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Effects of temperature on sustained swimming performance and swimming kinematics of the chub mackerel Scomber japonicus

Kathryn A. Dickson^*, Jeanine M. Donley, Chugey Sepulveda and Lisa Bhoopat

Department of Biological Science, California State University Fullerton, Fullerton, CA 92834, USA
Present address: Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093, USA
Present address: Anaheim High School, 811 W. Lincoln Avenue, Anaheim, CA 92805, USA

View larger version (15K): [in a new window]   Fig. 1. Maximum continuous swimming speed (Umax,c) versus fork length (FL) in chub mackerel (Scomber japonicus) acclimated to 18°C (open squares) or 24°C (filled squares) measured at the respective acclimation temperature. The lines are the best-fitting linear regressions (with coefficients ± S.E.M.): Umax,c= (0.168±0.075)FL+(36.6±16.0), r2=0.33, N=12, P=0.049, at 18°C (dashed line); Umax,c=(0.308±0.114)FL+(31.4±22.9), r2=0.48, N=10, P=0.027, at 24°C (solid line). At a given FL, Umax,c was significantly greater at 24°C (ANCOVA; P=0.001), but Umax,c increased with FL at the same rate at the two temperatures.

View larger version (29K): [in a new window]   Fig. 2. Rate of oxygen consumption (O2) versus swimming speed for all individual chub mackerel at 18 °C (blue symbols) and 24 °C (green symbols). The fork length (FL) and mass of each individual are indicated. The best-fitting regressions for each individual at 18 °C are presented in Table 1, and those for each individual at 24 °C are given in Sepulveda and Dickson (2000).

View larger version (54K): [in a new window]   Fig. 3. Rate of oxygen consumption (O2) at 18 °C (blue plane and symbols) and 24 °C (green plane and symbols) as a function of both swimming speed and fish mass for all individuals studied. The maximum and minimum values of speed and mass at 18 and 24 °C were used to solve the multiple regression equations for O2 (Table 2) for the four corners of each plane. At a given speed and mass, O2 is significantly higher at 24 than at 18 °C, and the rate of increase in O2 with speed is greater at 24 °C (ANCOVA, P<0.0001).

View larger version (15K): [in a new window]   Fig. 4. The mass-specific net cost of transport (COTnet) for chub mackerel at 18 °C (open squares) and 24 °C (filled squares) as a function of fish fork length (FL). The lines are the best-fitting equations: COTnet=-253FL+8387, r2=0.72, N=12, P<0.001, at 18 °C (dashed line); COTnet=-31383logFL+46734, r2=0.48, N=12, P<0.02, at 24 °C (solid line). At a given fish size, COTnet was greater at 24 than at 18 °C (ANCOVA; P=0.02), even if the highest point for the 14.0 cm FL mackerel at 24 °C is omitted. Values are means ± S.E.M.

View larger version (54K): [in a new window]   Fig. 5. The dependence of tail-beat frequency on both swimming speed and fish fork length (FL) in chub mackerel at 18 °C (blue plane and symbols) and 24 °C (green plane and symbols). Each symbol indicates the tail-beat frequency versus speed data for one individual. The maximum and minimum values of speed and FL at 18 and 24 °C were used to solve the multiple regression equation for tail-beat frequency (Table 2) for the four corners of each plane. There was no significant effect of temperature on the relationship between tail-beat frequency and speed and FL (ANCOVA, P<0.05).

View larger version (49K): [in a new window]   Fig. 6. The increase in tail-beat amplitude with both swimming speed and fish fork length (FL) in chub mackerel at 18 °C (blue plane and symbols) and 24 °C (green plane and symbols). Each symbol indicates the tail-beat amplitude versus speed data for one individual. The maximum and minimum values of speed and FL at 18 and 24 °C were used to solve the multiple regression equation for tail-beat amplitude (cm) (Table 2) for the four corners of each plane. There was no significant effect of temperature on the relationship between tail-beat amplitude and speed and FL (ANCOVA, P>0.05).

View larger version (55K): [in a new window]   Fig. 7. The increase in stride length (l) with both swimming speed and fish fork length (FL) in chub mackerel at 18 °C (blue plane and symbols) and 24 °C (green plane and symbols). Each symbol indicates the l versus speed data for one individual. The maximum and minimum values of speed and FL at 18 and 24 °C were used to solve the multiple regression equation for stride length (Table 2) for the four corners of each plane. There was no significant effect of temperature on the relationship between l and speed and FL (ANCOVA, P>0.05).

View larger version (17K): [in a new window]   Fig. 8. Mean propulsive wavelength () versus fork length (FL) for individual chub mackerel at 18 °C (open squares) and 24 °C (filled squares). Because there was no significant effect of speed on , the mean of the propulsive wavelengths at all swimming speeds was calculated for each individual. Error bars represent ±1 S.E.M. The lines are the best-fitting linear regressions: =1.11FL-1.32, r2=0.89, N=9, P<0.001, at 18 °C (dashed line); =1.09FL+1.32, r2=0.83, N=12, P<0.001, at 24 °C (solid line). Mean increases with FL at the same rate at the two temperatures but, at a given FL, is significantly greater at 24 than at 18 °C (ANCOVA, P=0.0024).