Sagami River originates from Oshino-Hakkai 忍野八海. Along its journey to Sagami Bay, there are lots of springs on its banks, like the one we’ve visited last week. The water seeps in the forests alongside the river joins the mainstream from such springs. Or, the other satoyama forests do not stand right next to the mainstream of Sagami River. The water from them first comes out to a tributary that eventually joins the mainstream. A tributary itself could have even smaller tributaries, or rills, running along a tiny valley between tiny hills. Sagami River has lots of such systems in its basin. One such place for Sagami River is in Atsugi Kodomonomori Park (Atsugi Kids’ Forest Park あつぎこどもの森公園) in Atsugi City.
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| The map of Atsugi Kodomonomori Park |
Atsugi Kodomonomori Park is 8ha of satoyama forests where volunteers maintain the ecology of forests and rice paddies through their activities. My first impression of the place was like “Oh, it’s similar to Niiharu!” The forest of the Park invited me to stroll freely with lots of vegetations and insects … The place itself deserves one independent post. I spare the introduction of the forest for my later adventure. Today, the topic is aquatic creatures we’ve found in Kodomonomori Park. Certainly, the streams we met there were about max 50cm wide trickles running beside rice paddies volunteers taking care of. At the upstream end of such rivulets, there are small ponds, of 10m in diameter for the biggest. Some ponds are natural, and the others were man-made when yesteryear farmers cultivated the place for their rice and veggies. The tricklets pour into Ogino River 荻野川 whose ultimate water source is in the slopes of Mt. Takatori 鷹取山 (ASL 522.1m) near Lake Miyagase. Some 7km downstream from Kodomonomori Park is near JR Atsugi Station where Ogino River joins the mainstream of Sagami River. For the entire river system of Sagami River, the water from Kodomonomori Park is for downstream part. Very interestingly, the creatures we’ve encountered there were different from those near Camping Ground last week which located a bit upstream from the Kodomonomori Park.
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| Ogino
River. Could you figure out a white bridge over there? Beyond it there is a mouth of a streamlet we did a study the other day. |
The way water moves was also different. Sure, the rill flows to lower ground but the speed of it was not much for one sunny autumn weekend. The amount of water was also not threatening as we’ve encountered in the mainstream, or in Yadoriki Stream for steep Tanzawa mountains. Its “riverbed” could be sometimes a bedrock, but the majority was mud. The banks were often constructed by retaining walls made of wood panels. Never mind for such man-made structure, wild vegetations are covering the slope of banks, which is a typical scenery of traditional Japanese rice paddies. Unless you’re careful enough you may dunk your feet into muddy stream. The ponds have shores continuing from the vegetation for rivulets, and their offshore have bushes of common reeds. There were lots of dragonflies flying over our heads … Shaking plants as we did last week would yield some catch, but the best approach here could be plunging the landing nets in the mud to capture the living things in one swoop.
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| The flow of a rill was like this. |
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| The
left of the photo is a pond / a rice paddy. Across the wooden footpath on the right is actually a rivulet. Could you see lots of satoyama vegetation? |
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| Natural
shore of a pond in Kodomonomori Park. Arrow-leaved tearthumb was in full-bloom. |
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| Have you noticed a small stream running on our left? |
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| Golden-ringed dragonfly was everywhere. |
So did I play a mud game in the small trickles of Kodonomomori Park. At the beginning of our research, the pros from Environmental Research Center said “The number of species we’ll encounter here will be far smaller, as the water mass we enter today is definitely smaller.” Hm. I see. The number of species could be limited compared to these from tributaries or mainstream, for sure. But, surprisingly, it was far easier to capture aquatic creatures from the mud in the Park. It was like the dwellers of mud were disrupted their idyllic country life suddenly by our landing nets. There were lots of pond skaters and water striders. My specimen jar captured lavae of several kinds of dragonflies from big to small. River snails were also there. It was so effortless to capture Lefua echigonia, Hotokedojou in Japanese. In contrast, I have not met American crawfish.
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| The way to collect creatures is, first, scoop the mud, then wash it away in the pond until mainly leaves and other things remain in the net. In this way, we can find our catch in a plastic vat. |
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| My specimen |
If American crawfish thrived in Kodomonomori Park, they would eat up all Lefua echigonia for their lunch. Lefua echigonia is Japanese endemic, and endangered species. Once upon a time before industrialization, the fish was ubiquitous in rice paddies surrounded by satoyama forests all over. Now such combo of forest + agricultural field is endangered scenery and so for Lefua echigonia. They need this particular ecosystem for survival. Moreover, the fish is carnivorous, which means it competes with American crawfish. Alas, they do not have super-weapon of craws as the crawfish to fight for survival. It is a common story in Japanese satoyama water where American crawfish is present Lefua echigonia lose their survival game for food. They are eaten for extinction by Americans. Yet, it was so simple on that weekend to capture the fish there. There was not much presence of American crawfish in Kodomonomori Park. Why?
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| Lots of Lefua echigonia and Japanese
freshwater crabs, sans American crawfish |
There is at least one explanation. For years, the Park constantly solicits help from local kids who come to play in the Park to fish American crawfish and bring their catch to the admin office. There, the crawfish becomes roast crawfish to be discarded as garbage (… I think it might be possible to make a gourmet snack from the crawfish if they wish). In addition, when adult volunteers find some trace of crawfish, they execute mop-up operations in their field. The Park was opened in 2016 and such endeavor of citizenry from the beginning protects the endangered species. Once Toshiko Kitagawa 北川淑子of Tokyo University told us in a seminar for Niiharu (; my post on June 24, 2016). Satoyama environment of Japan has been the way to maintain biodiversity of our neighbor. It was replaced by commercial mono-cultivation during the 1950s to the 1980s. Biodiversity of our forests declined rapidly. Once we restore our previous way of satoyama management, some creatures can come back, and prosper as before … so she said. Abundant but endangered Lefua echigonia in Atsugi Kodomonomori Park would be one evidence, I guess.
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| We also encountered many mantises near the water,
together with |
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| Gordian worms. It means these poor mantises were infected and brought to the water to jump in and die for the grown-up worm to enjoy aquatic adult life. Let’s pray for them … |
Oh, I have to tell you one thing, really. When we did our research in the waters of Kodomonomori Park, we obtained permissions from Atsugi City and Kanagawa Prefecture. We showed several green banners around our activity notifying we were doing official water quality survey. If you visit Kodomonomori Park please refrain from picking flowers or fishing Lefua echigonia. They are precious members of biodiverse Park that is now a rare species in suburbs. Thank you indeed for your cooperation. 😉 I have not yet finished microscopic study with the specimen collected during the activities … Hopefully I will meet the deadline for reporting in early January. Later in this blog, I’ll let you know exactly what we’ve found during this year’s field study.
1-3-39 Shinomiya, Hiratsuka City, 254-0014
〒254-0014平塚市四之宮1-3-39
Phone: 0463-24-3311
FAX: 0463-24-3300
k-center@k-erc.pref.kanagawa.jp
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