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Dive Dry with Dr. Bill

#341: San Miguel Island... Exotic, But Cold!

Many divers, especially those from wintry climates, like to travel to the tropics for their diving. Although my son Kevin and his wife Mary are enjoying the weather in their new Colorado home, I'm guessing another winter or two will drive them towards the equator for a vacation! As for yours truly, I recently enjoyed a fantastic trip to colder waters as the guest of Rod Roddenberry and the Roddenberry Dive Team. Our destination was San Miguel Island, the furthest north and west of the eight Channel Islands. Its location at the edge of the south-flowing California Current, chilled even further by upwelling of deeper water along the coast north of Point Conception, leaves the island waters far from toasty!

Catalina waters, especially those from Long Point to our East End, are among the warmest in the Channel Islands, so this trip came close to being in a completely different biogeographic zone. You might even refer to it as exotic... cold, but exotic! Although my dives were all well above 100 feet to increase my bottom time for filming, I experienced temperatures as cold as 50 degrees. You may remember that colder waters contain far more nutrients than our comparatively toasty ones, and the consequences were obvious from the moment I submerged.

San Miguel's waters teem with a wide variety of plankton including crustaceans like krill, jelly "fish" and fish fry. The productivity here is obvious from the minute you open your eyes and peer through your mask. The plankton definitely made filming more difficult, but it also meant there was plenty of food for critters from sea anemones to whales. In fact, during the dive briefing at our first site I saw a blue whale spout close to the dive boat. We saw at least half a dozen blues and a number of humpbacks fin slapping and even fully breaching out of the water.

The differences below water were very obvious to this highly trained marine biologist... er, dive bum. Sponges abounded thanks to plenty of food to filter out of the surrounding water. I saw orange and gray puffball, gray moon, red volcano and other species all over the rocks. Beautiful nudibranchs were in shallow water making them easy subjects to film compared to the 100+ foot depths they frequent off Catalina. Likewise cold water rockfish and lingcod were fairly numerous in the shallower waters and I didn't have to dive to deep depths to film them. Red algae were far more abundant here, perhaps due in part to the reduced light levels created by the plankton clouds.

Speaking of algae, I was thrilled to film several colder water species of kelp that I don't see in our more "tropical" waters. The first was Laminaria dentigera, commonly called oar weed. It was first described from specimens collected off Bering Island in the former Soviet Union, but is known down into Baja. The second kelp was Pterygophora californica, known as the southern palm kelp. I saw small forests of this kelp growing at the third site. Looking more closely, several had a limpet attached to and probably feeding on them. This species is not to be confused with the southern sea palm, Eisenia arborea, found in our waters. I did see a few specimens of it off San Miguel too, including one which had an unusual appearance.

Since these kelp are photosynthetic, they must be close enough to the ocean surface to receive enough sunlight to build carbohydrates for energy. Therefore they can't descend into the colder deep water off Catalina since there is not enough light. Many of the other cold water species of fish like rockfish and lingcod, or invertebrates like nudibranchs, can live happily in the temperatures at greater depths in our local waters.

What about the warmer water species so common off Catalina? Our warmer water black sea urchins were replaced by large numbers of colder water red urchins. I also saw a rainbow starfish which I've only seen once in deep water off Catalina. Garibaldi, members of the largely subtropical and tropical damsel fish family, were not to be seen off San Miguel. Although they are occasionally reported as far north as Monterey, temperatures off San Miguel are probably too cool for successful reproduction. Good thing we humans can use blankets, eh? Since I couldn't dive with my usual buddy, Gary Baldi, I chose to dive with Brian Ko. He had tried several times to get to San Miguel but the boat he was on turned back each time, while I have been there all four times I've tried dating back to 1976. He was quite happy that my record remained intact... and his was broken!

We did see several sheephead, also members of a warm water fish family, the wrasses. However, almost every individual was a reasonably large male like the four Oscars found in the Casino Point Dive Park. I only saw two females, and they were already transitioning into males. My scientifically trained cerebral cortex immediately formulated a hypothesis. Perhaps sheephead only arrive at San Miguel as larval forms during warm water events such as El Ninos. They begin life as juveniles, all female. As they age, the females transition into males, perhaps because the waters are too cold there for reproduction. Now I just have to write a $1,000,000 grant to study this phenomenon more carefully! I felt sorry for these poor males... I'm sure their love life must mirror my own.

Although I've been to San Miguel several times, this was a truly fantastic trip. The weather was gorgeous, the seas were calm, the diving great and the people on the trip were fun to be with. My thanks to Rod and Greg Martin of the Roddenberry Dive Team, and to Captain Kevin and the crew of the Peace dive boat out of Ventura. Brian Ko was a great dive buddy and very patient as this underwater imager stopped frequently to film. Despite the cold water temperatures, I never felt a chill thanks to my brand new IST 3mm hooded vest. I ordered my usual size, but IST is a Taiwanese manufacturer of SCUBA gear and their sizes differed from most American manufacturers. The vest fitted me so tightly that Brian had to help me pull it off after the dives. However, I don't think a single drop of cold water reached my ample German torso!

© 2009 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 and on Charter Communications Cable channel 33 at 7:30 PM on Tuesdays in the Riverside/Norco area. Please help me climb out of self-imposed poverty... buy my DVD's (see this link). Yes, take Dr. Bill home with you... we'll both be glad you did!


Cloud of plankton, colder water kelps oar weed (Laminaria dentigera) and southern
palm kelp (Pterygophora californica) with limpet, gray moon sponge.

This document maintained by Dr. Bill Bushing.
Material and images © 2008 Star Thrower Educational Multimedia