Figure 1.
Metabolic rates (mg O2 kg−1 h−1) over 24 h in lake sturgeon Acipenser fulvescens.
Data collection comprised three test groups: control (100% O2sat; 12L∶12D), treatment A (30% O2sat; 12L∶12D), and treatment B (100% O2sat; 24L). Colours of the symbols indicate light levels with white, black and grey data points representing light, dark and intermediate light levels, respectively. Different letters indicate significant (P<0.05) differences between measurements within each test group. Note that y-axes differ between the three panels.
Figure 2.
Hourly behavioural variables in lake sturgeon Acipenser fulvescens from 16:00 h to 23:00 h.
Data collection comprised three test groups: control (100% O2sat; 12L∶12D), treatment A (30% O2sat; 12L∶12D), and treatment B (100% O2sat; 24L). Colours of the symbols indicate light levels with white, black and grey data points representing light, dark and intermediate light levels, respectively. Behavioural variables included total activity (% of time moving) (triangles) and the frequencies of body undulations with tail excursions<90° (squares) or >90° (circles) (min−1). Within each test group, behavioural variables were compared over time to identify significant changes. Different letters indicate significant (P<0.05) changes over time, whereas identical or no letters indicate non-significant (P>0.05) changes over time.
Figure 3.
Metabolic rates (mg O2 kg−1 h−1) correlate positively with behaviour in lake sturgeon Acipenser fulvescens.
Behaviour involved body undulations with tail excursions>90° (min−1). Data were collected from 16:00 h to 23:00 h. Data collection comprised three test groups: control (100% O2sat; 12L∶12D), treatment A (30% O2sat; 12L∶12D), and treatment B (100% O2sat; 24L). Note that symbol colours indicate the three test groups: control (black symbols; long dash line), treatment A (gray symbols; short dash line) and treatment B (white symbols; solid line). The three corresponding linear least squares regressions are highly significant (all P<0.001) and the coefficients of determination (r2) are 0.68, 0.64 and 0.15, respectively.
Table 1.
Metabolic variables (mean ± S. E.) in lake sturgeon Acipenser fulvescens representing three different test groups: control (100% O2sat; 12L∶12D); treatment A (30% O2sat; 12L∶12D); and treatment B (100% O2sat; 24L).
Figure 4.
Forced maximum metabolic rate (MMRF30.5) is influenced by hypoxia in lake sturgeon Acipenser fulvescens.
Measurements of MMRF30.5 are body mass adjusted to a 30.5 g fish. MMRF30.5 decreased significantly across the range from 100% O2sat to 70% O2sat (P<0.03; r2>0.94).
Figure 5.
Forced maximum metabolic rate (MMRF) is repeatable in individual lake sturgeon Acipenser fulvescens.
Spearman's rank statistics were used to test for correlations between initial and final residual (i.e. body mass corrected) maximum metabolic rate (residual MMRF; mg O2 h−1) measured in individual A. fulvescens. The significant relationship (P<0.006; ρ = 0.76) indicates repeatability of MMRF. Time interval between initial and final measurements was 4.50 h.
Figure 6.
Relationships between forced and spontaneous maximum metabolic rates in lake sturgeon Acipenser fulvescens.
Data collection comprised three test groups: control (100% O2sat; 12L∶12D), treatment A (30% O2sat; 12L∶12D), and treatment B (100% O2sat; 24L). Spearman's rank statistics were used to test for correlations between forced (MMRF) and spontaneous (MMRS) residual (i.e. body mass corrected) maximum metabolic rate (mg O2 h−1) measured in individual A. fulvescens. In the control group, there was no significant relationship between the residuals (P = 0.40; ρ = 0.27). In contrast, the residuals correlated positively in both treatments A and B (both P<0.05; ρ≥0.66).