Orca are hugely impressive animals. They have come to symbolise power, intelligence, grace and – sometimes – ferocity. Often known as killer whales, largely due to the way they would attack harpooned baleen whales, or harry and gradually wear down larger whales in a similar fashion to wolves on land, they are in fact large dolphins. Few of us will not have seen the BBC footage of orca powering on to beaches in Peninsula Valdes in Patagonia to grab unwary elephant seals. The power of these animals is quite awe-inspiring. Large individuals may weigh up to 11 tonnes, and females may life to be at least 80 years old. We now think of orca as a highly variable species, or species complex, with up to nine different types recognised. Advances in science may eventually split these into sub-species, or possibly separate species.
I took this photograph a few miles off the coast neat the southern tip of New Zealand South Island. We were sailing from Stewart Island, the small, rugged island to the south of South Island, heading towards the city of Dunedin. It was a perfect evening in mid-November, summer in the southern hemisphere, around 8.30pm. The sun was already almost touching the horizon, creating deep shadows in the troughs of the ripples pushed along by the light breeze. The orcas approached our bow from the northeast, then passed close by on our port side. This was going to be the best shot I would get, before he disappeared towards our stern. However the low sun was directly behind him, casting his curved back and giant dorsal fin almost in silhouette. I had a couple of seconds to decide. I could ramp up the camera ISO and expose my shot to bring out the details on the orca’s back, but doing so – shooting straight in to the sun – would blow out all detail in the water around him, or… I could do the opposite. I could aim for silhouettes and shapes, patterns and texture on the water. If this were a studio shot it would be termed ‘low key’; but of course this was not a studio, there would be no posing, no running around with a hand held light meter, no test shots. I dialled down the ISO, ramped up the shutter speed, quick check of the viewfinder light meter …. focus… and click, click, click. And that was it. I watched as the dorsal fin slipped beneath the water, to reappear several minutes later, far behind us. The sun was dipping beneath the horizon, and the light was gone.
I find wildlife photography is often like this. Animals don’t appear on que, they don’t appear when you’re standing waiting with your camera gear all set correctly, they don’t appear in the right place or the right conditions and often they don’t allow you time to think through your choices and your settings. This is where practice and experience comes in. After years of taking shots in all sorts of conditions, you learn to instantly recognise situations, and dial in settings almost with muscle memory. Not that you can ever become complacent. Camera technology is constantly improving; that means that the rules that you automatically followed three years ago may no longer be the best way. Advances in technology may mean that the settings you used last year may now be improved upon by turning them on their head. So successful wildlife is a continual process of learning, practice, relearning, practice..repeat.
Art prints and downloads
The orca picture shown here is one of my images I have selected to make available as fine art prints. These are available as stretched canvas, canvas wraps, flat canvas, dye-infused aluminium prints and acrylic on alumimium in a range of sizes and crops. They can be ordered directly from my website colinmunroimages.com. Default printing is my Bay Photos professional fine art printers in California. For orders from the UK, contact me directly and these can be supplied by Loxley professional printers in the UK. It can also be downloaded as a digital file, for private or commercial use, in a range of file sizes.
An account of photographing blue sharks off Cornwall, Southwest Britain, a few years back, and a link to buying fine art prints of these amazing hunters of of the oceans at colinmunroimages.com.
On a clear July morning I stumbled out of my bunk (I was living on a boat at the time) at 5.30am, forced out my the insistent buzzing of my phone alarm. One hour, and one strong coffee later, I squeezed my dive bag into the back of Ritchie’s car and we were off. We had over a hundred miles to cover, and a boat to catch.
Charles Hood runs the best, and most successful, blue shark snorkelling operation in the UK. His boat, a large rigid-hulled inflatable (RIB) operates out of Penzance, almost at southwesternmost extremity of the British mainland, so that’s where we were headed. The boat is a fast open boat, perfect for getting us 10 miles offshore quickly, but small and devoid of any shelter from the elements. So we changed in to wetsuits on the quayside, packed our camera gear in dry bags carefully padded with towels and sweatshirts for the bouncy ride out, and we were off.
Each year blue sharks arrive off the coast of Southwest Britain, normally sometime in mid-June and remaining until mid-October. Blues are true oceanic sharks; they inhabit deep water, only infrequently venturing on to shallower, continental shelf waters. They are found in tropical and temperate oceans around the globe. However, in the tropics they tend to stay in deeper, cooler water but are often observed in surface waters in temperate seas. They feed on fast moving prey such as squid and schooling fish. Much of their feeding appears to be done in deeper waters. We know this partly from studies looking at gut contents, identifying the hard tissue remains of the prey species, and knowing where those prey species live, and partly from small data loggers, recording depth profiles, that are attached to sharks and then recovered at a later date. Below 100 metres, it seems they predate mostly on squid, in particular those belonging to the Histioteuthidae family, more commonly known as cock-eyed squid. Cock-eyed squid are bizzare creatures that inhabit the twilight zone of the oceans, so-called because their left eye is around twice the size of their right. Observations with deep water remotely operated vehichles (ROVs) have shown that they swim with the left eye facing upwards, and the right facing down. It’s believe the the huge left eye is used to pick up the faint sunlight coming from far above; the smaller right eye, staring into the depths, serves a quite different purpose. It picks up bioluminecent glows and flashes from prey (or predators below). But blue sharks are not fussy eaters. Studies off the coast of Brazil have found they eat large numbers of oilfish (a deepwater member of the mackerel family) but will also sometimes grab seabirds such as shearwaters. Those off Southern Brazil were found to be mostly scavenging on dead baleen whales. But I have digressed somewhat from our trip. Some ten nautical miles out Charles stopped the RIB and allowed us to drift. Sure we were a fair way from shore, and in pretty deep water, but still well within continental shelf depths, probably 50-70 metres, as we drifted. The 100 depth contour was still over 20 miles distant. So what tempted the blues, normally oceanic species, this close inshore? As we drifted Charles began to prepare the chum bag that hopefully would draw nearby sharks to our boat. A small hessian sack was filled with chunks of mackerel and mackerel guts, including some caught angling off the stern of his RIB. Tied just off the side of the RIB, a slick of fish oil drifted away down current. This is the clue to why blue sharks arrive in coastal waters of southern and western Britain. Mackerel also arrive around British coasts during the summer months, often found in huge shoals numbering thousands of fish. Like their deeper water relatives, the oilfish, mackerel are an oily fish, so a high energy food source for any predator fast enough to catch them. And the blue shark is just that; generally a sedate swimmer it can move with lighting bursts of speed.
Once our bag of chum was positioned, and final checks on cameras completed, all we then had to do was wait. Charles dug out his fishing rod and started supplementing our chum supply with a few extra mackerel. And we waited. There was no wind, and just a slight, rolling swell on the sea. The sun was hot and the sky a clear blue, so it was not extactly a hardship. The sun climbed to its zenith, then slowly fell westward as morning gave way to afternoon. We were woken from our torpor when, around 2pm, a group of three sunfish drifted close. Sunfish are odd-looking disc shaped fish. They feed on There was a flurry of activity as we grabbed cameras and donned fins, but they were skittish and disappeared in seconds. We settled back in to watching and waiting. At around 3.30pm Charles announced that we should start heading back to shore at 4pm. The minutes ticked by; 4pm arrived and still no blues. Charles apologised but, as we were well aware, there is never any guarantee with wildlife. He announced we would give it another 20 minutes. At 4.15 the first blue arrived. Rather than leap in immediately, we gave it time to settle and get used to the boat. A couple of minutes later a second arrived. Charles had been very clear on the safety aspect, wearing gloves, no shiny jewellery. The necessity for this was made abundantly clear when one of the sharks managed to grab to chum bag. Its razor sharp teeth ripped through it like paper, and bits of mackerel guts spilled out into the water. The bag was quickly quisked out of the sea and we gave it a minute for the cloud to disperse. Once Charles was confident the sharks were no longer likely to disappear immediatly, we, one by one, slowly slide over the side of the boat and in to the water.
Once in the water I dipped my head to check all around me, then slowing finned away from the RIB. Once around 8 metres away I stoppped finning, and started checking around. I could clearly see my three companions at this stage, floating 5-10 metres away from me. Every so often a shark would cruise in, swimming below or between us, to to check out us or the RIB. The water was clear, visibility a good 15-20 metres, but the sun was now low in the sky. When the sun is overhead, and light hits the waters’ surface more or less perpendicular, then much of that light penetrates the surface; but late afternoon, when the sun is low and its rays hit the water at a shallow angle then most of that light bounces off the surface and it becomes markedly darker just below than above. My photographic problems were two-fold. The reduced light levels made focussing a little trickier, and when a blue shark came fast out of the expanse of blue water, the camera would struggle to pick up contrast and focus quickly. I fiddled with the settings, pre-focussed using my colleagues as targets, fired off test shots and again readjusted my settings. All the time keeping looking around me. A RIB, with its large surface area above the water, will drift with wind and tide, but a swimmer, around 90% below the water’s surface, will drift with the tide alone. So as I floated I was aware that the distance between was growing. This was not a concern; conditions were perfect and I knew Charles would be fully aware of our positions. On the contrary, it gave me space around me. As I drifted I also became aware that one of the sharks had become interested in me, and was moving with me, not steadily but zig-zagging. It would pass close, then swim off , to turn and pass close again.
This was not in a threatening or aggressive manner, but rather one of curiosity. A couple of times it would swim straight towards me, only to stop maybe 18 inches in front of me. Whether it was seeing reflections in the large glass dome port of my camera housing I am not sure. Whatever the reason it provided me with more perfect photo oportunities than I could have hoped for. Thirty minutes passed in what seemed like three, and Charles was recalling us to the RIB. We may have had to wait, but performace at the end far exceeded our expectations.
Fine Art Prints and Wall Art
I have made two of my images from this trip available as fine art prints and wall art. These are available to be purchased in a wide range of media and sizes directly from my Colin Munro Images website. media available include traditional giclée prints, stretched and flat mounted canvas, metal prints (dye directly infused on sheet aluminium) and acrylic, from 8 inches up to 48 inches across. My prints are produced by Bay Photo Labs in Santa Cruz, California. I choose bay Photo Labs for the excellence of their quality, with over 40 years providing printing services to professional photographers, their constant innovation, combining the latest technology and innovation with the finest traditional techniques, and their committment to the highest environmental standards using green technology. You can buy my prints directly here at www.colinmunroimages.com. If you are outside of North America, and would prefer a printer in your region, please contact me directly. I will be adding printers in Europe and S.E. Asia soon.
I am slowly moving my marine biology orientated blogs to my other blog site: www.marine-bio-images.com/blog. I may eventually remove them from this site. This article can now be found here.
“I turned around and saw him about one hundred rods directly ahead of us, coming down with twice his ordinary speed of around 24 knots, and it appeared with tenfold fury and vengeance in his aspect. The surf flew in all directions about him with the continual violent thrashing of his tail. His head about half out of the water, and in that way he came upon us, and again struck the ship.” So wrote Owen Chase, First Mate, in his 1821 account of the sinking of the whaling ship the Essex.
A sperm whale raises its tail flukes as it begins a dive.
The whale in question was a cachalot, or sperm whale. Probably the best known whale; the whale in Herman Melville’s Moby Dick (which was actually based on the sinking of the Essex). The sperm whale, Physeter macrocephalus, is the largest toothed whale, and indeed the largest toothed predator that has ever lived. Males average 16 metres in length and over 40 tonnes in weight (females are significantly smaller); some may exceed 20 metres and 50 tonnes. They are the sole extant (living) species in the family Physeteridae, though fossils of several extinct species have been found. Sperm whales look like no other whale; their massive head and relatively tiny lower jaw coupled with their huge size renders them unmistakable when seen underwater. However that is not how they are commonly seen. The best view most of us get of a sperm whale is of them resting almost motionless on the surface, between dives, with only the top of their back and their blowhole visible, followed by the rise of the tail flukes as it descends beneath the surface.
The blow hole and wrinkled skin of a sperm whale resting on the surface
As sperm whales are air breathing mammals it is tempting to think of them as animals that live at the surface, diving occasionally to hunt. Not so. When feeding they will spend 8-10 minutes on the surface breathing, replenishing their oxygen supplies. In contrast they will spend 35-50 minutes underwater searching for prey.
The low, bushy, forward-directed, blow of a sperm whale is almost unmistakable
Studies indicate that sperm whales will spend 70-95% of their time in these foraging cycles so, in terms of where they spend most of their time, these are creatures that inhabit the ocean depths and surface only briefly to breathe.
Unlike most other great whales, the sperm whale does not venture into polar waters to feed, preferring tropical and temperate seas (adult males will venture in to high latitudes). But even in the tropics it inhabits a cold world. At a thousand metres depth, well within the normal foraging range of sperm whales, the temperature is only 4-8 degrees centigrade. It is also a world of almost total darkness. At 200 metres depth, even in the open ocean the light levels are less than 1/1000th of those at the surface. At a thousand metres one enters the aphotic zone (the midnight zone) where no sunlight penetrates. But that does not mean it is a world devoid of light. It is a world full of bioluminescence. Light produced by chemical reactions within living organisms. It has been estimated that that 90% of the animals that live below 1000 metres are capable of bioluminecence; glowing, flashing or pulsing green, red, but or white. This includes many of the prey species of sperm whales. Although they do also consume fish, cephalopods (octopus, cuttlefish and squid) are by far the greatest portion of their diet. Famously they predate on giant squid and the even larger colossal squid (which may be longer than a full grown sperm whale and is the largest known invertebrate) but they also consume a wide variety of other cephalopod species. This includes the wonderfully named vampire squid (Vampyroteuthis infernalis is its scientific name, which translates as ‘vampire squid from hell). Neither a vampire nor a squid it occupies a cephalopod Order all of its own, the Vampyromorphida.
There are a few spots in the oceans renowned for sperm whale sightings. These are mostly along the edges of underwater canyons and steep drop-offs, where shallow coastal seabeds plunge sharply to hundreds or thousands of metres. Off the Kaikoura peninsula of New Zealand is possibly the best known area, followed by the Azores islands (where volcanic seamounts rise up from deep water). The images of mine in this blog were all take off Vesteralen, northern Norway, where a complex of deep canyons direct the seabed offshore from the Lofoten Islands and Vesteralen archipelago. It appears sperm whales hunt along these canyons, thus time spent cruising along the margins of the canyons is often rewarded by sightings of sperm whales as these surface between foraging dives to expel carbon dioxide and replenish their oxygen supplies.
A Mako shark make a half-hearted attempt to grab a cape petrel.
When one thinks of sharks one thinks of sleek, powerful predators that appear to cruise effortlessly but are capable of dazzling bursts of speed when they attack prey. This image of the shark is exemplified by the shortfin mako. We know makos are fast, but how fast? Many sources will tell you it is capable of speeds of 74kmph or greater. The truth is a little less dramatic. We now know that around 35kmph is probably the maximum speed of any fish through water, and that makos are probably capable of speeds around 30kmph, which still puts them right up there among the ranks of the elite fish speed merchants, and around four times faster than any human (for a more detailed, scientific account you read my marine-bio-images.com blog XXX). Makos are generally accepted as being the fastest of all sharks, and with that powerful, missile-like shape, they are definately built for speed. I have yet to get in the water with a mako – it is one of my goals for this year. In the meantime I have an unexpected surface encounter off Kaikoura to savour. Kaikoura, as many of you will know, is a small town on the north east coast of New Zealand’s South Island. It is famous as one of the best places in the World for whale watching, especially sperm whales. It also came the wider world’s attention in November 2016, when the region was struck by a 7.8 magnitude earthquake, cutting off road and rail links to the town, uplifting areas of seabed and causing a localised tsunami up to 7 metres in height. When we visited in February 2017, road connections were still disrupted and whale watching boats had difficulty operating due to sea level changes affecting there berthing alongside. The town, highly dependent on tourism, was suffering markedly. We were not there to look for whales though, we were looking for dolphin and albatross. Kaikoura may be most famous for whales, but it is also a fantastic place to see many species of albatross up close, and it was albatross and dolphin we were there to see.
Albatross squabble over food. Kaikoura, New Zealand.
Whilst the big whales grab most of the international headlines, the sheer drama of seeing several species of albatross up close – really close – soaring, wheeling and plunging down to feed, is pretty hard to beat. Nor was it just the albatrosses and giant petrels that noticed the food in the water. The scent of chum in the water attracted in predators from below also. A dark triangular fin broke the surface and began weaving through the wary seabirds. The shark was a juvenile mako, approximately 5-6ft (1.5-1.8m) long. Whilst clearly drawn towards us by the fish scraps in the water, it then became interested in the birds splashing around.
An albatross warily eyes the mako shark, whilst a westland petrel flaps away from the sharks path.
The great albatrosses eyed the shark with a mixture of wariness and belligerence; with a wingspan probably exceeding the length of the shark they may have seemed a little large to tackle. The smaller petrels were more anxious. It made a grab for one cape petrel that did not move out of its path fast enough, but the attack seemed have hearted and the petrel skittered away easily enough. There was probably enough fish remains floating in the water to keep the shark happy. Makos will occasionally take seabirds, but mostly feed on pelagic fish species such as mackerel, herring and anchovies. Larger individuals have been found to have young seals and even common dolphins in their stomachs, as well as billfish such as marlin. Common dolphins and marlin are both renowned for their speed, so whilst it is possible that these were injured individuals snapped up by the mako, it is also these fell prey to the makos lightening speed.
Graham, J. B., DeWar, H., Lai, N. C., Lowell, W. R., & Arce, S. M. (1990). Aspects of shark swimming performance determined using a large water tunnel. Journal of Experimental Biology, 151(1), 175-192.
I clearly remember my first in-water encounter with a basking shark. Quite a few years ago now, I had gone out specifically to try and video a basker underwater. After a couple of hours we spotted a pair slowly circling a ball of plankton. I slipped mask, fins and snorkel on and slid in to the water. Basking sharks can be sometimes be wary and dive when one gets close, but these two seemed quite unconcerned by my presence. I floated on the edge of the plankton ball and watched them circling. As one approached out of the gloom I started to swim towards it. Even through you know it’s quite harmless it is still a strange feeling watching a six metre long shark swimming straight towards you with its mouth wide open. A mouth I could easily fit inside. At the last moment the shark would alter course slightly and cruise past me. The experience was similar to standing too close to the edge of the platform watching a train go past. Again and again the sharks would circle and cruise past, sweeping by less than a metre from me. Just me and two large sharks. It was a mesmerising experience, but I could not help thinking ‘this is so easy!’ Little did I realise at the time quite how lucky my encounter was. Several years and quite a few attempts would pass before I was able to repeat the experience.
The basking shark, Cetorhinus maximus, is the second largest fish in the World. Mature adults commonly reach between six and and seven metres in length, occasionally reaching around nine metres. Despite their massive size basking sharks are quite harmless. They are gentle filter feeders. During summer in the north-east Atlantic they can often be seen swimming close to the surface with their mouths gaping wide. A baskers’ gape can be over a metre top to bottom, so that’s pretty wide. As they swim forwards water is forced in to their mouths, passing across their gills where oxygen is extracted, and out through their large gill slits. This water flow serves a dual purpose. The arches between the gill slits are covered in long stiff bristles called gill rakers. These gill rakers sieve the water flow, retaining planktonic organisms. This is the food of basking sharks. In northern Atlantic waters they feed especially on copepods (planktonic crustaceans) particularly those of the genus Calanus, which occur in enormous numbers in the North Atlantic. Large numbers of such tiny creatures are required to sustain something as large as a basking shark. Therefore baskers need to filter very large volumes of water. It has been estimated that around 1.3 million litres of water will pass through the mouth and over the gill rakers of a large basking shark every hour.
Basking shark feeding, showing large gill slits the almost encircle its head
In the North East Atlantic basking sharks start to appear off the tip of Cornwall (SW England) in early May. This co-incides with what local fishermen call ‘May-water’, where the coastal seas turn green and turbid due to the seasonal population explosion of plankton. Throughout the summer months sharks will move northwards through the Irish Sea and around the west coast of Ireland. In the years immediately following WWII the author Gavin Maxwell ran a basking shark fishery from the island of Soay in the Inner Hebrides, exploiting this northward seasonal migration. The operation was beset with problems and drove him to the edge of bankruptcy. Basking sharks were hunted by Norwegian and Irish boats also. Due to concern over dwindling numbers, the basking shark received full legal protection in U.K. waters in 1998. The last British shark fisherman, a larger than life character called Howard McCrindle, ceased operations a year earlier. The basking shark is now protected throughout E.U. waters. In 2006 hunting also ended in Norwegian waters.
A basking shark swimming through plankton rich waters off Southwest England
Despite their large size, relatively slow movement and surface feeding habits there is much that remains unknown about the life history of basking sharks. Each year the they appear in late spring, then disappear again at the end of September. Where they go and how they live for the rest of the year has been a mystery, and remains so today, though we are starting to get tantalising clues as to the the answer. Occasionally, basking sharks would be caught in trawl nets during the winter months. Some of these were found to have shed their gill rakers, suggesting they were not feeding. This lead to the theory that they became dormant in winter, hibernating on the seabed. This theory had a certain plausibility to it. Basking sharks have enormous oil-filled livers. The liver can be 25% of the sharks body mass (the low density oil gives the shark buoyancy, allowing it to swim efficiently at the surface; it was also this high quality oil for which they were hunted). It was suggested that this enormous store of liver oil could sustain the shark for months without feeding. Recent research using data logging tags has begun to shed light on shark behaviour during the winter months. The tags used detach after a predetermined time and float to the surface, where they transmit the data data to satellites. The data at the time of writing indicates that basking sharks are active all year round, but spent much of their time at considerable depth, 200 and 1,000 metres. It also seems they are highly migratory. One 5 metre female nicknamed ‘Banba’, was tagged off Malin Head, the most northerly point of Ireland, in the summer of 2012. On the 13th December 2012 the tag popped off and was located by satellite – just west of the Cape Verde islands 5000km to the south. The still sparse, but growing, body of evidence now suggests that – in the North East Atlantic move in to coastal waters from deep water in April or May. As the water warms and daylight lengthens (and so plankton blooms) there is an erratic movement northwards. At the end of the summer they return to deeper water, heading west away from the British isles and mail and Europe, and some probably heading south also. So in reality we should maybe consider the basking shark as a deep water species that happens to congregate in shallow water during the summer months in pursuit of rich feeding.
As a final aside it is often written that basking sharks are toothless filter feeders. Basking sharks are filter feeders utilising gill rakers in a similar fashion to the baleen plates of great whales to trap small planktonic creatures but surprisingly they also teeth. In fact they have hundreds of tiny, backward-pointing teeth. What, if any, purpose these teeth serve is not known. They may be a vestige from a more predatory ancestry; equally there may be more still to learn of the basking sharks feeding habits.
Jellyfish, or sea jellies as they are now often called (clearly they are not fish) are amongst the most ancient of multi-organ animals. Fossils of jellyfish (or scyphozoans, to give them their scientific name) are found only rarely as they contain no hard structures within their bodies, which are 95% water. However, under the right conditions fossils of soft bodied creatures will form; current fossil evidence suggests they first evolved at least 500 million years ago.
The lion’s mane jellyfish, Cyanea capillata, is the largest known species. The bell of individuals in colder northern waters can reach two metres across.
The lion’s mane jellyfish (Cyanea capillata) common throughout the North Atlantic, epitomises this image of a large, slowly pulsing, gelatinous bell (or medusa) and long trailing tentacles that pack a powerful sting, but this is in fact only one stage of a complex life cycle. Lion’s mane medusae begin to appear in April or May in the Northern Atlantic, but are quite tiny at that stage. These jellies are voracious predators and grow rapidly through the summer. By August the medusae are commonly one third to half a metre across, with trailing tentacles many metres long. However there is considerable variability; large specimens have been reported at over two metres across with tentacles up to 37 metres long, though these generally occur within the more northern parts of their range. As they grow large in late summer they will often drift, under the influence of wind and tides, in to sheltered bays where they may aggregate in large numbers. This is when sperm is release and egg fertilisation takes place. In common with most scyphozoans (the taxonomic group to which jellyfish belong) the sexes are separate; lion’s mane jellies are either male or female. Sperm is released from the mouth of male jellies and drifts in the current, some reaching female jellies, where the eggs are fertilised. Fertilised eggs are stored in the oral tentacles of the female, where thy develop in to tiny planulae larvae. Once fully developed the planulae larvae detach and, after drifting for a short time, settle on the seabed. Here they metamorphose into a polyp, not dissimilar to tiny sea anemones or coral polyps (both of which are relatives of jellyfish). These polyps then grow, taking on a layered appearance until they resemble a stack of wavy-edged pancakes. Each one of these ‘pancake layers’ will then separate from the parent polyp, once again becoming free living and drifting with the currents. The ‘pancakes’, more properly ephyra larvae, will grow throughout the summer into the giant lion’s mane jellies and the cycle is complete. With a lifespan on only one year, during which they can grow to be as long (possibly even longer) than blue whale, lion’s mane jellies need to catch and consume considerable amount of prey. Each trailing tentacle is packed full of vast numbers of stinging cells, known as nematocysts. When touched these cells fire out a harpoon-like structure which pumps toxins in to the hapless victim (this is what causes the painful sting from jellyfish). These toxins incapacitate the prey, which is then drawn up towards the mouth of the jellyfish. A large lion’s mane may have over 1,000 tentacles trailing far behind them. Many SCUBA divers in Scotland and Scandinavia have experienced the situation where, having completed their dive on a sunken wreck and returned to the buoy line they planned to ascent to the surface, only to look up and see numerous lion’s mane jellies strung out along the line. As the current sweeps the jellies along so their tentacles catch on the buoy line, leaving the divers with the unpleasant prospect of ascending through thousands of jellyfish tentacles.
A diver warily watches a large lion’s mane jellyfish (Cyanea capillata) drift past. Isle of Arran, West Scotland.
Not every creature lives in fear of lion’s mane jellies however. Leatherback turtles, the only species of marine turtle that can tolerate the cold waters these jellies inhabit, consume them with relish, apparently oblivious to the stinging tentacles. Lion’s mane jellies can make up 80-100% of a leatherback’s diet. When you consider that a full grown leatherback weighs up to 800kg and may consume up to its own weight in jellyfish daily (bear in mind jellyfish are 95% water) then that equates to pretty large numbers of jellyfish being eaten.
As summer wanes and autumn approaches the lion’s mane jellies begin to die. This provides a feeding bonanza for many scavengers. On the surface seabirds will peck away at the gelatinous bell, whilst those that sink are often torn to shreds by shore crabs (Carcinus meanus) and velvet swimming crabs (Necora puber).
Dying lion’s mane jellyfish (Cyanea capillata) that has sunk to the seabed being eaten by a velvet swimming crab (Necora puber).
At the other end of the scale these deadly tentacles can provide refuge to some unlikely creatures. Juvenile whiting (Gadus melangus) have long been known to swim underneath the bell of lion’s mane jellies, apparently unconcerned by the curtain of tentacles they weave between. In fact they have been observed to rush into the mane of tentacles when startled by predators. A series of fascinating experiments by the Swedish zoologist Erik Dahl in the late 1950s showed that, compared to other fish species, juvenile whiting were able to adapt their movements such that even when surrounded by tentacles they rarely came in to contact with them. Also, unlike other fish species, when they did brush against them it seemed to cause them little concern. Biopsies of the tissue of whiting where they had contacted tentacles showed that very few if any stinging nematocysts had fired into the fish’s body; this compared to hundreds per square millimetre for other fish species. We still don’t understand the mechanism behind this protection. So does the lion’s mane get anything in return for the refuge afforded the young whiting? Well another creature found on lion’s mane jellies is the tiny planktonic amphipod (a type of crustacean) Hyperia galba. Hyperia is, for the jellies, a rather irritating ectoparasite. It lives on the outside of the jellies’ bell, nibbling away at it. Now whiting don’t appear to like the taste of lion’s mane jellies, instead they are rather partial to planktonic crustaceans; in particular (you’ve guessed this already) Hyperia galba. It is these elegant little symbiotic collaborations that make nature so beautiful.
I’ve spent most of this summer sailing along the coast off Western Scotland and Norway, with a brief swing by the Faroe Islands. I think this includes some of the most dramatic scenery in the World and some of the best marine wildlife. From the wild remoteness of St. Kilda to the sheer majesty of Troll Fjord there is little that betters the coastline of the northeast Atlantic. The one downside is that internet has been working only intermittently and then at a glacially slow speed. However it has been a great trip for marine mammals, with regular sightings of grey and common seals, harbour porpoise, common and bottlenose dolphins and even the occasional orca and sperm whale. So whilst siting in a bar in Bergen on a chilly and rainy August evening I thought I’d take the opportunity to upload a few images of orcas (Orcinus orca) and common seals (Phoca vitulina).
Male orca cruising off the Lofoten Islands, Norway
We were lucky with around the Lofoten Islands, where a small family group of orcas altered course to swim alongside us for a few minutes, rather like overgrown dolphins (which is exactly what orcas are).
A female orca (or killer whale) Orcinus orca, cruising along near the Lofoten Islands, Norway.
The western isles are always good for seals, with common seals pupping whilst we were there. We had particularly good sightings around the Shiant Islands and The Isle of Skye, where both common seals and grey seals (Halichoerus grypus) occur together.
A curious common seal, Shiant Islands, Hebrides, Scotland.
Very often they would pop up behind our Zodiac, always at a safe distance, but curious as to what we were doing.
A common seal cruises with its eyes and nostrils just above the water. Dunvegan, Isle of Skye, Scotland.
With only the tops of their heads, eyes and nostrils visible, seals can be tricky to spot. A glance in their direction frequently results in a loud splash as they duck dive out of sight, rather like inquisitive but shy children.
Common seals playing on rocks, Shiant Isles, Hebrides, Scotland.
Basking on the rocks they were often quite playful.
Female common seal or harbour seal, Phoca vitulina, dozing on the rocks, Dunvegan, Isle of Skye
The blue shark, Prionace glauca, is possibly the most beautiful of sharks. It is a slender, fast and graceful shark, but it is the vivid, almost electric blue colouration that is most striking.
A blue shark passes close by.
Blues are oceanic sharks, uncommon in shallow coastal waters. In the tropics they are normally found in deeper, cooler waters, but in temperate seas they are more likely to be found in surface waters (thus are described as being epipelagic). This does not mean that in temperate waters they occur only in the warmer surface layers. Recent data from satellite tags have shown that they blues may regularly undertake dives to more than 1000 metres. One male blue shark, nicknamed Bodi by the researchers, was logged as having dived to 1250 metres off the Bay of Plenty (New Zealand) three weeks after being tagged in 2013. An earlier joint British- Portuguese study recorded a female blue shark diving to 1160 metres off the coast of Portugal (Queiroz et al, 2012). This behaviour is probably linked to hunting activity. Blue sharks are quite catholic in their diet, eating a wide range of mid-water fish and cephalopods, but appear to be particularly fond of squid, and of course squid will often undertake marked vertical migrations, with many species occurring at considerable depth. That this deep diving behaviour of blues is primarily foraging for food is supported by a preponderance of deep water quid species found in the gut of contents of blue sharks caught by long-lines, in particular the wonderfully named vampire squid, Vampyroteuthis infernalis, a small deep-water squid those scientific name literally translates as the vampire squid from hell.
In the northern Atlantic at least, they appear to undertake seasonal migrations. They are unusual amongst ocean sharks in that they will sometimes aggregate in groups, often all same sex, as they roam. This pack-like activity has lead to them being dubbed the wolves of the sea. Around Southwest Britain blue sharks start to appear in June each year, and hang around until late October or early November. Although there have been attacks on humans by blue sharks, aggressive behaviour is relatively rare. Certainly in British waters, where large blues are rarely seen, most are quite timid and easy to scare off accidentally. The largest blue caught in UK waters was approximately 2.5 metres long and weighed 107kg. This was caught off Penzance, Cornwall, in 2012 (but was also released). Blues can grow up to 3.5 metres or more (the largest on record was 3.83 metres long) the females being significantly larger than males.
Blue shark, Prionace glauca. A female blue shark swimming close to the surface off Southwest Cornwall, UK.
An underwater encounter with a blue shark is a wonderful experience, and provided one takes sensible precautions (i.e. wearing gloves, not wearing shiny bits of equipment and NOT trying to feed them) is normally quite safe. Blue sharks have been one the shark species hardest hit by the practice of shark fining in various parts of the World and there numbers appear to have declined markedly. Consequently it’s worth remembering that most blue sharks have far more cause to fear us that vice versa.
The above, and more of my blue shark images, can be found on my stock image website www.colinmunroimages.com. They can be licensed for publication, or purchased as fine art prints and canvas wall art.
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References cited: Queiroz N, Humphries NE, Noble LR, Santos AM, Sims DW (2012) Spatial Dynamics and Expanded Vertical Niche of Blue Sharks in Oceanographic Fronts Reveal Habitat Targets for Conservation. PLoS ONE 7(2): e32374. doi:10.1371/journal.pone.0032374
A few days ago I was fortunate enough to get in to the water off Cornwall with a couple of blue sharks (Prionace glauca). Getting some good images of blues had been high on my ‘to do’ list for several years, but for one reason or another it had not happened. In part this was a result of the dreadful summers we have had in the UK for the past few years; wet and windy and severely limiting the number of days when it was possible to spend all day offshore in a small boat (and limiting even more the number of days one would want to). This summer has so far been perfect, high temperates and light winds.
Blue sharks are highly migratory, with strong evidence for there being a single well-mixed population within the Atlantic Ocean and seasonal trans-Atlantic migration. Some studies indicate a crosswise annual migration across the temperate zone of the Atlantic but evidence for this is inconclusive. What we do know is that blue sharks start to appear off the tip of Cornwall in early July and remain around Southwest England until late September.
Off the tip of Cornwall is one of the best areas to see blues; it also has the advantage of exceptionally clear water. Most are found at least five miles offshore, so with the longish drive an early start was required. By 10a.m. we were drifting with the current, a nice fish oil slick trailing from our chum bag, cameras ready and waiting. The sky was blue, the sun hot, the sea ruffled by a light breeze and our spirits were high. And we waited. Mid-afternoon a brief flurry of excitement: two sharks arrived within the space of an hour, grabbed our mackerel bait….. and disappeared. By 4.30pm our hopes were fading and our thoughts turning to when we could schedule the next trip. Suddenly at 4.45pm a third shark arrived. A smallish female, probably around 5ft, but most importantly she showed none of the skittishness of the previous two. She was interested in the fishy smell from our chum bag and she was hanging around. It took a real effort of will to stay calm, remain on the boat and allow her time to settle – what if she also suddenly disappeared? However, after a few minutes Charles, the boat skipper, gave us the nod and Richie and I slipped gently and quietly in to the water. As we swum towards her she showed no fear at all, appearing quite curious about us, to the extent that she temporarily lost interest in the chum bag and began cicling us as we drifted slowly from the boat. Time and again we would swing around to make close passes, to the extent that she occasionally had to be gently pushed away as she came nose to nose. A more obliging photographic model I could not have wished for. Around 20 minutes passed in a flash, at which point she became bored with us and disappeared. Yet no sooner had we climbed back in to the boat than a larger female arrived. She definately wasn’t timid; before anyone could react she had grabbed the chum bag and was tearing it to pieces. Within seconds the water around the boat was a murky brown from the contents of the chum bag and the bag itself shredded.
This was too good an opportunity to miss, all four of us hit the water. She was a real beauty. Between 6 and 7 ft long, the most dazzling vivid blue on her dorsal surface with deep indigo patches near her dorsal fin, pure white on her underside. As she passed close the mating scars left by the males teeth could be clearly seen on her head neck and back. For more than 30 minutes she hung around. circling us. It was almost 6pm when we finally climbed out of the water. Tired but very happy.
Our trip was on board the RIB of Charles Hood (charleshoodphotography.com). Charles regularly runs basking shark and blue shark trips from Penzance, Cornwall. I would heartily recommend him.
Sunset corals (Leptopsammia pruvoti), a little natural history.
Leptopsammia prouviti, growing on undercut limestone ledges, Lyme Bay, Southwest England.
For most, the word coral conjures up images of living reefs surrounded by shoals of colourful fish, in clear, brightly lit tropical waters. Whilst this is the type of environment where the vast majority of coral species are found, it is not the exclusive habitat. That corals are found in the chilly and turbid seas around Britain would probably surprise most of theBritish public. In fact there are five known species of coral found in shallow waters around the UK. The two best known species are the Devonshire cup coral, Caryophyllia smithii, and the sunset coral, Leptopsammia pruvoti. Like all our shallow water corals they are solitary corals (apart from the Weymouth carpet coral, Hoplangia durotrix, which forms small clusters of polyps growing from a basal plate). They don’t form large, colonial skeletons and hence don’t form reefs.The Devonshire cup coral is familiar to many divers and may even be found intertidally in shady overhangs at the very bottom of the tide.
Leptopsammia pruvoti is rather more enigmatic. It is known to occur in only a handful of locations around Southwest Britain (The Scilly Isles, Lundy Island, Plymouth Sound, Lyme Bay and Portland Bill) though it is more widely distributed along the Atlantic coast of southern Europe and in the Mediterranean. Leptopsammia pruvoti belongs to the taxonmic family Dendrophylliidae, a sub-group of corals. An interesting feature of nearly all (around 91%) Dendrophylliidae corals is that they lack symbiotic zooxanthellae (technically speaking they are azooxanthellate). At this point you may be asking ‘so why is that a big deal … and what exactly are symbiotic zooxanthellae anyway?’. A common feature of most reef building corals (hermatypic corals) is the presence of tiny unicellular algae, termed zooxanthellae, living within their tissues. This is a symbiotic relationship; Zooxanthellae gain protection and some nuitrients from the coral whilst the coral gets glucose, glycerol and amino acids from the unicellular algae. One of the key benefits for the coral is that this facilitates the production of large amounts of calcium carbonate, the material from which coral skeletons are formed. Thus the calcuim carbonate based, skeleton-forming process in corals containing zoozanthellae is ‘turbo-charged’; they are able to produce skeletal material at a greater rate and so can grow to form large, colonial skeletons that meld together and form reefs. Azooxanthellate corals do not have this advantage, but their lack of dependence on photosynthesising algae frees them to expand beyond the brightly-lit surface waters. Azooxanthellate corals in the family Dendrophylliidae can be found from a few metres depth down to over two thousand metres. This takes them deep into the aphotic zone, the parts of the ocean completely devoid of light (roughly, below 1000 metres). It also allows them to colonies niches that are out of direct sunlight, such as caves (e.g. the recently discovered coral Leptoseris troglodyta, troglodyte= ‘cave dweller’, found around Indonesia and the Philippines) or the rock overhangs of Lyme Bay.