DIVE DRY WITH DR. BILL #859: A PRICKLY SUBJECT

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drbill

The Lorax for the Kelp Forest
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Rest in Peace
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DIVE DRY WITH DR. BILL #859: A PRICKLY SUBJECT

People often ask how I could keep diving for 58 years and not get bored. I reply that I'd get bored watching baseball games or golf matches (but not my great uncle George Halas' Chicago Bears!). Too often I see a new species (thank you global warming) or a new behavior that keeps me intrigued with our local kelp forests.

One could live several lifetimes and still not piece together all the intricate relationships within the Macrocystis pyrifera community. Sadly I only have one as far as I know, but if not I probably won't be reincarnated as a marine biologist. Been there, done that.

A while back several divers, including my friend Daniel Rugenstein, over in Veteran's Park (Redondo Beach). spotted a fish that I've never seen. It was a prickly shark (Echinorhinus cookei but no relation to the cookie cutter shark). It is a species normally found in deep offshore canyons during the day, but makes a diel migration into shallow waters when the sun goes down. There is a submarine canyon off Redondo and others off San Diego and Monterey.

I was surprised to find that Dr. Milton Love's excellent guide to the fish on our coast had no entry for this species. Perhaps it will be included in the next edition? This shark received its name from the sharp, thorn-like dermal denticles ("skin teeth") that cover its body. Based on the structure of the mouth, it probably feeds by suction. Wikipedia shamefully described the adults as having a flabby, cylindrical body. Heck, these sharks appear far more svelt than some of the folks I've seen at Walmart... but then I really shouldn't body shame. I once had a six-pack but now it's more like a pony or a keg.

The head is somewhat flattened and the mouth is underslung and fairly wide.In my research I found out that this species has about two dozen rows of teeth in both the upper and lower jaw. The two dorsal fins are set far back near the tail. The body is brown or gray and the fins may have a dark trailing margin. They can reach a length of 13 feet.

The prickly shark is known from throughout the western and central Pacific Ocean including Japan, Australia, Palau, Tonga and Hawaii. Off our coast in the eastern Pacific it may be found from Oregon to central America. It is reported to be fairly common in Monterey Canyon, but less so elsewhere along this coast. It is a cold water species, preferring chilly waters less than 52°. I begin to shiver about that temperature especially since my cancers have caused me to lose some "bioprene" (aka insulation... fat). Thus it spends daytime at significant depths believed as far down as close to a mile! It can tolerate much lower oxygen levels than other sharks.

Its "flabbiness" comes from a wide range of dietary entrees. They munch on many species of fish, both bottom dwellers and midwater. The menu includes other sharks, flounder, rockfish and lingcod as well as schooling fish such as topsmelt and mackerel. They also like octopuses and squid. Since there was a squid run off Redondo, that may be the reason Daniel and others saw one there. Or perhaps it just wanted to watch Shark "Weak." Juvenile pricklys may fall victim to sixgill sharks but the adults face few threats.. at least that we know of. Down there in the deep there could be anything (except me)!

Almost nothing is known about their mating behavior. Maybe it's because, like mine, there isn't much to tell! It is believed the males may be sexually mature at about 6 1/2 feet and the females at 8-10 feet. Fertilization is internal and the embryos survive off the yolk in their eggs. Only one female with young has ever been taken. She had 114 embryos! Holy mackerel... er, prickly shark. Imagine the cost of child care.


© 2020 Dr. Bill Bushing. For the entire archived set of over 850 "Dive Dry" columns, visit my website Star Thrower Educational Multimedia (S.T.E.M.) Home Page

Image caption: Prickly shark image courtesy of Wikipedia.


DDDB 859 prickly shark.jpg
 

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