Photo of the Week: August 23, 2010

Hi Gang!

Once again Mexico’s Sea of Cortez delivered some great diving, and it gives me the opportunity to share some of her beauty with you through this week’s POTW, a silhouette of three California sea lions resting at the surface.

Populations of California Sea Lions can be found in pacific waters from Alaska to the equator as the species thrives at Ecuador’s Galapagos Islands. California sea lions occur in Mexico on both the Pacific and Sea of Cortez sides of the Baja peninsula

Collectively, sea lions, seals and walruses are referred to as pinnipeds in reference to their order, Pinnipedia, from the Greek for “fin feet.” Sea lions are further described as members of the family Otariidae, a word that is Greek in origin and means "little ears.” Sea lions are often confused with true seals, but there are several easily uable distinguishing characteristics that enable observers to distinguish between the two groups. Sea lions have easily visible, external ears that are lacking in true seals. Sea lions are more agile on land because they can rotate their rear flippers forward, and sea lions use their rear flippers to provide thrust when swimming while seals use their rear flippers as a rudder. Seals generate thrust with their fore flippers. Finally, sea lions possess harsh coast while seals have much finer coats.

Full-grown California sea lion males (bulls) attain proportions of 700 pounds and 10 feet in length. Females grow to 250 pounds and up to 8 feet in length. At approximately five years of age, males develop a bony bump known as a sagittal crest on the top of their skull. This crest often becomes lighter with age.

California sea lions are highly social animals, preferring to gather together in groups throughout the year. On land, California sea lions are very vocal and bark incessantly. They tend to congregate in distinct areas when they gather on shore. Breeding groups congregate in areas known as rookeries while non-breeding populations tend to occupy strips of land called hauling-out sites. In addition, sub-adult males and males that are incapable of establishing a breeding territory sometimes gather in isolated bachelor colonies. When gathered together on land, groups of sea lions are referred to as colonies while smaller groups that gather in the water are usually referred to as rafts.

California sea lions are superbly equipped for their lives in the water. They use their long fore flippers to make powerful strokes that can propel their streamlined bodies up to speeds of 25 miles per hour. Unlike dolphins and whales, California sea lions exhale before diving. Even so, they have been documented to dive as deep as 900 feet and to stay submerged for as long as 20 minutes.

When they are not buzzing around you at breakneck speed, California sea lions often rest on the surface. That is what the group pictured in this week’s POTW was doing when I encountered them. I was careful to move slowly in an effort not to startle or otherwise disturb them, and I believe that this type of approach helped me get into position where I could look up and see a distinct silhouette that I was able to capture with my camera.

As I have written about before in previous POTW columns, I am not a big proponent  of hard and fast rules in underwater photography, but when it comes to silhouettes it is necessary to see distinct contrast between your subject and the background in order to create a silhouette. In this case, there was plenty of contrast. The photographic challenge for me was to be able to use a fast enough shutter speed to freeze any action and to help create crisp lines that distinctly separated the sea lions from the water while also properly exposing the water in the background that was immediately surrounding the sea lions. I used a shutter speed of 1/750^th of a second and took a spot meter reading on the blue water next to the “sunburst”. I used a Nikon D2x camera, a12-to-24 mm lens in a Subal housing, an ISO of 200, and no strobes when creating this picture.

I hope you enjoy this week’s POTW!

Hope to see you here again next week,

Marty

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