Dive Dry with Dr. Bill

#211: Like a Rainbow... Scorpionfish

Although the Rolling Stones have been among my favorites ever since high school, the songs on Their Satanic Majesty's Request album (remember those... before CD?) were not on my all-time hit list. However, the lyric above from "She's a Rainbow" makes for a suitable introduction to the species I have chosen this week... the rainbow scorpionfish. Although a variety of colors can be seen on this species, the red end of the spectrum certainly dominates for reasons I'll clarify if you read on!

The first time I remember seeing this species was probably in the "nooks and crannies" of the Casino Point breakwater. It usually is a fairly cryptic critter, preferring to hide away during the day when its bright colors make it more obvious to potential predators. They also spook easily when my regulator emits bubbles as I breathe, or when I turn on my video light to capture their colors. At first I thought this was a red color phase of the more common spotted or California scorpionfish. Later another diver said she thought it was the vermilion rockfish. However, I have confirmed (by the dark spot on its gill cover) that it is indeed the rainbow scorpionfish.

Dr. Milton Love of UCSB confirms that there is a red phase of the California scorpionfish. However, it appears to lack the dark spot on the gill cover of this closely related species which Dr. Love didn't even cover in his "Probably More Than You Want to Know About the Fishes of the Pacific Coast." I did additional Internet research to confirm that the rainbow scorpionfish is still recognized as a distinct species, and has been since the 1880's.

This species may be found from southern California to Peru and the Galapagos. However, it is considered rare to uncommon in the waters of our region. Despite this, I do run into them with some frequency at various Catalina dive sites. Their depth preferences appear to be from 20 to 60 feet, although they may extend their range to a maximum of 100 feet. Rainbow scorpionfish prefer rock overhangs, crevices and holes in rocky reefs, or walls and other steeply sloping hard bottom types. Paul Humann's excellent fish guide lists their maximum size as 6" but I have seen individuals somewhat larger than that in our waters... and not because of the magnification commonly experienced underwater, or nitrogen narcosis since they are at fairly shallow depths!

Most scorpionfish remain sedentary or hidden during the day. They may function as ambush predators, waiting for an unsuspecting tasty morsel to venture too close and then... bam! At night they leave their shelters to feed on large zooplankton, small fish and crustaceans. Like many scorpionfish, this species relies on two primary strategies for defense: camouflage and toxic dorsal spines. Their red color makes them harder to see in dark recesses. They can also change color somewhat to more closely match their background. When they venture out at night to feed, the red color makes them almost invisible since there is very little red light at water depths greater than 15 feet (especially at night!). The poisonous dorsal spines can give an unsuspecting predator, or diver, a painful wound if they penetrate the skin.

Over the summer I have encountered a number of rainbow rockfish paired off and hiding together in their rock crevices. I have never seen any significant interaction between these pairs. It appears they also prefer to remain a bit cryptic as far as their mating is concerned. Whatever weird sex rituals they may indulge in, the young larvae are planktonic and drift with the currents. Like many marine species, this allows them to "see the world" and escape from Mom & Dad and the old hometown ("it's boring here") to colonize new habitats and mix up the gene pool a bit.

The extremely warm waters this summer may have increased the number of rainbow scorpionfish in our waters. They are known to expand their range further north during El Nino and other warm water events. Dr. Jack Engle of The Tatman Foundation reported their numbers in the colder northern Channel Islands increased during previous El Ninos. I have also seen these fish and other marine life like octopuses and lobster coming out of their hiding places to rest or wander out in the open during the day. Although I haven't scientifically tested this hypothesis, warm water contains less oxygen so these species may be out in the open to ensure more water flow past their gills despite the increased potential for being "munched." I guess "breathing" really must assume some priority over "munching" and "mating" at times, unless the latter (or getting into hot water) takes your breath away!

© 2006 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. Please help me climb out of self-imposed poverty... buy my "Munching and Mating in the Macrocystis," "Great White Sharks of Guadalupe," "Calimari Concupiscence: Mating Squid, " "Playful Pinnipeds: California Sea Lions," "Belize It or Not: Western Caribbean Invertebrates, Fish and Turtles" or "Gentle Giants: Giant Sea Bass" DVD's. Yes, take Dr. Bill home with you... we'll both be glad you did!

Rainbow scorpionfish in hiding place, resting nearly upside-down;
pair hiding in rock crevices and individual out in the open.

This document maintained by Dr. Bill Bushing.
Material and images © 2006 Star Thrower Educational Multimedia