[1][2] In August 1945, Shimada moved to U.S. Army Air Forces headquarters in Tokyo to take part in the occupation of Japan.

He collected and synthesized economic and infrastructure data on the effects of the strategic bombing of Japan until he was discharged from the military in February 1946.

[1][2] Remaining in Japan, Shimada accepted a civilian position as a fisheries biologist in the Natural Resources Section on the staff of the Supreme Commander for the Allied Powers (SCAP).

After graduating cum laude on December 20, 1947, and receiving his bachelor's degree, he remained at the School of Fisheries to pursue postgraduate studies, during which he worked as a laboratory assistant maintaining aquaculture facilities for the Atomic Energy Commission.

[4][5] Under Sette's guidance, Shimada worked with many accomplished fisheries scientists and oceanographers while at POFI, including Wilbert McLeod "Wib" Chapman, Roger Revelle, Milner Baily "Benny" Schaefer, and Sette himself, as well as young scientists who would become notable in their fields as their careers progressed, such as Townsend Cromwell, Fred Cleaver, Warren Wooster, Alan Tubbs, William Aron, Gerald Howard, Richard Hennemuth, Howard Yoshida, and Tom Hida.

[1][2] In February 1952, Shimada was assigned to the Inter-American Tropical Tuna Commission (IATTC),[1][2] which was collocated with the Scripps Institution of Oceanography and the Fish and Wildlife Service Bureau of Fisheries laboratory in La Jolla, California, and he cooperated professionally with those institutions on matters of mutual interest, sharing scientific ideas and manpower and cooperating in research.

Their cooperative work, following the principles of fisheries oceanography Sette, Shimada, Cromwell, and other members of Sette's team had pioneered at POFI, combined Cromwell's insights into the forces such as temperature gradients that drive currents with Shimada's findings regarding the availability of forage for the tunas, leading to useful research results for both men.

[1] Plans called for Shimada and Cromwell to make one more cruise to Clarion Island in 1958 aboard the Scripps Institution research ship Horizon to continue their research there before Shimada left the IATTC to take up a position as the first director of the Fish and Wildlife Service Bureau of Commercial Fisheries' new Eastern Pacific Tuna Investigations office in July 1958.

Shortly after takeoff, the airliner crashed into La Latilla Mountain, only 16 kilometers (10 miles) from Guadalajara Airport, killing all 45 people on board in what at the time was Mexico's deadliest aviation accident.

[8] The dedication read: This Symposium is dedicated to Townsend Cromwell and Bell M. Shimada, associates in research of many of the participants in this Symposium, who lost their lives, June 2, 1958, in an airplane crash near Guadalajara, Mexico, while en route to join the research vessel Horizon to make further observations on the changing conditions in 1958.