Albacore Morphology/Physiology

Albacore, as well as other species of tuna, have unique biological characteristics that enable them to swim continuously at very high speeds and cover vast areas during annual migrations. Albacore are literally ‘built for speed' in an ocean environment, with torpedo-shaped (fusiform) bodies, smooth skin (tiny, cycloid scales), and streamlined fins, which enable the fish to reach speeds of over 50 miles per hour (80 kilometers per hour) for short periods of time. Albacore are metallic dark blue along the back, with dusky to silvery white coloration along the sides and on the belly. The pectoral fins of this species of tuna are exceptionally long, extending to nearly half the length of their body; albacore are commonly referred to as ‘longfin tuna' by the angling community. Their tail fin is deeply forked and lunate in construction, which helps generate the tremendous thrust needed to maintain high speeds.

Albacore are negatively buoyant fish that lack a swim bladder and have lost many structures needed to pump water over their gills to obtain oxygen, which collectively, translates to a life history strategy that requires constant swimming. Their mode of breathing, by swimming with their mouth open, forces oxygen-rich water over their gills. In addition to these morphological adaptations, albacore possess highly specialized physiological functions that allow for rapid movement and sustained endurance. First and foremost, many tunas, including albacore, have a highly evolved circulatory system that includes countercurrent exchangers that act to reduce the loss of heat generated by increased muscular activity, which allows them to regulate their body temperature and ultimately, increase the efficiency of their muscles. That is, albacore maintain their body temperatures at higher levels than the temperature of the water in which they swim. To maintain elevated body temperatures, albacore have high metabolic rates that demand a good supply of oxygen; the oxygen-gathering surface in albacore approaches that of the respiratory surface area found in the lungs of mammals of comparable weight. Additionally, albacore have higher blood pressure and volume than that exhibited by most of the other species of fish, as well as hemoglobin concentrations similar to that found in humans, which collectively, increase oxygen-absorption processes.