The harbour masters of Guernsey and Alderney are to jointly lobby lighthouse managers over the decision to scrap the islands' foghorns.
The signal at Alderney's Quesnard Lighthouse has been stopped and the light dimmed. Others are due to follow.
Guernsey harbour master Captain Peter Gill said they were a safety necessity.
Trinity House, which oversees British lighthouses, previously said stronger beams and horns were no longer needed for larger modern shipping.
It said less powerful lights were adequate for local mariners and the reduction in power from cutting the light and stopping the foghorn would save about £1,500 a year.
Alderney's harbour master Captain Steve Shaw said: "Given the limited power consumption of foghorns, they would have been worth keeping."
He said this was particularly the case as the main route for all Channel Island shipping was just off Alderney.
Captain Gill has written to Trinity House on behalf of the Bailiwick.