HMCS Mastodon was built by W. Simons & Co. Ltd. Renfrew, UK in 1910 as a Bucket Dredge under Canadian Registry 129529. She was a steel hull measuring 200.3′ x 36.6′ x 12.8′ with a tonnage of 748. She was powered by a 145nhp compound steam engine of the builder’s brand. She was owned and operated by the Department of Public Works, Ottawa as ‘No. 508’ and later as ‘D.P.W. Dredge No. 306’.
She was involved in dredging the entrance into Vancouver 1912-1917 including removing the Parthia Shoal. On Jan 28, 1913 she was dredging outside Vancouver harbor with the barge tender ‘Point Ellice’ alongside in heavy fog. CPR steamship ‘Princess Charlotte’ was in a collision with Mastodon and the Point Ellice. It is reported that the steamship lost some paint but the tug and the dredge were reported to be quite battered. In 1918 she was sent to dredge the harbor at Port Alberni and the Fraser River. In 1925 she was laid up due to the depression. There is no indication of when she returned to active dredging.
In 1942 she was converted to a tanker and commissioned on 09 Dec 1942 as HMCS MASTODON, a Canadian Naval Tanker Auxiliary and was in service with the Canadian Navy form 1942-1946. She worked transporting oil from refineries in the Lower mainland area to northern ports on the west coast throughout her war service. On July 4, 1947 she was sold and transferred to Peruvian Registry.