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 Dangerous Ocean Animals 

whales

Many TV shows and nature guides have been dedicated to educating the public on the most poisonous and venomous spiders, snakes and even frogs, but what about fish? Unlike spiders or snakes, we rarely hear about which fish are the most poisonous (or venomous). This week we are dedicating our blog post to these hazardous fish.

(Cooney)


First though let’s clarify some terminology. Poisonous and venomous are terms often used interchangeably but they have different meanings. A venomous animal has a means of injecting their toxin into another animal, whereas a poisonous animal can only deliver their toxin in a more passive manner (by being touched or eaten). A common example given to clarify this difference is that frogs are poisonous while snakes are venomous. It is also important to note that the affects from a venomous fish sting can often be relieved by immersing the wound in hot water (~105–115F) because these toxins are heat labile (meaning they can be destroyed or altered by heat).

1. Pufferfish (some species are also called toadfish) have been given the title ‘Most Poisonous Fish’ and have also been labeled the second most poisonous vertebrate in the world. The toxin responsible for ranking this fish so high in the “danger zone” is called tetrodotoxin. Tetrodotoxin is neurotoxic and inhibits neural transmission leading to weakness, paralysis, and even death at relatively low concentrations (~2mg). This toxin is found in the fish’s liver, ovaries, intestines and skin, leaving muscle tissue with relatively low and somewhat safe levels to eat. However, only highly trained and certified chefs are allowed to prepare this fish for consumption; a common practice in Japan where pufferfish are considered a delicacy.

 Inflated Pufferfish (Source)
Pufferfish (Source)

2. Stonefish have usurped the title of ‘Most Venomous Fish’ in recent years. They often resemble encrusted stones (hence the name), blending into their natural environment with ease. They deliver their venom through a row of spines on their back that can be extended when threatened (or stepped on). Venom is involuntarily expelled when pressure is placed on the fish and the more pressure the more venom. They reside in the Indo-Pacific region and northern Australia. A sting from one of these fish can cause excruciating pain, rapid swelling, tissue death, muscle weakness, temporary paralysis, and in very rare cases death.

Stonefish (Source)
Stonefish (Source)

3. Lionfish were thought to be the most venomous fish until recent years when stonefish stole the title. These conspicuous fish have venomous dorsal, anal, and pelvic spines covered by a loose sheath that moves down and compresses venom glands when the spine punctures tissue. A sting from these fish can cause extreme pain, swelling, and in very severe cases, cardiovascular collapse. Most lionfish naturally reside in the Indo-Pacific but they have become an invasive species in recent years; most notably along the Atlantic coast of the United States where they are having a major impact on Atlantic coral-reef communities. Lionfish were likely introduced along the Atlantic coast through aquarium releases.

Lionfish (Source)

4. Stingrays are one of the most common groups of fish responsible for human envenomations; largely because many rays bury themselves on the seafloor where people unintentionally step on them. Stingray venom is generally cardiotoxic. The Bluespotted (native to the Indo-Pacific) and Southern (native to the southeastern US) stingrays are some of the most venomous of all stingrays. As a form of warning others, the Bluespotted stingray generally displays its bright blue colored spots as a warning to predators of its highly venomous sting.

Bluespotted stingray (Source)

5. Boxfish and trunkfish are closely related to pufferfish. While these fish are not nearly as poisonous as puffers, they do have an impressive way of defending themselves with poison. When threatened or stressed, they excrete a toxin from specialized skin cells into the water, poisoning marine life in their vicinity. The Hawaiian boxfish in particular excretes a toxin called ostracitoxin or pahutoxin that is known to breakdown or destroy red blood cells.

Boxfish (Source)

Some other venomous fish to check out are other scorpionfish (besides the stonefish and lionfish mentioned above), stargazers, which have two venomous spines in addition to organs near their eyes that cause electric shocks, and striped eel catfish.

Ocean’s Toughest Predators: Great White Shark vs. Killer Whale

When we think of the ocean’s top predators, most of us are probably going to picture sharks. More specifically, we’re probably picturing the massive great white shark.

But a couple weeks ago we shared an article about an interesting way to scare sharks away from Australia’s beaches: playing recordings of killer whale ‘screams’. If the great white shark is truly the ocean’s top predator, why would it be so scared of killer whales?

Well, it turns out that killer whales have been known to prey on sharks.

Orcas have also been known to eat mako sharks and several other species. When hunting sharks, killer whales always end up flipping the shark upside down, regardless of how the attack starts. When flipped upside down, the shark goes into a paralyzed state known as ‘tonic immobility’ and can’t fight back, which suggests that the orcas understand a little something about shark biology. It doesn’t necessarily mean they understand the process, just that they know if the shark is upside down, they won’t get hurt.

Before we get into some examples, here’s what you need to know about our competitors:

Killer Whale, Orcinus orca:

  • Size: Males can reach lengths of 32 feet (9.6 m) and weigh up to 9 tons. Females can reach 23 feet (8.2 m) in length and weigh up to 4 tons.
  • Speed: They usually swim at speeds of 3 to 4 miles (5 to 6.4 km) per hour but can reach speeds of up to 30 miles (48 km) per hour in short bursts.
  • Diet: Killer whales have 40-50 large conical teeth (3 in / 7.6 cm) that they use to capture and tear prey, not to chew. Their diets differ in based on population. In the North Pacific, resident killer whales eat fish, primarily salmon, while transient killer whales prey on marine mammals. In New Zealand waters, killer whales have been known to feed on stingrays and sharks.
  • Killer whale inspecting a Weddell seal before wave-wash attacks.

    Killer whale inspecting a Weddell seal before wave-wash attacks. Photo credit: R Pitman, NOAA/SWFSC.

    Hunting techniques: Killer whales are highly social animals and live in groups (pods) that range from 2 to 15 animals, but they have occasionally been seen hunting in groups of up to 40. Killer whales work together when hunting and they teach each other techniques. Mothers have been observed teaching their young how to beach themselves to hunt seals. In Antarctica, they make waves to wash seals off of floating ice, a behavior that isn’t seen anywhere else in the world.

Size of a killer whale compared to a human.

Size of a killer whale compared to a human. Photo credit: Chris huhCC BY-SA 3.0.

Great White Shark, Carcharodon carcharias:

  • Size: White sharks can reach lengths of more than 20 feet (6 m) and weigh more than 5,000 pounds (2,268 kg).
  • Speed: They usually swim at speeds of around 15 miles (24 km) per hour.
  • Diet: White sharks are the largest predatory fish in the world. Their razor-sharp, triangular teeth can measure more than 2.5 inches (5.7 cm) long and they use them to tear big chunks of flesh off their prey. They feed primarily on fish and actively hunt small marine mammals, including dolphins, seals and sea lions, but they also occasionally eat sea turtles, molluscs and crustaceans.
  • Great white shark.h

    Great white shark. Photo credit: 126 Clubvia photopin cc.

    Hunting techniques: Generally they are solitary animals, swimming alone or with one other shark. Sometimes, usually when feasting on a carcass, groups of about 10 or more have been spotted. Their hunting techniques vary based on the prey. When hunting brown fur seals, they ambush the seal from below, hitting the seal at high speeds. They often ambush from above or below to avoid being seen, but many Altantic great whites will hunt close to shore in shallow waters. They have also been known to scavenge on whale carcasses.

Size of a great white shark compared to a human.

Size of a great white shark compared to a human. Photo credit: AnyCC BY-SA 3.0.

Winner: The great white shark might have scarier teeth, but the killer whale is bigger and faster. Killer whales also have an advantage when hunting in big groups.

Notable examples of sharks vs. killer whales:

Blue Cliffs Beach, Tuatapere, New Zealand – Boxing Day 2011
A group of sharks had been swimming near the beach when a pod of orcas showed up. The orcas herded the sharks towards the shore, forcing them into shallower waters — one shark tried so hard to get away it actually beached itself. None of the beachgoers were sure if the orcas ended up getting a good meal, but they did notice some of the sharks were injured. You can see a video of it in this article.

Farallon Islands, off the coast of San Francisco, California – October 1997
A group of whale watchers was already enjoying a successful outing, having seen two orcas that had just killed a sea lion. They watched the orcas for a while longer when something much more interesting happened. A great white shark swam towards the boat (probably coming towards the smell of the dead sea lion) and then promptly switched directions when one of the orcas started swimming towards it. Both disappeared for a short time and then the orca resurfaced with the dead shark in its mouth.

Watch the following clip to learn more about this incident:

Blue whale
CC BY 2.0 //www.flickr.com/photos/38504374@N02/3600141170/" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-variant: inherit; font-weight: 600; font-stretch: inherit; line-height: inherit; font-family: inherit; vertical-align: baseline; color: rgb(182, 84, 30);">filckker photosFlickr

So colossal are these majestic marine mammals, their hearts alone weigh as much as a car.

Picture in your mind a 10-story-tall animal walking down the street and you probably start channeling images of Godzilla or King Kong. But if you imagine it as a marine mammal and place it on its side, swimming … now you’ve got a blue whale.

Balaenoptera musculus, the blue whale, is the largest animal ever known to have lived on the planet – movie monsters aside. Even at birth it is one of the world’s biggest animals! The planet is covered with amazing, fascinating creatures, but the blue whale ranks among one of the most superlative. Consider the following.

1. They’re ginormous
They’re gigantic, they’re enormous, they’re ginormous! Generally ranging in length from 80 to 100 feet (24 to 30 meters), the longest one ever recorded was a magnificent 108 feet long.

Blue whale size© Ocean Institute

2. They’ve got mass
Blue whales weigh up to 200 tonnes, or around 441,000 pounds.

3. They’ve got big thumpers
The blue whale's heart is huuuuge! As in, the size of a car; its beat can be detected from two miles away.

4. And tongues
A blue whale’s tongue alone weighs as much as an elephant.

5. They’re big babies
Not as in sissies, but as in born big. The biggest babies on earth, easily, and at birth already rank amongst the largest full-grown animals. They pop out at around 8,800 pounds with a length of some 26 feet. They gain 200 pounds a day! Their growth rate is likely one of the fastest in the animal world, with a several billion-fold increase in tissue in the 18 months from conception to weaning.

6. They’re loud … and make long-distance calls for free
Blue whales, in fact, are the loudest animals on the planet. A jet engine registers at 140 decibels, the call of a blue whale reaches 188. Their language of pulses, groans, and moans can be heard by others up to 1,000 miles (1,600 kilometers) away.

7. They’ve got big appetites for tiny fish
Blue whales feast on krill; their stomachs can hold 2,200 pounds of the tiny crustaceans at a time. They require almost 9,000 pounds of the little guys a day; and around 40 million krill daily during the summer feeding season.

8. They can scoot
They travel a lot, spending summers feeding in polar regions and making the long trip to the Equator as winter comes along. While they have a cruising speed of 5 MPH, they can accelerate up to 20 MPH when needed.

Largest living things - blue whaleNOAA Photo Library/CC BY 2.0

9. They’ve got long lives
While not nearly as old as the Earth’s oldest trees, blue whales are among the planet’s longest-lived animals. Kind of like counting tree rings, scientists count layers of wax in the ears and can determine a ballpark age. The oldest they’ve discovered this way was calculated to be around 100 years old, though the average life is thought to be around 80 to 90 years.

10. They were once numerous
Before whalers discovered the treasure trove of oil that a blue whale could provide, the numbers were generous. But with the advent of 20th century whaling fleets, nearly every last one of them was killed before receiving worldwide protection in 1967. According to WWF, from 1904 to 1967, more than 350,000 were killed in the Southern Hemisphere. In 1931, during the heyday of whaling, an astounding 29,000 blue whales were killed in a single season.

11. Their future is unclear
While commercial whaling is no longer a threat, recovery has been slow and new threats plague blue whales, like ship strikes and the impact of climate change. There is one population of around 2,000 blue whales off the coast of California – but all told there are only around 10,000 to 25,000 individuals left. The World Conservation Union (IUCN) Red List rates them as Endangered. Hopefully with time, the planet’s giantest gentle giants will again roam the seas aplenty.

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