Fr T.J. Linane, From Abel to Zundolovich, Vol. 2: Biographies of Priests on the Australian Scene up to 1900, 1980, p 32:
Castagnier, Pierre Marie, SM, French, Visitor
Golden Jubilarian Among Marist Fathers
Actually he was a 'passer-by' to the Australian scene in 1858, and perhaps on other occasions, when he was on his way to missionary work in the Pacific. Father John Hosie S.M., Marist historian, supplies the following essential details: Born 14 December 1820 in the Nimes Diocese; professed on 18 June 1853. Died on 3 July 1910 at the age of 89. Directories place him at Vavau, Vicariate of Central Oceania
(1886), (1899), Tonga (1893) (1898), Vavau (1904). After the last-named year he fades from the missionary scene, so probably he returned to the homeland scene.
(Footprints, Vol. 2, No. 3)
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Fr. Michael Fitzgerald, SM and Fr. François Grossin, SM, Alive in Memory: A Biographic Necrology of Oceania Marist Province 1836-2011, 4th edition, Suva, 2011, pp 146, 295:
Fr. Pierre Castagnier, d. 1910
Tonga
He was born in Gard, France in 1830. He was professed a Marist in 1853. He left for Tonga in 1857, at the age of 27. After a year in Mu'a, he was sent to found the mission in Vava'u. After 5 years he had a small group of 100 Catholics. He then went to Mu'a for 7 years and to Hihifo for 10 years before returning to replace Fr. Breton on Vava'u. He wrote a Bible History and a History of the Church in the Tongan language. His last 30 years were spent at Vava'u, where he built a fine church and gradually built up the Catholic community. He died there, aged 80 after 57 years of Marist life.