HGCA appears to be the oldest hobbyist koi club. There were Japanese producer organizations prior to 1959 although it is not known (by me) if these same producer organizations still exist today.
Cut and pasted below is some info from Koi Talk - Newsletter of the Hawaii Goldfish and Carp Association, June, 2005.
"It would be interesting to document some of the early history of the Hawaii Goldfish and Carp Association. Below are some notes from the files of ZNA in Japan. After being translated and passed through several hands, the information may not be correct or may be incomplete. If you can add to or correct any of this, please let us know...
According to Doctor Takeo Kuroki, the first chairman of ZNA, koi were first exported from Japan in 1938 when one hundred specimens were sent to the International World’s Fair in San Francisco. For obvious reasons, the Second World War then effectively ended all exporting of nishikigoi.
In 1947 the staff of a Japanese fishery society visited the Yamakoshi area in Japan and decided to promote export of Nishikigoi. A few months later, there was the second export of koi from Japan when a group of 2,500 fish were sent to Hawaii. The Japanese dealer, Koichi Inouye, probably participated in these transactions. The fate of these koi is not well-documented, but a Japanese koi dealer named Kaneko noted that there were koi in the ponds surrounding the Pagoda Hotel in Honolulu in 1951.
Thus, it is not surprising that Hawaii is the home of the oldest koi club (our very own Hawaii Goldfish and Carp Association) and a very early series of exhibitions and koi shows.
The first koi show in Hawaii was between 1959 and 1961. The manager of Miyakoya koi outlet in Japan took part in the 1961 show. A dealer named Konishi, form the Hiroshima area, started selling koi in Hawaii in 1962. He became acquainted with Mits Nakamura, who lived in Hawaii, and Nakamura did much to promote Konishi’s business.
The first ZNA All Japan Nishikigoi Show was held in 1968. As it happens, the Grand Champion at this show was owned by Mits Nakamura. There was evidently some controversy about the fact that someone form Hawaii won the first ZNA show.
Kuroki noted that he was invited to judge the HGCA show in 1964. After observing how much our members were enjoying the show, Kuroki regretted that there was no similar type of koi organization in its birthplace, Japan. Upon returning to Japan, he appealed to koi keepers there to form a similar koi appreciation organization. The West Japan Nishi Nippon Airinkai was created shortly thereafter and the name was soon changed to Zen Nippon Airinkai (ZNA) which we know today.
In November of 1965, the Hawaii Goldfish and Carp Association became a sister club to ZNA (before the name change). A total of seven ZNA judges came to Hawaii in those early years to assist with shows.
Since that time, ZNA has been reorganized into districts and chapters. Hawaii would be in the USA District. Presently, ten US-based koi clubs are listed as chapters in the USA District of ZNA. However, the Hawaii Goldfish and Carp Association is not one of them."
-ste vehok