Dive Dry with Dr. Bill

#159: Up in a Cloud of "Smoke"

A few weeks ago it was a glorious time in Catalina's underwater world. Warm currents and good visibility were the highlight. After "losing" my hooded Tilos dive vest somewhere on the streets of Avalon, I was thankful for what almost approached tropical conditions! And the marine life was putting on a good show, too. An encounter with a pair of courting black sea bass in the dive park, a trip to Italian Gardens with Scuba Luv to film at least seven black sea bass in clear water, and then a second dive off the boat at Garibaldi Reef with a number of harmless soupfin sharks. I'll write more about those experiences in future columns. Today I want to focus on mating... as my readers know, a subject near and dear to my heart.

Over the past few weeks I've observed and filmed small "mating swarms" of rock wrasse in the dive park. However, before rushing right in to describe their mating ritual, I'll refresh your memory about this interesting species. Rock wrasse are relatives of the sheephead and senorita, falling in between them size-wise reaching a maximum of about 15 inches. They go through a "change of life" similar to the sheephead. The young are green in color initially, then change to orange-brown with a thin white line along their sides. All are born female and when sexually mature (at 2 years and 5-6") they range in color from yellow to orange to dirty green to almost red in color with a yellow body, occasionally with several faint to dark bars along their side. These females exhibit the same characteristics as some of our own species- changing outfits frequently. Those that undergo the big "change" (about 5% of the population) turn into males with a dark vertical bar behind their gills.

Rock wrasse are diurnal meaning they are active during the day. At night they shelter like many wrasses here and in the tropics. Shortly after sunset they will hide themselves in clumps on algae along the bottom, arising shortly after sunrise. There are also reports of these fish burying themselves in the sand with only their heads showing. I guess this fish is just not interested in Catalina's night life!

These fish may be found along the rocky reef, in the kelp or out in the open on sandy bottoms. Their habitat preferences are broad, and largely determined by the search for that other essential in life... food. The entrees on their menu include bottom-dwelling snails, crustaceans like crabs, algae and encrusting forms like bryozoa. Although ichthyologists (fish biologists) have said they are not known to be habitual "cleaners" like their senorita relatives, I have observed them picking parasites and dead tissue off garibaldi, halfmoon and other fish. I have also observed them "shadowing" fish like the sheephead and rubberlip seaperch as those fish bottom feed. They will snap up small marine life that the larger fish overlook or stir up. I frequently observe them following divers whose fins are too close to the bottom. They look for food exposed by the diver's as they kick near the bottom.

While feeding, these fish are usually solitary. They may also have "dinner for two" (my preference!) and if a dive class is nearby, they may "swarm" in the dust created by the mostly bouyancy-challenged newbies. These "swarms" are merely casual aggregations driven by the possibility of food. The swarms I'm referring to today are the true mating swarms in which the search for food is abandoned and their only interest is passion. Mating occurs from June through September in this species (no cold winter nights cuddled in front of the fireplace for them).

Most of these swarms consisted of 6-12 males and 1-2 females. They are easy to detect since the "boys" were swimming with a purpose... driven by all those hormones coursing through their bodies just like our local Catalina youth at "Horny Corner." Their path was often somewhat erratic, making it difficult to follow and keep them within my viewfinder as I swam after them filming. Fortunately I didn't hit the reef or any large rocks while doing so. The females would largely determine where the love-struck males would go. Unlike our own species, only the females can read the road map.

Most of the swarms I filmed were still moving after my legs gave out. It is hard work kicking those fins like crazy as I tried to follow these lust-driven creatures of the deep (well down to about 130 feet). I achieved success with the last swarm I followed. I swam with them for a minute or two as they weaved in and out of the reef and through the kelp. Suddenly the swarm shot up vertically so quickly my camera couldn't follow them. I looked up and there was a white cloud where the fish had stopped briefly. One (or more likely several) of the fish had achieved their climax and the swarm broke up quickly. I was able to get some footage of the remnant cloud as it dispersed in the water. And that is all I can write about this interesting observation without risking the wrath of the censors!

© 2005 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. Buy my "Munching and Mating in the Macrocystis" DVD so you can take Dr. Bill home with you... we'll both be glad you did!

Female and male rock wrasse; mating swarm in motion and cloud of gametes.

This document maintained by Dr. Bill Bushing.
Material and images © 2005 Star Thrower Educational Multimedia