Rates of Intraperitoneal Temperature Change in Lake Trout Implanted with Archival Tags

Abstract

AbstractThe rates of change in the intraperitoneal temperature of lake trout Salvelinus namaycush weighing between 817 g and 2,230 g were examined in the laboratory. Nine lake trout implanted with archival tags were moved between three tanks containing different water temperatures. The intraperitoneal temperatures recorded by the archival tags lagged behind the external temperatures when these thermal changes were encountered, but the smallest fish shifted temperature about twice as fast as the largest fish. The rate of core temperature change can be described by Newton's law of cooling, which states that the rate of temperature change of an object is proportional to the difference between its own temperature and the ambient temperature. This time lag can provide ample opportunity for fish to make brief forays into water temperatures outside an optimal range, while experiencing minimal change in intraperitoneal temperature. The relationship between the rate of temperature change and body mass varies with the body shape and the location where measurements are taken. The rate of thermal exchange was calculated from each temperature trial, and a regression derived from the log–log plot of these rates versus body mass was used to determine a standardized rate of thermal exchange for lake trout of any body mass within the range tested.