Tag Archives: Sheephead

Sheephead Transformation

Ever seen a fish cake before? This one might look a little unusual. It’s one of the most exciting fish to find on a snorkel (or as your birthday cake), called the California sheephead (Semicossyphus pulcher). Sheepheads can grow to be over thirty five pounds and a full three feet long. They can live over 30 years and they play an important role in marine ecosystems by eating sea urchins that might otherwise eat all the kelp.  However, their lifecycle is the reason why sheepheads often take the cake as most interesting fish. If you’re looking for a fish to satisfy your intellectual hunger, check out the California sheephead!

Sheepheads are all protogynous hermaphrodites, meaning they all start out female with the potential to morph into a male later on in life. When they hatch, juvenile sheepheads have bright red bodies with a white stripe across their body and black splotches on their fins. As they grow, the white stripe fades and the fins lose the black spots, becoming entirely red while their lower jaw turns white. A sheephead can have vivid colors like bright red or more subdued tones such as a pale pink. After growing from anywhere from six to twelve years, a sheephead can finally change into a male!

The change from male to female varies between individual fish. Usually a female can morph into a male when there are no other males living nearby (or not enough males) and she is the most dominant of the females in the area. Dominance can be established by big mouth competitions – two sheepheads will swim at each other while opening their mouths as wide as possible, sometimes even locking jaws. However, other factors can influence whether or not this change occurs, including where the sheephead lives, how large she is, how quickly she grows, when she matured, and the amount of fishing in the area. Sometimes, slower growing females will never change.  

If a female successfully starts morphing into a male, it’s no cakewalk. There are a couple changes she’ll experience. Her body colors adjust: her torso remains red but her caudal fin (tail fin) and head turn black, except for the chin. Talk about a five o’clock shadow! The fish also grows a large hump on the forehead. Finally, the sheephead’s reproductive organs change due to changing hormones. The ovaries reabsorb any eggs inside while transforming into testicular tissue. Then, the newly male sheephead can claim his own territory and begin life as a male!


Hamilton, Scott L., Jennifer E. Caselle, Julie D. Standish, Donna M. Schroeder, Milton S. Love, Jorge A. Rosales-Casian, Oscar Sosa-Nishizaki, 2007. Size-Selective Harvesting Alters Life Histories of a Temperate Sex-Changing Fish. Ecological Applications, 17(8), 2268-2280.

Loke-Smith, Kerri A., 2007. 15 California sheephead, Semicossyphus pulcher. Status of the Fisheries Report, 2011.

Love Milton.

Warner, Robert B., 1975. The Reproductive Biology of the Protogynous Hermaphrodite Pimelometopon pulchrum (Pisces: Labridae). Fishery Bulletin 73(2).

Mucus in the Animal Kingdom

Boogers. There. I said it. Now you are all thinking about thoseooey gooey slimy’s that drip from our noses when we are sick. But our bodies produce mucus every day—it helps protect our lungs by capturing dust and dirt when we inhale. Mucus production ins’t only a human process, however. Lots of different animals produce mucus for a variety of different reasons. Take these Catalina ocean dwellers, for instance:

California Sheephead

Mucus sheephead

At night this fish may produce a mucus cocoon around its body. This inhibits predators from using their sense of smell to find these fish while they are resting.

For more on this species: https://www.montereybayaquarium.org/animal-guide/fishes/california-sheephead

Sea Hare

mucus sea hare

As a defense the sea hare can produce a purple ink and something called opaline. This slimy, sticky secretion was studied a few years ago. It is believed to interfere with a predator’s ability to taste and smell.

For more on this species: https://blogs.scientificamerican.com/running-ponies/sea-hares-thwart-spiny-lobster-attack-with-goo/

Pacific Hagfish


The slimiest of them all. Pacific hagfish create slime as a defense against predators. Their slippery bodies allow them to flee from the mouths of predators and slip into tiny crevices.

For more on this species: https://news.nationalgeographic.com/2017/03/hagfish-oceans-slime-deep-weird/


Keystone Species: Guardians of Ecosystems

The keystone of an arch is the center stone that holds the whole structure together. If that one stone is shifted, the entire archway will no longer be able to hold its shape. Similarly, a keystone species is a species that plays a very influential role in maintaining the balance of an ecosystem. If it is taken out of its environment, the ecosystem it leaves behind will take on a drastically different structure.

Still 1

A common example of a keystone species in the Pacific Northwest is the sea otter. Sea otters are marine mammals that feed on sea urchins, crabs, abalone, and other shelled animals. Because a sea urchin’s favorite foods are kelp holdfasts and other algae, it is important for their population levels to be regulated so overgrazing does not occur. As the primary predator of sea urchins, sea otters ensure that urchin population levels never get too high. However, sea otters have faced several obstacles to their survival over the years. Overhunting in the 1800s completely wiped out otter populations in Southern California, and today Northern California otters continue to face threats from fishing practices, pollution, and predatory changes. As sea otter populations continue to decrease in some areas, “urchin barrens” have been found dotting parts of the ocean floor. These are created when urchin populations get too high and start to eat every piece of algae in sight, taking down whole kelp forests in their search for more food. Without the kelp to hide in and feed on, fish move on to other places, leaving only a barren wasteland of hungry urchins behind. The habitat collapses when the sea otter is not there to maintain its healthy balance.

Still 2

The California Sheephead is a keystone species that stops urchin barrens from happening in the waters around Catalina. Just like otters, Sheephead’s love to feed on those algae-loving echinoderms. Their sharp teeth are perfectly suited to breaking through the urchin’s spines and hard exoskeleton. However, also like otters, the California Sheephead faces its own set of challenges for survival. Commercial and recreational fishing have given it a vulnerable population status, which has led to higher restrictions being placed in recent years on the size and amount of the fish that can be taken. Due to the important role it plays in Catalina’s ocean ecosystem, we can only hope that the California Sheephead continues to thrive in these waters for many years to come.


Sheephead are Protogynous Hermaphrodies

Hermaphrodites are animals that start out as one sex and switches to the opposite sex at a point in their life. This process is called sequential hermaphroditism, differing from simultaneously hermaphroditism in which the animals can produce sperm and eggs at the same time. Protogynous hermaphroditism is the change in gender from a female to a male over some time. Protogyny is the most common form of hermaphroditism in which 75% of all sequentially hermaphroditic fish change to male in their lifespan.

female 1

Wrasses are a common fish species of protogynous hermaphroditism, which belong to the Labridae family. The California sheephead, a type of wrasse, is an excellent example, born a female with light pink coloration and turning into a male after about 4-6 years. Male sheephead have two black stripes on the head and tail with bright red in the middle of their body. The ovaries degenerate and sperm appears in the gonads.


California sheephead form a harem of one large male and multiple smaller females. The primary role of the male is defending its territory against other males and to fertilize females in its territory. If the male dies whether being fished or natural causes, a female in the harem will undergo a sex change and can take anywhere from five days to two weeks transforming to a male. The new male will take the responsibilities of the previous male.

California Sheephead

California Sheephead – Semicossyphus pulcher

Maximum length: 36in
Maximum Weight: 40.4 lb

Although sheephead are known to eat sea urchins, our female sheephead prefers shore crabs. It is known that all sheephead are born females and later on become males.  This is referred to as protogynous hermaphroditism. In an unhealthy population of sheephead, it is believed that the change is triggered by a social behavior between two females comparing mouth size. The larger-mouthed female will turn to a male. In a healthy population of sheephead, females off of Catalina Island will automatically turn male at age 6.

Adult Male Sheephead by Desmond Ho

Messages Image(1096895216)

Sheephead are one of the few animals around Catalina Island that exhibit multiple growth patters. Juveniles will appear orange, gold, salmon or lemon-yellow with a white strip down it’s side and two black dots on the dorsal fins, one on each anal and pectoral fin and caudal peduncle. Mature females are pink with a white chin. Mature males are pink in the mid section and have a black caudal and head section with a white chin.

Female Sheephead by Desmond Ho

Messages Image(300185263)

Juvenile Sheephead by Michal Ross

Messages Image(637728021)


We would like to thank you for visiting our blog. Catalina Island Marine Institute is a hands-on marine science program with an emphasis on ocean exploration. Our classes and activities are designed to inspire students toward future success in their academic and personal pursuits. This blog is intended to provide you with up-to-date news and information about our camp programs, as well as current science and ocean happenings. This blog has been created by our staff who have at least a Bachelors Degree usually in marine science or related subjects. We encourage you to also follow us on Facebook, Instagram, Google+, Twitter, and Vine to see even more of our interesting science and ocean information. Feel free to leave comments, questions, or share our blog with others. Please visit www.cimi.org for additional information. Happy Reading!