Dive Dry with Dr. Bill

051: Blacksmith

Face it... our waters are considered cold, or cool at best, by divers and swimmers. The ocean off California is not meant for sissies and wimps who need bath water or hot tub conditions to get wet. We are real men and women. I am always disappointed when I meet a diver who says they can't dive kelp forests because it's too cold. Of course if she wants to dive in the tropics during our winter, I won't complain!

There are some members of normally tropical fish families that seem to have adjusted just fine to our waters. We are all familiar with the beautiful orange garibaldi, a member of the normally tropical and subtropical damselfish. It has adopted our waters and eventually became our state's salt water fish, a pretty impressive accomplishment for a "foreigner." However, it is not the only damsel found in our waters. Its relative the blacksmith is one of the most common species found in our Dive Park.

Adult blacksmith aren't as colorful as their orange relatives. They are bluish to grayish with small, dark spots on their fins and rear end. Only the young blacksmith live up to their colorful family reputation. These juvenile fish (less than 2") are blue-gray in front and a brassy orange on the rear. Unlike the garibaldi, which can be very aggressive towards other garibaldis especially when driving other males away from the nest, the blacksmith is a schooling species.

Blacksmith can be found from Monterey Bay to central Baja California. Of course true to their warmer water relatives, they are more common south of Pt. Conception. Here they may form very large schools close to shore in depths to 150 feet. While the older individuals form large schools feeding on plankton, younger ones are often closer to the bottom where the rocks may offer protection.

Although larger individuals may be a foot long, they are sexually mature at half that size. Blacksmith mate in summer and early fall, releasing their eggs to drift in the plankton. The young larvae often remain in open water up to 100 miles offshore, but eventually end up settling close to shore. Schools of the beautifully colored young fish are a joy to see in the late summer.

Blacksmith can often be seen in groups in crevices and caves among the rocks. Frequently these fish show signs of injury or disease. Dr. Milton Love and his associates identified a bacterium called Vibrio damsella (who gives bacteria a common name?) that causes open sores on their bodies. Blacksmith are especially susceptible to this infection in the late spring. Dr. Love reports seeing hundreds of dead blacksmith on the bottom off Catalina due to this disease.

Although most blacksmith remain in the open during the day, almost all seek hiding places at night to avoid predators like the harbor seal and sea lion. Years ago a scientific study showed that these fish are important to algae on the rocky bottom since they provide "fertilizer." The plankton they eat during the day are converted to nutrients which they excrete in the rocky crevices and caves at night. No need for Bandini here! Due to their large numbers, this can be an important mechanism for providing what the seaweeds need to grow.

Like garibaldi, the male blacksmith prepares a nest site in caves or on rocky overhangs and guards it. These males are often much lighter in color, a very light gray. They also guard the eggs until they hatch and enter the plankton as young larvae. ** Blacksmith form interesting aggregations when a cleaner like the senorita is nearby. Often many such "balls" of fish can be seen throughout the water when visibility is good. The blacksmith will rest head down in the water column when they want to be cleaned. The senorita will then selectively pick parasites or scales off them. Usually these balls get so large (dozens of fish) and the blacksmith so persistent that they chase the senorita away, defeating the original purpose.

While underwater in the Dive Park I have often observed large schools of many thousand adults moving quickly through the water column. Sometimes they swim like jet planes dodging an enemy, and one can usually see large kelp bass, a cormorant or a marine mammal swimming after them. In addition to these predators, moray eels feed on them when they shelter in the rocks and bald eagles take them along Catalina's coast. At other times these fast moving schools are very focused and directed as if swimming to a specific location. I have yet to figure out the reason for this behavior. It looks like a dinner bell rang somewhere.

© 2003 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.

Image caption: Adult blacksmith; juvenile blacksmith; blacksmoth feeding on plankton; large
school of plankton; injured blacksmith sheltering in rocks; blacksmith being
cleaned by senorita

This document maintained by Dr. Bill Bushing.
Material © 2003 Star Thrower Educational Multimedia