The St-Lawrence paleorift system hosts three active seismic zones in eastern Canada, including the Western Quebec, Charlevoix and Lower St-Lawrence Seismic zones from south to north. Here we summarize our recent studies on the source mechanisms of earthquakes in this region and ongoing work of using seismic recording to detect whale calls in the St-Lawrence River. We apply a neural network based phase picking and detection method (EQTransformer) to enhance the seismicity catalog in the Western Quebec Seismic Zone (WQSZ) during periods of denser station coverages (2013-2015, 2020-2022). The application of EQTransfomer results in about a five-fold increase in detected earthquakes from the Natural Resources Canada catalog. Relocation of the enhanced catalog highlights several local clusters near the Greater Montreal Area, highlighting previously unmapped active fault structures. Further downstream in the Charlevoix Seismic Zone (CSZ), relocated seismicity is diffusely distributed around the paleorift faults and earthquakes on average have higher stress drop values within the meteorite impact structure, indicative of distributed fracture networks and compositional alteration. Stress inversion using a recently compiled CSZ focal mechanism solution database reveals a systematic clockwise rotation of the maximum horizontal stress with depth, which may reflect the transition from a shallow crustal stress regime to glacial isostatic adjustment influence at depth. Finally, we identify clear seasonal and spatial variations in the baleen whale calls along the Lower St-Lawrence Seaway using 2020-2022 land seismometer data, which provides a rich labeled dataset for the development of a machine learning based detection algorithm.