It is possible, some surmise, that being confined to a net, no matter how spacious, has an effect on fish born to be long-distance travelers. And despite their size, they appear to be delicate creatures. Water temperature is an issue, and the team is making plans to move the research station farther south and west to warmer waters. Yoshifumi Sawada said that if anything goes awry with temperature or the oxygen supply during spawning, which, at the research station, occurs in tanks on land, a bell goes off in his nearby house. He lives, literally, at the project.
Bluefins also appear to be timid.
They are very sensitive, very afraid of the flashing. But when I don't move, they come closer. The fish also need a constant supply of food. Unlike most fish, they are warm-blooded and must take in enormous supplies of oxygen to stay alive. There are, of course, days in the wild when food is scarce, too.