My first session was about using photos to identify individual Great Whites. Photos provide a non-invasive method of tracking individuals. You simply take a photo of the dorsal fin of each shark and compare it to previous photos. I say simply, but it is actually a fairly tough job to get a good picture of the dorsal fin out of the water, at the right angle, and close enough that the notches on the trailing edge of the fin (the easiest identification marks) are clearly visible. In fact, the main job of the bait handler is to use the bait to maneuver the shark into a position where the photographer can get just such a shot. Yesterday, however, was all about what is done with the photos after they're taken.
We use Lightroom to sort the photos. Each photo is given a 1-5 star rating based on clarity, orientation of the fin (perpendicular or at another angle and curved or rigid), protrusion (how much the fin is out of the water), exposure of the shot, and composition (how closely the fin was photographed, if things were in the way of the shot, etc). We then narrow down our selection of photos to those which were rated 3 stars or higher. These are then edited to improve what exposure and clarity issues we can, without distorting the color variations that can be used as further identifications, of course. Once the best left and right view of the dorsal fin have been selected, the photos are assigned a sequence of keywords based on the appearance of the dorsal fin as well as other data recorded during the original observation; things like whether the shark is male or female and whether they have significant portions of any fins missing or deformed. All this means that, when a new photo comes in, you can narrow down your selection of photos for comparison so that you can determine if a new photo is a new shark entirely or one you already have on record.
The afternoon's session was about fishing. In addition to free-diving to collect sharks, we fish for them with rods and reels or hand lines from shore or boats. Braham, a young Oceans employee who works in the aquarium, taught us about the techniques we'll use when fishing for the sharks--everything from tying knots to setting up the line to making good bait presentations. My knowledge of fishing technique and jargon has increased 100-fold since I woke up yesterday morning. We'll see how well I do when it comes to a practical application!
What camera is used to photograph these dorsal fins? Does it have to have a LONG focal length so you don't have to get close? And how close does the baiter need to get?
ReplyDeleteThey're using a Nikon SLR. I can't tell you more specific than (I haven't looked at the camera myself). They weren't using an overly long lens. The sharks come very close to the boat. The baiter is simply manipulating a long rope with the bait on the end. They themselves really aren't any closer to the sharks than the photographer (who generally tries to stand fairly close to where they are). The sharks come right next to the boat.
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