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Marine Life & Conservation Blogs

Diving with British Marine Life: The John Dory

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Part 1 of a new series by our latest blogger Georgie Bull…

A few years ago, I attended a work experience placement at the London Aquarium. During a school session, the staff members gave the children a group of 20 photo cards and asked them to choose which ones they thought showed native species. The cards pictured the likes of corkwing wrasse, orca, basking sharks, cod, whiting, mackerel, and vibrant nudibranchs. Of these, colourful species were seldom selected. At the end of the activity, it was revealed that all the cards showed permanent or seasonal UK residents, which was met with shock from both the pupils and staff.

From this experience, and many more like it, I’ve come to realise just how underappreciated British marine life is.

Over the next six blogs, I will explore just a handful of the charismatic species encountered in the South West of England. I aim to introduce each species, describing my encounters with them before highlighting any relevant literature. There is still so much we don’t know about the species living on our doorstep.


In the build up to my first night dive at Chesil Cove last year, sighting reports circulated that john dory (Zeus faber) were seemingly everywhere. This species had been on my ‘to see’ list for quite some time so any likelihood of seeing one filled me with excitement. Halfway through the dive I noticed a faint, but frantic undulation centred around what looked like a large grumpy dinner plate. It was indeed a john dory. This individual was so full of expression that I found it hard not to fixate myself for the duration of the dive! This was the start of what became a frequent occurrence throughout the season.

Profile

As well as their false eyespot, elongate fins, and disc like body, john dory demonstrate distinctive behaviour in the water. Their movement is relatively slow, though their soft anal and dorsal fins (positioned behind their spined counterparts) move frantically to alter their position in the water. While small, their mouth is capable of rapid extension to draw in prey, and they’ll manoeuvre their bodies into all sorts of strange positions in the water to do so.

Zeus faber are often associated with warm water, but their distribution conflicts this idea, with their Northern range extending as far as Norway!

John dory are categorised as data deficient by the IUCN. The IUCN ranks species based on their population trends, and they are particularly famous for their ‘Red List’ which categorises endangered species. Sometimes insufficient information is available, and the organism is regarded as data deficient. As this is the case for the john dory, questions arise about how their population is coping with its value to the fishing industry.

Literature

It’s true that anglers and divers value john dory, but scientists have been finding out more about the species in recent years. One of their most distinctive features is the false eyespot. These spots are found in a variety of organisms from butterflies to lizards and are thought to divert predator attacks to less essential parts of the body (e.g. the tail) which may offer increased chance of escape. The role of eyespots in nature is understudied, but lab experiments in 2011 and 2013 showed that predators were inclined to attack eyespots spots more so than other areas of the body. This provided evidence in favour of eyespots acting as attack diversions.

On a different note, sound in the marine environment is receiving increased attention recently. Iconic footage captured by the BBC for Blue Planet 2 of reef noise, or hot topics like noise pollution from boat traffic are taking centre stage. But sound in the marine environment is used by individuals to communicate in a variety of different ways. John dory create sounds with sonic muscles that surround their swim bladder. Until 2018, this sound had only been recorded in air. A study recorded the species using baited remote underwater video (BRUV) footage and found that individuals would make the sound when predators were near. This caused predators to flee, suggesting the sound could serve as a territorial defence mechanism. As with all species, there are still many aspects to the life of john dory that we are only just beginning to understand.

References:


Hear more from Georgie here: https://georgiebullphotography.home.blog/

Georgie is a Marine Biology and Coastal Ecology student at Plymouth University and an active diver in the South West of England. This year she will be completing the HSE Scuba qualification with the University in the hope that scuba will become part of her future career. She is particularly interested in native species and has a soft spot for elasmobranchs and molluscs.

Marine Life & Conservation Blogs

Sharks: The Oceans Greatest Mystery – Part 1

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The word ‘Shark’ can instill a mixture of emotions in the human psyche, they are referenced in human cultures throughout the world, and stories of Sharks were commonplace on the decks of Ships for millennia. They have been represented in myth as both powerful guardians and vicious villains, in the 16th Century sailors and whalers of the time referred to sharks as “Sea Dogs” and are referenced in the Bible as being manifestations of the devil, even the word Shark is translated from the German word Schurke which means “scoundrel”. However, in French Polynesian and Hawaiian cultures they are revered as powerful gods and guardians who watch over fisherman and their families.

With such huge differences in how we view them, it is no wonder how inaccurately Sharks are portrayed in modern day media, therefore throughout this three-part blog series I am hoping to help you to better understand what a Shark truly is, and I will be covering subjects such as: What is a Shark? What we know and what we do not know about them, what is threatening them, and how we can be better ambassadors to Sharks worldwide.

What is a Shark?

In this first blog I want to give you a better idea as to what a Shark is and how they have become our oceans top predator. What a lot of people think of when they first imagine a shark is that they have sharp teeth and tend to always have ominous music following wherever they go, however there is much more to these animals than their teeth. Recent discoveries have shown that the Greenland Shark can live to be up to 500 years old, and the Bonnethead Shark is the first known Omnivorous Shark where up to 60% of its diet consists of Sea Grass. These are just two of many recent exciting discoveries, and scientists predict that we are about to enter the golden age of Shark discovery!

Sharks are a part of the fish family, although they are part of a distinct group that separated from Bony fish around 306 million years ago. Early relatives of Sharks have existed on our planet for as far back as 400 Million Years, they have been around longer than Humans, Dinosaurs and even trees. Throughout time sharks have taken many shapes, sizes and forms, but all have one thing in common, the makeup of their skeleton. The skeletons of Sharks and their relatives (Rays & Ratfish) all have a skeleton made of cartilage which is the same substance as your ears and nose, this allows them more flexibility in their movements and gives them an edge over their prey by allowing faster turns and giving them access to tight spaces and crevices.

Sharks, like other fish, also have Hyostylic jaws which means that the upper jaw isn’t connected to the skull, this allows more movement and flexibility in their strike when hunting. Sharks are also accompanied by two additional senses compared to humans, they have a lateral line which allows them to detect movements over 100 metres away and can detect frequencies as low as 25 Hertz, they also have their Electroreceptors which can pick up minute amounts of electricity given off by their prey’s muscles, such as the heart, and Sharks use this to help find prey buried in the sand, or to help pick off individual fish in the dark.

When it comes to sharks and what they eat, the best way to sum it up would be to imagine that for every animal in our Earth’s Oceans, there will be Shark that is designed and capable of eating it. This means that Sharks have become an incredibly diverse group, and as it stands there are over 500 species of Sharks, which range from the 14-Metre-long Whale Shark, all the way down to the Dwarf Lantern Shark, which is the smallest known shark species and it can fit into the palm of your hand. In between these we have large species such as White Sharks that breach from the water whilst trying to capture Seals, and smaller species such as the Dark Shy Shark that curls into a doughnut and covers its eyes with its tail when it is startled.

Another interesting point about Sharks is that they have come up with many different ways of tackling prey and have specially adapted teeth that match their diet, Sharks that have very needle like teeth such as the Sand Tiger Shark or Mako feed mainly on fish or other slippery prey, if the teeth are large and triangular like those of the White Shark or Tiger, then they prey on larger animals such as marine mammals, and if the teeth are flat like that of Nurse Sharks or Port Jacksons it generally means they feed on hard shelled and tough animals such as Shellfish and Snails. Teeth are not the only adaptation Sharks have evolved to use to their benefit, their differences in body shape or design can also indicate to us the hunting techniques they use, a good example of this would be the Hammerhead Sharks, which use their unique shaped heads to pin their prey against the seabed.

Sharks are often thought of as cold blooded, however this isn’t true for all species, some Sharks, such as White Sharks and Makos, are able to warm their bodies a few degrees warmer than the water, Scientists have predicted this is caused by the movement of the muscles generating heat. This heat has most notably been found around the eyes and brain; this may be an adaptation to help their eyes and brain react faster whilst tracking prey during high-speed chases.

Are Sharks Maneaters?

Sharks have been negatively portrayed in the media for as long as we’ve been swimming in our oceans and it is only recently that we’re starting to discover the positive impacts of Sharks and just how important they are to our Oceans and our Planet. Sharks have been represented as maneaters, but in fact sharks are only accountable for an exceedingly small number of incidents relating to a Shark bite, Sharks are in fact more likely to avoid human interaction and encounters with wild Sharks are a lot rarer than you would once think. To put things into perspective you’re more likely to be killed by a falling coconut or vending machine than you are to be bitten by a shark.

Even the age-old myth that Sharks are attracted to Human Blood has been proven to be false, after it was recorded that Human Blood and other bodily fluids have no effect on a shark’s behaviour or heart rhythm, this is due to our blood having a higher iron content than that of their regular prey. Even the way we look and move doesn’t resemble the prey of Shark. But the question people always ask is why do Sharks bite if they do not view us a food item? This is due to Sharks curious nature, Sharks have to be curious to discover what is and isn’t edible and, in our case, when Sharks bite it tends to be very quick lasting mere seconds before it lets go of us and swims away this is due to the animal realising that we aren’t a part of its regular diet and releases us.

If you want proof that Sharks aren’t what media would have you believe just look for any image with a Sharks and Diver, Snorkeler, or Swimmer if the media or movies have any ounce of truth then these people would’ve been killed a long time ago but these images solidify how wrong we’ve been looking at Sharks throughout the years.

So that’s it, an introduction to the Oceans Greatest Mystery, I hope that you have a greater understanding into what a Shark actually is and to how fascinating this amazing group of animals are but stay tuned for the next entry in this series where we dive deeper into the strange world of Sharks and discuss what we do and don’t know about them.


Follow Donovan on Instagram at www.instagram.com/donovans_reefs

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Marine Life & Conservation Blogs

BLUE EARTH – Future Frogmen Podcast Series – Advocating for Ocean Literacy

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A series of conservation educational podcasts from Future Frogmen, introduced by Jeff Goodman.

Advocating for Ocean Literacy

Dr. Syma Ebbin explains why it is important to build Ocean Literacy and why we should bring science and the humanities together so we can embrace different perspectives in order to make progress in our fight against climate change.


Richard E Hyman Bio

Richard is the Chairman and President of Future Frogmen.

Born from mentoring and love of the ocean, Richard is developing an impactful non-profit organization. His memoir, FROGMEN, details expeditions aboard Jacques-Yves Cousteau’s famed ship Calypso.

Future Frogmen, Inc. is a nonprofit organization and public charity that works to improve ocean health by deepening the connection between people and nature. They foster ocean ambassadors and future leaders to protect the ocean by accomplishing five objectives.


You can find more episodes and information at www.futurefrogmen.org and on most social platforms @futurefrogmen.

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Explore the amazing triangle of Red Sea Reefs - The Brothers, Daedalus and Elphinstone on board the brand new liveaboard Big Blue.  With an option to add on a week at Roots Red Sea before or after. 

Strong currents and deep blue water are the catalysts that bring the pelagic species flocking to these reefs. The reefs themselves provide exquisite homes for a multitude of marine life.  The wafting soft corals are adorned with thousands of colourful fish. The gorgonian fans and hard corals provide magnificent back drops, all being patrolled by the reef’s predatory species.

£1475 per person based on double occupancy.  Soft all inclusive board basis, buffet meals with snacks, tea and coffee always available.  Add a week on at Roots Red Sea Resort before or after the liveaboard for just £725pp.  Flights and transfers are included.  See our brochure linked above for the full itinerary.

This trip will be hosted by The Scuba Place.  Come Dive with Us!

Call 020 3515 9955 or email john@thescubaplace.co.uk

www.thescubaplace.co.uk

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