We present results from a study of the modifications induced by the short-timescale response of a shelf break baroclinic jet to the presence of a downstream canyon. The field site was the Canyon of Palam¿s, located in the northeastern edge of Spain. To determine the short time scale variability of the area, three intensive surveys were carried out at approximately 10-day intervals. Data indicate that the jet's location, usually over the slope, is subjected to significant onshore-offshore displacements. Analysis of the data has shown the importance of a small-scale temporal variability induced by river runoff and the climatology of the area. This variability generates on(off)shore displacements of the jet which interacts with the head(mouth) of the canyon. The different interactions with the canyon induced by these displacements produce different regimes of shelf-slope exchange in the canyon domain that strongly modify the biomass patterns in the area. ¿ American Geophysical Union 1996