No interactions present.
Looking at this photo I originally decided that the identification of Common Darter was correct, but only after considering the possibility of Moustached (S. vulgatum).
However, after seeing the following observation (which appears to be the same individual?), I am not convinced that it can be safely identified from this photo:
Both Observations are probably of the same individual as they were taken within 20 seconds of each other.
I have yet to positively ID a Moustached Darter here, although they do exist in the area (Dijkstra). Common Darters are plentiful. All I can add is that it was relatively large.
Lat/Lng: 42.5486, 2.8762