[1] In October 1939, he joined the Australian Army and fought overseas during the Second World War, serving with the 7th Division, 2/5th Field Artillery Regiment, first in North Africa and the Middle East and then in New Guinea.
[1][2] His first work was a study of Australian bass (Macquaria novemaculeata) in the Maroochy and Noosa rivers, and he was the first to show that this species was catadromous.
[1][2] In the 1960s, he completed the first official stocking of Australian native fish, releasing southern saratoga (Scleropages leichardti) into Borumba Dam on the Sunshine Coast.
In 1975, Midgley was elected to the American Institute of Fishery Research Biologists, and was granted Emeritus status in 1992.
[1] In 1994, he received an Honorary Doctorate of Science from the University of Queensland for his contributions to freshwater fish research.