Silvercarp: Catla; stocking ratio optimization in polyculture system. Optimization of stocking ratio of Silvercarp and Catla in Mola-Carp-Tilapia polyculture system

Indeed, some competent authorities are convinced that such a decline has already taken place and is continuing. "Un]der conditions that are both soft and unregulated," writes Dr. W. H. Sheldon, "our best stock tends to be outbred by stock that is inferior to it in every respect. . . . It is the fashion in some academic circles to assure students that the alarm over differential birth]rates is unfounded; that these problems are merely economic, or merely educational, or merely religious, or merely cultural or something of the sort. This is Pollyanna optimism. Reproductive delinquency is biologi]cal and basic." And he adds that "nobody knows just how far the average IQ in this country [the U.S.A.] has declined since 1916, when Terman attempted to standardize the meaning of IQ 100." In an underdeveloped and over-populated country, where four-fifths of the people get less than two thou]sand calories a day and one-fifth enjoys an adequate diet, can democratic institutions arise spontaneously? Or if they should be imposed from outside or from above, can they possibly survive? And now let us consider the case of the rich, industrialized and democratic society, in which, owing to the random but effective practice of dysgenics, IQ's and physical vigor are on the decline ...»