Meeting Abstract

P3.217  Sunday, Jan. 6  Heat Transfer in Free-Swimming Swordfish, Xiphias gladius STOEHR, A.*; FOWLER, A.; SEPULVEDA, C.; BERNAL, D.; Univ. of Massachusetts, Dartmouth; Univ. of Massachusetts, Dartmouth; Pfleger Institute of Environmental Research; Univ. of Massachusetts, Dartmouth astoehr@umassd.edu

Swordfish, Xiphias gladius, are large, active pelagic predators renowned for their ability to undertake extensive, prolonged vertical movements and rapid temperature changes in excess of 18C. Several high performance fishes maintain elevated body-core temperatures relative to ambient, and are capable of physiological thermoregulation; yet despite the presence of morphological traits typical of regional endothermy (i.e. medial red muscle, central rete, muscular lateral vessels), elevated temperatures have not been definitively characterized in swordfish. This study analyzed water and deep tissue temperatures from archival tags deployed on six free-swimming swordfish in the Southern California Bight, and developed an alternative mathematical model to investigate the effects of conduction, retial convection, and myogenic heat production during foraging dives. Results indicate rapid changes in whole-body thermal conductivity resulting in faster rates of heating compared to cooling during ascents and descents, respectively. Estimated body temperature curves indicate that less than 5% myogenic heat retention is necessary to simulate heat balance during dives, changes in heat exchanger efficiency become increasingly important with heat production, and both tissue temperature and efficiency are affected by volumetric blood flow rate. For swordfish, it appears that physiological thermoregulation retards the effects of rapid ambient temperature change and permits foraging expansion into disparate thermal regimes.