The stories we hear, the stories we tell

Sunset on Gwithian Beach
© 2018 Duncan Greenhill

The relationship we have with nature is critically important, but an extinction of experience is making it dysfunctional. Like many dysfunctional relationships it is shaped by the stories we hear and the stories we tell, to others and ourselves. Stories where the narrative does not always match the truth.

Humans have always told stories to make sense of the world, and stories have both power and magic. The way we see the world is moulded by these stories, how they are presented – how they are framed – and who the story says is the villain and the hero. It all affects our ideas of what is good and bad, right and wrong. Some of the darkest parts of history are characterised by stories that paint some group as an other, as an enemy, stories that then reach horrific expression. The narratives we tell, the stories we choose to live by, will shape how nature will fare when faced with an expected nine billion people on Earth by 2050, and by extension, how we will fare.

As Sylvia Earle has said – “no blue, no green”, meaning that without a healthy ocean there cannot be a healthy, well-functioning planet. And there are many stories we can tell of how the ocean supports us. It gives us breath courtesy of photosynthetic algae expelling oxygen, it feeds us by providing the main source of protein for three billion people. Humans and the ocean are, as the ocean literacy principles state, “inextricably interconnected”. It quenches our thirst and irrigates our crops – much of our freshwater comes from the ocean, evaporated from the surface to fall later on land and start its journey back, carrying the dissolved substances that make the ocean salty. Seagrass meadows provide nursery grounds for fish, and habitats for other creatures, boosting biodiversity. They capture carbon out of all proportion to their abundance, helping us by removing carbon from the atmosphere and lessening the severity of the climate change to come.

The things that the ocean provides us are sometimes called ‘ecosystem services’, which means the ‘goods’ (like fish) and ‘services’ (like carbon capture) that are provided from the ocean to us. I understand why the concept is used, but it’s one I dislike. An ecosystem providing services to humans. From nature, to us. It’s a bad story, the wrong story. It does a disservice because of what it implies – the term to me suggests a hierarchy, a ranking of who is the dominant party in that particular exchange. It does not suggest a parity between the two. That’s not to suggest humanity should be subservient to nature instead. A diver is not ‘subservient’ to their equipment, but sensibly recognises that care and maintenance is better than dealing with gear failure while still thirty metres under water.

To see ourselves as somehow superior to nature, above it, having ‘dominion’ over it, just shows the arrogance that we, as a species, have in its own exceptionalism. For all our advances and achievements from antibiotics to space travel we are simply one more species of primate, albeit with less fur, bigger brains and better tool-making abilities; this exceptionalism insulates us from our connection and dependence on the natural world.

Here in the UK the issue of poor water quality in rivers and coastal waters is, at the time of writing, receiving a lot of attention. Water quality can be degraded by run-off from agricultural land, such as excess fertiliser, or discharges of raw sewage into rivers and coastal waters. Water companies are permitted to discharge raw sewage under certain conditions, for example during heavy rainfall when the volume of water needing treatment exceeds the capacity of the treatment works to process. Enforcing the regulations by prosecuting those that breach them is necessary, but not enough by itself. In 2021 one company received a record fine of 90 million pounds for discharges that were not authorised by environmental permits, with the discharges into waters where the majority were covered by domestic and international environmental protections. But this is prosecution and protection after the fact, when the damage has already been done. The fine was given out in 2021, while the discharges happened between 2010 and 2015.

But poor water quality also affects our ability to enjoy the coast and ocean. When my daughters were small we were in the surf off a Welsh shore, jumping over and diving under the breaking waves. There had been heavy rainfall a few days earlier, so a permitted discharge may well have happened. There is little that will get me out of the water, but coming face-to-face – literally – with one particular “floating hazard” was enough to send me and my family back to the beach. Is this a story we want to tell, a narrative we want to embrace, that our ocean is simply a receptacle for our waste?

Some go to the ocean to lose themselves in nature, some as a group to share the experience with others, bonding in the light from the flames of a driftwood fire on the beach as daylight retreats. Still others go for a challenge, like kite surfing among the breakers or fighting through the sleep deprivation of single-handed sailing in a long-distance race. We can tell the stories for each of these, but should not forget the one that matters most: that the fate of the ocean and our fate are intertwined, and cannot be separated. This is the story that we most need to tell, and the story that most needs to be heard.

The Extinction of Experience

A pair of great spotted woodpeckers at a nest
A pair of great spotted woodpeckers at a nest.
© 2021 Duncan Greenhill

It’s the relationships we have that give meaning to our lives. We may achieve what passes for status – career success, possessions – via the consumption and competitiveness that marks and mars our society, but it is the relationships we have and nurture that define who we are. The relationships with our friends, our family, our ‘significant others’. But there is one significant other where the relationship is being undermined, neglected, where it’s faltering, right at the point where it’s at its most important for us. Our relationship with nature. As the world warms, our future is intimately linked to the natural world that sustains us. It’s always been that way of course, but the severity and speed of the change is about to refresh the memory of that in those that have forgotten it. This loss of connection, this ‘extinction of experience’ as Miller has called it, disadvantages us. It removes a source of knowledge that gives context to the challenges we face, and a source of comfort as we face them.

The public health measures around Covid placed restrictions on where and how we could connect with our fellow human beings, and in response many found connection to nature instead, experiencing benefits physically, but also mentally, in a world that had lurched away from what we recognised as ‘normal’. I live about as far from the coast as you can get in the UK, so travel restrictions meant that I could not journey to the ocean for significant periods of time. I responded by revisiting some of my local sites containing my second favourite habitat: woodland. I found familiar friends, like yellow lesser celandine flowers that reminded me of early morning walks to lectures at university. I saw both parents at a great spotted woodpecker nest as they changed shifts to look after their young inside, the male with a red flash on the back of his head. I saw nesting swans hatch four chicks, only for two of them to be lost, presumably to predators or illness. I found badger tracks, latrines, and spoil heaps from freshly dug setts in an area I have known since childhood, yet never knew they were there. The truth was I’d never looked, always discounting the area as too enclosed, too urbanised, too small to support a badger population. Walking through a woodland reminds me of the ocean in some ways. Where sunlight is fractured by the canopy and shards of light dance over the woodland floor I feel much of the same immersion, the same enclosure, that I do snorkelling through shallow water.

The connection between nature and us is one where each depends on the other. That may seem strange – it’s easy to see our dependence on nature, but how is nature dependent on us? Perhaps dependent is the wrong word, perhaps reliant instead. Nature is relying on us to stop inflicting the damage we are.

There’s a concept in ecology called ‘shifting baselines’, that the losses we register, the comparisons we make, are only to the earlier times we have experienced. We only compare change and loss to what we have previously known. We can see the change, like the maximum size of an particular fish landed for example, but assume that past point in time represents an undamaged state, a starting point of decline. But old photographs show fish of a size we would consider giants, fish that would dwarf what a fisherman now would call exceptional. Change is overlain by change and damage and loss accumulates, but we see only the latest phase of that damage, the rest hidden, like looking only at the outermost shell of a set of Russian dolls.

We learn the attitudes we hold as adults from our family, carrying them into independence. They colour the value we place on things. Our attitudes to nature we also bring from childhood, and childhoods devoid of messy play, sat in front of screens immersed in counterfeit experiences, divorce us from our ecological identities. We are as dependent on nature for our survival as an otter twisting through water chasing a fish. Richard Louv, co-founder of the Children and Nature Network talks of the ‘last child in the woods’, and how modern society, at least in developed nations, is increasingly isolating our children from experiencing nature in the way that earlier generations did. The consequences could be profound. What policies are made more difficult to introduce or implement when a community, without the knowledge that comes from that connection to nature, doesn’t see the importance and relevance of them? The changes we will need to make to deal with the climate emergency come to mind.

In the end, people protect what they love, they love what they know, and they come to know what they experience. That what we strive to protect is what we are ultimately dependent on makes immersion in those experiences all the more vital.

Sea-grey shadows under a Cornish sea

© 2018 Duncan Greenhill

High water on a September spring tide reduces Gwithian beach to a sliver. Dark wet sand curves upwards on the ramparts of the most seaward dunes where we dodge to keep feet dry from the more persistent waves. In the surf, aground, something sizeable appears to writhe. Something grey and smooth. Something that glistens where the sunlight catches it as the sun slumps lower to the horizon. We approach closer and see that it is a dead seal, the waves rolling and animating the corpse. My trousers wick seawater to the knee as I wade in and bend over it to get a closer look. It is a young grey seal, this year’s brood. How it died I don’t know. There are no wounds, there have been no recent storms, and it appears to be well fed. Yet here it is, carrion in a Cornish sea.

Death is part of every species’ life-history. Not all pups will become adults; it’s one of the central principles of evolution that more must be born than can survive to reproduce. We know this as an abstract fact, but not as a physical reality where a young corpse floating at your feet is not so easy to reason away.

But what if this pup had not died? What would her life have held? Where would she and us have come together, and what would that have meant for both of our species? What would our shared story look like if we could return to her birth, and follow her down a different path?

A head appears between her mother’s hind flippers, a membrane stretched over it, and then one final surge and tear and there are two seals on the sand, one breathing air for the first time. Blood from the placenta leaves a jagged trail across the sand as the mother shuffles around to check her pup. Soft white fur is slicked down to the pup’s body, while around her are more females with their own pups. The mother bares her teeth and snorts if the others come too close, warning them away, maintaining ownership of her own patch of beach as effectively as a towel placed amongst regiments of sun loungers.

The males arrived first in these coves, a few days before the females, and displayed to each other with mouths agape, marking territory and asserting dominance. When dominance fails, they fight, trying to pin down their challengers and bite them. Blood marks the necks on both, overlaying the deep scars from previous years where the failure to deter meant an obligation to fight. The bigger males, at least a decade old, are the more frequent winners of these conflicts. These contests for dominance continue after the females have given birth as the males protect their right to mate, a right they will soon exercise. The males can be up to two metres long and 230 kilograms in weight. The females are shorter and much lighter – up to 180 centimetres and 160 kilograms – and they scatter from these brawls for safety, their pups shuffling after them.

Fourteen kilograms at birth, our pup increases in size as if inflated. Seal milk is rich in fat, at around 60 per cent, and with this calorie-packed nutrition her birth weight doubles in nine days. She lays down blubber under her skin for her seaborne future to come. Her mother feeds her from her own body’s reserves. For around three weeks she will feed our pup, and only in the later stages will she leave the pup to briefly feed herself. Then comes separation.

Our pup is alone. How likely she is to survive her first year depends partly on how well her mother has fed her. She already has an advantage in that she is female; males, the bigger risk-takers, are less likely to reach their first birthday.

She fasts. She must replace the white fur of her birth with her adult coat before she can go to sea, in much the same way that a baby bird must grow its adult feathers before it can leave the nest and fly. She fasts for anywhere from a week and a half to almost six weeks while she moults, losing perhaps up to a quarter of her body weight. As an adult, she will return to this site every year to moult again but for now, she must go to sea and learn to fend for herself. There is no parental instruction – her mother has gone – and her prey is scattered in the coastal waters like the first spots of rain on pavement. She is still substantially smaller than an adult, and her size means she cannot dive for as long. Time is limited. She must learn to search for, find, and catch her prey before her protein and blubber reserves fall too low for her to survive. She undertakes an extended hunting trip of many days at sea, like an apprenticeship but without a master, gradually extending the depth and duration of the dives. She will learn.

At the surface she prepares herself to dive and then she does something strange and unexpected: she breathes out. Her nostrils close naturally as she relaxes the muscles holding them open. Her ribcage and lungs will collapse as the water pressure increases. Any air that remains in them is pushed up into the bronchi and trachea, the tubes that carry air from the mouth to the lungs, and away from the parts of the lung where gases could be exchanged with the blood. We might think that evolution took a wrong turn, lost an opportunity to take more oxygen on board, but it is we who are wrong. In seals, oxygen is stored primarily not as a dissolved gas, but within the muscles, where it is bound to a molecule called myoglobin. Her muscles are rich in this molecule, containing between ten and thirty times more than a mammal living on land. More oxygen still is stored in the bloodstream, where it is bound to a molecule called haemoglobin. Both avoid the need for gas under pressure to enter the bloodstream directly from the lungs. We would fill our lungs before venturing underwater; our seal breathes out. Her physiology is exquisitely evolved to diving underwater; ours is not. Our seal, once adult, could easily descend to over 250 metres in a dive lasting up to half an hour.

She dives. Her heart rate slows. Some blood vessels constrict, concentrating the flow of oxygen-rich blood to those organs that need it the most. She will feed at the bottom, although in around a third of her dives a chance encounter on the descent will mean she will feed in mid-water. She is not a fussy eater. She will eat what she can catch, and what she catches will depend mostly on what prey is available and in what numbers. Sand eels are a favourite; small, long and thin like knife blades. Silver slivers that disappear as one into the sand at the approach of a predator. She will learn to find these. Another popular choice is cod and its close relatives: whiting, haddock, saithe, pollack and ling. Flatfish such as plaice and lemon sole are another favourite. But she has a competitor for many of these species: humans. And competitors can be dangerous.

A seal may compete with us for fish in two ways. They may damage the fishing gear or they may take fish before we can catch them. Fishing gear can be active or passive. A trawl net is active gear. A boat tows a net through the water either close to the seabed or in mid-water. Mid-water, or pelagic, trawls are the ones that pose the risk to seals as they swim around the net picking off fish as the trawl is towed. Nets that are left to hang in the water are passive gear. Gill nets catch fish in a single ‘hole’ of the net as they swim into it and become snagged by their gills, but there is another, more deadly type. Tangle nets are more loosely hung than gill nets, like net curtains in a window, with perhaps 300 metres of netting making a 100 metre wall of fishing net. As the name suggests, fish do not need to be held by the gills to be caught by this net. Fish caught here offer an easy meal, but our seal must be wary; a careless seal may find that their prey are not the only animals entangled. If a seal cannot break free, they drown. Dead seals hauled onto the deck of fishing boats with the nets are often juveniles, often male. Whether this is from the curiosity of the young not yet tempered by experience, or a lack of strength to break free remains unknown. Those that do break free tear the nets. Some seals may eat the fish and escape without being tangled. The end result is a spoiled catch and damaged gear. The fishers are not happy.

One species of fish links fishers and seals more than any other: cod. Cod live close to the seabed and are caught by trawls that fly just above the bottom. Cod is a totemic fish in the U.K. with a special place in British culture. It is the fish of fish and chips on a bleak rain-lashed seafront promenade, the fish of fish fingers from childhood meals, of brave British trawlers facing down Icelandic gunboats in stormy sub-arctic seas in the 1970s. But the amount, the stock, of cod in the sea is low, and staying low, especially in the Irish Sea and the West of Scotland, although the stocks are recovering in the North Sea. Who to blame for this situation? The seals of course.

The truth is more subtle, as it so often is. Seals eat some cod, but the fall in fish stocks has come not from the seals but from our greed of catching too many fish, of politicians setting catch limits year after year above those that scientists recommend. And year by year the stocks have fallen. Seals have played their part, not in the decline, but by slowing the recovery. Seals eat young cod, small cod, too small to be caught and landed by the fishers. Seals take the cod before they grow large enough for the fishers to legally catch, and before the fish reach an age and size to spawn.

Fisheries scientists have an acronym to describe the part of the fish population that can breed and contribute to the next generation: the SSB or spawning stock biomass. The number of fish reaching a size to be legally landed is called the recruitment. Recruitment is kept lower by the seals eating the young fish, and with recruitment lower any increase in the SSB is much slower. Imagine you’re trying to save money for something special, a holiday perhaps. Your salary is like the fish born each year. You pay your bills and expenses and the amount left over is your disposable income. The bills and expenses are like the natural mortality of the fish, those that die or are eaten by something other than seals, and the disposable income – the amount left over – corresponds to the recruitment. But this month there has been an extra expense. Perhaps something went wrong with the car, or an extra household expense became due. This extra expense that reduces the disposable income is like the extra mortality from the seals. This extra mortality slows down the growth of the population in the same way that the car breakdown slows how fast you can build your savings.

Some fishers say that there are too many seals, but perspective matters. The UK has over a third of the world’s population of grey seals, but over 95% of the European population. We have a responsibility for their conservation, both morally and legally. The legal responsibility is one given to us through the habitats directive of the European Union. If a plant or animal is unique to one country it’s easy to recognise the obligation to protect it. If a plant or animal is common and found in many countries that obligation is much weaker. Grey seals fall into an uneasy middle ground; nationally common but globally relatively rare.

The oceans, especially our coastal waters, are polluted places. Much originates from the land. Sewage pipes discharge directly into the water, and although treated, the discharges can remain high in nutrients and bacteria. Rivers carry litter seawards. More nutrients are washed from fertiliser applied to agricultural fields, and feed blooms of algae off the mouth of estuaries. And some problems come from the sea such as lost fishing nets – ‘ghost’ gear – that continues to fish. The large pieces kill immediately through entanglement and drowning. The smaller pieces, and the thin nylon line from anglers, kills more slowly and painfully. The pieces wrap themselves around flippers or encircle the neck, gradually tightening, constricting, cutting in. The wounds deepen. In 2004 around one in every twenty seals in a single Cornish seal colony had some form of entanglement with debris, the majority of it originating from the fishing industry. For a seal entangled around the neck the options are not good: starvation, strangulation, or death through blood loss or infection. In rare cases, there is another option – capture, rehabilitation and release by conservationists.

Conservation can be a benefit to more than the seals themselves. They are good business, one of the charismatic megafauna – the big beasts that engage our imagination – that live or visit Cornish seas. Others are whales and dolphins, basking sharks, sunfish, and perhaps a leatherback turtle on passage northwards to feast on the jellyfish in Cardigan bay. One of the largest leatherbacks ever recorded washed ashore dead on Harlech beach in Wales in 1988. Three metres long, one hundred years old, and almost a tonne in weight, it died from entanglement in fishing lines.

There are wonders in our waters, but seals have the advantage of being predictable. They haul out on rocks and sandbars as the tide falls to rest and sleep. They use the same sites again and again, making it easy for a boat to bring tourists to see them. Predictability is good for business. After all, no one wants a wildlife watching trip that fails to find any wildlife.

Sometimes the seals come to you. Around St. Ives harbour tourists sit on benches trying to guard chips from seagulls that can swoop and snatch them between lap and mouth. High tide approaches. As the fishing boats return the tourists rise and make their way around the harbour to gather on the quay. The seals arrive and wait for the boats to discard some of their catch. There is one large male and two smaller females. One of them could be our seal; Gwithian beach is only a short swim across the bay. The tourists crowd the edge of the quay, trying to capture them on smartphones and cameras looking for the sea-grey shadows below the water, judging where they will surface. Signs on the harbour office warn against swimming with the seals, warning that they are wild animals. The seals feed as dusk falls and the crowd thins, photographs taken.

Wildlife tourism brings people and money to an area, but fishers see the seals, look at their catches, and place the blame. Calls for culls or other controls may follow. The income from the wildlife boats may offset some of the losses, real or otherwise to the local economy, but this is of little use. Those that benefit are not the same as those that lose, and even if they were, viewing the seals in terms of their contribution to the community coffers is pure arrogance. It’s an arrogance that humans are frequently guilty of, one that views an animal as enigmatically beautiful as our seal primarily in terms of their contribution to our economic well-being. We are part of, not apart from, the ecosystems in which we reside. We should not think that we are above them simply because we are a more sophisticated tool builder than most animals.

Our seal is four years old, and an adult now. She has learned the intricacies of catching prey. She has avoided the hazards of fishing net and line. It is spring and she is hauled out to moult, when the previous year’s fur is replaced by new growth. The juveniles have already moulted, and now it is the turn of the adult females. Last autumn our seal returned to the beach where she was born and mated, but her pup is not yet growing. Birth is an annual affair, with mating on the same beach shortly afterwards. The problem is that seal pregnancies only last for thirty-five weeks. Grey seals solve this problem by pausing the development for fifteen weeks before the pup actively starts growing inside her. In this way, births can be tied to an annual cycle, and with all the pups being born around the same time there is protection from predators through numbers. Moulting is complete, the creamy brown old hairs have been replaced by pristine black and grey fur, the pattern or pelage unique to her, a fingerprint to identify her with. She returns to the sea building up her blubber that will be used to feed her pup.

It is autumn again, the fifth since our seal first drew breath on this beach. She stakes her claim to a patch of beach and gives birth to a single pup. He has soft white fur and weighs fourteen kilograms. Many hazards await him, but first, he suckles.

Extraordinarily Crabby

Carcinus maenas © 2018 Duncan Greenhill

Carcinus maenas © 2018 Duncan Greenhill

I think it was the first creature on the shore I learned to identify; certainly the first I learned the Latin name for: Carcinus maenas, the green crab or shore crab. My family lived in Birmingham, which is about as far from the sea as you can get in the UK, and we went on holidays typical of the early seventies: a week in a caravan on a windy headland site, and the days spent at the beach.

I would head down the shore to explore, bucket in one hand, a nylon net with a bamboo cane handle in the other. Tides didn’t matter unless they were rising; as long as I could reach a rock pool, any rock pool, I was happy. It would be a long time before I would find a crab that was not a shore crab; zonation was still a mystery to me, and both the velvet swimming crab, red-eyed and aggressive, and the edible crab, its claws black-tipped, lived lower down the shore. The shore crab, tough and adaptable, able to tolerate the physical conditions of the shore in a way the other species could not, would prosper higher on the shore where they would not. But also where it should not, its larvae hitching a ride in the ballast water of ships to reach Australia, South Africa, and North America.

I would turn over rocks and try to catch them as they scuttled away for a new refuge. Once on one particular rocky headland, I found a cleft in the rock too deep for the grasping fingers of a child, and a crab just visible under the overhang at the bottom. On this occasion I was without my net but I did have a small ball of string in my pocket, the reasons for which are lost from my memory. I pulled a large mussel free from a clump and threw it against the rocks. I tied the smashed shell to the end of the string and lowered it close to the hiding place of the crab. I waited. The crab began to eat. I lifted the string. Slowly, slowly to the surface until I could grasp the crab and lift my prize from the pool for a more detailed examination. I returned him a few minutes later and left the mussel as compensation for disturbing him.

Carcinus, like many common animals, fools us with its ubiquity. We disregard it. We overlook it simply because it is so common, but its life has characteristics that can draw us in, if only we look closely enough. Its diet is wide; as both predator and scavenger it eats many things. One of the favourite prey items is the mussel, Mytilus edulis, but this choice has consequences for both crab and habitat.

Mytilus edulis shell

Mytilus edulis by H. Zell (CC BY-SA 3.0 from Wikimedia Commons)

Carcinus prefers a certain size of mussel, but how to breach the shell? The claws, or chelae, of shore crabs are not identical. They differ in both size and musculature. It has a larger claw, the ‘crusher’ claw, that is the more forceful of the two, but at the cost of speed. The smaller ‘cutter’ claw doesn’t develop as much force, but can close faster and is more dextrous. The claws have bumps, called teeth, on the inner edge. The claws on the male are larger than those of the female; they are needed for more than just securing a meal.

A crab finds a mussel and picks it up, taking one or two seconds to assess whether this mussel is worth the effort of attempting to gain access. If it is and the mussel is small the crab crushes it with the crusher claw and feeds. A larger mussel needs a different approach. The crab steadies the mussel in its cutter claw, the smaller end of the mussel uppermost, and applies pressure to the narrow end. The shore crab doesn’t squeeze steadily but gives a few pulses of pressure before moving the mussel slightly and trying again. The crab is an engineer – it’s not brute force that will secure the meal, but the propagation of stress fractures through the structure of the shell. If the shell is too robust or large for this approach then the crab changes strategy. This time the claw is forced between the shell halves and pieces are chipped off, gradually dismantling the shell and eating the flesh as it becomes available. In this way Carcinus can chip its way into any size of mussel. A mussel can’t find refuge from predatory crabs simply by growing larger.

The meal is not cost-free. Optimal foraging theory, the idea that animals maximise the energy they gain for the lowest cost they expend, doesn’t quite hold for Carcinus, even though as an experimental animal it was one of the examples used in support of the theory in the 1970s and 80s. Carcinus should pick mussels of an intermediate size. Too small and the mussel isn’t worth the effort of breaking in; too large and the time spent to crack it reduces the gain in energy from feeding on it. They should pick intermediate-sized mussels, but they don’t – they pick mussels slightly smaller. Remember those stress fractures? Well, they not only occur in the mussel shell, but also in the crab’s claws. The teeth on the claw become worn. The claw weakens, and in some cases can be lost completely. By feeding on smaller prey it prioritises the longevity of the claw over the immediate benefit of more food now.

Carcinus maenas underwater

Carcinus maenas – note the five distinctive ‘teeth’ along the side of the carapace and the three bumps between the eyes (CSIRO Image Library CC BY-SA 3.0)

The damage or even the loss of a claw does not have to be fatal. They can be replaced, but only when the crab moults – when it sheds its shell and forms a new one with growing room to spare. The loss of a claw may not be due to the wear and tear from feeding. Carcinus can choose to shed a claw or limb if it needs to, for example, when escaping a predator in a similar way to a lizard shedding its tail. This deliberate shedding is called autotomy.

It can take up to three moults to replace a lost claw, during which time it may have to feed on less armoured prey, particularly if it’s lost its crusher claw. Time may be critical. Carcinus has a limited number of moults and the length of time between moults gets longer as they grow larger and older. For a large or old crab the loss of a claw means that it may never fully replace it simply because it doesn’t have enough moults left. One way to speed up the replacement process is to ‘swap sides’. The old cutter claw develops into a new crusher claw and the new claw becomes a cutter claw.

The loss of a claw doesn’t just restrict the diet; for males it has other consequences. The females can only mate when they moult, and as they become ready to moult they release a pheromone into the water. Males will seek the females out and fight for access to them, and then protect her both before and after moulting. For this they need their claws. They show their dominance by holding them wide in front of them, with pincers parted, and use them when fighting. A large crab with a missing claw may just hold its own against smaller males, but against an intact male of a similar size it will lose.

After mating the female creates a cavity in the sand in which to lay her eggs and attach them to her pleopods, the appendages under her abdomen. A female can lay up to 165,000 eggs and the egg mass is carried beneath the abdomen, which she fans to oxygenate the eggs. At first coloured orange the eggs turn a brown and then a dull grey as they mature. Once hatched, the live in the plankton for two to three years, feeding on other planktonic organisms, moulting through four stages as a spiny zoea before finally moulting into a megalopa, the stage that will eventually leave the plankton and once again live on the bottom.

Crabs can’t increase their size continuously; they moult to grow. Their bodies are encased in a hard shell, and like a child with too-tight shoes, eventually they need to trade up to a larger size. This brings problems because the shell is both armour and skeleton. Without it the crab can neither protect itself nor easily move. Before it sheds its shell the crab will start to break down its existing shell, which will soften. If you’ve ever found a crab on the shore whose shell is soft, called a ‘peeler’ crab by fishermen, then that’s the reason why – it’s close to moulting. It’s vulnerable in this state: put it back where it has good cover and can hide. The cells of the epidermis will pull away and separate from the inside of the shell and start to secrete the layers of a new carapace. The crab takes up water, the pressure splitting the old exoskeleton along the sides and at the rear, and the crab wiggles itself free from its former shell. This shedding of the shell is called ecdysis, and leaves the animal with a new soft, paper-thin exoskeleton. The crab’s tissues take in more water while the new shell hardens, after which the crab expels the water and shrinks, leaving room in which to grow before it again needs to moult.

One of the common names for this crab is the green crab, but it isn’t always green. Some are various shades of a reddish-orange. All newly moulted shore crabs are green but the pigment in the carapace that gives it the green colour can be degraded by light. The longer a crab spends between moults the more likely it is that its colour will change towards the ‘red’ form, and the more likely it is to have other creatures living on its shell. The colour isn’t the only difference. The red forms have heavier and thicker shells and can tackle larger mussels than a green crab of the same size. But there is also a downside. Unlike the green-coloured crabs these can’t tolerate environments with low oxygen or large changes in salinity. That makes a summer rock pool an unfriendly place for a ‘red’ shore crab, and so they tend to be found lower down the shore or below the low water mark.

It’s been close to half a century since I first encountered a shore crab, but its familiarity hasn’t lessened my fondness for it. I still head down the shore bucket in hand but this time not alone. Two years ago my daughter sent me a father’s day card using one of those online sites that make the card from your own image. She chose a photo from our summer holiday. On the cover was my own water-wrinkled hand holding a shore crab.

Creative Commons Licence
This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

Cat around the Dragon – How it ended

Last August I set off to sail around Wales in a small catamaran for charity, and called the expedition ‘cat around the dragon’. The expedition lasted four days. Team 109 from Portishead RNLI are planning to cycle from Portishead to the RNLI headquarters in Poole. How are these two connected? Well, funny you should ask that.

Edit: In the rush to get this post out I failed to include a link to team 109’s fundraising page. The link for the RNLI donation page is  If you don’t feel you can donate then please share the link.

catamaran moored in marina.

Moored at the events pontoon, Portishead marina. (CC-BY-SA 4.0)

The departure point was Thornbury sailing club, who had kindly let me use their facilities for the launch. I’d gone down the previous day and assembled the boat so that on the Saturday morning I could be dropped off with the kit, load the boat and launch a couple of hours before the high spring tide that was due around noon. The plan was that the rising tide would work against me initially, but flush me out later in the passage as I rounded Lavernock point and headed for the destination of Barry Harbour. We arrived at the sailing club late and loading the boat to a state that I felt happy with also took longer. I launched two hours after high tide, literally shin-deep in mud shoving the boat off the end of the slipway. Ten minutes later, and I wouldn’t have been able to launch at all. Reaching Barry was now a challenge, and heading into the prevailing south-westerly wind meant tacking all the way.

Progress, at least at first, was good. The boat handled well, and the GPS reassured me with speeds of between 7 and 9 knots. The compass told me the direction of my tacks were close to due west and due south. That was to cause me problems later. I passed under the old Severn bridge, and I now had the English coast on one side of the estuary only. Wales was to starboard. The voyage had officially begun. Eddies in the current slewed the boat from side to side as I approached the second Severn bridge, but strong corrections on the tiller kept me on course. The tide has fallen and there were sandbanks to both sides as I emerged from under the centre span.

The Welsh grounds is a huge sandbank that runs from the second Severn crossing for a number of miles south-west. I was aiming for a buoy called the Welsh hook that marked the edge of the sandbank where it turned west, but the GPS showed me there were still a few miles to go. Once I reached it I could turn and head towards the Welsh side of the estuary. The wind had decreased and the falling tide had slowed in anticipation of the turn in an hour or so. I’d marked the buoy as a waypoint in the GPS and monitored the distance left to go. About three-quarters of the way to Welsh Hook the distance was barely changing. I would make reasonable headway on the southerly tack, but on the westerly tack the tide pushed me back northwards and I lost most of the distance I’d just covered.

The alternative passage plan was simply to make landfall where possible overnight. The catamaran would float in half a metre of water, could easily take the ground (or anchor off), and despite it’s small size, was self-sufficient for three or four days. I would not be able to make the Welsh coast so I tacked, eased off the wind slightly, and sailed south-east looking for a likely spot for the night. I could see Clevedon pier in the distance and the curve of a shore behind. Choice made.

The wind was still dropping and the tide was against me. Sunset was less than an hour and a half away. The pier was getting closer. And then it wasn’t. I checked the GPS to confirm, and unclipped the paddle. The pier was less than a hundred metres away. I started paddling. The pier was getting closer. And then it wasn’t. So long Clevedon. I stowed the paddle and turned north, letting the tide help rather than hinder me as I looked for somewhere to land. The wind had now died completely so I started paddling again, this time with the tide. It was getting dark.

Then a call came on the radio from Portishead coastguard for “unknown white catamaran” and we had a brief chat about my intentions, before asking if I would like the lifeboat to assist me. I was already a member of the RNLI, and I’d joked before the trip that I’d be mortified if I had to call them out, the aim of the trip to be on the right side of the dividing line between adventure and stupidity. Another brief chat with the coastguard and I agreed that Portishead lifeboat would be called out.

I furled the sails and rigged a bridle for the inevitable tow, and as the light was fading fast I retrieved my dive torch and strobe from the locker (the legal requirement for lighting a sailboat of this size is to shine a torch on the sails). I could see the lights of large commercial ships leaving Avonmouth and heading seawards and clipped the strobe onto the forestay. I used the paddle to keep reasonably close to the shore but not too close.

The lifeboat arrived and checked I was OK. We had a discussion about where to take me since they (understandably) assumed I was day-sailing and had a fixed destination to return to. I explained about my trip and we decided Portishead marina was the best choice. A little while later I was moored to the events pontoon.

The forecast for the second day was a pitiful force two. Sunday would be a shore day. The cat is only 14 feet long and was moored not far from one of the footbridges across the marina so there were a few people who leaned over the railings to talk to me. I was having a lovely chat to a woman called Caroline and her daughter about the trip and mentioned that I’d been towed in the day before. “I know,” she said, “I was in the crew.”

Day three and the forecast was “westerly/south westerly three or four, decreasing two; north-westerly four or five later”. High tide was just after noon. A lock separates the marina from the channel and, slot booked, I paddled in, trailing the larger vessels that dwarfed me. A woman caught my lines and I moored to the pontoon as the lock levels became equal with the channel outside. I clipped my lifeline onto the boat: fall overboard sailing solo and even in a drysuit you have a very real, and potentially lethal, problem. I set two waypoints in the GPS: Welsh Hook, and South Cardiff. Once I reached the second I could follow the coast, turning the corner at Lavernock Point and finally head along the south Wales coast. The destination was to come ashore at Sully Island, or failing that find a suitable landing point before Lavernock point.
This was a good days sailing. Sun shining, I pass Welsh Hook. The hulls cut through the swell, rocking as the peak first passed under the port hull and then starboard. I pass South Cardiff and turn to follow the coast. I spot a pier and just beyond, two boat ramps. I pass Lavernock point and turn west. The wind is coming strongly from the west and the sea state is a lot lumpier now that the land is not shielding me. I’d assessed Sully Island as a possible stop before the trip and knew that there were many boulders there. Sully Island is only an island at low tide and unsure of how much shelter from the weather I would get I turned back towards the pier and boat ramps.

My timing was unfortunate, arriving  between the pier and the ramps fifteen minutes before low tide. My normal launching trolley hadn’t been suitable for the trip and I’d not been happy with the portable replacement I’d made so I’d left it behind. So now I would have to walk the boat up the beach as the tide rose, but at least those extra fifteen minutes were just enough to make a brew and pack the stove away before the boat refloated.

The two boat ramps belonged to Penarth RNLI, who were conducting a training session based on the reasoning that they might as well be at the station because it was Bank Holiday Monday, and a callout was very likely. I wandered over and explaining what I was doing and asked if I could beach the boat between their two ramps for the night. A little while later one of the volunteers came down the beach with a mug of tea and a Mars bar, which was very welcome. The lifeboat went out to a yacht that was aground on a sandbank near Flatholm to standby should it was needed as the rising tide lifted the yacht off. Back the lifeboat came and was recovered to the station. A little while later the crew come down the beach again. “Seeing as we’re already here” they said, and carried the boat up to the high water mark. This gave me a couple of hours to eat and sort out equipment before bedding down for the night between the hulls as the tide dropped.

Day four. The destination was Porthcawl, 22 nautical miles away. The wind was westerly, which again meant tacking all the way. Changing the batteries on the GPS and a spring from the battery compartment pinged off into the sand. I couldn’t find it. There was a GPS built into the radio but I’d have to dig into the manual to set it up. I checked over the boat and saw bare wood where there shouldn’t be any. There was a block on the upper inner surface of the hull that the cross beam fitted into. It had sheared off and the hull had moved inwards.

The damaged beam support

The damaged beam support. The glued joint had failed between the deck and beam support.(CC-BY-SA 4.0)

The hulls are pulled inwards by the tension on the rigging. The only thing stopping it would be the 4mm rope lashing on the outer end of the beam. The entire tension of the rig through three turns of 4mm rope. Losing the rig overboard would be a very real possibility in rough water and I’d been warned of the overfalls around Nash Point. I sat on the hull with my head in my hands. The voyage was over: the boat was no longer seaworthy.

Ashore on Penarth Beach

Ashore on Penarth Beach. (CC-BY-SA 4.0)

Would I have succeeded without the beam support shearing? Unlikely. I camped on the Llyn peninsula around the time I would have been passing there with the boat. The wind was blowing the tent virtually flat and the breaking waves left a wide, wild foamy border to the lee shore. It was not the only storm that week, and the weather between storms could also be described as ‘challenging’.

Will I try again? Yes, but perhaps in two or three segments rather than try to do it in a single trip, and after ironing out any other issues with the boat with weekend trips this year.

Safety equipment carried:
Drysuit, lifejacket, lifeline; permanently clipped on when under way.
Standard Horizon HX870E handheld VHF with DSC and built-in GPS.
Handheld GPS.
Imray 2600 and 2700 series charts; dividers and portland plotter.
Steering compass and handheld compass.
Crewsaver coastal flare pack.

Creative Commons Licence
This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

Cat around the Dragon

It’s been a while since my last post, so I’m opening with an announcement. Later this summer I’m going to be sailing around the entire coast of Wales in a small catamaran to raise money for two charities – the Marine Conservation Society and the Shark Trust. I’ve been wanting to do something like this for a while, and when I bought the boat off ebay last year I was pleased but there was also the thought “it’s a pity it’s not a bit bigger because then I could …”, which then turned into “hang on, what could I do?” The more I looked into it, the more feasible the trip looked. The boat is a Wharram Hitia 14. I’ve been a big fan of Wharrams for many years and I’m really looking forward to the trip.

Duncan Greenhill

Photo by Lucy Withell

The plan is to sail from the Severn estuary around to the Dee estuary over a period of three weeks from the 26th August. I’ll either be coming into marinas and harbours overnight or beaching the catamaran and coming ashore. As well as raising money for charity I’ll be taking part in some citizen science projects. I’ll be doing surveys as part of the Capturing Our Coast project, and searching the strandline to contribute to the Great Eggcase Hunt. My plan is also to conduct some two minute beach cleans and record some videos to highlight not only some of the issues affecting our marine environment, but also some of the wonderful marine life we have here in the UK.

The journey is approximately 500 nautical miles, and I’m setting a fundraising goal of £5000, which works out at £5 per charity per mile. The donations page is now available at . Please share the link if you don’t feel you can contribute a donation.

I’ll be posting updates here and on my twitter account (@ourCommonOcean) using the hashtag #CatDragon.
Creative Commons Licence
This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

What future for wild sea bass?

There are many things that can cause problems for a species. Sometimes it’s some aspect of the biology that makes them vulnerable. Sometimes it’s human pressures. And sometimes it all comes together to really cause problems for an animal. Sea bass are a popular fish for commercial fishermen and anglers, and are a popular fish for eating. Despite the fact that most of the sea bass consumed in the EU is farmed wild sea bass populations are in trouble. While assessments of the stock are not easy, ICES, the intergovernmental organisation that gives advice on sustainable fishing to the EU has said that the losses from the population due to fishing have consistently been above sustainable levels1 and also recruitment of young fish has been very poor since 20081.

Swimming Sea Bass

Sea Bass by Bjoertvedt is licensed under creative commons (CC-BY-SA 4.0)

Sea bass grow slowly and mature relatively late. They mature between four and seven years old when the males are around 35 cm long and the females are around 42 cm2. Before the 1st September 2015 the minimum size for landing was 36cm nationally2, although some regions such as Cornwall had a slightly larger size3. Not surprisingly, having a minimum size where the female fish could be landed before they had had a chance to breed is not the best route to a sustainable fishery. Sea bass behaviour also increases their vulnerability to over-exploitation. The juveniles congregate in groups in estuaries, and as adults migrate offshore to spawn (where they are targeted by trawlers4) and then return to the same coastal sites year after year5. This site fidelity means that once local populations are overfished recovery is slow, especially if there are cold winters that can kill juveniles, reducing the number of new individuals recruited to the population5. All these factors mean that the breeding population has dropped from around 16,000 tonnes in 2009 to less than 7,000 tonnes in 2015. ICES state that the ability of the population to reproduce successfully is seriously compromised below 5,000 tonnes.

So what has been the response? The minimum landing size has been increased to 42cm6 and is now called the minimum conservation reference size, which at least gives the females a chance to breed but comes at a cost for the fishermen. The fish that are above 35cm now and could have been caught under the old rules are now not available to be caught until they grow large enough to exceed the new minimum. There is also to be a closed season for six months of the year between January and June to allow the fish to spawn. For the other six months of the year recreational anglers will be allowed to land one bass per day, while commercial fishers are restricted to catch limits of one tonne per month. The EU proposes that catch limits should fall from 2,656 tonnes in 2015 to 1,449 tonnes in 2016, a reduction of around 45%7. The problem is, though, that ICES has said that the limit should be set at 541 tonnes for 20168, which would be a reduction of 80% on the 2015 figures. In other words, the limit set by the EU is nearly three times larger than what the scientific assessment says it should be. This may be an attempt to spread the impact on fishermen over a longer period, but with the stock at such a low level this may backfire. A collapsed fishery supports no one.

What else could be done? Save Our Sea Bass suggest that the lower landings limit (the ICES figure) should be adopted as a matter of urgency, and that both anglers and commercial fishermen should only be allowed to catch sea bass by rod and line or hand lines. They also suggest that the share in the 541 tonnes should be distributed in line with article 17 of the common fisheries policy, which means based on environmental criteria and economic benefits to coastal communities. The idea behind using lines to catch sea bass is that line-caught sea bass fetches higher prices. The marine conservation society has a good fish guide, and currently (November 2015) lists wild-caught sea bass as a fish to avoid. Farmed sea bass are a more acceptable alternative to wild-caught fish.

You can keep up to date with sea bass issues either from the Marine Conservation Society or Save Our Sea Bass site.


1,8 ICES Advice on fishing opportunities, catch, and effort Celtic Seas and Greater North Sea Ecoregions 2015
2 European sea bass (Dicentrarchus labrax) exploited around Welsh waters – preliminary results: December 2013.
3Cornwall Inshore Fishery and Conservation Association new minimum size for bass
4Protecting Sea Bass
5Parliamentary briefing on sea bass.
6Bass fishing: catch limits, minimum size, and where you can fish (
7Commission proposes fishing opportunities in the Atlantic and North Sea for 2016

Creative Commons Licence
This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

Losing the plural

There’s been a slight change of name from ‘Our Common Oceans’ to ‘Our Common Ocean’. So why the change? Well, I went to the EMSEA 15 conference early in October and one of the first people I spoke to was Peter Tuddenham of the College of Exploration, who quickly spotted the ‘mistake’ on my name badge and argued that it should be ‘ocean’ rather than ‘oceans’. It makes sense. After all, looking at the thermohaline circulation shows the connections clearly.

Map of the thermohaline circulation of the oceans

Thermohaline Circulation

Plus, it’s the first of the ocean literacy principles: The Earth has one ocean, with many features. So goodbye oceans, hello ocean.

Creative Commons Licence
This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

No limits, no future

Recently, I volunteered with the Shark’s Trust at the Dive Show in Birmingham helping to raise awareness about their ‘no limits no future‘ campaign to stop uncontrolled shark fishing. Shark and ray populations worldwide are under increasing pressure, and the total number of sharks caught annually may be over 100 million. One study1 published earlier this year (2014) estimated that up to a quarter of shark and ray species are threatened if assessed using the IUCN red list criteria. If we think about risks to shark populations we might think about shark finning in the Pacific, or sharks being caught as part of longline fisheries for tuna2 but the problem is actually a lot closer to home.

Originally, sharks were an unwanted part of the catch (bycatch) as fishermen pursued species such as cod and tuna, but now there is an increasing trend for the targeting and retention of these bycatch sharks. They are caught for their meat, their fins and their liver oil. Unfortunately, the life-history and behaviour of sharks makes them vulnerable to overfishing and populations are declining. Sharks reach maturity late and have relatively few young compared to other fish. In addition, they often congregate in groups of individuals that are either all a single sex, or are very close in age. Should a fisherman catch these sharks it has a bigger effect than catching the same number of sharks at random from the population.

In 2012 there were 280,000 tonnes of reported shark landings worldwide, with EU vessels landing 40% of this world total, the majority of which came from the Atlantic ocean and Mediterranean sea. One issue in that this is reported landings – the true level of landings is thought to be three to four times higher3. Worse still, most of this European catch from the Atlantic and Mediterranean is concentrated on just five species4.

These five species are:

97% of all sharks caught and landed from the Atlantic and Mediterranean in 2012 are no limits species, which has been estimated to amount to 6,400,000 individuals. This is why although some of the species above are currently listed as of ‘least concern’ it’s important to make the fisheries sustainable before the populations crash due to overfishing. Once overfished, there is no guarantee that populations will recover as demonstrated by the collapse of the cod fishery on the grand banks off the eastern coast of Canada. In addition, sharks are important components of ecosystems as top-level predators. The shark trust is campaigning for science-based catch limits. Please sign the petition, and see the ‘get involved‘ page for other ways to contribute.


3 4

Creative Commons Licence
This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

Seawater – not as simple as it looks

It’s a typical question you’d get from a child: ‘How salty is the sea?’, and as it’s National Marine Week here in the UK it seems a good one to answer. The simple answer is that there’s around 35 g of salt in every litre of sea water, but that’s only a starting point. Oceanographers are often interested in small differences in salinity, so how else can we express this measurement? Well, a litre of water weighs a kilogram so 35 g amounts to 3.5%, but percentages are too big a unit to be useful, so we use a unit called parts per thousand (‰ or ppt). If we think of percentages as parts per hundred then it’s a straightforward conversion because 3.5% becomes 35‰ – it’s the same relationship as converting a distance in centimetres into one in millimetres. Salinity is now measured using the electrical conductivity of the water and either given as just a number (35) or with a unit called ‘practical salinity units’ (35 psu).

“Coast” by Chris Luczkow is licensed under Creative Commons (CC BY 2.0)

“Coast” by Chris Luczkow is licensed under Creative Commons (CC BY 2.0)

Another question the child might ask is ‘where does the salt come from?’. An obvious source is the rivers, but that’s not quite the whole story. If we look at the composition of seawater we find an interesting characteristic. While the salinity may vary between different locations, the dissolved chemicals that make up that salinity are found in the same proportions. It’s called the constancy of composition. The first seven major components of seawater are, in order, chloride (Cl), sodium (Na+), sulphate (SO42-), magnesium (Mg2+), calcium (Ca2+), potassium (K+) and bicarbonate (HCO3). If we look at typical components of river water we find much less sodium and chloride, and more calcium and bicarbonate, as well as additional dissolved substances such as silicate (SiO2). The difference between river water and sea water is even greater because much of the chloride in river water has come from the oceans via rainfall. So if the river water is the source of the salts in the ocean, why are the proportions so different?

The answer is to do with something called ‘residence time’, which is a measure of how long the element remains in the ocean before being removed. While sodium and chloride flow into the oceans in smaller amounts than other elements of river water, they stay in the ocean for longer. The residence times are also long compared to the time it takes the water to circulate through the oceans, which means that the oceans are well mixed, and this is one of the reasons we have the constancy of composition.

The proportions of the major components are constant but the total salinity can vary, and these small variations in temperature and salinity identify water masses that can be followed by oceanographers. For example, more water flows into the Mediterranean Sea than flows out. This is because a lot of water is lost through evaporation making the remaining water more salty and denser so it sinks. The straits of Gibraltar are relatively shallow compared to the Mediterranean and the Atlantic, so the salty water (called the Mediterranean water) flows out over the straits while lower salinity Atlantic water flows in at the surface.

There’s another important circulation driven by salt. As the Gulf stream crosses the Atlantic it heads north and cools. The remnants of the Gulf stream pass north of the United Kingdom as the Norwegian current. As sea ice forms the remaining water becomes very salty and sinks, forming a water mass called the North Atlantic Deep Water that flows south along the bottom of the ocean all the way to the Antarctic and drives a global pattern of ocean circulation called the thermohaline circulation.

Seawater has a more interesting story to tell than simply the answer to ‘How salty is the sea?’

Creative Commons Licence
This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.