The iwana, Japanese charr
Salvelinus pluvius dwelling mountain stream is one of popular game fish in the country. A study was made on the analysis of stomach contents of the fry collected and simultaneous survey of natural food organisms in the area for the understanding of their feeding habit in early larval stage leading to the management of natural population.
The stomach contents were examined on 67 charr fry (St. L. 18-58 mm) collected in a branch flow of the Nippara River (Fig. 1), about 93 km from the estuary to the Tokyo Bay, collection of the fry and food organisms carried out during day time, May to August, 1983 (Table 1) .
Harpacticoida and Chironomidae larvae occupied 43.1 and 32.6% respectively in the stomach of the fry 18 to 22mm St. L., indicating the significance of initial food items for the fry. The ratio of Plecoptera and Ephemeroptera larvae increased along with the growth of fry, the former occupying 23.8% and latter 48.9% in the stomach of fry 30 to 36 min St. L.. Trichoptera larvae and terrestrial animals were found to occupy 20.9 and 46.5% respectively in the fry 51 to 58 mm St. L. (Table 2, Fig. 4) .
It was also apparent individual size of food organisms became larger with the growth of fry (Table 3, Fig. 6) .
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