Dive Dry with Dr. Bill

#581: Blacksmith Don't Get No Respect

I've stated several times that a key to understanding the ecology of our kelp forests, or any other ecosystem for that matter, often rests with the identification and understanding of the most common species in it. Usually they have the greatest impact on the system if only due to their high numbers. The exception to this is the top predators which are present in lower numbers but are important to ecosystem functioning. Of course many biologists and divers look for the rare critters, species like the beautiful California blue dorid (Felimare californiensis). They praise the beautiful but uncommon species, perhaps in the same way that a birder likes adding new but infrequently seen species to their life list like one possessed of the "collector mentality.". To me that is not the way to understand the communities we dive in.

Even I fall victim to this as I tend to write equally about all the hundreds of species I encounter whether they are present by the millions or seen in one dive out of a thousand. Today I thought I'd focus again on one of the true kelp forest commoners, the "lowly" blacksmith (Chromis punctipinnis). This fish is a cousin of the much revered state salt water fish, Gary the Garibaldi (Hypsypops rubicundus) which seems to get all the glory in the damsel family.

The poor blacksmith is the Rodney Dangerfield of the kelp forest. For those youngsters reading this, he's the actor in "Caddyshack" and "Back to School" that always always claimed he got no respect. Likewise the poor Chromis is picked on by many other denizens of the deep. During the day when they bunch together in sometimes humongous schools for safety, they are picked off by cormorants from above and larger fish from below. On my night dives when they are sheltering in the rocks for protection they are attacked and munched by kelp bass and morays, as well as by seals that often hunt them using the beam from a diver's light. Recently I even filmed two octopus capturing and eating them.

Blacksmith perform an important service to the biological community not just by providing an abundant source of food. During the day when they are schooling, they feed on the plankton in the surrounding waters by sucking the tiny critters up with their mouth. Then at night when they shelter in the rocks, they defecate (aka poop) and add nutrients to the reef that can be utilized by algae as fertilizer. This transport of nutrients is an interesting example of how matter and energy are cycled through an ecosystem.

Found from Monterey Bay to central Baja, these fish reach a maximum length of one foot but are usually a bit smaller. Their color is reported as gray to blue-gray with black spots, but I tend to see them as more blue with a touch of green. Of course I suffer from mild color blindness, but I can tell a red light from a green light (most of the time). The youngsters are more colorful with a blue-green front end and an orange to reddish rear.

Blacksmith are a diurnal species, exhibiting local movement on a daily cycle. While the sun is shining they are out in the open, munching away on the plankton. I've also seen them feeding on larger fare, including dead squid and even squid egg capsules. But at night when the demons (like me) come out, they are tucked into crevices and small caves in the rocky reef. Dr. Milton Love states that the larger fish may be bolder while the smaller ones stay closer to shelter.

These fish reach sexual maturity at about six inches. When the love bug strikes, usually from July through September, the male blacksmith clears a rock nest safely hidden deep in the reef. Once it is ready, he entices an egg-filled babe into the nest by nudging and biting her! Perhaps I should try that approach with the ladies? Her salmon-colored eggs are attached by small threads to the roof of the nest cavity and the male defends the nest from potential predators and keeps oxygen flowing to the youngsters by fanning his tail at the entrance. Yep, just like his cousin the garibaldi, he gets stuck with child care... often for the young from several females.

According to researchers, these males undergo a marked color change. They turn pale, becoming light gray to nearly white and develop two dark bands slightly above and behind the eye. I've wondered about this since I've seen this pattern during periods when they aren't supposed to be spawning. However, in all my years of diving, I have yet to see a single blacksmith nest or eggs. I really should head over to my optometrist so I can get prescription lenses for my dive mask. Who knows what glorious creatures I could write about if I could actually see!

© 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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Individual blacksmith sheltering in rocks at night and one with wound from predator;
schools of blacksmith feeding on plankton during the day.

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