The Coast Guard suspended its search for 42-year-old Jess Lopez on Tuesday evening after scouring the waters for him from around 7 a.m. until just after sunset.
Lopez is believed to have gone overboard sometime around 6:30 a.m. Tuesday, Coast Guard Station Monterey Executive Officer John Suckow said.
The man's shipmates said they had not seen Lopez since their boat, the Elaine, was about 12 miles off the coast of Moss Landing, Coast Guard officials said.
The Coast Guard sent two 87-foot cutters, two 47-foot lifeboats and one helicopter to search for Lopez, but he was not found. Three other fisherman on board the Elaine assisted in the search, Suckow said.
Although Lopez was reportedly dressed in bright orange rain gear, which would have made him more visible to search parties, he is not thought to have been wearing a flotation device or anything that would protect him from hypothermia, Suckow said.