This parasite is Parafilaroides gymnurus. They are found in the lungs of seals and can cause bronchopnemonia and even death. Pictured below are the parafilaroides found during a necropsy at NMLC.
Gosselin, J.F., Measures, L, (1997) Redescription of Filaroides (Parafilaroides) gymnurus (Raleigh, 1899) (Nematoda: Metastrongyloidea) with comments on other species in pinnipeds. Canadian Journal of Zoology 75: 359-370