The Study of temperature fluctuations effect on growth and age of Schizothorax pelzami (Kessler, 1870) in two river and lake habitats in north eastern of Iran

</em></strong>Age structure and growth characteristics of  the Schizothorax pelzami</em> (Kessler,1870) in the  two different  habitate (Frizi river and  Cheshmeh Sabz lake in Khorasan province) were studied from January, 2009 through January,2010. Age and growth variables were determined by examining 495 opercular bones, 261 samples from the river habitat and 234 species from the lake habitat of the S.pelzami</em> populations from specimens ranging between 69 and 274 mm total length. The instantaneous growth rate of young (one and two year old) S. pelzami</em> in the river habitat (mean higher temperature) was observed higher than the population living in the lake habitat (mean lower temperature).The results also showed that S. pelzami</em> has living longer in the lake habitat. Almost all of S. Pelzami</em> had reached maturity in 2-3 year-old in River site but age maturity of this species in lake site was 4 and 5 years old. Von Bertalanffy growth parameters showed that L(¥)in the lake population(♂464.66, ♀514.70)was higher than river population(♂303.15 , ♀ 456.92). Growth performance index(φ') was calculated in the lake habitat (♀9. 386, ♂9.225) and in the river habitat (♀9.253, ♂9.074). Overcoming the sex ratio in the river habitat was related to the male genus and in the lake habitat to the female sex.results of this study show that differences in habitat conditions,especially water temperature and geographical location of two habitats, have led to the formation of different strategies in age structure and pattern of growth in each population.