In the present study,the growth performance and the effects of overwintering weight loss on the growth of Heilongjiang carp(Cyprinus cario haematopterus)(YL),selective line of German mirror carp(Cyprinus carpio L.mirror)(JL)and coldresistance line of Hebao red carp(Cyprinus carpio var.wuyuanensis)(HL)are evaluated by using passive integrated transponders(PIT)technique.The offspring populations of YL,JL and HL were generated at the same hatching time and under the same rearing conditions,PIT tags were implanted in the muscle of all experimental individuals on 135 d(day).Afterwards,the related growth indexes were measured on 135 d(before overwintering),325 d(after overwintering),385 d and 445 d,respectively.The results demonstrated that the special growth rate for body weight of JL was significantly greater than that of YL and HL only during 1-135 d(P<0.05),while YL had faster special growth rate for body length than that of JL and HL not only during 1-135,but 325-385 d(P<0.05).The coefficients of variability for body weight in each breed(line)exceeded 20% in each detected period indicating there was a large variation of body weight between individuals within the same breed(line).For each population examined,though male fishes had greater gonad weight and mature coefficient of gonad than female fishes on 445 d(P<0.05),significant difference of growth rate between male and female was not observed during the whole experiment.In addition,there was significant positive correlation between overwintering weight loss rate and body weight before overwintering in three carp breeds(P<0.01).Interestingly,overwintering weight loss rate between individuals with the same body weight scale in each carp breeds(lines)varied greatly,and these individuals could be subdivided into 2 populations with low weight loss(LWL)and high weight loss(HWL).The body weight of the LWL population was significantly lower than that of the HWL population on 135 d(P<0.05),while the LWL population had higher body weight on 325 d,385 d and 445 d than the HWL population(P<0.05).For body length performance,the LWL population was higher than that of the HWL population in each detected period(P<0.05).The overwintering weight loss rate had no correlation with the special growth rate for body weight during 325-385 d and 385-445 d,but had significantly negative correlation with the body weight on 385 d and 445 d(P<0.01).