Fig 1.
Occurrence of round goby (red dots, from Azour et al. [48]) in the Baltic Sea-North Sea transition zone in relation to salinity at 0-5m depth.
Salinity data (yearly mean) are provided by Myocean and are output from the Baltic Sea 3D physical model code HBM (HIROMB-BOOS) with a spatial resolution of 2 km and temporal resolution of 1 hour.
Fig 2.
Relationship between ambient salinity and measured averages (circles, mean ± SE) and modelled (lines) round goby maximum metabolic rate (MMR, upper graph), standard metabolic rate (SMR, middle graph), and aerobic scope (AS: MMR minus SMR, lower graph).
For all groups n = 8, except for 10 and 15 PSU where n = 7 for MMR and AS. * indicate p<0.05, ** indicate p<0.01 and ***indicate p<0.001.
Fig 3.
Relationship between ambient salinity and round goby plasma osmolality (mean ± SE).
For all groups n = 10, except at 10 and 30 PSU where n = 9. Different letters denote significant differences in plasma osmolality between treatment groups.
Fig 4.
The salinity gradient between the brackish Western Baltic Sea and the full oceanic North Sea, with expected physiological performance and survival of round goby in relation to the ambient salinity.
Salinities between approximately 20 and 25 PSU are considered ‘pejus’ salinities, i.e. where things are getting worse, whereas performance is significantly reduced at salinities of 25 PSU and above. Present occurrence (until 2013) of round goby is shown with red dots (modified from Azour et al 2015 [48]).
Table 1.
Size (mean ± SD) of round goby used in respirometry and for blood plasma osmolality experiments.
Length is total length, and Fulton’s condition factor (K) was calculated as K = 100×W×L-3 (where W is in g and L is total length in cm).
Fig 5.
An example of the oxygen consumption rate during an experiment and the determination of standard metabolic rate.
Upper panel: Open circles represent oxygen consumption rate (ṀO2) and solid circles represent the corresponding R2. The values were recorded at 25 PSU and 18°C. Lower panel: a histogram of all ṀO2 values with an R2 above 0.95, fitted to a double Gaussian distribution (solid line). The standard metabolic rate is shown in both panels by punctuated lines, and was determined as the lowest mean of the two Gaussian distributions.