You’ve probably seen pictures of jellyfish floating gently through the water, but did you know that some jellyfish spend most of their lives in one spot?
Stalked jellyfish, which are funnel shaped, with eight legs joined by membranes surrounding a mouth, are one example. Only an inch or two tall, they live in cold shallow water in the North Pacific.
When stalked jellyfish mature, they attach themselves to a piece of seaweed or eelgrass with an adhesive disk. Scientists believe they might be able to basically cartwheel short distances, but for the most part, they are sessile – meaning they stay in the same place.
Because stalked jellyfish can’t follow prey, they use their tentacles to catch small fish and shellfish, although they have to spit out shells, as they’re too difficult to digest.
Although adult stalked jellyfish cannot eat large prey, immature jellyfish, called planula, have developed a collaborative approach to offer more dining options. At this point in their lives, the jellyfish are mobile, so while they can’t kill by themselves, they can gang up on rotifers, nematodes, copepods, and other ocean snacks.
Stalked jellyfish are also notable for having relatively developed nervous systems compared to their relatives.
You can learn more about stalked jellyfish from Oceana’s marine wildlife encyclopedia.
Underwater masters of disguise, leafy seadragons take their name from their greenish coloring and their many appendages that look like seaweed.
They belong to a group of fish closely related to seahorses and are found exclusively along the southern coast of Australia. Like their more famous cousins, seadragons have armor-like exoskeletons, and fertilized eggs are tended by the male. But seadragons have longer snouts than seahorses and cannot use their tail to grasp onto their surroundings.
Leafy seadragons are weak swimmers, so they avoid predators by blending in with their surroundings. They also move with the waves just like seaweed, which makes them even more difficult to spot.
Scientists aren’t sure how well leafy seadragons are doing these days. Unlike seahorses, they are not sought after by the traditional Chinese medicine market. There are anecdotal reports of seadragons accidentally caught by fishermen, but no estimates of how many fish this affects.
The more pressing concern is habitat loss: seadragons live in only a small strip of Australian waters, and their habitat is being destroyed by sewage from nearby cities. On the other hand, local governments have enacted several protection measures, and leafy seadragons, which are an important ecotourism draw, are the official fish of South Australia.
Learn more about the leafy seadragon and other fascinating animals at Oceana’s marine encyclopedia.
Unsurprisingly, the Caribbean reef octopus is found throughout the Caribbean, deep within coral reefs. It can grow up to 40 inches long, including its tentacles. As a defense mechanism, it can change color—from blue-green and brown to shimmery red—as well as texture.
Caribbean reef octopuses establish lairs in the reef, which they often disguise with rocks and coral. Although they move their dens regularly, they protect them fiercely. If a strange octopus does not retreat, the defender will sometimes even strangle and eat it.
The same fate awaits unlucky male octopuses who try to mate with uninterested females. If attacked when hunting, the Caribbean reef octopus can pull water into itself, then shoot it out to speed the other way, often also releasing a cloud of ink to confuse predators.
Octopuses hunt at dawn or dusk, which is typical for crustaceans like crabs and shrimp. These cephalopods are fished locally, but not on a large scale, and they are not believed to be at risk of extinction, although they may struggle if the reefs they call home disappear.
Learn more about the Caribbean reef octopus and other fascinating animals at Oceana’s marine life encyclopedia.
You’ve probably seen tiger cowrie shells, which can be as large as six inches long. In cream, brown, and black, with a variety of patterns, they are so popular that they were once used as money.
The residents of these shells, which are a type of snail, are nocturnal. During the day, they take shelter from predators in coral reefs; at night, they eat algae and sponges. They can also eat fire coral and anemones despite their stings.
Most of the time, a live tiger cowrie’s shell is covered by its mantle, which is its outermost layer. The mantle forms spikes that may help the cowrie breathe or avoid predators. The cowrie can also pull its entire body inside its shell to protect itself.
Tiger cowries are found in tidal areas and shallow reefs in the Indian and Western Pacific Oceans. You can learn more about tiger cowries and hundreds of other marine animals in Oceana’s marine life encyclopedia.
Starting today, we’ll be doing a weekly feature of one of the fascinating species that lives in the oceans. Today's animal is the little penguin.
The little penguin is, as you might have guessed, the smallest species of penguin. It can be found off the coasts of Australia and New Zealand, where it nests each night in sand burrows or caves along the rocky shoreline. Little penguins can be very noisy at night, and each penguin has its own unique identifying call, used to recognize family members, mates, and strangers.
Because the little penguin is so small, it is a tasty target for dogs, cats, foxes and rats. They penguins are especially vulnerable each night when they come ashore to roost and each morning when they head back to sea, so they seek safety in numbers by “parading” together in stable groups, a spectacle that draws as many as a half million tourists each year to places like Phillip Island in Australia.
Little penguins also fish in groups, working together to gather fish together before they all begin eating. They are particularly fond of anchovies, sardines, and small squid, all of which are suffering population declines, which may prove difficult for little penguins. However, current population estimates for the birds stand at almost a million, and they are considered a species of least concern by the IUCN.
To see more animals, check out Oceana’s marine wildlife encyclopedia.
For millennia, people have wondered just how many species live on Earth. The latest study looking to answer this question suggests there are about 8.7 million species, the majority of which scientists can’t even name.
The oceans, as almost three-quarters of the Earth’s surface, are home to millions of species—and only about 1 in 10 has been officially discovered by scientists. Here are ten ocean-dwellers we think are especially fascinating:
1. The box jellyfish, which lives in the waters off North Australia and Indonesia, is one of the most venomous species in the ocean. Its 10-foot-long tentacles can kill even cautious swimmers, yet some kinds of sea turtles can eat box jellyfish without even an upset stomach.
2. The lovely hatchetfish might be redefining lovely, but its thinness when viewed head-on helps it hide from predators, as does its silver color and bioluminescence.
3. Sailor’s eyeball is the oceanic equivalent of skinless grapes at Halloween. This seaweed lives in waters around the equator, where it reproduces by disintegrating once young plants have formed inside of it.
4. The blue-ringed octopus may look pretty, but its vivid colors, which become brighter when the animal is disturbed, mark it as extremely poisonous—it is the most dangerous cephalopod and its saliva can kill a human.
5. The stonefish, the most venomous fish, can also kill a human with one sting. It takes its name from the camouflage that allows it to lie in wait for passing fish.
As you can see, these cetaceans have a bulbous head and short jaw, with flippers that almost look like elbows due to their sharp backward bend. Long-finned pilot whales feed mainly on deep-sea squid and octopus, and they are quite sociable, often living in groups of hundreds. They sometimes become disoriented in shallow waters and have been known to strand in large numbers.
Stay tuned for a new photo each week!
This is part of a series of posts about our Pacific Hotspots expedition. Today's highlights: rockfish, basket stars and hydroids.
Oregon Leg, Day 1
Last night our six Oceana crew slept aboard the R/V Miss Linda, tied to the dock at the Charleston Marina. The captain and his two crew members arrived at dawn, started up the engines and walked our tired souls through an important safety briefing. The Miss Linda is a 76-foot research charter vessel that formerly worked these Pacific Ocean waters as a commercial fishing boat. The captain is experienced, confident and will certainly lead us safely through our five-day expedition.
Our objective today was to get situated working aboard the Miss Linda with our Remotely Operated Vehicle (ROV) while exploring a large area of rocky reef just south of Cape Arago. Over the next four days we will use the ROV to capture high definition video footage of some of the most remote and rugged areas off the southern Oregon coast.
By our third dive this afternoon, five miles offshore and over 150 feet down, the Miss Linda crew and Oceana crew were in sync. With each drop of the ROV we saw schools of rockfish hovering over a rich tapestry of seafloor life.
This is part of a series of posts about our Pacific Hotspots expedition. Today's highlights: humpback whales and orcas!
California Leg, Day 3
Yesterday was a spectacular day as we saw some of the most colorful and rich habitats we’ve seen yet! The objective was to gather footage from some of the more spectacular areas of pinnacles and rocky reefs that we started to explore last year.
At the outer edge of the Monterey Peninsula, just off Pebble Beach, is a spectacular reef that we explored last year. While golfers marveled at the sites from the world famous course on shore, we marveled at the wildlife above and below the ocean offshore.
We brought several guests with us including a representative from Mission Blue, another organization focusing on ocean exploration and conservation. The weather was sunny and warm, however a medium-sized southerly swell made the ride a bit bumpy and our cable operators got soaked.
The Carmel Pinnacles were protected as a marine reserve in 2008. This combination of rocky reef at the edge of a steep canyon wall that drops thousands of feet provides a rich feeding ground, as nutrient-rich water is pulled up from the deep through a process called upwelling.
As we set our ROV equipment up for the first dive, we saw two large humpback whales swimming right by our boat. We explored a depth range of 90-150 feet. The habitat was composed of large pinnacles and boulders, jutting out of a sandy seabed. Nestled in the cracks and crevices were china rockfish, gopher rockfish, and treefish, while we encountered several schools of black rockfish hovering at the tops of the reefs.
In the latest update from the Latitude, Oceana scientist Jon Warrenchuk describes the ROV’s dive near Key West.
The underwater ridge looked promising: South of Key West, 10 miles offshore and 200 meters deep. The bathymetric lines piled up steeply on the chart, indicating some steep relief in some otherwise flat habitat. As far as I knew, no one had ever seen what the seafloor looked like in that area. We deployed the ROV some distance from the site, trying to take into account the drift of the boat.