溜池の生産増進に關する研究溜池水生植物の生産量と魚類生産との關係に就て

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I found the following relation between the increase of the fishes and water plants in the irrigation pool. By too many water plants, the lowering of temperature will be caused, the effective elements consumed, the increase of plankton and bottom fauna hindered, and the swimming of fishes hampe??ed, but without water plants, the spawning of fishes will also be hindered. For effective production of fishes in a pool, such as 0-ike, in which a lot of water plants are found, we should decrease the water plants by the weeding, use of medicine, manuring, or keeping of Ctenopharyngodon idellus, leaving as little water plants as are necessary to the spawning of fishes. For effective production of fishes in a pool, such as Shin-ike, where are found little Hydrophyte, we should transplant a Hydrophyte into it which are necessary to the spawning of fishes. But, it is hard to produce fishes by transplant of plants, in a pool such as Asama-ike in which the submerged and surface aquatics can not keep their lives because the water is so muddy that it appears yellowish brown. In this case, we should put the egg-collector into the water to help the spawning of Carassius carassius. We were able to produce more fish by 26.4% in the O-ike, (in which we find a lot of water plants) by setting the Ctenopharyngodon idellus free in the pool and feeding them there to consume the plants.
公益社団法人日本水産学会の論文