For sex-changing fish, size matters in urchin battle

A sex-changing California fish is growing bigger and gobbling up more sea urchins after a decade of being protected from fishing, a new study finds.   In the Channel Islands offshore Southern California, the sheephead fish population has bounced back from overfishing since marine protected areas were established around the islands in 2002. Biologists are finding more large males and more egg-producing (larger) females.   And the bigger fish have bigger mouths, which is all the better for breakfasting on the rampant, kelp-destroying populations of sea urchins in the region. An 8-inch sheephead fish has a diet that is only 2 percent urchin, whereas an 18-inch sheephead munches on so many urchins that they make up 30 to 40 percent of its diet, according to the study, published Dec. 10 in the journal Proceedings of the Royal Society B.   “Sheephead are very important players in the kelp forest,” study co-author Jenn Caselle, a biologist at the University of California, Santa Barbara, said in a statement. “By keeping urchins in check, they maintain healthy kelp, which, in turn, provides habitat for many, many other species.”…MORE