REGARDING ECONOMICAL IMPORTANCE OF PRODUCING ALL FEMALE TRIPLOID POPULATIONS OF SALMONID FISH IN AQUACULTURE AND CONSEQUENT EFFECTS OF TRIPLOIDY INDUCTION ON SOME MORPHOLOGICAL ALTERATIONS OF SOME CELLS LIKE BLOOD ERYTHROCYTE, IN PRESENT STUDY, ERYTHROCYTE STRUCTURAL ALTERATIONS WERE INVESTIGATED IN ALL FEMALE DIPLOID AND TRIPLOID RAINBOW TROUT IN THE SECOND YEAR OF CULTURE AT 20 MONTHS OF AGE IN WINTER. FINAL RESULTS ON THE 43 TRIPLOID AND 46 DIPLOID FISH BLOOD SMEARS STAINED WITH 10% GIEMSA SHOWED SIGNIFICANT DIFFERENCES (P<0.01) ABOUT 5.18 % ERYTHROCYTE NUCLEI SEGMENTATION AND 0.27 % LINKED ERYTHROCYTES IN ALL FEMALE TRIPLOIDS IN COMPARE TO 0.00 % IN DIPLOID COUNTERPARTS. IT IS HYPOTHESIZED THE PECULIAR ABNORMALITIES ARE THE STAGES OF AN ERYTHROCYTE DIVISION PROCESS TO INCREASE BLOOD HEMATOCRITE AND OXYGEN CARRYING CAPACITY OF RESPIRATORY STRESSED TRIPLOID FISH.