The Chesapeake Bay blue crab, a tasty and valuable crustacean, is in big trouble. Populations are down 80 percent. Desperate to reverse the trend, scientists are hoping to boost populations by hatching thousands of baby crabs and releasing them into the bay. Such ranching or "stock enhancement" programs have drawn criticism in the past. Skeptics say they raise false hopes and do little to boost wild populations. But the ranchers say they have improved their practices.