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Dive Dry with Dr. Bill

#607: Don't Get Trigger Happy

My recent columns have focused on some of the warm water subtropical and tropical critters that have entered Catalina's cooler temperate waters during El Ninos and other warming events. If the waters in our "quarter-sphere" (the intersection of the northern and western hemispheres for the geometrically challenged) continue to warm due to global climate change, we may see a host of new species enter and a few of our good friends leave the waters off Catalina. Get ready to dive coral reefs... well, maybe not in my lifetime.

In ecological circles we scientists refer to the "establishment" of a species in a new area. Some enter our waters as microscopic larvae from other locations when currents carry them here. Others may arrive by "drifting," attached to kelp, logs or even an old jacket or plastic bottle as I discovered during my research on dispersal in the 1970s at the old Toyon School. Some arrive through their own powers as adults able to swim. Moving from one area to another is referred to as dispersal and is step number one in colonizing a new location.

My readers all know my obsession with "Munching" and "Mating." No, not me personally (yeah, right Dr. Bill)... our marine life! A species which enters a new region for the first time must be able to tolerate its temperate range and other conditions as well as find food suitable to its tastes. This is ecological establishment. If it is to persist in the new location, it must be able to mate and produce offspring. This critical function may require a warmer temperature range than that which they can merely survive in. Of course humans can mate under colder temperatures by cuddling under the electric blankets in their igloos. If critters are able to create kiddies in the new region, they become reproductively established.

Another example of a species which has entered our waters in prior years from the south is the finescale triggerfish (Balistes polylepis). Actually I was shocked when I read in Dr. Milton Love's incredible fish guide that this species has been observed as far north as Metlakatla, Alaska! It is fairly rare in southern California and can be found south to Chile and out to Hawaii. During a prior El Nino event in 1982-84, they became fairly common in southern California although their numbers declined since then. Here on the island most of the sightings are in Lover's Cove where they are protected due to the Cove's status as a Marine Protected Area (MPA).

Most of my encounters with this species were during the early part of the last decade when I worked as a marine biologist and underwater videographer on Lindblad/National Geographic eco-cruise ships in the Sea of Cortez based out of La Paz. The ones there are bigger than those I see in our waters and may reach a length of 32 inches and weigh up to 16 pounds.

Triggers get their name from their sharp dorsal spine. This serves at least two purposes. One, it makes them less desirable for a predator to eat. More commonly it allows them to erect the spine against the rocks when they wiggle into a crevice at night and secures them in a safe place for their evening rest.

Triggers feed on a variety of munchables. These include snails and clam-like critters, crusty crustaceans including crabs and possibly young lobster, echinoderms such as sea urchins and starfish, sponges, worms and the occasional fish. They have parrot-like beaks that can crush hard-shelled critters. While feeding over sand, they often expel a jet of water through their mouth to expose invertebrates burrowed under the surface. Predators include striped marlin (in Lover's Cove?) and California sea lions.

While diving in Tahiti years ago, I came to realize why the natives there fear triggerfish more than sharks. Not one of the 50 or more sharks of four different species tried to take a bite out of me while diving the reef passes. However, I made the mistake of entering the inverted defense cone above the nest of a triggerfish in a depression on the bottom 30 feet below me. The trigger swam up to me and tried to take a chunk out of my ample German thighs! I had to fight it off by kicking and swimming backwards until I was outside the cone it defended.

SCICo Port Captain Renzo Sampson tells me that he has seen depressions in the sand in Lover's Cove with our finescale triggerfish sticking close to them. If so, this may confirm that these fish have not only become ecologically established but also reproductively established in our waters. Heck, what fun would it be if all you could do is munch, but not mate?

If the finescale trigger does not mate here, their continued presence suggests we see infrequent pulses of their larvae coming into our waters from the south to replenish the earlier "colonists" as they age. Young triggers will also drift with floating objects including kelp rafts so they could arrive as miniatures of their parents instead of as larvae. Once the fish reach adulthood, triggers tend to remain close to home... letting their youngsters travel the world.

Way down in Mexico (as sung by James Taylor), finescale triggers are the target of a commercial fishery. I recently learned that a local resident speared one in our waters and ate it. Since they are fairly rare here (and are completely protected in Lover's Cove), I'd like to ask that spearos focus their guns on more common and tasty species like kelp bass. Those darned bass have been ruining my attempts to video the night life in the dive park and I have yet to get good local video of the triggers here!

© 2014 Dr. Bill Bushing. Watch the "Dive Dry with Dr. Bill" underwater videos on Catalina Cable TV channel 29, 10:00 AM weekdays and on Charter Communications Cable channel 33 at 7:30 PM on Tuesdays in the Riverside/Norco area. You can also watch these episodes in iPod format on YouTube through my channel there (drbillbushing). 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!

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Finescale triggerfish filmed off La Paz in the Sea of Cortez.

This document maintained by Dr. Bill Bushing.
Material and images © 2014 Star Thrower Educational Multimedia