Effects of Different Exercise Conditioning Velocities on the Energy Reserves and Swimming Stress Responses in Young-of-the-Year Striped Bass (Morone saxatilis)

Abstract

Young-of-the-year striped bass (Morone saxatilis) were exercise conditioned for 60 d at four different water velocities: <0.02 (control), 0.5–1.2 (slow), 1.5–2.4 (moderate), and 2.4–3.6 body lengths∙s−1(fast). Exercise conditioning at the moderate velocity increased body weight and standard length. Lipid contents and wet weight lipid percentages in the carcass were higher in the moderate- and fast-velocity fish than in the controls, and dry weight lipid percentages in the carcass and whole fish at the moderate velocity were higher than in those conditioned at the fast velocity. Moderate-velocity fish had resting (nonstressed) cortisol levels lower than those in the controls. After swimming stress, plasma cortisol, lactate, osmolality, and hematocrit levels in all fish were very high with no significant differences among treatments, while muscle pH values in all fish were lower than those in resting fish. Within the post-swimming stressed fish, muscle pH was lower in the controls than in those conditioned at the fast velocity. Overall, exercise conditioning in the moderate to fast velocity range increased body lipids and decreased post-swimming stress acidosis in young-of-the-year striped bass.