Hobbyist Interview　Hiroshi Kanashima (Chiba)

Enjoying the Joys and Hardships of Wild-Pond Keeping
Harvesting is the Ultimate Enjoyment with Friends

Chiba Prefecture’s Choshi City faces a sea area where the Kuroshio and Oyashio currents meet, making Choshi Fishing Port one of Japan’s leading fishing ports. It is also known for scenic spots like the Inubosaki Lighthouse. Inland, there are narrow valleys (yatsu) formed by eroded plateaus. The lowland parts were once used as rice paddies (yatsuda), but over time they fell into disuse, with some being repurposed as wild ponds for Nishikigoi.
Hiroshi Kanashima, who runs Kanashima Construction Co., Ltd. in this city, is one such person who uses these wild ponds to raise Nishikigoi. Behind his company, there are approximately six wild ponds (totaling about 1,000 tsubo/3,300 sq m) created by redeveloping unused yatsuda. We visited him as he planned to harvesting on November 3rd, Culture Day.

Started Keeping Koi at 49

Challenged Wild Pond Keeping at 60

― We heard you are harvesting your ponds today. Could you tell us what prompted you to start keeping koi?
Kanashima: Around 1967, when I was 15 or 16, my father built a small garden pond of about one tsubo and started keeping koi. That was the era when Prime Minister Kakuei Tanaka was a famous koi enthusiast, so here in Choshi, you’d see koi ponds everywhere you looked. I think my father was influenced by that trend. After he passed away in 2001, I took over the management of the pond. However, I cleaned it too thoroughly, I replaced all the water and within two or three days, all the fish died. My mother told me, “They didn’t die like that when your grandfather was doing it.” Looking back, I realized he always left about one-third of the old water in the pond.
― That’s a path every beginner goes through. So, you started keeping koi relatively late?
Kanashima: That’s right. I started bit by bit around age 49. The pond at my current home was built in 2004, three years after my father passed away, when we rebuilt the house as a two-generation home and included the pond. The plot is only about 60 tsubo, so my family initially fiercely opposed, saying if we built a pond… But when I said, “Then let’s not rebuild the house,” they reluctantly agreed (laughs). My sons below probably sensed my determination and helped out, so my wish came true. We designed it thoughtfully so it can be viewed from the living room and second floor, and made it flat for easy work.
― To secure enough water volume in a limited space, is the pond quite deep?
Kanashima: The depth at the four corners is 1.8 meters, and the center reaches 2 meters. The pond holds 30 tons of water, and the filtration system holds about 3 tons.
― Is that outside the pond enclosure the filter tank?
Kanashima: Yes. The depth is a little over 1m, and inside it’s divided into four chambers. When it was first built, we stood about 60 sheets of Inoue Sangyo filter matting inside, but now they’ve deteriorated and cleaning is troublesome, so we put them in nets.