Today on Animal Fact Files we’re discussing pelagic stingrays.
These fish are named for their preferred habitats: the open ocean!
They're described as the only pelagic stingrays in the whiptail stingray family.
Originally, these unique rays were classified in another genus along with the common stingray.
Because little footage of pelagic stingrays is available online, much of the video shown
in this episode actually features this previous congener.
Pelagic stingrays, however, we're moved to their own genus!
These rays are not often seen in their natural habitat because they swim over the deep, open
ocean.
They typically stay between the surface and 330 feet deep (1-100 m), but they've been
observed down to 1,250 feet (381 m)!
That's down into the ocean's twilight zone where light barely penetrates!
It's for both these reasons - their preference for deep, open ocean, and their ability to
dive deep below the waves - that these fish are rarely seen.
When they are seen, it's usually as bycatch from other fishing operations.
For example, long line fishing, which is called so because it involves a series of hooks connected
to a long line suspended in the water column, is intended for catching other fish such as
tuna, but also snags unintentional prey, such as pelagic stingrays, at the same time.
When caught, pelagic stingrays are sometimes used for meat, but they're also simply thrown
away.
Some are donated to science which is where much of the information surrounding them comes
from!
Pelagic stingrays are also known as the violet stingray and the blue stingray for their dark,
cool coloration.
They're difficult to spot from above because their dark back blends in with the sea below,
and they're difficult to see from below because their pale stomach blends in with light from
above.
This is known as countershading and is present in many marine animals from dolphins to sharks.
Countershading is beneficial for avoiding detection from predators and prey alike.
White tip sharks are believed to eat pelagic stingrays, and they also likely fall prey
to other larger fish.
In turn, pelagic stingrays eat jellyfish, squid, octopuses, small fishes such as herring,
and small crustaceans such as copepods.
Unlike the crushing teeth present in many other stingray species, pelagic stingray teeth
are sharper and used for cutting.
These fish also earn the name stingray for their long, sharp stinger.
Located about one third down the pelagic stingray's tail, this barb is believed to be more potent
than other stingrays because nearby fish give them a wide berth.
Fortunately, pelagic stingrays don't often come in contact with humans because of their
remote habitat, so there's less to worry about– unless you're a long line fisher!
Per the whiptail stingray family, a pelagic stingray's tail is about double the length
of its body.
Their pectoral fin, or "wing", width is between two and three feet (61 to 91 cm) wide as adults,
and their total length, including the tail, reaches about five feet (150 cm).
Pelagic stingrays live in tropical and temperate ocean waters around the world.
They have different mating seasons depending on where they live, although they most commonly
time their breeding so that their young are born in warmer months.
Only the left ovary and uterus work in female pelagic stingrays which is typical of members
of the whiptail stingray family.
Their eggs develop and hatch inside the mother after a gestation period of approximately
two to four months.
The pups, of which there are up to a dozen per litter, are supplied with uterine "milk"
until they're born live.
This "milk" is a nutrient rich fluid produced by the mother to supplement her growing offspring.
It takes two to three years for pelagic stingrays to reach reproductive maturity, and they're
estimated to live at least a decade in the wild.
For more facts on pelagic stingrays, check out the links below.
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