Kyushu dam survey warns of shrinking fish

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http://www.mainichi.co.jp/english/news/news05.html

 

Sunday, March 11, 2001

 

Kyushu dam survey warns of shrinking fish

 

By Manabu Yoshikawa

Mainichi Shimbun

 

SAGARA, Kumamoto - A dam proposed for a Kumamoto Prefecture river could

cause large-sized fish for which the river is famous to shrink, a nature

conservation society warns.

The Nature Conservation Society of Japan (NACS-J) says there is a high

possibility that a dam on the Kawabe River in the Kumamoto Prefecture areas

of Sagara and Itsuki will reduce the size of ayu in the river.

 

Ayu, or sweetfish, are a delicately flavored type of fish that spawn in

clear waters. In the Kawabe river, their size averages about 23 centimeters,

but a survey conducted by NACS-J last September found significant reductions

in sizes of ayu near a dam in the area. The society warns that Kawabe River

ayu could also shrink if another dam proposed by the Ministry of Land,

Infrastructure and Transport goes ahead.

 

In the society's survey, 382 fish were taken from the Kawabe River, the main

section of the Kuma River, which merges with the Kawabe River, and another

upstream section of the Kuma River that is dammed.

 

Ayu in the Kuma River averaged 22.7 centimeters in length, and weighed an

average of 122 grams. Those in the dammed section of the Kuma River measured

22 centimeters on average and weighed 103 grams, while those in the main

section measured 22.1 centimeters and weighed 109 grams - both significantly

smaller than the Kawabe River ayu. The ayu in the Kawabe River also had a

higher weight- to-size ratio.

 

Officials of the ministry's Kawabe River office said their surveys in the

past found no such difference in ayu sizes.

 

But Ryuichi Yokoyama, managing director of NACS-J, said colder water near

dams can affect the size of fish.

 

" If a dam is constructed (in the Kawabe River), according to Ministry of

Land, Infrastructure and Transport figures, the temperature of the water

will drop about three degrees and there are fears that the size of ayu will

get smaller, " he said.

 

When a dam is constructed, the quality of downstream water often worsens. To

counteract this problem, cold, clear upstream water is washed downstream.

This reduces the temperature of the water.

 

On Feb. 28, a cooperative holding fishing rights in the Kawabe River

rejected a fishing compensation proposal from the ministry, effectively

halting the start of construction work on the dam this fiscal year.

 

Because of their size, ayu in the Kawabe River are often referred to as

shaku-ayu. A shaku is a Japanese unit of length equal to about 30.3

centimeters. Kawabe River ayu are also renowned for their quality flavor.