Energy savings achieved by changing fish-hold temperature on a large-distant-water type tuna longline vessel

We examined the energy-saving effect of changing the fish-hold temperature on a large-distant-water type tuna longline fishery. For the first half of the fishing trip, the fish-hold temperature was set to -55 degree C, which is the ultra-low temperature that is conventionally used for this purpose. For the latter half of the trip, the temperature was set to -45 degree C. We then compared the electric energy consumption of the refrigerator compressor for these two temperature settings. Increasing the fish-hold temperature from -55 degree C to -45 degree C reduced the electricity consumption by 34.1% during non-operational periods, and by 11.9% during operational periods. We estimated the change of the fish-hold temperature reduced the fuel consumption by 32.65 kL per a fishing trip (130 days of non-operation and 200 days operation). Thus, changing the fish-hold temperature is an effective method for saving energy on large-distant-water type tuna longline vessels.