Marine scientists weren’t successful yesterday in freeing an endangered northern right whale off Cape Cod from a fishing line caught in its jaw. The jaw has become infected and the 50-ton whale also seems to be malnourished, probably because the line is interfering with its feeding. The scientists didn’t know if they’d be able to mount another rescue effort and weren’t sure the whale would survive, even if the rope were removed. Only about 320 of the whales remain in the North Atlantic. “Every whale counts,” said Nina Young of the Ocean Conservancy.