These are from various unofficial sources. As always with utility radio, it's only as good as the people who've taken the time to research it.
JGx This block for government and fishery:
JGA Fuji meteorological observatory
JGC Coast Guard/ Customs, Yokohama
JGD Coast Guard/ Customs, Kobe
JHx This block for fishery, with some gaps:
JHA Ibaraki Prefecture Fisheries Cooperative Wireless Nakaminato
JHB Fisheries Kushikino
JHC Chiba Prefecture Fisheries Cooperative Radio
JHD Fisheries Hakodate Radio Association
JHE Ehime Prefectural Fisheries Cooperative Wireless, Fukaura
JHF Niigata Fishery
JHG Fishing Usuki
JHH Fisheries Owase
JHI Fisheries Cooperative Wireless Natikatsuura, Wakayama Prefecture
JHJ Fisheries Cooperative Ootsuti Wireless
JHK Hakodate
JHL Fisheries Tosashimizu
JHM Aomori Fisheries
JHO Otaru fisheries
JHP Fisheries Ofunato
JHQ Fisheries Shiogama
JHS Fisheries Karatsu
JHT Miyako (Terrestrial radio facilities for fishing)
JHU Nemuro fishing cooperative
JHW Abashiri Fisheries
JHX High-Samani Fishing (Terrestrial radio facilities for fishing)
JHY Port of Nagoya
JHZ Fisheries Monbetsu