Sometimes my mind just overlooks the obvious when I'm writing future columns for this paper. My current DVD project focuses on the generally tropical and subtropical family of fish known as wrasses. We have three representatives here in southern California's more temperate waters: the sheephead, rock wrasse and senorita. I looked back to see when I last wrote about the largest of these, the sheephead, and discovered it was my second column out of the nearly 300 in this series. Time to give the sheephead its due.
This wrasse species is found from Monterey Bay to Cabo San Lucas with an isolated population in the northern Sea of Cortez. However, it shows its subtropical affinities by being much more common south of Pt. Conception. These fish prefer rocky bottom habitats, especially where kelp forests are present, but can also be seen over sandy bottoms. Although they have been reported as deep as 300 feet, adults are rare below 180 and juveniles below 100.
Large males may live over 50 years, reaching lengths in excess of three feet and weights of 35 pounds or more. However most of the older individuals in our waters are 20-21 years and 18 inches in length. The Casino Point Dive Park is well known for a large dominant male, affectionately called Oscar. What most divers don't realize is there are actually four "Oscars" that may be seen in the park, although of slightly different sizes. I know, one day I filmed all four of them swimming in a line over Little Casino Reef. The "real" Oscar is missing his right front canine. Occasionally I scare him off by showing my own perfectly formed set of fangs!
Why are the big ones only male? Because all sheephead begin life as sexually immature "females" usually referred to as the juvenile phase. These youngsters are quite attractive with their bright red to orange color, white stripes running the length of the body and black spots on their fins. They retain this coloration to about four inches in length. They are able to reproduce at about 5-6 years and 8-12 inches in length. At this point, referred to as the initial phase, the females are a solid pinkish to reddish in color with a white chin. I have also observed them with an interesting mottled pattern while they are feeding or resting, but this disappears once they start swimming. I've also seen mature females with a broad white stripe along their sides.
Sheephead are sequential hermaphrodites, meaning they change genders as they age. Females become mature males at varying ages which depend on local food resources, water temperature and other environmental factors. The ratio of males-to-females and the size of the existing males in the population may also be factors. It was previously believed that only a percentage of the females turned into males. However, current thinking is that almost all of them will undergo the transition... if they live long enough. Males have dark gray to black head and tail regions with a pinkish to reddish band in the middle. Large ones have a prominent bump on their forehead.
Sheephead are among the top carnivores in kelp forest and rocky reef ecosystems. They feed on sea urchins, lobster, shrimp, crabs and various molluscs include snails and clams. Barnacles, worms, octopus, starfish and sea cucumbers may also be found on their menu. Females, and to a lesser extent males, are often seen digging for food over the sandy bottom. Males occasionally chase the females away after they've done the hard work, and take the prey for themselves. Most males are more considerate and seem to prefer hunting over the reef.
These large wrasses may be a major factor in regulating the population densities of prey species, especially sea urchins like the red and purple. In areas where sheephead are overfished, urchin densities may be very high, preventing giant kelp forests from re-establishing and thus creating large urchin barrens devoid of algae. Here in our waters, where sheephead densities are often much higher than the mainland, urchins are rarely a threat to the kelp. Most of them remain hidden deep in crevices and holes where the sheephead can't reach them easily.
One species, the black or Coronado urchin, has evolved to take advantage of the fact that sheephead are strictly diurnal, that is active only during daylight. As night approaches, the fish seek shelter holes and crevices where they rest until daylight returns. While the sheephead rest, black urchins come out of their protective holes and forage on the bottom nearby until daylight returns.
Sheephead are also occasional cleaners, picking parasites like copepods and isopods off other fish. I usually see them cleaning the huge giant sea bass. Of course they have to be careful not to get too close to the bass' mouth or they might become a meal themselves. Other potential carnivores include seals and sea lions, cormorants and our own bald eagles.
Large males hold territories which they defend against other males through highly ritualized combat known as "mouth fighting." Generally neither fish is hurt, but the loser scampers off leaving the victor the spoils that include food... and females. Just in case you ladies thought this was just a case of male hormones gone wild, the females and even juveniles engage in mouth fighting as well. In their case it is probably just practice for when they become "big boys."
Spawning occurs from June to September in our area. The lovely ladies gather in the male's territory about an hour before sunset. The male approaches each female, swims side-to-side with her and leads her off in circles. Yep, just like the Chi Chi Club. If smaller males attempt to court females, they are chased away by the dominant male. Females may spawn almost daily during season, releasing nearly 6,000 eggs per event. The eggs and resulting larvae drift in the plankton for about 40 to 80 days before settling out over reefs at about one inch in length. Those females that transition into males do so in winter following the spawning season.
Sheephead are "reef associated" fish. They generally stay close to the same reef for their entire lifetime. Therefore intensive fishing activity on one reef can radically alter their populations. Anglers initially did not consider sheephead a desired catch... until the populations of more preferred fish began to drop due to overfishing. Sheephead bones were common in the middens of Native Americans out on the Channel Islands, suggesting they fished for them with shell or stone hooks. Over the past decade fishing pressure on this species has increased, and greater restrictions were placed on their size and bag limit by the State. Much of the current take is for the live fish trade. Sheephead are sold live in Asian markets and restaurants where they are known as "the fish of good health," in part because they look and taste like a popular fish in China. Unfortunately this fishery targets sheephead before they even reach reproductive age and is not well regulated.
© 2008 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 "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," "Gentle Giants: Giant Sea Bass," "Common Fish and Invertebrates of the Sea of Cortez" or the new "Sharks and Rays of Southern California" DVD's. Yes, take Dr. Bill home with you... we'll both be glad you did!
Juvenile sheephead (courtesy of Scott Gietler), female, male showing bump
on forehead, and two males "mouth fighting" over territory.
This document maintained by
Dr. Bill Bushing.
Material and images © 2008 Star Thrower Educational Multimedia