In late June 1959, the USFWS completed the installation of a new observation chamber aboard Charles H. Gilbert, located within her hull in a special blister aft, below the fishing racks and below the waterlinecfrsep59coverphotocaption>Commercial Fisheries Review, September 1959, cover photo caption.Commercial Fisheries Review, November 1959, p. 30.Commercial Fisheries Review, September 1959, p. 27. Testing showed that the new chamber was free of the problem of cavitation and the resulting bubbles that had hampered photography from the overside dry chamber she had used earlier, and it had ample room for a photographer to employ still and motion-picture cameras to record fish behaviors. The change made Charles H. Gilbert the world's only tuna-fishing vessel at the time with underwater observation windows,Commercial Fisheries Review, November 1960, p. 25. a distinction she held until similar windows were installed amidships aboard the California Department of Fish and Game research vessel Alaska in 1961.Commercial Fisheries Review, August 1961, p. 17. With her new observation chamber ready, she departed Kewalo Basin in early July 1959 to make use of it in studying skipjack behavior in Hawaiian waters during her 45th FWS cruise. She experimented with the use of various baits and various amounts of bait, with the use of glittering tinsel and water sprays in conjunction with bait, and with the effect of colored dyes and sounds on feeding skipjack. She filmed skipjack from her observation chamber, finding it to be an "outstanding success;" it was comfortable for an operator to use for several hours at a time, and was free of the bubbles that had plagued the earlier overside platform. She also tested the chamber's performance against that of two types of closed-circuit television. Neither television system showed any advantage over the use of the observation chamber;Commercial Fisheries Review, October 1959, p. 25. although the television cameras often could see farther underwater than the cameras used in the chamber, the television systems proved too delicate to adjust and operate under tuna-fishing conditions. She placed 73 skipjack in her live wells – 37 of which later were placed in tanks at the USFWS Honolulu laboratory at Kewalo Basin – and conducted a seal and marine turtle census at the French Frigate Shoals in the Northwestern Hawaiian Islands. She completed her cruise on 3 September 1959 after 60 days at sea. The film she brought back made the USFWS Honolulu laboratory the first fisheries research center to record successfully on film the behavior of skipjack underwater, and it allowed scientists to gain a better understanding of tuna behaviors.Commercial Fisheries Review, December 1959, p. 44.
