California's sea otters have struggled for years with diseases, parasites and even the occasional collision with boats. But now the fuzzy coastal mascots are increasingly facing another threat: shark attacks. It's difficult to say that white shark numbers are increasing. Last year, the first comprehensive study of the number of white sharks off the California coast estimated there are 219, fewer than previously thought. Block said other species of sharks, including sevengills and makos, might also be attacking otters. She said having a population of large predators is healthy for any ecosystem, and that more research is needed before...