The Right Blue: September 2014

Hunting Together: A Bar Jack and a Southern Stingray

A Bar Jack and a Southern Stingray hunting together

by B. N. Sullivan

We spotted this pair of hunters in the Caribbean. The dark colored fish in the photo is a Bar Jack (Caranx ruber). This fish makes its living as an opportunistic feeder. In this instance, it is swimming a little above and behind a Southern Stingray (Dasyatis americana) hoping to snag a free lunch.

The stingray finds its food by rummaging in the sand, looking for little creatures to eat -- worms, small clams, tiny crabs, and such. To locate its prey, it fans away the top layer the sand by fluttering the wing-like tips of its body disc.

The crafty Bar Jack follows closely, letting the stingray do the excavating. If the stingray uncovers something that looks tasty to the Bar Jack, the jack will snatch it in a lightning strike, then resume its position keeping watch over the stingray's shoulder, as it were.

We've seen Bar Jacks throughout the Caribbean. In addition to pairing with hunting stingrays, we've also seen them following goatfish -- another species that digs around in the sand and rubble for food.

By the way, the Bar Jack doesn't always look so dark. When it's not feeding, it is a handsome silvery blue color, with a black bar running along its back from its dorsal fin down to the lower lobe of its tail fin like a racing stripe.

Find the lobster in this photo

Sculptured Slipper Lobster (Parribacus antarcticus), Hawaii

by B. N. Sullivan

What you are looking at in the photo above is the ceiling of an underwater cavelet in Hawaii. The bright red stuff is an encrusting sponge. Most of the rest of the surface is covered by various kinds of algae. The purplish blob in the center of all that red is not a clump of algae; it is a slipper lobster wearing a clever disguise.

This is the Sculptured Slipper Lobster (Parribacus antarcticus), a member of the Scyllaridae family. It is said to be the most common slipper lobster species found in Hawaiian waters, but if you polled a sample of divers there you would find that relatively few have seen these critters. Part of the reason is that their camouflage makes them easy to miss, and their flattish profile also helps them to blend into the background. In addition, they are rather small -- maybe five or six inches long at most.

The individual in the photos here was snuggled into a crevice in a cavelet we visited during a night dive at Puako, Hawaii. We had been inside this cavelet many times during the day and often found pretty nudibranchs on the walls and roof surface. Expecting that we might see some of those at night as well, we shined our lights all around as we entered. We didn't find any nudibranchs that night, but as it happened, our bubbles hit the spot on the ceiling where this little slipper lobster was hanging out. Annoyed, it skittered across the surface to escape the bubbles. We hadn't noticed it until it moved, even though the beams from our lights had swept the area several times.

Below is another photo of the same creature. Note the snazzy fringe along the edge of its carapace. In case you are still scratching your head about what you are seeing, the little lobster is facing left in the photo below. If you look very carefully you may be able to distinguish its widely spaced eyes from the rest of the mottling.

Sculptured Slipper Lobster (Parribacus antarcticus), Hawaii

The Bluespotted Ribbontail Ray

Bluespotted Ribbontail Ray (Taeniura lymma)

by B. N. Sullivan

The Bluespotted Ribbontail Ray (Taeniura lymma) is one of the smaller members of the stingray family, Dasyatidae. We think it's also the nicest looking stingray, sporting those wonderful, eye-catching blue spots.

An Indo-Pacific species, this ray is found in the Red Sea, in coastal areas of the Indian Ocean, and around the coasts and islands of Southeast Asia. Despite its wide distribution range, these critters are becoming scarce in some areas due to the aquarium trade: their pretty coloration and smallish size make them attractive to keepers of saltwater aquariums. Unfortunately, these rays do not do very well in captivity.

They are dependent on coral reef habitats for their survival. They forage in sand patches for small crustaceans, molluscs and other invertebrates. Naturally, their populations also have declined in areas where reefs have been degraded by development, overfishing, and so on.

The Bluespotted Ribbontail Ray pictured on this page is an adult, roughly one foot (30cm) wide. I photographed it at Pulau Sipadan, Malaysia.

The Hawksbill Sea Turtle, a Critically Endangered Species

Hawksbill Sea Turtle (Eretmochelys imbricata)

by B. N. Sullivan

This is the Hawksbill Sea Turtle (Eretmochelys imbricata), listed as Critically Endangered by the International Union for Conservation of Nature (IUCN). This turtle species inhabits all tropical and subtropical seas around the world, but its numbers continue to decline.

The IUCN Hawksbill Turtle page notes:

extensive subpopulation declines in all major ocean basins over the last three Hawksbill generations as a result of over-exploitation of adult females and eggs at nesting beaches, degradation of nesting habitats, take of juveniles and adults in foraging areas, incidental mortality relating to marine fisheries, and degradation of marine habitats.

The IUCN estimates that "the overall decline of the species, when considered within the context of three generations, has been in excess of 80%."

While habitat degradation, trafficking in turtle eggs and meat, and incidental catch by marine fisheries threaten all sea turtle species, the Hawksbill population also has suffered due to what is known as the Tortoiseshell trade. "Tortoiseshell" -- the material used for combs, hair ornaments, and inlays on furniture and other decorative items -- comes not so much from tortoises, but from the carapaces of Hawksbill Turtles. Tortoiseshell collection and trade has been banned under CITES (the Convention on International Trade in Endangered Species) since 1973, yet enforcement in some parts of the world remains lax.

I photographed the Hawksbill Sea Turtle on this page at Thomas Reef in the Tiran Straits of the Red Sea.

More information about Hawksbill Sea Turtles;