Marine Biology

Spearfishing has been practiced for thousands of years; pointed sticks, barbed poles and harpoons are mentioned from ancient Greece to the Bible. Nowadays iron spears are shot from elasticated guns and travel at speeds of 200 km an hour. It is highly likely that you are familiar with the spear fishers’ tell-tale floating orange buoys as they hunt along our coasts, a black camouflaged snorkel just a few metres up front.

• 

• 

Spear fishing is widely held to be a less wasteful form of fishing, with no by-catch, leaving behind no lines or ghost nets, requiring no bait, and with hunters being able to decide exactly which “piece” (they call fish “pieces”) to take. When fish were plentiful I’m sure this romantic notion was true, yet how does spearfishing fit in with what we are now discovering about the state of our seas?
I grew up in Menorca and my friends spearfished, I’d often go out with them on weekends, and some of my best times at sea were spent exploring new drop offs and underwater caves.

Only 20 years ago I remember larger fish around, close in shore, groupers in particular. It’s rare to see anything very big in the Mediterranean now, and even smaller fish like bream flee in terror at the sight of a snorkeler. None of my friends fish anymore.

• 

• 

Across the globe, now depleted reefs were initially fished with spear guns, fishermen systematically taking out one top predator species then moving to the next, until they had to resort to lines and nets to get the smaller remaining fish. Increasingly, thanks to satellite navigation and fish finders, previously inaccessible, remote reefs, are now also being targeted. Thus, there is ample proof of how damaging spear fishing can be.

I have been battling with my position on spearfishing for years, until I came to work in Madagascar; where subsistence fishermen still use spears everyday. My fellow western colleagues were intrigued, and for a brief period were all very interested in joining on a spearfishing trip. They were telling me “it’s fine because it’s very selective”. One day I came across a 20 yr old sitting with his prey before him, a squirrel fish and a young picasso triggerfish, he hadn’t hit it square and there was only about half left. It all made for a combined edible area of about 2 square inches. I recoiled in disgust. He looked up at me and smiled ‘I caught my first fish’. Then I realised that the drivers behind spearfishing are many, yet are similar across the world, no matter your income, culture, nor livelihood. Interestingly, food provision is but a small part of why people fish.

I was surprised to find out that our Malagasy boat captain, even though provided with a good salary and thus having no need to fish for food, still goes out to spear fish most nights after work. This is also true for subsistence fishermen in the Pacific. When questioned they answered that they went because they enjoyed the challenge of the hunt, and being out together with their friends on the water.

Australian recreational fishers explained that parents would far rather their children burnt off their energy out at sea spearfishing, or spending quality time with their friends and family on a fishing trip, than causing trouble on the streets. Therefore, there is a large social component to fishing, such as bonding amongst young men as they jostle to earn respect in their societies by becoming the best hunter… Older adults who also fished competitively in their youth explain how they used to earn their reputation by taking as many fish as possible in the shortest time, taking risks to get the largest pieces, and that there was definitely a large part of machismo to it. Take a look at some Facebook images of hunters flaunting trophies- it’s not like any one fish of any size would do because it’s simply nice to eat, but grounds for a show of masculinity and ego. Again, this may not be such an unnatural thing per se, – if there were plenty of fish left to exploit for that purpose!

Encouragingly, older fishermen did want to guide their youngsters towards a more relaxed and sustainable form of fishing. They also explained that fishing was a platform that introduced them to a means of getting away from modern day stress, and thus afforded huge physical and psychological benefits. one man was allowed to spend the day out with his mates as long as he brought something nice back for his wife for supper! These motivators to spearfish are rooted in basic human nature and very hard to argue against.
No one wants to be told what they can and can’t do, and there is definitely an element of hypocrisy in slating spear fishers then buying a trawled scorpion fish at the market, or ordering a grouper at a restaurant, illegally poached from the Marine Reserve (also known to happen). Nonetheless, I believe we have a choice nowadays to partake in less damaging hobbies, such as underwater photography, snorkeling and freediving.

GROUPER BIOLOGY, HOW AND WHY SELECTIVE SPEARFISHING IS SO DAMAGING

Grouper, or the coveted “Mero”, are often taken by spear fishers and sold to restaurants, for up to 300e apiece. During spearfishing competitions you get points for larger fish, and on the practical side of things it also makes more sense to take out the largest possible fish. In the 80’s it was common to catch up to 15 large grouper a day. Fishers train up to 5 hours a day 5 times a week so it doesn’t take that long to wipe out a large proportion of adult grouper. Research shows an estimated decline of ~88% over 10 years for southern Europe and the Mediterranean prior to 2001; No wonder I remember seeing more of them when I was a young girl. Though it is said that grouper have moved to deeper waters in response to fishing pressure, in any case, good spear fishers can still reach them, even at 50 m. These men (mostly) are well-trained athletes that have paid their annual license fees to FEDAS, and hopefully respect the catch and size limits. So what is the problem?

In a nutshell, larger fish produce more young. Fish eggs float in the plankton for many days, and a lot of these are eaten during this time, thus it is very hard to say quite how many eggs must be laid for any to survive at all. Dusky grouper ( Epinephelus marginatus) are born female, and spend the first 12 years of their life growing big. Once they reach sexual maturity they divert their energy to producing eggs, and after many more years, they may or may not change sex and become males, thus most of the larger older groupers are male. I’ve had a mate argue that he only takes out the older non-reproductive males. This is exactly the problem; first of all, you can’t be sure it’s a male based on size alone, as some of the larger fish are also female and never undergo the sex change. We need the largest females to produce many eggs. We also need some males left to fertilize the eggs. Indeed, research shows that females may not spawn if there are no males (or not enough males) around. The current minimum catch size for grouper is 45 cm from snout to tail, yet we now know that not all females have began reproducing by this size, and that the minimum size should be increased to 50 cm at the very least. Dusky grouper can live to 60 years of age, thus in order to maintain enough males to fertilize eggs, or larger females that produce high amounts of eggs due to their old age, the biggest individuals in the population must be allowed to survive, and scientists recommend only catching grouper between 50 & 80 cm. Size limits need to be constantly reviewed. This research dates from 2010, yet the current (2015) fish sizes from the CAIB still set a minimum size of 45 cm and no upper limit. Even the most respectful well-meaning fisherman can be misled by the continued lack of information and regulations.

In order for them to be effective, new fishing reserves need to ban all forms of fishing, recreational or otherwise, and we need to understand that that should temporarily be the end of the story! Until stocks have a chance to recover, and to be properly managed, we all have to take responsibility for our choices. Spear fishers feel that they are often, ironically, an easy target for environmentalists, as recreational spear fishing is not allowed in marine reserves, whereas line fishing from shore and boats usually is. We shouldn’t discriminate between the two as, in order to glean as much local knowledge as possible, we need all types of fishermen to unite with scientists. All fishing is damaging when the seas are so depleted and humans are so numerous; whether it’s with a rod, a harpoon, or a net in a rockpool, the cumulative impact is huge and relentless. Investment in research, community education, and sharing of knowledge between fishers and scientists is required to ensure the future of our seas. Well, all that and a huge kick up the bot to policy makers that prioritise short term investment over long term sustainability. As Dr Rainer Froese says in his podcast for Blue Marine Foundation , you can’t take credit on loan from the sea today and give it back tomorrow, it just doesn’t work like that.

Every year come August, my friend’s father used to pack their camper van full of tables and chairs, buckets and spades, food, the dog, and even a portable T.V. They would then drive to Son Saura, literally across the sand dunes, to the far end of the bay where they would spend the next three weeks. That was only 30 years ago. Not quite the same today. The sudden increase in mass tourism has a huge impact on our ecosystems, and that is exactly the point I’d like to make; beaches are living ecosystems, made up of different parts that rely on each other, and that change from year to year. Fundamental to the creation and maintenance of our beaches is the seagrass Posidonia oceanica, also known as Neptune grass, or eel grass. To start with, most of the sand that creates our beaches comes from dead calcified animals that lived on their blades. Every winter the grass sheds its old leaves. Over 80% of dead leaves are transported off the meadows in autumn by waves and currents, and lots of these then ends up on our beaches. The leaves help protect the beach from storms by making the water more viscous near the shore, which reduces onshore wave action. They further protect the beach by accumulating on the sand and forming a physical barrier that stops wind and waves from taking the sand back out to sea. This same barrier prevents water from reaching the dunes at the back of the beach, where the high salt levels would kill the plants. When they decompose, the leaves supply nutrients to both the organisms living within the sand and back in the dunes. Some of the leaves are carried out to deeper waters where they, (plus poop from the organisms housed within the meadow), provide carbon and fertiliser to offshore sediments.

In the water seagrass traps sand and sediment, keeping the water nice and clear for us snorkellers, and for travel agents’ marketing photos. As a photosynthesising plant, seagrass produces mountains of oxygen, and acts as a carbon sink, regulating the chemical properties of the sea. Not bad for one plant! Some years there is naturally more seagrass lying on the beaches, others there is less, and that’s just the way it should be. Beachside businesses urge authorities to ‘clean’ the beaches by using large tractors that sieve the sand free of all particles larger than the mesh size they are rigged with. This removes vast amounts of sand, twigs, and seagrass. These heavy machines, together with thousands of pairs of feet, also compact the sand making it water and oxygen-proof, which is not much use if you’re a cockle or a worm that lives inside of it. Altering the shape of the beach by flattening it all out removes natural windbreaks at the shoreline and near the foot of the dunes. While 30 years ago seagrass was just another part of the beach you either liked or you didn’t, now we seem to think that beaches need to be raked, sieved, and ironed into a flat, barren, and lifeless plateau whose only function should be that of providing humans with a place to put our towels down.

The word snorkel comes from the german schnorchel, and has something to do with noses, snoring, and submarine airshafts. Etymology aside, snorkelling is the Mediterranean equivalent of rockpooling, in that if you want to find animals then it’s into the sea you have to go.
So what exactly is Posidonia?? Originally a land plant, it returned to the sea relatively recently. With extremely slow lateral growth, it photosynthesises, has flowers, seeds, fruits, and a root system, unlike algae or seaweed. Posidonia only lives in good quality waters and so, is what we call a bioindicator of the health of the sea as a whole. It can be found from 5 to 40 m, but most of the life that we see on their leaves (and so excellent for snorkelling) occurs in shallower located plants. The deeper dwelling Posidonia has more species living near its root systems, such as worms, sponges and crabs.

In terms of fish life, seagrass meadows are extremely important as nurseries, in which young fish settle, feed, and hide from larger predators. In summertime you can often see baby barracuda (Sphyraena spp.) in small groups, individuals no more than a finger long. They are unmistakable due to their fusiform shape and pointy noses. Salema, or cow bream (Sarpa salpa) are herbivorous, deep-bodied with yellow stripes, and graze in seagrass, leaving clearly visible nibble marks along the grass blades. Apparently, they retrace the same route every day. Don’t be surprised to find faecal pellets falling through the water column in a trail as they graze their way through the meadow. Salema are of the few bream in the Mediterranean to become herbivorous as adults; most of our bream begin life as omnivores then become carnivores and shift to eating invertebrates.

Young green wrasse and pipefish also live in the meadow, the latter, often hanging motionless near the top of the canopy, can be very hard to spot. Pipefish are related to seahorses and similarly, it’s the males that have pouches to carry the offspring.

Today I was fascinated to observe the zonation of communities inhabiting the leaves. Due to the leaves growing so quickly, (up to a metre a year) and lasting on average 300 days, species must be quick to find a suitable patch on which to settle, grow and reproduce, before other competitors do instead. Hydrozans (Sertularia perpusilla) competing for space follow the new leaf growth and grow downwards. Calcareous red algae (Fosliella sp.) grow on the outer margins of the blade, whilst bryozoans (Electra posidoniae) branch up the middle wherever they can find space. Near the tip of the leaf, we find fleshy red algae and brown algae (Dictyota spp.) that need lots of light for photosynthesis.

Calcified bryozoans may choose to live right on the tip of the leaf, where there is enough water movement for them to catch food from with their tiny tentacles. In spring, fresh new shoots are bright green and squeaky clean, yet as the summer wears on the leaves gradually become colonised by sea squirts, anemones, and calcareous algae and animals, which make the leaves appear almost totally white.

When the leaves die off and break down, the skeletons of some of these organisms become our sandy beaches.
Mooring buoys are all the rage at the minute, but before we get carried away by distressing footage showing the seabed being ripped up, let’s check who made them, as hearsay is that private companies hoping to get rich are behind the making of some of these videos. Although, then again, so what really? While it is common sense to install buoys, these need to be specially designed in order to minimize damage, and one would hope, fairly managed. Boat hire companies should inform customers that it’s now illegal to anchor in seagrass, and that even if we choose a sand patch, we may still end up dragging in to the seagrass.
While anchor damage is a concern in areas where lots of boats gather together, the major threats to seagrass are pollution from untreated waters entering the sea (high nutrient input means that algae may bloom and smother the plants), and increased sedimentation due to harbour dredging and coastal development (which makes light levels so low that the plants can no longer feed themselves through photosynthesis).
Ostensibly, the Anglo-Saxon words for sea were “whale road”, “seal house”, and “fish home”, and with that I think I’ve made my point!

• 

• 

Stingrays, electric torpedo rays, skates, and more rays!

Rays and sharks are a cartilaginous group of fishes, which together form the Elasmobranch suborder. These are characterized by having 5 to 7 gill openings that are lateral in sharks and ventral in rays, slow growth, late age at maturity, low fecundity, and an extended lifespan. Unfortunately, many ray species are accidentally caught in fishing nets. As stingrays are of little commercial value they are discarded at sea, thus little is known about their population sizes and trends.

In Menorca divers are likely to see 6 species of ray;

Marbled torpedo rays (Torpedo marmorata). It was Aristotle (384-322 BC) who first dissected torpedo rays, and who described the electric shock they produce, by poking electric rays with a metal rod. The powerful jolt produced when touched was used to treat people suffering from gout, headaches, or epilepsy. A preference for water temperatures below 20⁰ C may explain why these rays are more often seen by divers in winter than in summer. most adult rays are a darker colour on their dorsal side, and lighter on their underside. This is called “countershading”; when seen from above, the animal blends in with the dark ocean depths or seabed. The underside blends in with the lighter surface of the sea when seen from below. This makes rays harder for predators or prey to spot.
Common eagle rays (Myliobatis aquila) and undulate rays (Raja undulata), not pictured, are less commonly encountered

Rough skates (Raja radula). Rough skates are endemic to the Mediterranean and have been classified as Endangered on the IUCN Redlist, which means they’re at high risk of becoming extinct in the wild. Eyespots on the pectoral fins may afford protection by deceiving predators into attacking the fin rather than the more vulnerable head. Eyespots can also dissuade potential predators by making the ray appear to be a larger animal, momentarily stunning predators when the ray unburies itself to flee.

The huge roughtail stingrays (Dasyatis centroura), which we only see on rare special occasions, can get to 4m long and weigh up to 300 kilos! A very lucky group of divers in the picture below give us an idea of scale.
By and large the most abundant ray sighted by divers in summer is the common stingray (Dasyatis pastinaca). Stingrays feed and live on the seabed. Electro sensory organs on their snouts and strong senses of touch and smell allow rays to root out prey. Their purely carnivorous diet is made up of shrimps and bivalves, as well as small crabs and bottom dwelling fishes. Many rays are nocturnal, making extensive forays to feed at night, and remaining largely inactive during the day.

Because it takes years for rays to become sexually mature, and because the number of offspring produced is then small, the majority of Mediterranean ray species are overfished and endangered (The Conservation Status of Sharks, Rays and Chimaeras in the Mediterranean Sea, IUCN Report). Solutions to their plight involve investing in technologies that reduce bycatch (such as exclusion devices, and different net designs), ensuring the complete eradication of driftnets, (which although illegal, are still widespread in the Mediterranean), and the establishment of marine protected areas in places that we know are important as nursery and feeding grounds (www.fao.org). Some law enforcement wouldn’t go amiss either.

Stingray courtship and mating
For most of the year stingrays are solitary, inhabit deeper waters, and are rarely seen by divers. However, during the mating season, from April to July common stingrays aggregate on inshore bays to mate, providing a unique opportunity to see their reproductive behaviour in the wild. Pregnant females are distinguished by their enlarged abdomens and backs. Swollen and sluggish, they also prefer to rest in seagrass beds rather than on sand. 4-7 pups are produced after a gestation of around 4 months. Ray pups are fed milk in the womb via special tubes and born as live young. Copulating and parturition in the wild haven’t been recorded for this species, and by July they all disappear, continuing their mysterious life cycle until they return to mate the following spring. During courtship, males often follow females with their acutely sensitive snouts close to the female’s cloacae, in search of a chemical signal that the receptive females emit. In some ray species, electro sensory stimuli emitted by buried females help males to detect them. This may be occurring when “grouping” is observed; groups consist of large females resting or buried in the sand, and numerous smaller males surrounding her, with their snouts orientated towards her.

The picture below was taken by a snorkeller (me!); disturbance to the rays is clearly reduced as opposed to SCUBA diving, due to the increased distance, and grouping activity is much easilier detected from the higher angle. Two large females and a small satellite male just discernable in the middle, facing the rear of the female.

So where is the best place to get our eyes on some stingrays?
For divers, Bluewater Scuba Dive centre in Cala’n Bosch, carries out ray dives on a daily basis. Stingrays abound in the shallow, clear waters of sandy bays, which makes them excellent subjects to view while snorkelling. They are found mostly on the south coast in depths as shallow as 2m. See if you can guess the gender by looking for the male’s claspers, although bear in mind that these only become visible once the ray has reached sexual maturity, which in the Western Mediterranean populations would mean a body width of around 40cm.

Photography
Bottom dwelling rays are often found partially buried in the sediment. Rays breath while buried by using the spiracles behind their eyes, through which they draw in water towards the gills, and then flush it out from the gill openings on their undersides. Unfortunately, photographers often ellicit flight responses to stage their pictures. While this may seem harmless in itself, we are not sure of the disruption caused and so it is best to move slowly and keep within a couple of meters of the rays. If we wait patiently, swimming rays will no doubt cross our screens of their own accord. Flash photography is a stressor to every animal I can think of, ourselves included, and should be avoided.

If you happen to be in Menorca in spring/early summer, chances of finding rays are pretty high, so I encourage you all to grab a mask and go find out for yourselves how very amazing they are.