Vertical energy seascapes and diving behaviour modulate metabolic scope in a pelagic predator.

Abstract

Pelagic fishes must obtain resources in prey-sparse habitats and may be considered energy speculators with maximization, gambling high energy costs (e.g. metabolism) for a high rate of return (prey capture). As such, they may have to carefully use their energy seascape to obtain the resources necessary for high growth rates. For diving animals, their energy seascape will also have a vertical component in addition to a horizontal one, which is rarely considered. Dolphinfish, Coryphaena hippurus, embody the maximization strategy as they have high metabolic rates and fast growth rates. We coupled biologging on wild individuals with lab-based respirometry to estimate dolphinfish swimming metabolic rates and vertical energy seascapes. Dolphinfish performed continuous yo-yo dives with deeper dives at night but higher activity during the day. Dive descents were approximately 27% less costly than the ascents. Fish modulated their behaviour so that metabolic costs during the descent/ascent phases of deeper dives were less than those for shallow dives. While temperature is likely the primary limit of dive depth, the vertical energy seascape may be secondary and limit maximum dive depths. Studies of pelagic animal energy seascapes should consider the vertical component that will help determine their ability to access and utilize prey.