Cardiorespiratory physiology and swimming capacity of Atlantic salmon (Salmo salar) at cold temperatures

Abstract

We investigated how acclimation to 8, 4 and 1°C, and acute cooling from 8 to 1°C, affected the Atlantic salmon's aerobic and anaerobic metabolism, and cardiac function, during a critical swim speed (Ucrit) test. This study revealed several interesting temperature-dependent effects. First, while differences in resting heart rate (fH) between groups were predictable based on previous research (range ∼28–65 beats min−1), with values for 1°C-acclimated fish slightly higher than those of acutely exposed conspecifics, the resting cardiac output () of 1°C-acclimated fish was much lower and compensated for by a higher resting blood oxygen extraction (ṀO2/). In contrast, the acutely exposed fish had a ∼2-fold greater resting stroke volume (VS) compared with that of the other groups. Second, increases in fH (1.2- to 1.4-fold) contributed little to during the Ucrit test, and the contributions of (VS) versus ṀO2/ to aerobic scope (AS) were very different in the two groups tested at 1°C (1°C-acclimated and 8–1°C fish). Finally, Ucrit was 2.08 and 1.69 body lengths (BL) s−1 in the 8 and 4°C-acclimated groups, but only 1.27 and 1.44 BL s−1 in the 1°C-acclimated and 8–1°C fish, respectively – this lower value in 1°C versus 8–1°C fish despite higher values for maximum metabolic rate and AS. These data: support recent studies which suggest that the capacity to increase fH is constrained at low temperatures; show that cardiorespiratory function at cold temperatures, and its response to increased demands, depends on exposure duration; and suggest that AS does not constrain swimming capacity in salmon when chronically exposed to temperatures approaching their lower limit.

Temperature and Dissolved Oxygen Lead to Behavior and Respiration Changes in Juvenile Largemouth Bass (Micropterus salmoides) during Transport

“…These changes in behavior are due to the impact of rapid temperature changes on the membrane excitability and synaptic transmission sensitivity of fish, which can negatively affect the normal functioning of the central nervous system [28,29]. Additionally, in a study of Atlantic salmon (Salmo salar), acute cooling from 8 to 1 • C significantly changed cardiorespiratory physiology and swimming capacity compared with those acclimated at 1 • C [25]. Acute cooling can damage the plasma membrane of fish, as demonstrated in a study of killifish (Fundulus heteroclitus) [30].…”

“…If the test subject dies, the dissolved oxygen concentration at the time of death is called the death concentration (mg•L −1 ). In order to ensure accurate measurements, we confirmed the absence of microbial respiration by measuring dissolved oxygen in a sealed tank without fish [25].…”