This strange looking fish, often called a living fossil, lives in the deep ocean where it is rarely encountered by mankind. When the first research on the goblin shark was published in 1910, the researcher described the specimen as ‘certainly grotesque’ with a ‘curiously elongated nose’. Because of its deep living lifestyle, comparatively little is known about the goblin shark, but as fisheries around the globe continue to trawl deeper and deeper more specimens have been accidentally caught in nets and brought to the surface for study. As technologies improve the challenges of deep-sea research may be more easily overcome and more can be learnt about the mysterious creatures of the abyss.
Image from https://www.planetdeadly.com/wp-content/uploads/goblin_shark.jpg
Evolution and History
Ichthyologist David Star Jordan first named the goblin shark in 1898, assigning this deep-sea denizen its own new genus after an immature specimen was caught in Sagami Bay off Yokahoma, Japan. The name Mitsukurina owstoni honours the Japanese zoologist Keigo Mitsukuri.
The goblin shark is a member of the Lamniformes family or Mackerel sharks, the home of such well known species such as the great white, the thresher and megamouth sharks. In fact, due to its primitive nature, the goblin shark is the basal member of this family. Well preserved fossil deposits found in Lebanon have shown that the goblin shark is a distinct species, and allowed zoologists to designate the species into 2 genera. Scapharorynchus is an extinct species identified through fossils, and Mitsukurina is the extant species cruising through our deepest oceans today.
The Lamniformes family tree: including the goblin shark. This shows the primitive nature of the goblin shark in relation to the rest of the family. Image from http://www.elasmo-research.org/education/shark_profiles/lamnidae.htm
Range, Habitat and Ecology
The vast majority of specimens and records of goblin come from the waters around Japan, but there are records of them in the Atlantic, Pacific, and Indian oceans. It is likely that they are distributed globally throughout our oceans, but their patchy distribution and deep living lifestyle make them hard to monitor and observe. In recent years, many specimens have been caught in the deep gillnet fisheries that operate around the Tokyo Submarine Canyon.
Most scientists suspect that this species naturally occurs rarely, and this coupled with its living range between 1300 – 1370 metres down in the ocean makes this freaky looking fish a rare find and a difficult research specimen.
Dissection of shark stomachs have shown that they predominantly eat teleost fish (also known as ray finned fish) that live in the deep such as rattails and dragonfishes, and also eat cephalopods and crustaceans. Scientists suspect they feed in the mid ocean, although teeth caught in the cables of submarines suggest they may feed even deeper.
Areas where Goblin Sharks have been seen or captured.
It ain’t easy living in the deep
Despite what scientists used to think, the deep ocean isn’t a barren wasteland devoid of life. There are rich ecosystems thriving down there in the gloom, with more new species being discovered each year. However, this doesn’t mean that living in total darkness under the crushing pressure of the whole ocean doesn’t come with its own set of challenges.
One particularly impressive adaptation the goblin shark has is a highly developed set of jaws that allow them to perform ‘sling shot’ feeding. For a long time, a lot of scientists observed goblin shark specimens with their jaws protruding forwards and believed that they were a completely separate species to goblin sharks with their jaws retracted inwards. In 2008 and 2011, deep sea researchers filmed goblin sharks feeding for the first time and were able to analyse the mechanisms of the jaws and how goblin sharks feed.
The amazing footage caught by deep sea scientists researching the goblin shark and its striking and prey capture behaviour. Image from Nakaya et al, 2016
Dissections of specimens have revealed that the sharks have poorly calcified skeletons and weak muscles, suggesting they aren’t fast swimmers and live a generally pretty sluggish life. Given that they can’t put on a burst of speed to get a snack, they use their ampullae of lorenzini (small electroreceptors) to detect their prey, swim slowly and silently up to it and then use their specialised jaws to snap forward and capture the unfortunate fish. Although their jaws are unique amongst sharks, they use a feeding technique called ram feeding, a common method used by other mackerel sharks. But their specialised jaw structure and extra elastic ligaments give the goblin shark 1.5-2.9 times more protrusible jaws than any other species. This is likely to be an adaptation to the resource poor deep oceans where it can be a real struggle to find a decent meal, and their slow approach to life, allowing them to catch speedy prey they wouldn’t have a chance at without their unique physiology. Once they get close enough, no fish is speedy enough to escape those fast moving, slingshot jaws.
Aside from this very unique aspect of their physiology, they have some further adaptations to make their life down in the deep a little easier. The elongated snout is packed with ampullae of lorenzini, so it is likely that it is adapted to help them find prey easier. The snout is also flexible and soft, and scientists hypothesise this is used to help them nose through the silt on the seabed to dig up a tasty morsel. Their teeth are thin and pick-like, perfectly designed for crushing prey.
Deep ocean conservation: out of sight, but shouldn’t be out of mind
Currently, the goblin shark is listed as least concern on the IUCN red list, as they are apparently rare but have widespread, albeit sporadic, distribution. However, the IUCN recognises that this assessment needs updating as more deep-water fisheries develop and research of the earths deepest places becomes more accessible.
Generally, the goblin shark doesn’t have much conflict with humans. They are occasionally caught as by-catch, except for a strange occurrence in 2003 when around 100 goblin sharks were caught by fisheries. Usually, the accidental captures are juveniles which has led many scientists to believe that the adult sharks may live even deeper, out of the range of most fisheries. The jaws are sought after by collectors, but aside from that, there are no direct pressures on goblin sharks.
However, the same can’t be said for the environments in which they live. Despite how out of reach the deep ocean is, it is still under pressure from human activity, just as every other ecosystem on earth. Fisheries are having to plumb even deeper depths to find fish as the waters above are increasingly depleted due to overfishing. Oil and gas industries are drilling more and more of the seabed to meet the needs of a fast paced, developing world. What’s even more worrying is that we don’t really know the true extent of biodiversity down in the depths, and we are running the risk of losing what we don’t even know we have!
It may not seem like the dark, cold depths are so essential for ecosystem and human health, but these deep habitats have many essential functions. Increasingly, fish are being pulled up from deeper depths to feed earths growing population, and deep ocean sea mounts and continental shelves are the home to spawning grounds of so many economically important fish species. Other species, such as the brilliantly coloured deep-sea corals and sponges, contain biochemical compounds that have proved to be important in treating many diseases. For example, compounds extracted from sea squirts (small filter feeding invertebrates) are used as anti-tumour drugs to treat cancer, and many scientists suspect that the next antibiotic may be derived from the deep, an exciting prospect in the face of increasing anti-microbial resistance.
So, it’s no surprise then, given this range of gifts the deep seas have to give, that scientists are concerned about over exploitation. There have already been some disasters for biodiversity, such as the Deepwater Horizon oil spill in 2010 that spilled millions of gallons of oil into the oceans, smothering the ocean floor and leaving the complex ecosystems that once existed barren, and the overfishing of orange roughy, a slow growing fish whose populations have been decimated by the high demand for their tasty flesh, leading to heavy fishing restrictions in some places. Deep sea trawling has completely destroyed vital deep sea coral reefs, leaving them as nothing more than rubble fields, with often chunks of shattered coral ending up in fisherman’s nets. Often these shards simply get thrown overboard, where it is highly unlikely they will fall onto the correct place in the sea bed and re-grow. On top of the threats from trawling, mining of the ocean floor can disturb huge amounts of sediment that can smother corals and other creatures, stopping their growth or killing them outright. Despite the damage done to these deep-sea corals however, in some places around the world, regrowth of these battered ecosystems gives hope that if we can leave them alone for long enough, we may see some recovery. Given the threats facing the more well-known shallow sea corals, it is possible their deep-sea relatives could be a vital lifeline that may secure a more certain future.
And the deepest oceans are not safe from the biggest scourge of our times, plastic. Bags and bottles have been glimpsed through the windows of submersibles as deep down as the Mariana Trench, and fish have been dissected with guts full of rubbish. Plastic has even worked its way into the very bottom of the food chain; plastic in the ocean gets worn down over time into microscopic particles and eaten by zooplankton, or falls into the depths along with other waste, called marine snow, where it is ingested by many species down there. Researchers still don’t fully know what this ingestion of plastic can do, but I think we can make a good bet that it isn’t going to be good.
This is all particularly relevant this year, as several deep-sea mining companies have been petitioning governments around the world to allow for increased deep-sea mining for oil and gas as well as minerals for the vast array of gadgetry used in society. But scientists around the world called for a global moratorium on deep sea mining at the IUCN world conference recently and rightly so; we simply don’t know enough about the deep oceans and their potential impacts on climate change, biodiversity and ocean health. We do know however, that the deep ocean helps to regulate ocean currents, and by proxy the weather we experience, and that up to 30% of human produced carbon is sequestered away, either through carbon dioxide dissolving directly into seawater, or carbon being ingested as a food source by microorganisms and sinking with them to the ocean floor when they die.
Given what small amount we do know about these unique and surprisingly rich ecosystems, we simply cannot put these places at risk, for the goblin sharks’, and our sakes.
Conservation Organizations, tips and heroes!
http://www.savethehighseas.org/
- This is the deep sea conservation coalition, consisting of many conservation and science organisations, including heavy hitters like the WWF, who are working to protect the deep sea and the vast biodiversity living hidden down there. Due to their work in the past, they have pushed through policy changes such as a ban on gillnet fishing in several key ocean areas, closure of several key biodiversity rich seamounts to fishing and have urged governments to rethink deep sea mining and brought attention to the importance of deep ocean ecosystem. Check out their website to see their goals and priorities.
- You can join the movement #KeepItInTheDeep on the deep-sea conservation coalitions website at https://www.defendthedeep.org/. You can add your name to petitions and help scientists lobby for protection of the deep seas.
- We can all think about the fish we eat and put pressure of governments to fish more sustainably to help not only the oceans, but also the fisherman who rely on the security of fish stocks for their future jobs. The WWF has a guide to more sustainable fishing at https://www.wwf.org.uk/what-we-do/addressing-unsustainable-fishing-and-seafood.
- For a great book about the biology and ecology of the deep oceans, read The Brilliant Abyss by Helen Scales, published in 2021. This is a fascinating book about deep sea ecosystems and how they are threatened. You can learn all about glowing worms, brilliantly beautiful invertebrates, deep sea cold water corals, the impossible physical feats of deep diving sperm whales and more!
References
Danovaro, R. Fanelli, E. Aguzzi, J. Billett, D. Carugati, L. Corinaldesi, C. Dell’Anno, A. Gjerde, K. Jamieson, A.J. Kark, S. McClain, C. Levin, L. Levin, N. Ramirez-Llodra, E. Ruhl, H. Smith, C.R. Snelgrove, P.V.R. Thomsen, L. Van Dover, C.L. and Yasuhara, M. (2020) ‘Ecological variables for developing a global deep-ocean monitoring and conservation strategy.’ Nature, Ecology and Evolution, 4(2), pp 181-192
http://www.elasmo-research.org/
https://www.iucnredlist.org/species/44565/2994832
https://www.mongabay.com/
Nakaya, K. Tomita, T. Suda, K. Sato, K. Ogimoto, K. Chappell, A. Sato, T. Takano, K. and Yuki, Y. (2016) ‘Slingshot feeding of the goblin shark Mitsukurina owstoni (Pisces:Lamniformes: Mitsukurinidae).’ Scientific Reports, 6(27786)
Parsons, G.R. Ingram, G.W. and Havard, R. (2002) ‘First record of the goblin shark ‘Mitsukurina owstoni, Jordan (Family Mitsukurinidae) in the Gulf of Mexico.’ Southeastern Naturalist, 1(2) pp 189-192
Starr, J.D. (1898) ‘Description of a species of fish (Mitsukurina owstoni) from Japan, the type of a distinct family of Lamnoid sharks.’ Proceedings of the California Academy of Sciences, 1(3), pp 199-201
The Brilliant Abyss, Helen Scales, 2021, Bloomsbury Sigma
Yano, K. Miya, M. Aizawa, M. Noichi, T. (2007) ‘Some aspects of the biology of the goblin shark, Mitsukurina owstoni, collected from the Tokyo Submarine Canyon and adjacent waters.’ Ichthyological Research
