“I think unpacking each one of these behaviors and finding out how each is relevant to their fitness is the next step,” says Prendergast.
Prendergast and his PhD students, Jharnae Love and recently graduated JP Riggle, have already observed that, like many other animals, striped bass go through periods in which their circadian rhythms have higher or lower “amplitude.”
“Think of a pendulum. Amplitude would be based on how heavy and long the pendulum is,” says Prendergast. It’s very hard to change the swinging of a huge, heavy pendulum with a large amplitude, like the ones at science centers. Whereas a nickel swinging on a string has a lower amplitude, which means it’s very easy to adjust or stop.
Generally, animals tend toward having high amplitude rhythms in stable situations, but certain situations call for lower amplitude rhythms. “There might be times of year when you need to change your clock and override your circadian rhythms, so that allows behavioral flexibility.”
From looking at how deep in the water these fish are through the day, the team can see higher or lower amplitude periods of their circadian rhythms. Right after the striped bass arrive in Eel Pond in May, and again right before they leave in October, their rhythms appear to be less robust and more chaotic. In other words, their depth doesn’t depend on the time of day during these transitional periods.