Colombia
Figure 4 shows the surface temperature measured at 4m of depth by the vessels thermograph, and Figures 5, a and b, show the profiles of the two hydrographical sections worked off Punta Guascama and Golfo de Tibuga respectively. The surface temperature is very uniform along the coast, except in the southern part were a small gradient of 1°C was observed, declining towards the south. This gradient was not present during the two previous surveys, The hydrographic profiles demonstrate a remarkably high similarity with the situation during the previous survey, except that the low salinity river runoff then reported in the Gulf of Tibuga, now is lacking.
Panama
Figure 6 shows the surface temperature and Figure 7, a and b the hydrographic profiles from the Gulf of Panama and the Gulf of Chiriqui respectively. The distribution of surface temperature is as found in during the two previous surveys uniform over large areas, predominantly between 28 and 29°C. From the hydrographical section in the Panama Gulf an upwelling situation is indicated. This can be seen from the 16°C isoline which has lifted from about 100m during the third survey unto about 70m during the last. From the oxygen profile it can be seen that large areas of the shelf in the gulf have been covered with water of less than 1 ml/L oxygen content. This probably also causes the change in the demersal fish community mentioned later. In the Gulf of Chiriqui on the other hand the hydrographic conditions have not changed notably between the different surveys, and this region seems to form a much more stabile hydrographic regime.
Costa Rica
Figure 8 shows the surface temperature and Figure 9 the hydrographic profile off Golfo de Nicoya. No major changes in the surface temperature picture has happened since the previous survey. The temperature of the surface layer is very uniform between 28.5 and 30.0°c with a slight tendency for increase towards the shore. The distributions of temperature, salinity and oxygen in the profile seems to indicate that some lifting of deep water masses had occurred since the previous survey. Following the 16°C and the 1 ml/L isolines, which seems to run in relative close paralell, it can bee seen that these lines have lifted from about 100 m depth in August to about 80 m in November. This will however hardly effect the biotic fauna on the main part of the shelf. Conditions of oxygen deficiency in Golfo Dulce remains as previously observed.
