Fig. 1. Schematic drawing of trout instrumented with (a) occlusion catheter in dorsal aorta (Da), positioned distal to celiacomesenteric artery (CMa); (b) catheter in sinus venosus (Sv); (c) percutaneous ECG-electrodes and (d) occlusion probe around ventral aorta (Va). A cross-section of the ventral aortic probe is magnified to illustrate (i) PE-50 catheter connected to latex-balloon; (ii) inflatable latex-balloon and (iii) doppler crystal with lead.