![]() >Outer Hebrides islands. |
>Basking sharks are easily recognizable by their large gaping mouths with gill slits that almost encircle their heads. The gill rakers, arranged along the gill arches, are specially adapted bones that passively strain plankton from the water in much the same way that filter-feeding whales use baleen. The basking shark gets its name from the way it feeds during warmer months at the plankton-rich surface of the ocean, with its exposed dorsal fin basking in the sun.
>The basking shark's brain is very small compared with those of predatory sharks, which must actively engage strategy to hunt prey. Its olfactory tract is larger than the rest of its brain, indicating how critical its sense of smell is to its survival, likely because it helps the shark to locate plankton.
>In contrast to its undersized brain, the basking shark's liver is comparatively large, comprising up to one-third of its total body weight. Basking shark livers are filled with squalene oil to provide both energy and buoyancy, the latter being necessary in the absence of a swim bladder. Unfortunately, the shark's oil-rich liver also makes it attractive to poachers looking to capitalize on the predictable behaviors of these calm animals, who swim slowly and close to the surface.

>close to pick us up. The dive ladder makes entry easy.
>I'm no stranger to coldwater diving, but basking sharks feed near the surface, which makes drysuit diving impractical. We were to gear up two at a time and get in the water upstream of the basking sharks with our guide. Wearing a wetsuit, I knew the cold water was going to hurt; nonetheless, it had to be done. I splashed in, shouted some expletives and turned my attention to the life around me. The bottom was a canvas of green and purple kelp with orange starfishes, white sand, lobsters, fish and, of course, the main attraction itself. It was thrilling the first time I had a head-on composition in my viewfinder and saw the shark opening its mouth agape.
>Basking sharks are often social, and we were lucky that our third day of diving was the best of the season for both weather and basking shark sightings. Calm conditions allowed the crew to deploy a drone over the channel, yielding views of several basking sharks working the surface. Excitedly, we entered the water upstream and were blown away when four sharks, one after another, came straight toward us.
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>Divers interested in encountering basking sharks may also be delighted by the broader ecosystem they inhabit, which in Scotland includes popular puffin nesting areas. My group and I took one afternoon away from basking sharks to visit the Isle of Lunga, where we trekked over a rocky shoreline to follow a path up a cliff. As the trail twisted upward, we could see a cloud of puffins riding the onshore wind to their destinations. With wings and feet spread, they landed on the grass-tufted cliff edge, where they would sit and gaze to the sea or disappear into a hole to check on their chicks. Since this was the end of the season, the chicks would soon find their parents had returned to sea, leaving them to fledge on their own.
>Historically,

>formations. On land you can hike into the cave and up to the top for the
>spectacular views.
>Possible future threats include global warming, which has already shifted the range of the basking shark's food supply northward, and microplastics, which are captured in the basking shark's gill rakers as it feeds. The consequences of both developments on populations of basking sharks remains to be seen, but the shark's long gestation and slow maturation mean that unnatural losses make species health unsustainable.
>On our last afternoon with Scotland's mysterious gentle giants, my companions and I explored between some shallow coves and low islands. Seals resting on the rocks watched us as we passed by. The area was full of basking sharks swimming in repeating sweeps between the islands. The water was choppier and less clear than before, but in the confined area the sharks seemed to be swimming more slowly but with purpose and directly toward us as they fed with open mouths. It was a frenzy of basking sharks of all sizes.
>We stayed in the water for more than two hours, getting front-on videos and close side shots all without much swimming. One by one, we became tired and cold and finally had to exit the water. Leaving the water with a full memory card, it was a perfect finish. I hope that continued protections will allow future generations to experience these mysterious and fascinating creatures.
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>© Alert Diver — Q3 Summer 2018