Dive Dry with Dr. Bill

#212: The Blues... Part One

When I began diving off Catalina in the late 1960's and early 1970's, blue sharks were a common sight even fairly close to shore. While captaining the old K.V. to take my Toyon students into town, or crossing the Channel to Long Beach on a seaplane or one of the early Catalina Cruises boats, we would play a "game" counting the number of shark fins sighted between Toyon and Avalon, or Avalon and the mainland. I don't ever remember getting skunked. These days it is a rarity to see a blue shark, a sad ecological reality brought about by decades of long lining, gill netting and other fishing methods.

Last week I jumped at the opportunity to go out on Scuba Luv's King Neptune to the Avalon Banks about five miles off our fair town. Here I was to dive with sharks of several different types, the cartilaginous fish kind... and a very nice future lady lawyer. Just teasing you, Laura. I filmed topside as Avalon's own mayor, Bob, captain Tony and tech diver Rene set up the shark cage on the rear deck. At least one of the divers gave the "flimsy" seeming (but quite sufficient) aluminum cage a skeptical once over before it went into the water. The boat's crew gathered all of us at the "pointy end" of the boat to give the dozen or so divers a briefing on the dive procedures and the biology, behavior and ecology of the shark species we were likely to see.

Laura was the first to get in the water and enter the shark cage. I think she was anxious to meet some of her future associates! She didn't remain inside the cage long, nor did the other diver who entered it. All the divers spent most of their time outside the cage underwater, even when the sharks began to appear. The first sighting was a blue shark about five feet long. After a brief assessment of us, it was pretty bold and made a number of close passes... I guess it felt comfortable that one of its own was diving amongst us (just teasing, Laura).

Watching and filming the blue shark was very rewarding. I've dived with many different sharks of both kinds over the years, but it had been decades since I've been so close to a blue shark. The last time I remember, I was diving below Indian Head Point for abalone (in the old days when you still could) and had a blue follow me at the surface all the way into the surf zone at Shark Harbor. The shark I saw on this dive had an accomplice (book 'em, Danno), a dark striped pilot fish that is actually a member of the jack family. Although pilotfish have been seen from Vancouver Island, Canada, south to Peru and the Galapagos, they are considered rare in California waters. These fish will also follow rays and whales.

Another interesting observation was the presence of a large hook in the shark's mouth with the leader trailing out the other side. Now I'm going to assume this fish was hooked incidentally by someone seeking marlin or swordfish. In my opinion, few sane individuals would catch them for food. Believe me, I've tasted blue shark. All but the most culinary challenged individuals would shun this meal, and even with my limited cooking skills I don't fall in this category!

I've dived with many different species of sharks from the Great Barrier Reef to Tahiti to Thailand to the Mediterranean. Blue sharks are somewhat different. They are a slender shark without the deep body of a great white, mako or many other species. Blues are also very graceful, and even though great whites are also I don't want to risk offending them by comparing them with ballet dancers. They might try to get back at me.

Despite these experiences, shark encounters worldwide are increasingly rare due to serious over harvesting of their populations. I've dived areas like Belize where sharks used to be abundant on the beautiful coral reefs, yet I never saw one other than a few docile nurse sharks. One of the most heinous acts in my opinion is the practice of shark "finning," harvesting the fins for shark fin soup. Commercial fishers catch enormous numbers of sharks of different species, cut off their larger fins, and toss the incapacitated but still living animal back into the sea. I once debated a dive buddy of mine from mainland China about this practice. She felt that shark fin soup, once a delicacy reserved for the royal and rich, should be enjoyed by the increasing middle class in her home country. Ecologically I find no basis to defend the practice.

Shark finning is not only gruesome, but ecologically harmful as well. Studies are finding that the tremendous reduction in shark populations may be having serious effects on ecosystems including coral reefs. As high level predators, sharks keep critters lower on the food chain in check. Without sharks, populations of large groupers may increase and remove greater numbers of smaller fish such as parrotfish from the ecosystem. Parrotfish and other algae eating fish keep algae from overgrowing the coral on the reefs. When they are diminished, coral reefs may become overgrown with out-of-control algae. So sharks of the fishy type have an important function in healthy ecosystems. Heck, even "sharks" of the "other" kind provide valuable services to human society... at least that is what Laura told me! More on the biology and ecology of the blue sharks and this shark dive in next week's column. Stay tuned!

© 2006 Dr. Bill Bushing. Watch the "Dive Dry with Dr. Bill" underwater videos on Catalina Cable TV channel 49, 10:00 AM and 5:00 PM weekdays. Please help me climb out of self-imposed poverty... buy my "Munching and Mating in the Macrocystis," "Great White Sharks of Guadalupe," "Calimari Concupiscence: Mating Squid, " "Playful Pinnipeds: California Sea Lions," "Belize It or Not: Western Caribbean Invertebrates, Fish and Turtles" or "Gentle Giants: Giant Sea Bass" DVD's. Yes, take Dr. Bill home with you... we'll both be glad you did!

Divers holding on to shark cage, videographer experiencing a harmless close-pass by a blue;
blue shark followed by striped pilotfish, blue shark approaching showing fishing hook in mouth.

This document maintained by Dr. Bill Bushing.
Material and images © 2006 Star Thrower Educational Multimedia