The swimming capacity of juvenile Murray cod (Maccullochella peelii): an ambush predator endemic to the Murray‐Darling Basin, Australia

Abstract

AbstractThis study documented the swimming capacity of a large ambush predator, Murray cod Maccullochella peelii, endemic to the Murray‐Darling Basin, Australia. It was evident that the species is a swimming generalist, maintaining moderate ability across all aspects of the swimming capacity parameters that were investigated. For instance, the species was capable of prolonged swimming performance (critical swimming speed, Ucrit: absolute, 0.26–0.60 m·s−1, relative, 1.15–2.20 BL s−1) that was inferior to active fish species, but comparable with other ambush predators. The species had low energetic demands, maintaining a low mass‐specific standard (21.3–140.3 mg·h−1 kg−1) and maximum active metabolic rate (75.5–563.8 mg·h−1 kg−1), which lead to a small scope for activity (maximum active metabolic rate–standard metabolic rate; 1.4–5.9). They were reasonably efficient swimmers (absolute and relative optimal swimming speed, 0.17–0.61 m·s−1 and 0.77–1.93 BL·s−1, respectively) and capable of repeat bouts of prolonged performance (recovery ratio = 0.99). Allometric changes in aspects of swimming capacity were realised with body mass, whereas broad swimming capacity was maintained across a wide range of temperatures. The swimming capacity demonstrated by M. peelii reflects a sit‐and‐wait foraging strategy that seeks to conserve energy characteristic of ambush predators, but with distinct features (e.g., lack of fast‐start ability) that may reflect their evolution in some of the world's most hydrologically and thermally variable rivers.