WWW.WA S .ORG • WORLD AQUACULTURE • DECEMBER 2022 43 ( C O N T I N U E D O N P A G E 4 4 ) entrance) to reduce interior flow. Basically, they work by throwing part of the system flow and, consequently, reducing the internal working pressure. These bypasses are made up of a ¼” pressure control valve and the other two are simple quick-connect ¼” valves. In the final part of the decompression process, when the main pressure control valve is no longer functional, the pressure is reduced by progressively opening the bypasses, starting with the control valve that offers greater precision and then the quick-connect ball valves. Depth values inside hyperbaric chamber were monitored throughout this process. Adjustments enabled the virtual depth inside the chamber to reach surface levels, even with a significant circulating flow. A drop in electrical energy is a risk factor that must be considered because it will lead to rapid decompression of the hyperbaric chamber, which can be harmful or fatal to fish. A simple electrical protection system was also adopted in case of failure of the base AC power supply. For that, the Biomarine team used a small contactor switch with NC poles4 and connected it to the stationary battery system, which would supply the CC system in case of a power failure. Although successfully tested, no power failure occurred during the process. A small ROV5 was implemented to support the operation. The equipment was very useful during the chamber’s recovery, to record part of the operation, and to monitor the diver’s condition. The two operations were planned and executed at the northeast region of Brazil, at 13° 01’ 32.2” S and 38°16’ 97.4” W (WGS 84). The location chosen was the coast of Bahia State, Salvador, because of the proximity of the continental shelf break and the availability of divers highly specialized in deep diving. The first operation took place on 1/22/22. The dive follow-up was uneventful, with a maximum depth of 122 m for diver 1 and 138 m for diver 2. It lasted 4.5 hours and resulted in the capture of two French butterflyfish specimens. Fish were brought to surface inside the hyperbaric chamber by the dive support team, who retrieved the equipment at a depth of 30 m and brought it on board the support vessel, while the deep-sea divers remained in the water to decompress. The chamber was successfully connected to the pressure system and kept running. After the deep-sea divers returned to the boat, the team came back to shore. Despite careful planning and execution, temperature shock and high levels of ammonia resulted in the mortality of the two captured specimens. In this work model, the entire team and the fish must wait for the dive team’s long decompression to return to shore, which increases the maintenance time of the fish on board, aggravating temperature issues if there is no thermal protection. Incidents linked to the temperature increase have been reported in the literature (Shepherd 2018). Although there was no success in keeping the fish alive in the first operation, Biomarine considered the result positive. Equipment and procedures were tested and demonstrated to be efficient. In addition, the decompression process successfully brought live specimens to the surface. A second dive operation was performed on 2/26/2022. Important improvements were adopted that focused on temperature maintenance using a thermal box6 with internal space to hold two hyperbaric chambers, including the hydraulic set, pump and line. The dive had a maximum depth of 123 m, with 10 min of descent, 21 min of effective bottom time and approximately 5 hr of decompression. Two more specimens of French butterflyfish were captured at 110 m depth and brought to the surface in the hyperbaric chamber under a virtual pressure of 60 to 70 m. Temperature at the collection point was 21 C and at the sea surface was 28 C. Improving procedures, recovery logistics were modified so that the hyperbaric chamber could ascend quickly. The ROVwas used to find divers Diver depth profile of dive performed on 1/22/22 (Diver László Mocsári). Biomarine hyperbaric chamber in operation. Specimens of Prognathodes guyanensis captured by Biomarine.
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