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6033901 
Journal Article 
Number and Distribution Pattern of the Black Spots on Body Surface of Rainbow Trout 
Aminul Islam, M; Nose, Y; Yasuda, F 
1973 
1 
Nippon Suisan Gakkaishi
ISSN: 0021-5392 
39 
7 
727 
1) Number and distribution pattern of the black spots in some definite areas of body surface of 1, 394 specimens of rainbow trout were surveyed from six hatcheries in Honshu, Japan during the time from 1969-1971. 2) Number of spots showed a definite increasing tendency with less variation in specimens below about 30cm in body length (about 500g in body weihgt). The variation was very wide without a definite increasing tendency in specimens beyond that size. 3) Concentration of the anaesthetics (Urethane and MS-222) and the anaesthetic time did not have any considerable effect on the number of spots. 10 percent formalin did not have any effect either. Number of spots was found independent of sexes and side of body. 4) A maximum variation was observed in the number of spots in area B which was polymodal in nature. Modes were situated at or very close to the same locations in all the hatcheries. 5) Interhatchery variation was observed in the number of spots in area B. Hiruzen exhibited higher average number of spots than the other hatcheries, where the eggs were introduced recently from U. S. under the name "steelhead". Number of spots was less in Akashina, Okutama and Oizumi while intermediate in Fujinomiya and Nikko. 6) Annual variation did not seem to occur in the number of spots in area B, but a significant difference was observed in the average number of spots within a particular spawning season at the Okutama hatchery. Early spawning group exhibited higher average number of spots than the mid and the late spawning groups. 
Fish And Fisheries