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We show that growth hormone enhanced transgenic salmon have a higher oxygen uptake during routine culture conditions and during forced swimming activity relative to similarly sized control fish. They also have a slightly higher critical oxygen level that limits oxygen uptake. However, they do not differ in regards to critical swimming speed. Growth hormone transgenic Atlantic salmon, Salmo salar, at 12-13°C were an F2 generation using eggs from a transgenic F1 female and milt from a nontransgenic male. They grew two to three times faster than control fish throughout the study period. Under routine culture conditions, both transgenic and control fish exhibited a diurnal cycle in oxygen uptake. However, oxygen uptake of transgenic fish was 1.7 times that of control fish at all times of the day. Oxygen uptake was independent of oxygen concentration above 10 mg/L in both groups of fish; critical oxygen uptake level was 6 mg/L in transgenic fish and 4 mg/L in control fish. During the oxygen decrease, transgenic fish and control fish lost equilibrium at the same low oxygen concentration levels. In the swim tunnel, oxygen uptake of transgenic fish was 1.6 times that of control fish at all swimming speeds. Critical swimming speeds did not differ between transgenic and control fish and were similar to literature values for salmonids.

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Observations of position holding by brook trout (Salvelinus fontinalis) in a stream channel indicate that they choose specific locations probably related to flow patterns around bottom obstructions. Bilateral denervation of the posterior lateral line system of trout has no effect on their ability to entrain on objects placed in flowing water, providing sufficient visual cues are available. Unilateral ablation resulted in a lateral bias in swimming position relative to the flow obstruction even when visual cues were present. Bilateral denervation of the posterior line system reduced the degree to which trout could entrain on objects when visual cues were omitted. It is suggested that in stream-dwelling fish, such as the brook trout, the lateral line may serve as a detector of flow or pressure discontinuities, enabling the fish to maintain position with minimum expenditure of energy.