The Beacon

Blog Tags: Filter Feeders

Top 5 Myths About Sharks

Basking sharks are gentle giants, nothing to fear here (unless you're plankton). ©NOAA

Happy Shark Week!

Sharks are the center of a lot of stories and urban legends, but you might be surprised by the truth behind some of the most common myths about sharks. In honor of Shark Week, we’re going to dispel some of the major myths surrounding sharks and shark behavior.

MYTH #1: All sharks are voracious predators, looking to attack anything in sight, including humans.
FACT:
While some shark species do have aggressive tendencies, most hunt only to find food (and humans aren’t on the menu). Just like other top predators, sharks make a meal out of animals lower in the food web, keeping the ocean habitat in balance. Only a few species have been known to attack humans unprovoked, and that’s often because of poor visibility or inquisitive bites. There are even species, like the whale shark and the basking shark, that are filter feeders that eat fish eggs, krill, and other microorganisms in the water.

MYTH #2: Sharks do not attack at midday.
FACT:
It’s true that there are fewer attacks in the middle of the day, but that’s not because sharks aren’t active then—it’s because everybody’s out of the water eating lunch. Sharks are most active at dawn and dusk, but it’s possible to encounter at shark at nearly any time of day.

MYTH #3: Sharks have walnut-sized brains.
FACT:
Sharks are actually pretty smart! They have some of the largest brains in the fish world (along with their close relatives, rays), and their brain-to-body size ratios are similar to birds and mammals. Sharks have been known to exhibit complex social behavior, curiosity, and play in the wild. Many species live in groups and hunt in packs.

MYTH #4: In order to stay alive, a shark must constantly be moving.
FACT:
The movement of swimming allows water to pass over a shark’s gills so that they can breathe, but some species have adaptations that allow them to stay still and breathe at the same time. When resting, some sharks can lie on the sea floor and actively pump water over their gills.

MYTH #5: Sharks have no predators.
FACT:
Yes it’s true that sharks are at the top of the food chain, but they have a very powerful predator: humans. Each year, tens of millions of sharks are killed for their fins, sport, or caught and killed as bycatch. By removing so many of these important predators without allowing them time to restore their populations, we’re disrupting the balance of the marine food web.

The great white shark, the most iconic shark in the ocean, faces serious threats off the West coast of the United States. Only a few hundred are left, and their populations aren’t recovering quickly — unless we do something. Sign today to help improve protections for great white sharks in the Pacific.


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Fact of the Day: Christmas Tree Worm

Christmas Tree Worms (credit: Nick Hobgood)

The subject of today’s FOTD is the Christmas tree worm, or spirobranchus giganteus for those of you who prefer the scientific name. 

Christmas tree worms are embedded in the surface of corals by the calcareous, shell-like tubes in which they live.  They have two beautiful, feathery spirals (which look like little Christmas trees) that extend into the water column and are used for filter-feeding and breathing. At the slightest disturbance, the Christmas tree worm retracts into its tube in the coral for safety. 

My favorite thing about these worms is their variety of vibrant colors and patterns- check it out!

See you tomorrow for another random FOTD! And if you’re like me and you just can’t wait for more, go to Oceana.org/Explore.   


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Whale Wednesday: Tiny and Weird Edition

An Australian paleobiologist has made a curious discovery about the origins of baleen whales. Studying the 25-million-year-old fossil of a primitive toothed baleen whale, Mammalodon colliveri, Dr. Erich Fitzgerald hypothesized that the early whale used its tongue and short, blunt snout to suck small prey from sand and mud on the seafloor. Yummy.

Fitzgerald’s work supports Darwin's notion that some of the earliest baleen whales may have been mudsuckers before they were filter-feeders.

And apparently the three-meter-long Mammalodon was actually a dwarf, though its name brings to mind its relative, the blue whale -- the largest animall in the history of the world.

As Dr. Fitzgerald said, “Clearly the seas off southern Australia were a cradle for the evolution of a variety of tiny, weird whales that seem to have lived nowhere else.”


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