title: Swimming performance studies on the eastern Pacific bonito Sarda chiliensis, a close relative of the tunas (family Scombridae) I. Energetics.
abstract: A large swim tunnel respirometer was used to quantify the swimming energetics of the eastern Pacific bonito Sarda chiliensis (tribe Sardini) (45-50 cm fork length, FL) at speeds between 50 and 120 cm s(-1) and at 18+/-2 degrees C. The bonito rate of oxygen uptake ((O(2)))-speed function is U-shaped with a minimum (O(2)) at 60 cm s(-1), an exponential increase in (O(2)) with increased speed, and an elevated increase in (O(2)) at 50 cm s(-1) where bonito swimming is unstable. The onset of unstable swimming occurs at speeds predicted by calculation of the minimum speed for bonito hydrostatic equilibrium (1.2 FL s(-1)). The optimum swimming speed (U(opt)) for the bonito at 18+/-2 degrees C is approximately 70 cm s(-1) (1.4 FL s(-1)) and the gross cost of transport at U(opt) is 0.27 J N(-1) m(-1). The mean standard metabolic rate (SMR), determined by extrapolating swimming (O(2)) to zero speed, is 107+/-22 mg O(2) kg(-1) h(-1). Plasma lactate determinations at different phases of the experiment showed that capture and handling increased anaerobic metabolism, but plasma lactate concentration returned to pre-experiment levels over the course of the swimming tests. When adjustments are made for differences in temperature, bonito net swimming costs are similar to those of similar-sized yellowfin tuna Thunnus albacares (tribe Thunnini), but the bonito has a significantly lower SMR. Because bonitos are the sister group to tunas, this finding suggests that the elevated SMR of the tunas is an autapomorphic trait of the Thunnini.
authors.affiliation: Center for Marine Biomedicine and Biotechnology, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093-0204, USA. csepulve@ucsd.edu
authors.forename: C A
authors.initials: CA
authors.lastname: Sepulveda
authors.forename: K A
authors.initials: KA
authors.lastname: Dickson
authors.forename: J B
authors.initials: JB
authors.lastname: Graham
mesh_terms: D000818:Animals; D005075:Biological Evolution; D002140:California; D004734:Energy Metabolism / Q000502:physiology*; D019344:Lactic Acid / Q000097:blood; D010101:Oxygen Consumption / Q000502:physiology*; D010473:Perciformes / Q000378:metabolism / Q000502:physiology*; D013045:Species Specificity; D013550:Swimming / Q000502:physiology*
chemical_list: D019344:Lactic Acid