Swim Tunnel Respirometer Research Articles

Aerobic respiratory costs of swimming in the negatively buoyant brief squid Lolliguncula brevis.

Because of the inherent inefficiency of jet propulsion, squid are considered to be at a competitive disadvantage compared with fishes, which generally depend on forms of undulatory/oscillatory locomotion. Some squid, such as the brief squid Lolliguncula brevis, swim at low speeds in shallow-water complex environments, relying heavily on fin activity. Consequently, their swimming costs may be lower than those of the faster, more pelagic squid studied previously and competitive with those of ecologically relevant fishes. To examine aerobic respiratory swimming costs, O(2) consumption rates were measured for L. brevis of various sizes (2-9 cm dorsal mantle length, DML) swimming over a range of speeds (3-30 cm s(-1)) in swim tunnel respirometers, while their behavior was videotaped. Using kinematic data from swimming squid and force data from models, power curves were also generated. Many squid demonstrated partial (J-shaped) or full (U-shaped) parabolic patterns of O(2) consumption rate as a function of swimming speed, with O(2) consumption minima at 0.5-1.5 DML s(-1). Power curves derived from hydrodynamic data plotted as a function of swimming speed were also parabolic, with power minima at 1.2-1.7 DML s(-1). The parabolic relationship between O(2) consumption rate/power and speed, which is also found in aerial flyers such as birds, bats and insects but rarely in aquatic swimmers because of the difficulties associated with low-speed respirometry, is the result of the high cost of generating lift and maintaining stability at low speeds and overcoming drag at high speeds. L. brevis has a lower rate of O(2) consumption than the squid Illex illecebrosus and Loligo opalescens studied in swim tunnel respirometers and is energetically competitive (especially at O(2) consumption minima) with fishes, such as striped bass, mullet and flounder. Therefore, the results of this study indicate that, like aerial flyers, some negatively buoyant nekton have parabolic patterns of O(2) consumption rate/power as a function of speed and that certain shallow-water squid using considerable fin activity have swimming costs that are competitive with those of ecologically relevant fishes.

Hematocrit in oxygen transport and swimming in rainbow trout ( Oncorhynchus mykiss)

The optimal hematocrit (Hct opt) hypothesis was tested by altering Hct (and arterial blood oxygen content, Ca O 2 ) between extreme states of anemia and polycythemia (Hct = 8–55%) in the rainbow trout. Since blood viscosity (η) effects on cardiac output (Q̇) and O 2 transport (Ṫ O 2 ) are likely to be greatest when O 2 demand and Q̇ are maximal, we challenged fish to swim to their critical swimming velocity (U crit) in a swim-tunnel respirometer at 13°C and measured maximal oxygen uptake (V̇ O 2max ), maximum Q̇(Q̇ max), and other cardiovascular variables. In addition, experimental temperature was lowered to 5°C to increase η. Consistent with the Hct opt hypothesis, the decreased Ca O 2 in anemic (Hct < 22%) fish caused significant reductions in U crit and V̇ O 2max . In contradiction to the Hct opt hypothesis, and despite an exponential relationship between η and Hct, maximal Ṫ O 2 (Ṫ O 2max ) and U crit increased with polycythemia up to Hct 55%. Although there was a peak for V̇ O 2max , it occurred at an Hct (42%) well above the normocythemic range (23–33%). These results clearly demonstrate that η is not significant in setting normocythemia in rainbow trout. The novel finding of an Hct-dependent relationship for exercise-induced arterial hypoxemia may be indicative of a diffusion limitation to normocythemia. We suggest that factors involved in setting normocythemia in vertebrates should include diffusion limitations to oxygen transfer in addition to blood viscosity and oxygen transport constraints.

Differences in Exercise Physiology between Two Atlantic Cod (Gadus morhua) Populations from Different Environments

Little attention has been given to the study of physiological variation within species of fish. This study examines whether a population of Atlantic cod (Gadus morhua) found in the brackish Bras d'Or Lakes of Nova Scotia, Canada, has different physiological characteristics than a nearby Atlantic ocean cod population. Chronically cannulated cod from both populations were exercised to exhaustion in a swim-tunnel respirometer. Although exercise performance was identical between populations, the physiological bases of that performance differed substantially. Cod from the Bras d'Or system had greater metabolic, ventilatory, and cardiac rates as well as a greater estimated resting metabolic rate. The Bras d'Or population used a greater proportion of anaerobic metabolism in attaining its maximal performance level as surmised from a relatively greater metabolic acid-base disturbance and higher lactate levels during recovery from exercise in the Bras d'Or population. Bras d'Or cod also had generally more dilute plasma and lower levels of hemoglobin in its erythrocytes than conspecifics from the Atlantic Ocean. These results are discussed as possible clues to the physiological adjustments necessary for cod to succeed in the Bras d'Or system.

A reappraisal of activity metabolism in Atlantic cod (Gadus morhua)

Atlantic cod (Gadus morhua) were forced to swim in a swim tunnel respirometer until fatigued; oxygen consumption rate (&amp;#x004d;̇O2) was measured during swimming at incremental speeds until the fish was exhausted and during recovery from exhaustion. Maximal oxygen consumption (&amp;#x004d;̇O2max) occurred during maximal activity as has been found for other fish species, but at odds with the current paradigm for Atlantic cod. Earlier experiments had drawn the conclusion that &amp;#x004d;̇O2max in Atlantic cod occurs during recovery from exhaustive exercise. We found no support for this paradigm in our experiments and we propose that the respiratory physiology of Atlantic cod is not unlike that of other fishes.

A reappraisal of activity metabolism in Atlantic cod (Gadus morhua)

Atlantic cod (Gadus morhua) were forced to swim in a swim tunnel respirometer until fatigued; oxygen consumption rate (ṀO2) was measured during swimming at incremental speeds until the fish was exhausted and during recovery from exhaustion. Maximal oxygen consumption (ṀO2max) occurred during maximal activity as has been found for other fish species, but at odds with the current paradigm for Atlantic cod. Earlier experiments had drawn the conclusion that ṀO2max in Atlantic cod occurs during recovery from exhaustive exercise. We found no support for this paradigm in our experiments and we propose that the respiratory physiology of Atlantic cod is not unlike that of other fishes.

Effects of graded exercise on blood gas tensions and acid-base characteristics of rainbow trout

A swim tunnel respirometer and an extracorporeal blood circulation technique allowed continuous collection of data from exercising fish below and near their critical speed. Swimming at speeds below maximum showed no changes in plasma Na +, Cl − and lactate concentrations but increased levels of blood hemoglobin and plasma K + . Pa O 2 and Pa CO 2 showed an exponential decreased and increase respectively and related to swimming speed. Increased swimming speed changed the acid-base status toward a mixed respiratory and metabolic acidosis. Upon reaching maximum speed sudden and large increases in plasma Na +, K + and lactate concentrations occurred associated with a large metabolic acidosis.