Studies of tuna swimming performance at the Kewalo Basin Research Facility, Honolulu, Hawaii are planned using a large water tunnel currently located at Scripps Institution of Oceanography. Objectives of the study include verification that tunas can be induced to swim steadily in the instrument to justify future shipboard experiments with albacore in the California Current. Use of the water tunnel at Kewalo, where tunas are kept routinely, will also permit more lengthy and elaborate experiments than are currently feasible or, for that matter have ever been carried out on tunas. The metabolic cost of swimming for tunas and its relationship to body size, velocity, and temperature will be examined. Also to be tested is the tuna's capacity for sustained swimming in the face of changes in ambient temperature and oxygen concentrations, environmental factors known to affect the movement pattern of Hawaiian tunas and most other species. Experiments with the thermoregulatory capacity of these tropical tunas will provide the first-ever in vivo examination, in a swimming tuna, of heat-balancing responses to acute water temperature change, and permit testing of the conflicting ideas that heat balance is passive or physiologically regulated. Water-tunnel studies will permit further examination of thermal effects on in vivo hemoglobin-oxygen affinity, another subject of recent controversy.
