The federal government says that two endangered whales have been spotted entangled in fishing gear off Massachusetts and that one is likely to die from its injuries. The whales are North Atlantic right whales. They number less than 400 and face existential threats from entanglement in gear and collisions with ships. The National Oceanic and Atmospheric Administration said Tuesday that an aerial survey found the whales swimming about 50 miles southeast of Nantucket on Dec. 9. NOAA said it would work with responders to see whether the whales can be assisted.