Comparative growth and condition of northern stream-dwelling rock bass,Ambloplites rupestris (Rafinesque)

Abstract

The growth and condition of rock bass,Ambloplites rupestris (Rafinesque), inhabiting the Middle Thames River near London, Ontario, Canada, are compared with growth in other northern streams and lakes, across the species' range in latitude, and between the sexes. Growth in streams was not less than in lakes, contrary to expectation. The condition and maximum size and age attained by stream inhabitants reflected the rigours of their environment. Growth in northern streams was less than in southern streams, due likely to the decreased ‘growing season’ length. Northern fish were typically in better condition, however. Sexual dimorphism in size was demonstrated, males being heavier and longer at age than females, although the sexes did not differ in condition.