In true whodunit style, there are many suspects in the puzzling deaths of sea otters up and down the California coast, but, as yet, no clear solution to the mystery. By yesterday, 44 dead sea otters had washed ashore from San Francisco to Santa Barbara, well above the 10-year high for the month of April of 29 deaths, and the high for any month of 34. This month's deceased sea otters brought to 91 the total death toll since Jan. 1 of this year. Possible culprits include parasites, boating accidents, a shortage of sea urchins and abalone (staples of the …