描述和比较鱼类生长的快慢不宜使用生长指标(lgl_(t+1)-lgl_t)/0.4343)×l_t

IT IS INADVISABLE TO USE THE GROWTH INDEX (lgl_(t+1)-lgl_t)/0.4343)×l_t TO DESCRIBE AND COMPARE WHETHER FISHES GROW FAST OR SLOW

生长率(l_(t+1)-(l_t))/l_t与生长指标((lgl_(t+1)-lgl_t)/0.4343)×l_t具有如下截然相反的数学特性：一个世代在t龄年初的平均体长l_t的年生长量l_(t+1)-l_t如果取常数值，则随着l_t增大，生长率单调减小表示生长减慢；但生长指标单调增大。由此可以看出，生长率符合而生长指标违背它们所要描述和比较的生长快慢固有的生物学概念。因此，有必要建议世界各国的鱼类生态学界停止使用生长指标。

The growth rate and the growth index have the following completely contradictory characteristics.If l_(t+1)-l_t being annual growing quantity of l_t,takes a constant value in which the l_t is average body length of one generation at the year's beginning aged t,then with the l_t increasing,the growth rate is decreasing monotonously to denote that the growth is slowing down;but the growth index is increasing monotonously.From this it is can be seen that the growth rate conforms but the growth index violates the intrinsic biological concept of growth fast or slow to be described and compared with them.Hence it is necessary to suggest the fish ecology field of all the countries in the world stopping using the growth index.