Photo of the Week: January 03, 2011

Hi Gang!

This week’s POTW is an image of a Galapagos shark, Carcharhinus galapagensis. Given the animal’s common and scientific names it might seem logical to conclude that the photograph was captured in the waters surrounding Ecuador’s Galapagos Islands. But that is not the case. This image was created in Hawaii, in the water off the North Shore of Oahu on a dive I made with Captain Steve a couple of winters ago. The shark’s names, both common and taxonomic, are derived from the fact that the first described specimens of this species were captured at the Galapagos Islands in the early 1900’s.

Captain Steve, several other friends, and I were led on our dive by now deceased shark enthusiast Jimmy Hall. Jimmy and his girlfriend, Stephanie Brendl, ran a shark diving business that Stephanie continues to run. The dive is first class. It is conducted in the open sea a little farther than three miles off the North Shore of Oahu. The cage floats at the surface, and most divers use surface supplied air, or hookah, and remain inside of the cage throughout the dive. The day we went we were able to get out of the cage and work in open water while surrounded by somewhere in the neighborhood of 30 Galapagos sharks and 3 sandbar sharks. In other words, it was quite a scene.

Galapagos sharks are considered to be active predators that prey chiefly upon a variety of bottom-dwelling bony fishes and cephalopods. That said, stomach content analyses of Galapagos sharks have shown that these sharks also feed on other sharks, sea lions, marine iguanas and human rubbish.

Galapagos sharks occur worldwide in tropical and temperate seas where they tend to prefer areas with relatively clear water bordering oceanic islands. These predators are found in both inshore and offshore waters from the surface to a depth of almost 600 feet.

Galapagos sharks reach a maximum length of just over 12 feet, but most mature specimens are several feet shorter. Males reach sexual maturity when they attain a length somewhere between 6.9 and 7,5 feet while females need to attain a length of 7.2 to 8.2 feet. Mature animals are thought to be at least 10 years old. Galapagos sharks are live-bearers with females giving birth to liters of 4 to 16 pups every 2 to 3 years. Galapagos sharks are believed to live as long as 24 years in the wild.

This week’s POTW image was created with my favorite lens for creating full-bodied images of medium-sized sharks, and that is my Nikon 17-to-55 zoom. In this case, the focal length of the lens was set at 22 mm. I was hanging around under the boat, not too far from the bait basket, when the shark approached the boat, and then turned and swam toward me. As is often the case, this Galapagos shark was relatively bold and passed within a foot or so of my camera giving me a great opportunity to get a head-on shot.

I hope you enjoy this week’s POTW!

See you next week,

Marty