BASKING SHARK (Cetorhinus maximus)
Basking sharks are basically big whales, if whales were actually fish. Like every living human on this earth with a lick of sense, I love sharks, but I'll be honest with you, I'm real tired right now. So this is going to be a very special zoological review where instead of pitting some unsuspecting animal against my unrelenting scrutiny, I'm going to pit my exhaustion against my excitement to talk about sharks. Let's see what comes out on top.
Appearance
Basking sharks are really big and have giganto mouths that inspire google search prompts like "can a basking shark eat a human?" The short answer to that question is "no," and I'll get into why they have such big mouths that they don't use for eating big stuff in a bit.
They are the second largest shark species, and also the second largest fish in the sea, both by length and by weight. Being the second biggest anything is kind of like being the second man on the moon. That is to say, it's a lot less impressive than it should be. So while it's cool that basking sharks are massive, they will always play second fiddle to whale sharks and, probably, getting progressively weirder, like Buzz Aldrin.
On the plus side, they have these really funny looking snoots which have a ton of electroreceptors called, slightly pretentiously, the ampullae of Lorenzini. The aMpUlLaE of LoReNzInI detect movement in the water, so the snoot probably helps the sharks detect their prey and makes them look damn adorable doing it.
Points: 0.5/1 for not being bigger but still being cute
Behaviour
Behaviour is really hard to study in marine animals because they tend to be able to swim for a really long time - they can just go under water and then we don't know what they're doing down there. Even marine mammals, like whales are seals, which still breathe air and have to be at the surface periodically, are extremely mysterious relative to land mammals. So we don't really know a whole lot about shark behaviour in general, and we know even less about the behaviour of basking sharks. They are known to aggregate in fairly dense groups at times when their preferred prey is plentiful, but whether or not they use some kind of group hunting strategy is debated. Courtship behaviour has been observed off the coast of the UK, but the rest of the reproductive cycle is relatively unknown, and only one birth has ever been seen by human eyes. Basking sharks are very private, and I respect that, but, like a nosy neighbour, I still want to know what they're up to
Points: 1/1
Distribution
Like other sharks, the basking shark lives in the ocean. This may seem like a limitation, but the ocean is really big so there's lots of places for them to swim. Basking sharks live all over the world, from the Bay of Fundy to the coasts of New Zealand. Though they tend to be found close to the coast where the humans are, we know approximately fuck all about them, which makes them sexy and mysterious like Keanu Reeves.
Points: 1/1
Ecology
Basking sharks are one of three species of filter feeding shark - the other two are the majestic whale shark, and the megamouth shark which has a really cool name. So even though they have those gigantic nightmare mouth, they use it to eat tiny plankton. How does that work, you ask? Well, my friend, let me tell you. First, the shark swims around with their mouth open. Plankton-filled water enters the mouth and passes over the gill rakers. The plankton gets stuck to the rakers and the water gets extruded out the gill slits. There's some evidence to suggest that they don't just swim around randomly with their mouths open hoping that plankton falls in, but actively hunt for their favourite type of zooplankton to eat (this is where those ampullae of Lorenzini would come in handy) and swim around with their mouths open there.
All of this would be really cool, except that they end up eating a shit ton of plastic. Even though the sea is really big, it's also chock full of microplastic, which the sharks filter out of the water and into their tummies. You know what else is chock full of microplastic? The euphausiid crustaceans that the sharks really like to eat. Either way, these sharks can't win.
Points: 0/1
Evolution
Despite being filter feeders, basking sharks are not closely related to other filter feeding sharks. Rather, their closest relatives are the mackerel sharks which are relatively small and fast and include everybody's favourite, the great white shark. So being really huge and having a big crazy mouth and eating plankton evolved at least twice in the sharks, as well as in whales, meaning it's probably a pretty sensible strategy for living in the ocean. So next time you think it seems impossible that an animal as big as a whale can go around eating tiny-ass shit, just remember that it's a good enough strategy that several different animals came up with it independently.
Points: 1/1
Life History
Basking sharks are ovoviviparous, which means that they give birth to live young (the viviparous part), but they also have eggs (the oviparous part). Now, if you're going "what the fuck does that mean, Andrea?", it's okay, because having live young and laying eggs are pretty much the opposite of each other. But ovoviviparous animals have found a way to make the paradox work. The eggs hatch inside the mother and then the babies are born the conventional way, out the cloaca like god intended. Because of the significant maternal investment associated with having eggs hatch inside you and then birthing them out the cloaca, basking sharks don't have very many kids. They also probably live for a long time, and if there's one thing we don't tolerate here, it's K-strategists.
Points: 0/1
Interaction with Humans
Back in the day, basking sharks were plentiful. So much so that they were considered pests of the fishing industry in British Columbia. Bear in mind that they don't even eat fish, so they weren't actually interfering with the fish themselves. There were just a lot of them, and they were there. Because of this, the government allowed targeted fishing of basking sharks as a pest eradication program up until the 1960s. In other words, anybody with a boat could go out and kill the fuck out of basking sharks for no good reason. This eradication program was so successful, basking sharks are now considered vulnerable by the IUCN, and the Canadian Pacific basking shark population is considered endangered under COSEWIC.
Furthermore, basking shark livers are harvested for squalene (an oil that sharks use to stay afloat in the water, and that humans use to make lipstick), and their fins are harvested for soup. So they have had, and are having, a pretty shit time out there in the world. Because we know next to nothing about them, it's hard to tell exactly how shit the time they are having is, but it's probably not great.
All this is to say, if basking sharks were smart, they would start using gas filled swim bladders for buoyancy like bony fish, stop having delicious fins, and go back in time and not be so plentiful off the coast of BC 70 years ago.
Points: 0/1
Final Score: 3.5/7 Basking sharks are okay. They're not great. With some work, they might improve
Further Reading
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| Image adapted from wikipedia Original image by Greg Skomal / NOAA Fisheries Service |
Appearance
Basking sharks are really big and have giganto mouths that inspire google search prompts like "can a basking shark eat a human?" The short answer to that question is "no," and I'll get into why they have such big mouths that they don't use for eating big stuff in a bit.
They are the second largest shark species, and also the second largest fish in the sea, both by length and by weight. Being the second biggest anything is kind of like being the second man on the moon. That is to say, it's a lot less impressive than it should be. So while it's cool that basking sharks are massive, they will always play second fiddle to whale sharks and, probably, getting progressively weirder, like Buzz Aldrin.
On the plus side, they have these really funny looking snoots which have a ton of electroreceptors called, slightly pretentiously, the ampullae of Lorenzini. The aMpUlLaE of LoReNzInI detect movement in the water, so the snoot probably helps the sharks detect their prey and makes them look damn adorable doing it.
Points: 0.5/1 for not being bigger but still being cute
Behaviour
Behaviour is really hard to study in marine animals because they tend to be able to swim for a really long time - they can just go under water and then we don't know what they're doing down there. Even marine mammals, like whales are seals, which still breathe air and have to be at the surface periodically, are extremely mysterious relative to land mammals. So we don't really know a whole lot about shark behaviour in general, and we know even less about the behaviour of basking sharks. They are known to aggregate in fairly dense groups at times when their preferred prey is plentiful, but whether or not they use some kind of group hunting strategy is debated. Courtship behaviour has been observed off the coast of the UK, but the rest of the reproductive cycle is relatively unknown, and only one birth has ever been seen by human eyes. Basking sharks are very private, and I respect that, but, like a nosy neighbour, I still want to know what they're up to
Points: 1/1
Distribution
Like other sharks, the basking shark lives in the ocean. This may seem like a limitation, but the ocean is really big so there's lots of places for them to swim. Basking sharks live all over the world, from the Bay of Fundy to the coasts of New Zealand. Though they tend to be found close to the coast where the humans are, we know approximately fuck all about them, which makes them sexy and mysterious like Keanu Reeves.
Points: 1/1
Ecology
Basking sharks are one of three species of filter feeding shark - the other two are the majestic whale shark, and the megamouth shark which has a really cool name. So even though they have those gigantic nightmare mouth, they use it to eat tiny plankton. How does that work, you ask? Well, my friend, let me tell you. First, the shark swims around with their mouth open. Plankton-filled water enters the mouth and passes over the gill rakers. The plankton gets stuck to the rakers and the water gets extruded out the gill slits. There's some evidence to suggest that they don't just swim around randomly with their mouths open hoping that plankton falls in, but actively hunt for their favourite type of zooplankton to eat (this is where those ampullae of Lorenzini would come in handy) and swim around with their mouths open there.
All of this would be really cool, except that they end up eating a shit ton of plastic. Even though the sea is really big, it's also chock full of microplastic, which the sharks filter out of the water and into their tummies. You know what else is chock full of microplastic? The euphausiid crustaceans that the sharks really like to eat. Either way, these sharks can't win.
Points: 0/1
Evolution
Despite being filter feeders, basking sharks are not closely related to other filter feeding sharks. Rather, their closest relatives are the mackerel sharks which are relatively small and fast and include everybody's favourite, the great white shark. So being really huge and having a big crazy mouth and eating plankton evolved at least twice in the sharks, as well as in whales, meaning it's probably a pretty sensible strategy for living in the ocean. So next time you think it seems impossible that an animal as big as a whale can go around eating tiny-ass shit, just remember that it's a good enough strategy that several different animals came up with it independently.
Points: 1/1
Life History
Basking sharks are ovoviviparous, which means that they give birth to live young (the viviparous part), but they also have eggs (the oviparous part). Now, if you're going "what the fuck does that mean, Andrea?", it's okay, because having live young and laying eggs are pretty much the opposite of each other. But ovoviviparous animals have found a way to make the paradox work. The eggs hatch inside the mother and then the babies are born the conventional way, out the cloaca like god intended. Because of the significant maternal investment associated with having eggs hatch inside you and then birthing them out the cloaca, basking sharks don't have very many kids. They also probably live for a long time, and if there's one thing we don't tolerate here, it's K-strategists.
Points: 0/1
Interaction with Humans
Back in the day, basking sharks were plentiful. So much so that they were considered pests of the fishing industry in British Columbia. Bear in mind that they don't even eat fish, so they weren't actually interfering with the fish themselves. There were just a lot of them, and they were there. Because of this, the government allowed targeted fishing of basking sharks as a pest eradication program up until the 1960s. In other words, anybody with a boat could go out and kill the fuck out of basking sharks for no good reason. This eradication program was so successful, basking sharks are now considered vulnerable by the IUCN, and the Canadian Pacific basking shark population is considered endangered under COSEWIC.
Furthermore, basking shark livers are harvested for squalene (an oil that sharks use to stay afloat in the water, and that humans use to make lipstick), and their fins are harvested for soup. So they have had, and are having, a pretty shit time out there in the world. Because we know next to nothing about them, it's hard to tell exactly how shit the time they are having is, but it's probably not great.
All this is to say, if basking sharks were smart, they would start using gas filled swim bladders for buoyancy like bony fish, stop having delicious fins, and go back in time and not be so plentiful off the coast of BC 70 years ago.
Points: 0/1
Final Score: 3.5/7 Basking sharks are okay. They're not great. With some work, they might improve
Further Reading
- Fisheries and Oceans Canada. 2018. Basking shark
- Fossi MC, Coppola D, Baini M, Giannetti M, Guerranti C, Marsili L, Panti C, de Sabata E, Clo S. 2014. Large filter feeding marine organisms as indicators of microplastic in the pelagic environment: the case studies of the Mediterranean basking shark (Cetorhinus maximus) and fin whale (Balaenoptera physalus). Marine Environmental Research. 100: 17-24
- Fowler SL. 2009. Cetorhinus maximus. The IUCN Redlist of Threatened Species 2009.
- Francis MP, Duffy C. 2003. Distribution, seasonal abundance, and bycatch of basking sharks (Cetorhinus maximus) in New Zealand, with observations on their winter habitat. Marine Biology. 140(4): 831-842
- Kempster RM, Collin SP. 2011. Electrosensory pore distribution and feeding in the basking shark Cetorhinus maximus (Lamniformes: cetorhinidae). Aquatic Biology. 12: 33-36
- Manx Basking Shark Watch: Reproduction
- Manx Basking Shark Watch: Feeding
- Martin RA. Biology of Sharks and Rays: Cetorhinidae
- Naylor GJP, Martin AP, Mattison EG, Brown WM. 1997. Interrelationships of lamniforme sharks: testing phylogenetic hypotheses with sequence data. In: Molecular systematics of fishes. Ed., Kocker TD, Stepien CA. 314p
- Roth A. 2018. There might be shark in your sunscreen. National Geographic.
- Sharkwater. 2019. Shark education.
- Siders ZA, Westgate AJ, Johnston DW, Murison LD, Koopmen HN. 2013. Seasonal variation in the spatial distribution of basking sharks (Cetorhinus maximus) in the Lower Bay of Fundy. Canada. PLoS One. 8(12). Open access
- Sims DW, Southall EJ, Quayle VA, Fox AM. 2000. Annual social behaviour of basking sharks associated with coastal front areas. Proceedings of the Royal Society B. 267(1455)
- The Marine Detective. 2011. Basking in history 0 the story of B.C.'s basking sharks
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