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Growth of fishes in different salinities Canagaratnam, Pascarapathy

Abstract

Juvenile sockeye, coho, and chum salmon and adult goldfish were studied for a period of ten weeks to determine whether varying degrees of salinity influenced their growth. The possible influences of such factors as temperature and food were rigidly controlled. Coho and chum salmon showed higher percent weight increase in the saline media. Coho grew best in 12% salinity and chum had a higher percent increase in weight in 30% salinity. The growth of sockeye in the saline medium was retarded for the first eight weeks, but during the last two weeks it surpassed that of the corresponding group of sockeye in fresh water. The early retardation in growth of sockeye, in the saline medium, is attributed to its longer fresh water life. The adult goldfish did not show any significant difference in weight increase. The records of the sizes attained by several species of fish inhabiting both sea and fresh waters show that salinity enhances growth. The evidence from experimental study, by other workers, on the influence of different environmental factors on growth of fishes, indicates that changes in meristic counts or body proportions, in early development, produces different growth rates. These changes could eventually affect the ultimate size. The physiological mechanisms of growth of fishes are not well understood, but it has been suggested that the influence of hormones on growth is probably ameliorated in the marine environment.

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