Dive Dry with Dr. Bill

#372: "Black is Black..." But Not Usually

Way back in the 60s, that era I can barely remember, a group known as Los Bravos sang the song "Black is black." However, the subject of today's column proves that is not always true! In fact, the black perch (Embiotoca jacksoni) is usually anything but black. Individuals I've observed in the Dive Park may be shades of brown, red, reddish-brown, orange, gray, silver, green or greenish brown. They can even change color, mostly to camouflage against their backgrounds.

Black perch have somewhat pronounced lips although not as prominent as their surfperch relative, the rubberlip seaperch. The lips may be orange or yellow to reddish brown. Distinctive features include a thin blue bar along the base of the anal fin, a patch of large scales between the pectoral and pelvic fins, and about nine dusky bars on the side of the body. They may live to a whopping nine or ten years old with a maximum reported size of 15 1/2 inches, and weight up to 4 1/2 pounds.

These surfperch are found from Fort Bragg to central Baja California, Mexico, but are most common from San Francisco south. They frequent rocky reefs and kelp forests, but may also be found over sandy bottoms, near piers and in estuaries. Black perch tend to stay within about three feet of the bottom. I guess they know the same trick I use to prevent attacks from great whites... neither of our predators can bury into the sand and attack from below! Although they have been taken from tidepools down to 165 feet, they usually frequent shallower depths to about 80 feet.

Feeding occurs during daylight and prey includes bottom-dwelling organisms like amphipods, crabs, brittle stars and worms. They show a strong preference for the amphipods which live in small tubes. Sounds simply delicious... not! Black perch usually feed over hard bottoms like rocky reefs but may also forage over sandy bottoms. Along with a few other surfperch, they utilize a feeding technique known as "winnowing." They usually feed over algal turf, the matrix of algae, inorganic matter and invertebrates that grows on top of rocks and occasionally soft bottoms. The fish takes in a mouthful of the turf, uses its throat muscles to sort out the prey items, swallows them and then spits out the non-nutritive debris, algae and non-edible critters.

This species is usually solitary, but may occur in small groups and even schools of 100 to 200 individuals on occasion. Both males and females are sexually mature at 1-2 years and about six inches in length. Spawning is believed to happen mostly in spring here in southern California, but possibly year-round. In cooler central California, it is delayed until waters warm up in late summer-early fall. The surfperch family's scientific name Ebiotocidae comes from Greek words meaning "offspring living within." When Harvard biologist Louis Agassiz first described this fish family in a 1853 publication entitled "Extraordinary fishes from California, constituting a new family," he was fascinated by the fact they gave birth to live young since this is a rarity among fish. Animals which give live birth are referred to as viviparous as opposed to those that cast eggs into the water which are known as oviparous.

During courtship the male performs a dance. Sometimes we human males try this although often without much success as we step on the toes of our ladies. Of course female black perch have no ties, just fins. The male rubberlip approaches the female from below, usually with its head pointing down towards the bottom. The swim together for a few seconds, then separate. Apparent this dance is repeated as often as necessary... either for the female to accept the male, or to just swim away and ignore him as so many (human ladies, not black perch) have done with me.

Because they are live bearing fish, black perch need to achieve internal fertilization. Most fish simply cast their sperm and eggs into the water column and pray for fertilization. Their reproductive style more closely approaches Las Vegas casino gambling. Male black perch accomplish this thanks to a "nipple" or bump that develops as a thickening in front of the male's anal fin. Since female black perch do not suckle their young, they lack structures with this name. One study found that the black perch was somewhat modest, retiring into caves to copulate in private.

The female may store the male's milt as long as six months before fertilization actually occurs. The developing embryos are carried internally for about a year. It is said a female may give birth to as many as 31 young measuring 2-2 1/2 inches with the number varying according to her age and size. However, their reputation for modesty was ruined when another study discovered that a single brood within the female may be fathered by as many as nine different males. Absolutely shameless!

Fish that cast their eggs and sperm into the water column usually possess eggs and larvae that drift in the ocean currents with the plankton. This allows the species to disperse over sometimes quite long distances. Because the surfperch bear live young, they do not possess a dispersal stage. This affects their ability to colonize new habitats and therefore their biogeographical distribution. For example, some species from the adjacent mainland are not found on the Channel Islands. I have found live-bearing surfperch associated with drifting kelp, so it is possible some members of this family colonized Catalina waters this way.

© 2010 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 and on Charter Communications Cable channel 33 at 7:30 PM on Tuesdays in the Riverside/Norco area. 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!

To return to the list of ALL of Dr. Bill's "Dive Dry" newspaper columns, click here.

Black perch with males courting females

This document maintained by Dr. Bill Bushing.
Material and images © 2010 Star Thrower Educational Multimedia