The effect of transportation and handling on the hematology of diploid and triploid Atlantic salmon (Salmo salar)

Fish red blood cells (RBCs) normally do not divide in the bloodstream, however, such a mechanism may be effective in coping with stress and differences in RBC mitosis levels have been observed in diploid (2n) and triploid (3n) salmon. This study compares the effect of: i) transportation and ii) repeated handling on the production of mitotic RBCs and RBC length/width ratios in diploid and triploid Atlantic salmon. The results indicate that percentages of mitotic RBCs show a positive correlation with transportation in both ploidies. The length/width ratio of RBCs also changed significantly. Fish handled and bled weekly for four weeks were compared to fish handled weekly but not bled, and fish left undisturbed. The percentage of mitotic RBCs increased with increased handling. These results show that transportation and handling stress increase the numbers of mitotic RBCs and change their length/width ratios. In addition, triploids appear to produce higher percentages of mitotic RBCs in response to transportation and handling stress.