Grupo Vivencia
Marina, or, in English, Marina Experience Group from the
state
of Mexico visited Manzanillo recently, bringing with them a diver who
interacted with nurse sharks, as well as rays and other fish.
Instead of regular SCUBA gear (regulator, buoyancy compensator device, tanks and weights), this diver used a regulator attached to a hose connecting to an out-of-water compressor, commonly known in Mexico as a "hooka." Rather than swim, a diver with a hooka-type apparatus, normally walks on the bottom. Divers who use this form of breathing in Manzanillo, commonly are fishermen hunting for octopus or oysters.
During
the one-hour show, which began with an informative and humorous narrative
about sea life--and sharks in general--the diver entered the large tank and
proceeded to demonstrate the tameness and gentleness of the 6 ft. predator
that most people are afraid of. "Not all sharks are dangerous," he
explained. "In fact," he continued, "this species is one of the most docile
creatures in the sea, although they are known to bite when provoked, and
have thousands of tiny serrated teeth arranged in rows, and rotate into
position as necessary to replace lost or broken teeth.
The origin of the name "nurse shark" is unclear. It
may come from the sucking sound they make when hunting for prey in the sand,
which vaguely resembles that of a nursing baby.
Or it may derive from an archaic word, nusse, meaning cat shark. The most likely theory though is that the name comes from the Old English word for sea-floor shark: hurse.
Nurse sharks are slow-moving bottom-dwellers and are, for the most part,
harmless to humans. However, they can be huge—up to 14 feet (4.3 meters)—and
have very strong jaws filled with thousands of tiny, serrated teeth, and
will bite defensively if stepped on or bothered by divers who assume they’re
docile.
They use their strong jaws to crush and eat shellfish and even coral, but prefer to dine on fish, shrimp, and squid. They are gray-brown and have distinctive tail fins that can be up to one-fourth their total length. Unlike most other sharks, nurses are smooth to the touch.
Nurse sharks are found in the warm, shallow waters of the western
Atlantic and eastern Pacific oceans. They are abundant throughout their
range and have no special conservation status, although the closeness of
their habit to human activities is putting pressure on the species.
In the photo, left, the diver hugs the captive nurse shark as an audience of more than 100 people watch in awe. Many people who live in Manzanillo have never seen a living shark, and this "shark show" is designed to share with residents and tourists the mysteries of the ocean.
The spotted eagle ray is commonly observed in bays and over coral reefs as
well as the occasional foray into estuarine habitats. Although it occurs in
inshore waters to depths of approximately 200 feet (60 m), the spotted eagle
ray spends most of its time swimming in schools in open water.
In open waters,
spotted eagle rays often form large schools and swim close to the surface. It
is known to swim long distances across open waters as evidenced by its
presence in Bermuda. This species is capable of leaping completely out of the
water when pursued.
It swims by "flying" gracefully through the water via the
undulation of the pectoral fins. When this ray is caught and taken out of the
water, it produces loud sounds. Although much research is still needed on the
life history of the spotted eagle ray, it is known that this species shows
high site fidelity (individuals often stay in or return to the same location).
This ray also interacts socially with other individuals within its own
species.
Clams, oysters, shrimp, octopus, squid and sea urchins as well as bony fishes
provide prey for the spotted eagle ray. This ray is well adapted with its
shovel-shaped snout and duck-like bill for searching in the mud for benthic
invertebrates.
When a prey item is found, the ray crushes it with its plate-like teeth and uses the papillae located in the mouth to separate the shells from the flesh. Upon scientific observation, the stomach contents of spotted eagle rays contained intact prey items lacking any remnants of shells.
A sting ray, (with diver
on right), normally is a bottom dweller, and likes to bury itself in the
sand. Stingrays are commonly found in the shallow coastal waters of
temperate seas. They spend the majority of their time inactive, often moving
only with the sway of the tide. The stingray's coloration commonly reflects
the seafloor's shading, camouflaging it from predatory sharks and larger
rays. Their flattened bodies are composed of pectoral fins joined to their
head and trunk with an infamous tail trailing behind.
While the stingray's eyes peer out from its dorsal side, its mouth, nostrils, and gill slits are situated on its underbelly. Its eyes are therefore not thought by scientists to play a considerable role in hunting. Like its shark relatives, the stingray is outfitted with electrical sensors called ampullae of Lorenzini. Located around the stingray's mouth, these organs sense the natural electrical charges of potential prey. Many rays have jaw teeth to enable them to crush mollusks such as clams, oysters, and mussels.
When they are inclined to move, most stingrays swim by undulating their bodies like a wave; others flap their sides like wings. The tail may also be used to maneuver in the water, but its primary purpose is protection.
The stingray's spine, or barb, can be ominously fashioned with serrated edges and a sharp point. The underside may produce venom, which can be fatal to humans, and which can remain deadly even after the stingray's death.
The show ran for 2 weeks, with 4 and 5 shows a day, all sold out. At one point during the first week, activists picketed the show, claiming cruelty to animals. The announcer explained that the show had a basis in educating the audience as well as entertainment. Vivencia Marina travels throughout the world. The group also has an act with 5 species of tropical birds, and another featuring sea lions. Web site: http://vivenciamarina.blogspot.com/