to try to avoid giving this impression.  Diving around nets and heavy moving fishing gear obviously involves a significant element of risk if not approached with great care and planning.  I have presented this in a fairly light-hearted manner and should be taken as such rather than a technical guide.

Common Dolphins, mother and calf

Common Dolphins, mother and calf
Mother and calf common dolphins (Delphinus delphis) swimming in close harmony. Colin Munro Photography. Image No. MBI000335.

Mother and calf common dolphins (Delphinus delphis) swimming in close harmony. Image No. MBI000335.

 These pictures were taken during a recent trip to look for blure sharks (Prionace glauca) off the north coast.  Although we did find one blue, we had no luck with pictures (next time!).  However we did come across a large group of common dolphins (Delphinus delphis) feeding.  Each summer substantial numbers of commons dolphins can be found around the coasts of Devon and Cornwall as they follow the mackerel shaols.  Hopefully I’ll be adding to these images this summer.  As ever, these images can be licenses for reproduction and are also available as fine art prints.  Email me , telling me the image number and what you require for further details. You can also search for additional images either from my main website homepage or using my Photoshelter website. Links for both are given in the sidebar.

Common dolphins (Delphinus delphis) swimming, showing tooth rake marks on back. Colin Munro Photography, Image No. MBI000333.

Common dolphins (Delphinus delphis) swimming, showing tooth rake marks on back. Colin Munro Photography, Image No. MBI000333.

 

Common dolphins (Delphinus delphis) swimming, head on. Colin Munro Photography, Image No. MBI000339.

Common dolphins (Delphinus delphis) swimming, head on. Image No. MBI000339.

 

Common dolphin (Delphinus delphis) swimming at high speed. Colin Munro Photography, Image No. MBI000337.

Common dolphin (Delphinus delphis) swimming at high speed. Image No. MBI000337.

Spring is in the air. Seaslugs mating: Polycera faeroensis.

Spring is in the air. Seaslugs mating: Polycera faeroensis.
The seaslug, or nudibranch,  Polycera faeroensis mating.  Like all nudibranchs, Polycera faeroensis is a simultaneous hermaphrodite.

The seaslug, or nudibranch, Polycera faeroensis mating. Like all nudibranchs, Polycera faeroensis is a simultaneous hermaphrodite. Image MBI000678

Spring is in the air, the sea is getting warmer – slowly – and the birds and bees, and most things beneath the waves too. Polycera faeroensis is a very common seasulg in British waters, and although colourful is often overlooked due to its small size, large individuals are no more than 4.5 centimetrs long. Like all nudibranchs they are simultaneous hermaphrodites – possessing both male and female sex organs at the same time (sequential hermaphrodites have either only male or only female sex organs at any given time). Copulation works both ways (reciprocal copulation, as it is termed). As the sex organs always appear to be on the right side or their bodies, Polycera faeroensis nudibranchs copulate head to tail. The missionary position has not caught on in the nudibranch world. One might think this was already exciting enough for any mollusc, but some nudibranchs, (such as the related Palio dubia found around the northern Uk shores) add a touch of S & M to their sex lives. Unlike many nudibranchs, Palio dubia does not have a complete vaginal opening. Thus copulation occurs by hypodermic injection; the barbed penis (or penile cirrus as it is properly termed) simply punctures the body wall into its mating partner. Ouch!
As always my pics are available to license – if you’d like to use one just email me

Basking shark images Cornwall

Basking shark images Cornwall
Basking shark, Cetorhinus maximus, feeding with mouth wide open

Basking shark, Cetorhinus maximus, feeding with mouth wide open

After a couple of years of bad weather I was lucky enough to get out and finally get in the water with a small group of basking sharks last year. We launched my Zodiac out of Newquay and headed west, through some fairly substantial rollers coming in off the Atlantic. After a few hours of steaming along we finally caught up with them. They were swimming steadily, completely ignoring us but also moving pretty quickly. So once you hit the water you had to move pretty sharpish, swimming diagonally to their path, before they cruised past and left you in their wake waiting to be picked up again my the boat. In the end we had two days with them, first day I was helped by Jules and on the second Kat boat-handled for me.
Baskers are never that predictable, but they should be arriving off the tip of Cornwall in the next week or two. I plan to get out again and hopefully improve on last year’s pics. Hopefully the weather will be kind – we’re currently having once of the coldest May’s in nearly 20 years.
For more basking shark (Ctenorhinus maximus) images from last here click this link here
Watch this space for updates on success (or not) this year! As always these are stock images and footage available for righst managed license. If you’d like to use any of these get in touch email me

A clip of a Large basking shark feeding near the surface, North Cornwall, 2009.
httpv://www.youtube.com/watch?v=s_-GIMCkP7Q

Basking shark, Cetorhinus maximus, feeding in surface waters.  Cornwall, UK. Colin Munro Photography

Basking shark, Cetorhinus maximus, feeding in surface waters. Cornwall, UK. Colin Munro Photography

Large basking shark, Cetorhinus maximus, feeding in surface waters.  Cornwall, UK. Colin Munro Photography

Large basking shark, Cetorhinus maximus, feeding in surface waters. Cornwall, UK. Colin Munro Photography