Low energy passive acoustic detection algorithms have been developed to enable a MyGearTag SLU, or device of similar cost, complexity and power, to detect the presence of cetaceans (e.g. dolphins). Algorithms for the detection of both click trains (echolocation) and whistles (calls) have been demonstrated on extensive recorded hydrophone data from the North Sea,  containing two species of dolphin. Detection rates as high as 92% with near zero false positives have been achieved on these datasets. The algorithms are now being ported onto real time hardware for long term testing in the North Sea with wireless communication back to shore delivering  live detection data. The longer term objective is to enable fishers to be able to  use their MyGearTag hardware (when not needed for locating gear) to gain early warning of cetacean encounters and use this information to potentially reduce bycatch events. However, an affordable, low power solution for cetacean detection has wider potential for a number of marine monitoring and mitigation applications in offshore construction.