DIVE DRY WITH DR. BILL #902: GET YOUR VITAMIN A FROM A JAR!

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drbill

The Lorax for the Kelp Forest
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DIVE DRY WITH DR. BILL #902: GET YOUR VITAMIN A FROM A JAR!

Way back in the late 60s, before I moved to Catalina, I feared sharks. All my diving had been in freshwater and I doubt any had worked their way thru the St, Lawrence River and Great Lakes to the shores of Lake Michigan. When I took the train to L.A. in 1969 to assume my new position at the Toyon school, I read a book about great whites and bought the biggest, baddest dive knife I could find.

After 50+ years of diving Catalina, as well as many exotic destinations around the world, I still have all my appendages even after a very few encounters with the landlord uncaged. Although I had dived with many other species in places like Tahiti, Palau and the Great Barrier Reef; my first encounter filming a large group of sharks in our waters was with about two dozen tope sharks (aka soupfins, Galeorhinus galeus). They were right in Lover's Cove in Avalon.

I filmed them as they paraded past my camera and published a front page article in the Avalon Bay News back in 2001. I wrote that these sharks were pretty much harmless as there had only been one "attack" on a human in recorded history. I cautioned that they may get defensive if harassed. Apparently four bozos went into Lover's Cove after reading my article and grabbed their tails and fins... earning them a "free" trip to our emergency room and increasing the number of "attacks" world-wide five-fold..

Thanks to the pandemic, there were few divers in the dive park last year for several months. When it reopened, divers (including yours truly) reported sightings of tope sharks right in the park. Cool. In my experience these sharks scare easily. I often had to hold my breath while filming them as the sound of the bubbles from my regulator would cause them to bolt.

Although the American Fisheries Society's official common name for them is tope shark, many of us have been called them soupfins for decades. Some object to that name because of the intensive exploitation of the species. Here off our coast, topes were fished hard, especially during World War II, for the vitamin A in their liver oil. After the war vitamin A could be synthesized and it was no longer necessary to fish them for it. We have been seeing an increase in the species around the island over the last 50 years.

Topes are sleek sharks with a gray or bluish dorsal and lateral surfaces and a white belly (but no belly button... they're fish, not mammals!). The dorsal lobe of the tail fin is elongated and wide. Mature females may reach 6 1/2 feet in length and around 100 pounds while males are smaller and lighter at about 60 pounds. They are found around the Ocean Planet in temperate waters. The distribution in the eastern Pacific is northern British Columbia to the Gulf of California in the northern hemisphere and Ecuador to Chile in the southern.

According to fish expert Dr. Milton Love, males are sexually mature at 8-9 years while females not until around 12 years. Makes me think back to my middle and junior high school days when the girls towered over me. Females ovulate in summer and the eggs are fertilized internally. The embryos develop inside the mother and anywhere from 6 to 52 youngsters just over a foot long may be released each season.

Since humans aren't on their menu, what do these beautiful sharks chow down on? Their diet consists mostly of fish, squid and octopus. Since it is The Mutual Eating Society, what feeds on topes? Native Americans would catch them and before vitamin A in their livers was discovered, they were fished locally and sold to Asian markets for... yep, shark fin soup. Now their main predators are great white sharks and California sea lions.


© 2021 Dr. Bill Bushing. For the entire archived set of over 900 "Dive Dry" columns, visit my website Star Thrower Educational Multimedia (S.T.E.M.) Home Page

DDDB 902a tope shark sm.jpg


Image caption: Images of tope sharks in Lover's Cove and Garibaldi Reef, Catalina.

DDDB 902b tope shark sm.jpg


Image caption: Tope shark showing general body configuration, elongated dorsal tail fin,
white underbelly and school of jack mackerel following one.

 
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