Archives for July, 2011

Sharks are amazing creatures. They have roamed the Earth’s seas since nearly the beginning of time. Their size, power, and great, toothy jaws fill us with both fear and fascination. Sharks have few natural predators allowing them to roam the earths oceans with relative ease.  There are over 500 types of sharks ranging in size from a few centimeters  to more than 15 meters.  They are found in all seas and are common to depths of 2,000 meters (6,600 ft). They generally do not live in freshwater although there are a few known exceptions, such as the bull shark and the river shark, which can survive and be found in both seawater and freshwater.

Sharks (Steven W Smeltzer)

White-tip Reef Shark, Triaenodon obesus, Maui Hawaii

They are “cartilaginous fish” meaning that the structure of the animal’s body is formed of cartilage, instead of bone. Unlike the fins of bony fishes, the fins of cartilaginous fishes cannot change shape or fold alongside their body. Even though they don’t have a bony skeleton like many other fish, they are still categorized with other vertebrates in the Phylum Chordata, Subphylum Vertebrata, and Class Elasmobranchii. This class is made up of about 1,000 species of sharks, skates and rays. They have five to seven gill slits and rigid dorsal fins, for which they are famous.  And though they kill only a few people each year, media coverage and movie portrayals of attacks have marked sharks as voracious killing machines. Our fears—and appetites—fuel an industry that hunts more than 100 million sharks each year and threatens to purge these vital predators from the oceans.

The pool is open…..

We were about 10 minutes into the dive when we entered the canyon and found it filled with Silversides.  These interesting schooling fish always make a great shot.  The Silversides typically come  between June and August and can be found in the many grottoes, wrecks, caves and swim-throughs, on the reefs surrounding Grand Cayman.

Silversides, Atherinidae (Steven Smeltzer)

Surrounded, Silversides and Scuba divers, Grand Cayman

Silversides, Atherinidae, are one of the key reef species in Grand Cayman and the Caribbean in general.  These great swarms of fishes provide an excellent food source for many of the larger species of fishes and provide a wonderful experience for divers as well.  It is a great experience to be surrounded by one of these “balls of fish” or to watch Tarpon or Barracuda dart through the swarms.

 

The large balls are a defensive mechanism for the fish and you will notice that the entire swarm tends to change direction at once, acting almost a s single organism instead of thousands and thousands of individuals.

The pool is open…..