mantle

To touch a gumboot is to feel the fuzzy texture of about 20 species of red algae that live on the mantle and give the gumboot its brick-red color. The gumboot also eats red algae, which probably adds to its color as well.

The gumboot uses its tonguelike radula to scrape algae from rocks. The radula has many tiny teeth capped with the element magnetite; the teeth contain so much magnetite, in fact, that a magnet can pick them up.

Mostly a bottom-dweller, a white sturgeon spends its time rummaging on the seafloor for food. Unlike most other fishes, its taste buds are on the outside of its mouth. These taste buds, along with barbels (feelers) under the sturgeon’s snout, help the fish select food, and a toothless mouth sucks it up.

Along with overfishing, habitat destruction—including dams that close off spawning grounds—and pollution contributed to the decrease in white sturgeon populations. Management of the fisheries is improving. As of 1997 in San Francisco Bay, the white sturgeon population is now larger than it has been since the 19th century.

Environmentally safe farms now raise white sturgeon for fillets and caviar.

A dolphinfish’s body is sleek and long, with a dorsal fin that extends from head to tail. A mature male’s forehead is high and sloping; a mature female’s forehead is less steep. That lunate (forked) tail propels this fast-swimming fish to speeds of 40 miles an hour.

Dolphinfish is a popular menu item. To distinguish it from dolphins (which are mammals), restaurants have popularized its Hawaiian name—mahi mahi.

Dolphinfish have never had a scientific stock assessment. Hopefully, fishery research will show that this fish is abundant. In the meantime, some state councils on the East Coast are regulating dolphinfish catches. Learn more about whether mahi mahi is a sustainable seafood choice in the Seafood Watch section of our website.

Their coloring ranges from reds to greens, blues and yellows, as well as grays, browns and blacks. Males and females of the same species generally look quite different and, like wrasses (the Labridae family), female parrotfishes may change into males.

Once attached, they change into juvenile barnacles, minatures of the adults. Then each builds its own fortress—a cone-shaped limestone shell with a trap door in the ceiling. When water covers a barnacle, the trap door opens, and the barnacle’s feathery legs emerge to sweep the water for plankton and detritus. When the tide is out, barnacles close their trap doors to conserve moisture. Barnacles spend the rest of their lives in this position—head down and feet up.

Mostly sedentary, an abalone clings to rocks while waiting for a piece of kelp to drift nearby. The abalone clamps down on the kelp with its foot and then munches on the seaweed with its radula—a rough tongue with many small teeth.

In the U.S., commercial fishing for abalone has ceased. Find out more about the sustainability of farmed abalone as a seafood choice in the Seafood Watch section of our web site.

Like all sharks, the white shark is equipped with two major food-finding senses: its sense of smell and its ability to detect electrical impulses. A shark smells with the aid of tiny structures called “lamellae,” located in two nostrils near the tip of its snout. The lamellae are so sensitive that they can detect one drop of blood in 25 gallons of water.

To hunt prey, a shark also depends on its “ampullae of Lorenzini,” a series of jelly-filled canals on its snout that sense electrical impulses. Combined with the sense of smell, this “force-field” detector makes the white shark an efficient predator.

Unfortunately the public’s impression of these animals often comes mainly from frightful stories and lurid pictures. Many photographic and diving-adventure businesses have formed around the white shark, primarily in South Africa, southern Australia and California. Although these events have drawbacks, many people hope that such increased exposure to the white shark will help foster public awareness about its welfare.

Box jellies’ eyes are more well-developed than other jellies'. Tripedalia has two complex eyes and one or more simple eyes.
They may help the jellies hunt. Their complex eyes have a lens, a cornea and a retina. In addition, the photoreceptors in box jellies' eyes are similar to those of vertebrates.

polyps

Mangrove forests are among the most threatened ecosystems on our planet. They’re cleared for development, agriculture, and fish and shrimp farms. Pollution and sediment from land flow into these shallow coastal habitats, threatening the diverse marine life that lives there. Without this nurturing habitat, it’s unlikely this tiny jelly would survive.

In Asia and elsewhere, dried seahorses have been used as medicine for thousands of years. But as the number of people living on our planet increases, the demand for seahorses grows—and the number of seahorses shrinks. Each year, tons of Pacific seahorses are caught, dried and shipped to Asia.

pelvic

A clingfish's suction cup does double duty. When the tide goes out, a clingfish's pool might be left high and dry. But the cup holds in moisture, so the fish can still breathe. Tucked safely beneath its rock, the clingfish waits until the tide rolls back in again.

Hagfish live in burrows on the seafloor and locate their food by smelling and feeling as they swim. They prey on small invertebrates living in the mud, as well as scavenging dead and dying fish. They are noted for their unusual way of feeding—they slither into dead or dying fishes and eat them from the inside out, using their "rasping tongue" to carry food into their funnel-shaped mouth.

Hagfish are notorious for their defensive slime. They secrete a sugar and protein matrix into the seawater. When expelled, it mixes with the saltwater and becomes a slippery slime. Protein strands within the slime make it extremely sticky.

These dolphins are familiar companions to sailors of many seas. As fast-moving ships slice through the water, common dolphins surf alongside. Dolphins also use this hitchhiking trick with their own cousins: sometimes they ride on the waves of large whales.

These jellies are very active swimmers. They change their swimming speed by changing the intensity of their bell contractions and can swim at a pace of about 60 feet (18 m) per hour.

These shrimp have light-producing organs on the undersides of their translucent, red-and-white bodies. Their blue glow matches the color and intensity of dim light from above. This “counterillumination” hides the shrimp from predators looking up from below.

Hatchetfish can regulate the intensity and color of light from these organs to match the light filtering down. Each species of hatchetfish has its own particular pattern of lights.

This use of bioluminescent light is called "counterillumination," a common adaptation in midwater fishes and cephalopods. Some midwater predators hunt by looking up for the silhouettes of animals. Counterillumination makes hatchetfish almost invisible from below.

If you’ve ever seen a Venus flytrap capture an insect, you have a clue as to how a predatory tunicate eats. Its mouthlike hood is quick to close when a small animal drifts inside. Once the tunicate catches a meal, it keeps its trap shut until it’s ready to eat again.

Monkeyface-eels’ body shapes allow them to live hidden in crevices and holes in rocky reefs, rocky tidal zones and kelp forests. These fish don’t move around much, seldom traveling more than 15 feet (4.6 m) from their home. They can breathe air and, in a moist area, can stay out of the water for at least 35 hours.

Many monkeyface-eels live close to shore. Tidepoolers turning over rocks are likely to see a monkeyface-eel scurry away. Experienced tidepoolers know it’s important to return rocks to their original positions so animals can return to their homes.

Muscular pectoral fins enable this shark to "walk" along the seafloor. When disturbed, instead of swimming out of danger, it sometimes quickly "runs" away.

Despite their small size, spiny dogfish are aggressive and have a reputation of relentlessly pursuing their prey. The name “dogfish” stems from their habit of feeding in packs—sometimes numbering in the hundreds or thousands. Gathered together, they sweep an area, eating the fishes in front of them. They’ll eat almost anything they can get their strong jaws and teeth on. Newborn dogfish will even attack fishes two to three times their size.

overfished

You can read more about the sustainability of sharks as a food item in the Seafood Watch section of our web site.