Ladies first: The manners of the California sheephead
A young lady sheephead on the move in Monterey.
Like many fish in the wrasse family, California sheephead (Semicossyphus pulcher) change genders as they age. All begin life as females and tragically/luckily become males later in life—depending on your perspective.
There are many reasons to change genders in the fish world. For sheephead, it’s a matter of how many offspring you can have—and size matters.
A big girl cruising off of Santa Rosa Island in the Channel Islands National Park.
Eggs are energetically expensive to make, and they take up a lot of room. Eventually, you could fertilize more eggs as a male than you could make as female—giving females an evolutionary incentive to cut their losses and make the switch.
As a result, sheephead change genders between 5 and 8 years of age if there isn’t enough food to get very big. When there is a lot of food—giving egg-making a longer shelf-life—females grow larger and make the switch as teenagers.
A large and in-charge male in the Channel Island—who is also a Giants fan, apparently.
Seeing large males is one of the great pleasures of diving in marine protected areas. By protecting their food, reserves help females—and the males they’ll become— grow larger. By protecting big males—which are the limited resource on the dating scene—sheephead are healthier genetically.
On your visit, you can find juvenile, adult female, and adult male sheephead in our kelp forest exhibits—and if you find our big boy, you can remember his life story with this little ditty:
There once was a little girl sheephead
Who recently her childhood completed
But one day on a date
She had outgrown her mate
So she became her own brother instead.
