Last week I mentioned that we were off to the 277 Bank to do a shark dive on board the King Neptune with SCUBA Luv. Then I disappointed all my shark enthusiasts by focusing on a spineless blob of "jelly," the salp, instead of writing a hair raising adventure tale about fighting off sharks as they darted in to investigate us... or worse! I'm not sure this column will get your adrenalin boiling, but I'll try as I write about a somewhat unpredictable shark species we encountered, the shortfin mako.
Avalon's own Kiwi transplant Tim Mitchell was the divemaster on board for this trip. I found that very appropriate, since the name "mako" reportedly comes from the Maoris of New Zealand. Apparently many different cultures and regions have coined names for this species since the shortfin mako is also known as the Pacific mako, blue pointer, bonito shark, mackerel shark, palome, taupe bleu and marrajo dientuso according to Dr. Milton Love. Tim is also partly responsible for the title "Shark and Awe" since like most Kiwis and Aussies, he pronounces the word shark like "shock."
On our last shark dive in December, 2006, only the blue sharks came in close to us. The makos kept a respectful distance, probably out of fear after they saw the fangs in my mouth! This time both the two blues and the two makos we saw came in close and gave us opportunities for some good footage. Yep, just four sharks... a very sad commentary on the state of regional (and global) shark populations, since we used to see dozens of them in the "good old days" (you know, B.J., Before Jaws).
I usually don't mention scientific names if a species has a commonly used common name. However, the name Isurus oxyrinchus, derived from Greek, is not used to honor some biologist like many scientific names. The first or genus name refers to the fact this shark has two nearly equal lobes on its tail or caudal fin, and the second or species name means "sharp snout." Although they are similar in color to the blue shark, their bodies... and teeth... differ. The blue has a longer dorsal lobe on the tail fin. The mako looks like it needs to go to a good dentist.
Shortfin makos are found around the globe in warm and temperate waters, from Washington and Oregon to Chile on our side of the Pacific. They are generally an oceanic species, usually seen in surface waters, but can be found near shore and down to depths of 500 feet according to Dr. Love (I'd "love" to have that name myself!). Local diver and spearfisher Jon Council and others have seen them around the island, occasionally off Pebbly Beach. Although most of the ones in southern California are juveniles, like the two we filmed, this species may reach 12-13 feet in length.
True to some of their common names, these sharks are largely fish eaters. Among their prey are baitfish like mackerel, sardines and anchovy; as well as more ambitious (and tasty) ones like tuna and swordfish. Like me, they love sashimi! Although they are not really man (or woman) eaters, there have been attacks on humans by this species. They do seem to be higher strung and less predictable than the blue sharks we see. It wasn't until the 1980's that these sharks became a popular game fish, perhaps in part due to Jaws... but largely due to the fight they give when hooked. Commercial fishers have also targeted this species since some think their steaks taste like swordfish. Drift gillnets and long lines have undoubtedly taken a big bite out of their populations worldwide.
Baby shortfin makos develop from eggs retained in the female's body. She is sexually mature at 7-8 years and six to nine feet in length. Those that grow faster indulge in cannibalism, munching their brothers and sisters while still inside the mother. Now that is a real example of sibling rivalry. It takes about a year for the two to sixteen pups to emerge, by which time they are a few inches longer than two feet. By the time they are 1-2 years old, they are about three feet long; and reach five feet within 4-6 years. Based on this, the individuals we saw were about three years old. Good thing they were past the "terrible two's," or I might have come back with a finger missing!
Some divers confuse the mako with the great white underwater. Of course saying you saw a great white is a lot more exciting than acknowledging it was "just" a mako. The mako rarely enters nearshore waters, although in the waters around offshore islands like Catalina this is probably more common than along the SoCal coast. Both are members of the mackerel shark family (Lamnidae), not the infamous requiem shark family (Carcharhinidae) to which the blue shark belongs. In fact, some evolutionary biologists believe the great white may have evolved from a now extinct species of mako shark. The teeth of the great white and shortfin mako are visibly different (if you ever get close enough to inspect them). Both species are considered potentially dangerous, especially when chum and fish blood are in the water. Had we seen a shark larger than the "kids" we encountered, I would have been filming from the deck of the boat!
NOTE: There is an excellent video about diving Catalina Island that is available over the Internet on the Bloomberg Financial News' website. It features interviews with Jean-Michel Cousteau, Mayor and SCUBA Luv co-owner Bob Kennedy, and Dr.Bill. The video was put together by Matt and Nadja Brandt for Bloomberg. To see it, log onto the Bloomberg web site (www.bloomberg.com), and search the site on the keywords "Cousteau" and "giant sea bass." You can read the accompanying article by Nadja, then to the right of it select the accompanying media "Diving in the Emerald Forest off Catalina." It's a pretty nice introduction to our underwater world and why many of us love to dive here.
© 2007 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," "Gentle Giants: Giant Sea Bass" or "Common Fish and Invertebrates of the Sea of Cortez" DVD's. Yes, take Dr. Bill home with you... we'll both be glad you did!
Shortfin makos making passes at me (they were females) and Tim Mitchell hand feeding a blue shark.
This document maintained by
Dr. Bill Bushing.
Material and images © 2007 Star Thrower Educational Multimedia