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Sex and death in the seagrass

A common or European cuttlefish, Sepia officinalis, trapped in monofilament bottom set nets, Brixham Harbour. Each year nets are set around seagrass beds (Zostera marina) where cuttlefish come in to breed. Colin Munro Photography
A common or European cuttlefish, Sepia officinalis, trapped in monofilament bottom set nets, Brixham Harbour.  Each year nets are set around seagrass beds (Zostera marina) where cuttlefish come in to breed. Colin Munro Photography

A common or European cuttlefish, Sepia officinalis, trapped in monofilament bottom set nets, Brixham Harbour. Each year nets are set around seagrass beds (Zostera marina) where cuttlefish come in to breed. Image No. MBI000305.

Intelligent life. Few divers who have ever encountered an octopus or cuttlefish underwater cannot have been struck by a sense of an alien intelligence staring hard at them, assessing whether you are friend or foe and what you are likely to do next. That cephalopods (octopi, cuttlefish, squid and their kin) are bright has now become common knowledge; yet this is still something that sits uneasily with their molluscan nature. Great apes, whales and dolphins are easier to accept; they are mammals and so not that distantly related to us. But cephalopods? They are not even vertebrates; first cousins to slugs, snails and slipper limpets. Their blood is greeny-blue not red as the oxygen carrying molecule is copper-based rather than the iron-based haemoglobin in all mammals. They really are shape-shifting aliens from inner space. And yet, when a cuttlefish rises out of the sand or seagrass to hover in front of you, you get a real sense of cogs turning and a logical decision-making process taking place. That may, of course simply be down their binocular vision; we tend to almost intuitively associate this with intelligence (it is designed, after all, to assess distance, form mental 3D images of the World and judge when and how to strike at prey). That there is real intelligence behind those eyes is most elegantly demonstrated by the octopus, which has joined the elite group of animals that have demonstrated the use of tools to manipulate their environment in the wild. The veined octopus has recently been filmed collecting and stacking discarded coconut shells halves to use as a shelter. So far it is the only invertebrate to do so.

Cuttlefish breeding. The seagrass beds of South Devon have long been a favourite dive habitat of mine. They provide gentle, sunlit dives where one can float along in the hope of encountering a pipefish, mating sea hares and, at the right time of year, cuttlefish arriving to lay eggs. Watching a female cuttlefish lay eggs is a fascinating experience. Each pointed black egg is attached to a tuft of seagrass or weed one at a time. The female will hover before it, then after a few minutes contemplation will move forward to firmly grasp the stem with her tentacles and pull it towards her. After a minute she draws back again, to reveal a new shiny, pointed black eggs bound to the stem by a band extending out of the egg case. This process with continue for over an hour, until the stem is wrapped in what resembles a bunch of black, pointed grapes.

A common or European cuttlefish, Sepia officinalis, trapped in monofilament bottom set nets, Brixham Harbour.  Each year nets are set around seagrass beds (Zostera marina) where cuttlefish come in to breed. Colin Munro Photography.

A female common or European cuttlefish, Sepia officinalis, trapped in monofilament bottom set nets, Brixham Harbour. A male hovers nearby and will eventually also be entangled. Other males hover in the background. Image No. MBI000270.

While the eggs are laid a gang of males hover in attendance. When cuttlefish mate the male transfers the spermatophores (sperm packages) to within the females buccal cavity, using his modified fourth arm (the hectcotylus). The hectocotylus is then used to break open the spermatophores, releasing the sperm which is then temporarily stored within the female’s buccal cavity. If she subsequently mates with another male it will direct jets of water into her buccal cavity to attempt to flush out earlier sperm deposits. Consequently the most recent mate will hover above her, warding off other males that will hang around, to ensure that it is his genetic material that is passed on rather than that of his upstart rivals.

Cuttlefish in nets. Cuttlefish are, of course, a valuable catch for fishermen. They are caught in trawls out at sea and also in set nets deployed around their inshore breeding grounds. Cuttlefish grow quickly and most die shortly after breeding, so those caught after they have laid their eggs will not have any real effect on future populations. Unfortunately however, nets are often laid around the edges of breeding grounds such as seagrass nets, thus cuttlefish are caught not only when leaving the breeding ground but also when arriving, before they breed. The nets do not kill them, but they are often quite badly damaged as they twist and the fine line cuts into their flesh. Indeed I often wonder how they can be sold after their flesh is so ripped up. If a female is caught then inevitably a number of males arriving will hang around her until they too are caught. A trapped female may remain their for up to twelve hours before the nets are hauled, so the potential for catching large numbers of breeding cuttlefish is quite high. So far, this practice does not seem to have noticeably affected local cuttlefish populations. It is nonetheless rather disconcerting to watch such lovely animals twisting and turning for hours on end.

Update. In the past couple of years I, and other local divers, have seen notably fewer cuttefish hanging around in the shallow bays of South Devon during the breeding season.  This may simply be due to factors like the lousy weather we’ve had during the past couple of summers; it may also be due to the almost impenetrable ring of nets set on the edge of these bays.

Images. All the images in this blog are available to license.  You can search all my online stock images at my  Cuttlefish images, Sepia officinalis images, fishing images, stock images.

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.

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

Old Piers and simple pleasures

Old Piers and simple pleasures
Mussels, Mytilus edulis, and Obelia indivisa hydroids on an old pier leg

Mussels, Mytilus edulis, and Obelia indivisa hydroids on an old pier leg

I took my first underwater pictures bimbling about between the uprights and cross-members of an old wooden pier. That was with second-hand Nikonos III, a set of extension tubes and a Sunpak 28 strobe. I’ve probably still got it somewhere. Underwater photography has moved on a long way since then but I still love exploring old wooden piers and the opportunities they present for macro-photography. The uprights are normally festooned with filter-feeding life: hydroids and sea squirts often forming dense carpets. Dahlia and Sagartia anemones add a splash of colour. To me the beauty of macro-photography is that the basic skills can be learned quite quickly and sharp, colour-saturated images can be created even in our often quite turbid coastal waters. There is also the fun of exploring and discovering small creatures in crevices and overhangs; the joys of being a kid again for an hour or so. Each pier or jetty presents its own particular hazard. This can range from watching that a dropping tide doesn’t leave you trying to clamber up the bottom rungs of a badly corroded and rickety old ladder when trying to exit the water, to avoiding being knocked unconcious by the weapons grade halitosis of betching bull sealions as they lie flopped across the jetty cross members. But the pleasures tend to remain the same; hunting for that perfect patch of jewel anemones or symmetrical cluster of featherduster tubeworms.

The above pic was taken on the legs of a fairly tide swept pier in Southern Ireland. Large, fat mussels gaped in the rich feeding currents and between them bright orange Obelia hydroids swayed like tiny sunflowers. The trick with all macro-photography (and indeed much temperate water photography) is to slow down and look closely at what is literally just in front of your nose. The other pleasure that often comes from macro-photography is that one often discovers new things in the image that you never saw at all when composing the photograph. To take the above example; I was completely oblivious to the tiny crustacean scuttling about between the Obelia polyps, only noticing it once I had developed the film (yes, this is a film image), scanned the slide and viewed it on my laptop. This still applies with our current top-end DSLRs. Although lcd screens are improving all the time, small details are only revealed when the image is downloaded and viewed on a much larger screen.

Underwater Photography Workshop
For those interested I will be running a one day workshop, an introduction to underwater photography, in Exeter, Devon next month (6th March). This is intended for those relatively new to underwater photography looking to acquire a good grounding in the theory and practical skills, or possibly decide which system they are going to go for. There are still a few places left as I write this. For more info go to: Introduction to underwater photography workshop

The worst whale picture you’ll ever see

The worst whale picture you’ll ever see
Humpback whale swimming under a fishing vessel, Lyme Bay, Southwest England

Humpback whale swimming under a fishing vessel, Lyme Bay, Southwest England

I have just uploaded what is probably the worst whale picture you’ve ever seen, or are likely to. For a start it was taken with an old Nikonos III camera, without use of an additional hand held light meter. Those old Nik IIIs were purely mechanical, so no built in light meter; thus exposure was based on the ‘guesstimate then bracket like hell’ maxim. Secondly, it was taken with the only wide angle lens I owned back in those days, a cheap plastic supplementary lens of rather dubious sharpness. To be honest the lack of sharpness was not really an issue. I was shooting in turbid coastal waters, where horizontal visibility near the surface was between 8-10 metres (26-33 feet); pretty good for the area as it happens but lousy for shooting whales. On top of this strong winds had been blowing so the shallow coastal water was nicely loaded with suspended sediment lifted off the seabed. This made for a rather hazy 8-10 metres visibility. As if that weren’t enough, conditions were further complicated by this occurring around 7.30pm, so the sun was getting low and light levels below the surface were dropping like a stone. To cap it all I had no fast colour film with me (yes this was waaaay back in the pre-digital days). I had not gone diving to photograph whales. I knew the visibility was likely to be lousy so I had arrived armed with a set of extension tubes for macro-photography and several rolls of Fuji Velvia 50 slide film. This produces wonderful, detail and rich, saturated colours, But it is slow! Certainly useless for photographing something the size of a bus in turbid, low light conditions. Throwing everything out of my camera bag over the deck of our dive boat I fished out an old roll of 400 asa film. Now that was more like it; still going to struggle but at least there was a chance of a recognisable image now. Only problem was it was black and white negative film (so long ago I forget exactly what). Still, it was that or nothing. So I loaded it with shaking hands are rolled over the boats gunnel into the water. The slowest shutter speed available on Nik IIIs is a 30th sec, so I wound it right down and hoped for the best. Black and white negative film is more forgiving of poor exposure than slide, which was just as well really.

So I guess I was quite fortunate (and there was a lot of luck) to get any recognisable images at all. But apart from nostalgia, why hang on to them, and why publish them online? The pictures are nearly two decades old now and after all, I have lots of lousy quality pictures from years gone by. The main reason, apart from being able to waffle on about the difficulties of photographing large marine mammals in lousy conditions, is that, eighteen years on, as far as I am aware these remain the only underwater pictures taken of a humpback whale in British coastal waters. I can still remember my utter amazement as I peered over the boat’s rail into the water below, watching a dark shape slowly rise up. As it approached the surface not more than two metres from the boat I could clearly make out a long, white object. When it was around a metre below I suddenly realised I was staring at a massive white pectoral fin. ‘Bloody hell! It’s a humpback!’ I remember shouting (okay, it may have been slightly stronger than ‘bloody’). By the time it broke the surface I was already throwing dive gear together. I loaded my camera, threw my cylinder on and rolled over the gunnel faster than any time before or since, oblivious to what anyone else was doing. I settled on the bottom at around 10 metres. I peered around but he (or she) was nowhere in sight. What now? Fortunately I didn’t have to wait long. The humpback was intensely interested in the boats echo sounder transducer and kept returning to make passes under the hull. I floated up to mid-water and simply hung there, waiting for him to return then clicked away frantically changing aperture sizes as I did so.

A small population of humpbacks inhabits the Eastern Atlantic, migrating each year between their arctic feeding grounds and breeding grounds off Cape Verde. They are frequently spotted off the West coast of Ireland as they head North or south. This guy somehow made a wrong turn off Cornwall and headed East along the English Channel. After our memorable dive he was not seen again, as far as I know. Let’s hope he made back on track.

I continue to muddle away at underwater photography, so if anyone is tempted I shall be running a series of workshops from March 2010 onwards. More info at Colin Munro photography Main Index under Courses and Workshops

If anyone knows of other humpbacks photographed underwater around the UK I’d be most interested to learn about it.

Colin Munro 3rd February 2010.

Lessons in stupidity…diving the trawl

Lessons in stupidity…diving the trawl

Please note. I should probably add the ‘don’t try this at home’ caveat. This is NOT intended as ‘how to dive on a trawl’ article. I have been careful to leave out most detail on methodology for that very reason. Diving on moving heavy gear does incur certain risks and should not be approached lightly. I should probably also add that this was quite a few years ago and we were a little fast and loose with safety. I’m quite a bit older and possibly a little wiser now; this is not how we dive on trawls today, where safety is paramount, and I would not encourage anyone else to do so. Enjoy the story.

Every now and then I go out on a trawler and dive on the trawl net. Sometimes its been for scientific research purposes, sometimes its been filming (most recently for Ocean Odyssey, a two-hour special by Impossible Pictures for BBC/Discovery, and providing clips for Countryfile, BBC). I’ve been doing this for nearly twenty years, and I reckon I’ve almost got the technique sussed now. We should have been out filming on nets again this summer, but various things got in the way: I was busy, the skipper was busy, some of the team were busy, the weather blew up, and then winter arrived. So it’s currently on hold for a little while. However it made me think about the first time I tried it.

Way back in the early 1990s, I was looking for a way to document the effects of trawl nets and other mobile fishing gear on fragile seabed habitats in a way that would really grab peoples’ attention. When the idea came it was so obvious. True I had never done it before, but it couldn’t be that difficult could it? This was an excellent example of the Doppler shift, where stupid ideas seem smarter when they come at you rapidly (apologies to Christian Doppler).

I had the big advantage that a good friend happened to be a trawler skipper and together we hatched a plan. I persuaded an old diving buddy of mine, Joe, that this would be a hoot and that of course I knew exactly what I was doing. We picked a bright summers day with only a slight breeze ruffling the water. We loaded our SCUBA gear aboard, slipped our mooring and headed out to sea.

A few miles offshore John, the skipper, shot the trawl. Now unless you happen to be a trawlerman you’re unlikely to have detailed knowledge of how a trawl net works, so this is probably as good a place as any to explain a little about the mechanics of it.

Filming John ‘shooting’ the trawl net before we dive. Most of the net is already in the water, the two wings remaining. The trawl doors can be seen hanging from the stern gantry, still to be attached to the trawl bridles. (This picture is from a subsequent trawl dive, many years later).

We were going to dive on a bottom-set otter trawl. Bottom-set meaning it dragged along the seabed catching near-bottom dwelling fish (as opposed to a mid-water trawl that catches mid-water…ok, you get the picture). The mouth of the net spreads very wide, tapering off into the net ‘wings’ that act rather like outspread arms, herding fish towards the mouth. The wings then attach to chain bridles, which in turn attach to wire warps that run all the way back to the boat.

John ‘shooting’ the trawl. The net is now completely underwater and the trawl doors can be seen just disappearing. The towing warps have been lifted in to the pulley blocks hanging from the transom. (Again this picture is from a trawl many years later).

There is a slight flaw with a simple design like this however; once the boat starts to tow the net the wings would be pulled together and the mouth of the net close up as the towing warps took up strain. To counteract this inward pull on the trawl wings, trawl ‘doors’ (or ‘otter boards’ as they are also known) are used to provide an opposing force. Trawl doors are large flat (or very slightly curved) plates that act as hydrofoils. They are attached to the net bridles and align vertically, sliding along the seabed on steel ‘shoes’ welded to their lower edge. On very small trawlers the ‘doors’ may be constructed out of wood and look rather like square-ish house doors with metal edges. On our trawler they were steel plates, around four feet high and five feet long by about an inch thick. As the net is towed forward, water pressure on the faces of the trawl doors forces then outwards, thus spreading the net wings and keeping the trawl mouth open. Remember the ‘doors’, they’re important.

A bottom trawl, otter trawl. © Colin Munro

Diagram of the bottm trawl used (not to scale)

The trawl was set. Joe and I had donned our gear. John killed the engine and we sat motionless on a perfect sea. With a nod to John we rolled over the boat’s gunnel and swam to the warps at the stern. Our plan was simple. We would pull ourselves down along one of the trawl warps until we reached the net. John would give us eight minutes to get there. He would then fire up the engine and tow at an agreed speed for fifteen minutes, then knock the boat out of gear and come to a halt. Twenty three minutes total seemed about the right balance between allowing sufficient time to get some useable footage, and not too long in case we got ourselves in to trouble. I would film the trawl in action. Once the trawl stopped we would then surface and wait for John to circle back and pick us up. What could possibly go wrong?

Preparing my video camera in the trawler wheelhouse. There’s not a lot of room (from a subsequent trawl dive, quite a few years later).

A trawl net is towed at quite a low angle; although we were in relatively shallow water, around 15 metres, we had around a hundred metres of steelwire warp to haul ourselves along. Although the upper layers were very clear a thick plankton bloom filled the mid-water layers and I found myself able to see only a couple of metres in front of me before the warp disappeared into a green gloom. I hauled myself one-handed, carefully keeping my video housing clear of the grease covered warp with my free hand. It felt like a very long time before I finally spotted the seabed. The warp changed to two lines of chain bridle lying on the seabed and I knew we were almost there. The trawl doors must be close, and then it was only a few more metres on to the wing on the trawl net.  Suddenly the chain jerked slightly in hand, and I felt the links snap tight. The chain started to move, jangling and clattering over the sand and stones. I caught firm hold of the chain and saw Joe do likewise. In seconds everything changed. The two metres visibility we had moments previously disappeared, to be replaced by utter blackness. The warps and chains scuffing along the seabed churned up a cloud of sediment that excluded all light. I could feel the chain links in my hand but could see neither chain nor hand, although both were only inches from my nose. Joe was somewhere out there in the blackness. The chain whipped up and down, momentarily going slack then snapping tight again.  Holding on with just one hand, my other was gripping tightly on to my video housing, I flapped up and down in the blackness, like a beach towel having the sand shaken out of it. Somewhere near me I could hear the other chain scraping and snapping similarly. A loud metallic banging started up very close by. I realised it was the trawl door. When the trawl was stationary the door would fall flat on the seabed. Only once the trawl was up at towing speed would the door rise up and slide vertically. As the trawl picked up speed the door was starting to lift and slam back down on the seabed.  I idled away the next few moments musing over the likelihood of my fingers being sheared off by snapping chains or how long it would be before I slammed into a boulder, lost my grip and slid backwards to have the trawl door plough a furrow through the back of my skull as it bounced over me. Maybe I would simply be scooped up by the net, falling inexorably back, to be slowly macerated and suffocated in the cod end.  Just stay cool I told myself, this sediment will clear in a minute, you’ll be able to see, and then you can judge what to do. One minute passed, maybe two; actually I have no idea how much time passed as I couldn’t see my watch. It felt like an hour but was probably more than a couple of minutes. The blackness was still absolute, and showed no sign of clearing.  I was convinced the banging was getting louder and the motion of the chains more violent. I bailed. Drifting up out of the sediment cloud I looked up to see Joe, floating way above me. Even at a distance I could see Joe’s weary expression. The look in his eyes said ‘Christ! Why on earth did I allow myself to be talked in to something so stupid’ more clearly than words.

John, of couse, was completely unaware of our little misadventure, so the trawler was gaily disappearing in to the distance when we surfaced.  But it was a calm, sunny day, and I’d known John a long time and knew how good a skipper he was, so I wasn’t really worried. About half a mile away I saw him stop, then after a few minutes slowly turn the boat and start heading back towards us.  By the time we were back on board we had started to see the funny side. It had been an elementary error but easy to rectify. So we came up with plan B.  Unfortunately, Joe’s ears were truly blocked now after bouncing about on the seabed and a swift ascent, so he could not dive again.  However John the boat skipper had been itching to get in the water, thus this was a perfect excuse (I should add, lest I am thought completely mad, that John is also a fully qualified and very experienced diver). That only left the minor detail of who would drive the boat.  Joe was a recent biology graduate about to start teacher training.  Unsurprisingly, he had never driven a trawler, or any boat for that matter, before.  No matter, Joe was given a quick lesson in how to start and stop a trawler,  and how to point it in a straight line.  Back then, I wasn’t fully aware of just how badly this could have gone, so I wasn’t nearly as worried as i should have been. John dragged his diving gear out of the hold, climbed into his drysuit, and we were ready to go again.

Our second dive went like clockwork. We got the trawl speed and our positioning just right so were able to move freely about the net. Indeed I became so relaxed my thoughts occasionally strayed to what was happening on the surface as we gaily careered across the briny in the hands of our novice skipper. I pushed them to one side telling myself to concentrate on the job in hand.  It was fascinating and exillarating to be able to haul myself across the top of the net and down the other side, to lie alongside the heavy chain and rubber footrope, watching fish being herded in by the outer wings of the net swim hard in front of the gaping net mouth. 

Close up of ground rope of the trawl, showing large rubber rock-hopper discs that allow the trawl to bounce over small boulders. Still taken from video footage.

Just how lucky we had been was brought home to me in future dives.  Not long after this trial I dived John’s trawl again (with John at the helm this time).  A slight miscalculation on speed and tides left me pinned to the top of the trawl for entire dive, unable to let go or move in any direction.  The water rushing past my spare regulator was causing it to freeflow like crazy, but I couldn’t change grip to stop it, and I was gasping for breathe with the effort of holding position.  In 18 minutes I almost emptied two ten litre air cylinders before managing to get to my buddy and signal to bail. 

The cod end of the trawl, full of fish as it is hauled at the end of a trawl. (This image was taken many years later, on a subsequent trawl dive).

But that was the future.  This dive progressed perfectly, ended uneventfully, and I gained some excellent footage.  All too soon we felt the trawl slow and then stop.  The adrenaline was still buzzing in my veins as John and I broke surface and began the long surface swim back to the trawler. 

The stupid grin you wear when it all works out.

Note: most of the photographs I have used here for illustration are from subsequent trawl dives, some 15 or more years later. I’ve used these simply because I don’t have any useable stills from back then.