DIVE DRY WITH DR. BILL #892: NO, MY OCTOPUS TEACHERS

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drbill

The Lorax for the Kelp Forest
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DIVE DRY WITH DR. BILL #892: NO, MY OCTOPUS TEACHERS

Many divers and non-divers have viewed a popular video recently entitled "My Octopus Teacher." Most have raved about it and it received a 4.9 out of 5.0 rating on Netflix. The score on Rotten Tomatoes, 3.5 out of 5.0, was probably closer to what I would have rated it. I enjoyed the opportunity to observe critters in the South African kelp forest as that is a region I've not had the pleasure of diving. The closest I've come on that continent was way up north in the Egyptian Red Sea. No kelp there!

So what didn't I like about this documentary? Well, first of all, as a diver of many decades, it just didn't ring true to me. I'm sure it was genuine for the free diver, a man by the name of Craig Foster. Perhaps I'm just a bit jaded after so many years of diving with critters including species of octopuses throughout the world. Foster claimed to have developed a real connection with the octopus (probably more than one as I didn't see a name tag on any of the ones in the film). As an ecologist, I wasn't overly concerned that he let a shark chow down on his new friend. After all, it is The Mutual Eating Society down under (and topside, too). What really made me question what he had learned was at the end when he kept handling several other critters of different species.

Now I've learned a fair bit observing and filming octopuses around the globe. My favorites are the two-spotted octopuses of our own SoCal waters as I've gotten to know them the best. We are blessed with not one, but two species of two-spot octopus here. The California two-spot (Octopus bimaculoides) and Verrill's two-spot (Octopus bimaculatus) are very similar looking but differ in the appearance of their blue "eye-spots." However Verrill's can get up to about a yard in length while the other reaches about half that size.

O. bimaculoides is found from San Simeon (home of the Hearst castle) down to Ensenada while O. bimaculatus has a somewhat wider distribution from Santa Barbara down into the Sea of Cortez (aka Gulf of California). The latter has a deeper depth range, reaching down past 160 fsw while the former rarely exceeds half that depth. I guess it doesn't have a tech diving certification. Verrill's tends to be active mostly at night while the California two-spot tends to prefer daylight.

Their reproductive behavior is also significantly different, with consequences for the dispersal of each species. According to Jensen, et al. Beneath Pacific Tides, female Verrills lay very small eggs (2-4 mm) which may number up to 20,000. These hatch into planktonic larvae which can then disperse in the currents. California females lay much larger eggs (10-17 mm) but their broods are much smaller in number. Their eggs hatch into small juveniles that crawl off rather than drift in the plankton. That, of course, can limit the ability to disperse to places like the Channel Islands. However, I have found these octopuses on drifting rafts of kelp which can transport them here.

Another species in our region, the red octopus (Octopus rubescens) has always left me wondering. Although it is known from the Gulf of Alaska down into the Gulf of California, I don't believe I've ever seen it in Catalina waters. However, it is a common component of similar ecosystems in places like San Diego. In fact, Wikipedia states it is one of the most common octopus species on the West Coast of North America! So why isn't it found in our island waters? Perhaps one reason is that the larvae that hatch from their eggs do not spend much time in the plankton and therefore can't disperse far from home. However, I noticed one source indicated that they are often found in kelp holdfasts that have beached so they should be able to disperse on drifting kelp rafts too. Hmmm... yet another Mystery of the Deep.


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

Image caption: Two-spot octopuses in Catalina waters.

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Hi Dr. Bill... general question...

One means of species identification is by location, as I've seen on iNaturalist. My question is, how do we know if a species has spread naturally or brought there by accident/purpose? Do we have established records enough to say that a certain species has already been present and finally recorded vs it being new/invasive to the region?
 
Yes!

I did an exploratory dive to 250' back in Nov 2020 on an unknown target in the Pt Loma area and found bits & pieces of something (more dives required, there is something there), but while searching around, I found this little guy peeking out of his little den in the middle of nowhere! He was tiny!

Who had the better dive?!


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Yep, PLENTY of them over on the mainland Phil... just not here
 
Hi Dr. Bill... general question...

One means of species identification is by location, as I've seen on iNaturalist. My question is, how do we know if a species has spread naturally or brought there by accident/purpose? Do we have established records enough to say that a certain species has already been present and finally recorded vs it being new/invasive to the region?

Well, the data would have to be many years back (even before human occupation) to know for sure.
 
I haven't watched the film, but my non-diving sister thought it was wonderful. My concern is that many non-divers will watch this - and him handling the critters - and get the idea that marine life likes being handled. Heck, I've seen divers doing this too. Do they, at any part in the film, recommend that folks not 'try this at home'?
 
I wonder if the woman who recently recorded herself holding a Blue-Ring octopus saw the film.
Octopus rubescens are abundant in Redondo Beach and Palos Verdes. We don't see as many up in the Santa Monica Bay nor along the south side of the peninsula. Perhaps Dr. Bill is correct about their minimal time in the plankton. We often find nests year-round in the same spots.

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I wonder if the woman who recently recorded herself holding a Blue-Ring octopus saw the film.
Octopus rubescens are abundant in Redondo Beach and Palos Verdes. We don't see as many up in the Santa Monica Bay nor along the south side of the peninsula. Perhaps Dr. Bill is correct about their minimal time in the plankton. We often find nests year-round in the same spots.

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Wow - incredible beautiful and cute at the same time.
 
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