Abstract: The present invention is a device for detecting the presence of a fish on a fishing line, comprising a sensor for measuring tension on the fishing line and generating an electronic signal related thereto. The signal is processed by a filter circuit which removes signal components caused by environmental conditions such as winds, wave and current action, boat drift or snags. The filter circuit produces a signal output only if the tension reading is characteristic of a fish bite on the line. The preferred form of the invention includes two parts: a detecting and transmitting device for attachment to a fishing rod, and a receiving device which also functions as a storage box. A rotatable control is provided for adjusting the sensitivity of the device. The filter output is encoded by the transmitting device, and transmitted as radio waves. The radio waves are received by the receiving device, converted back into an electric signal and decoded.