Blue Zoo: California Sheephead
Featuring one amazing marine animal per week.
California sheephead (Semicossyphus pulcher) are a fish species with an interesting life history. It starts out simply enough with the adult males and females spawning to produce larvae. The larvae grow and become juvenile fish. They are a reddish color with a white stripe and black spots on their fins, as in the photo below.
A juvenile California sheephead. Photo by Ed Bierman via Flickr, Creative Commons License.
A juvenile grows larger and matures, turning an all-over orange or pink color. These pink fish are all females. It may sound impossible – or at least seem impractical – but all juvenile sheephead grow up to be females! Then, later in life, some of those females transform into males! This makes them protogynous hermaphrodites; that means an individual animal is both sexes, but not both at the same time, and it starts with female. This isn't limited to the California sheephead - sex changes are common in many species of wrasses.
Females are pale pink or orange in color. All juveniles grow into females. Photo by Ed Bierman via Flickr, Creative Commons License.
It’s still not fully understood what factors determine if and when a female changes into a male. Usually the largest and most dominant females are the ones to change. It probably is also determined by the existing sex ratio in the population and the environmental conditions, like how much food is available. When a female switches to male, it develops much brighter and more distinctive colors. The secondary males usually have a black head and tail with a middle band of bright red. They also grow a large hump on their heads. Males can grow up to three feet (90 cm) long and 36 lbs (16 kg). Individuals have been found to be 50 years old.
Males have bolder colors. When a female becomes a male it develops a different color pattern and grows a bump on its head. Photo by Magnus Kjaergaard via Wikimedia Commons, Creative Commons License.
All of the adult California sheephead (males and females) have large teeth and strong jaws. This allows them to prey on animals with hard shells such as snails, crabs, and even sea urchins. They live in kelp forests from central California down to Baja California and they hunt during the day. At night, they hide in rocky crevasses and caves to avoid predators; sheephead can wrap their bodies in mucus so that predators are unable to smell them while they sleep.
Large teeth help them eat prey with hard shells. Photo by Tomás Castelazo via Wikimedia Commons, Creative Commons License.
The California Department of Fish and Game established fishing regulations to protect sheephead in 2001 because a commercial fishery had developed since the 1980s. Before then they were not typically a popular target. The first stock assessment was completed in 2004 and are continuing assessments to determine the California sheephead’s status and safe levels for harvest.
Male California sheephead. Photo by Ed Bierman via Flickr, Creative Commons License.