Study on relationship between body length and blood index of juvenile yellowfin tuna (Thunnus albacores)

In order to accumulate the basic physiological index data for juvenile yellowfin tuna (Thunnus albacores), we evaluated the blood potassium ion (K⁺), calcium ion (Ca²⁺), chloride ion (Cl⁻), hydrogen ion (H⁺), pH, glucose, lactic acid, sodium ion (Na⁺) and total hemoglobin concentration and hematocrit, osmotic pressure of the juveniles of different body lengths (20G: 20−30 cm, 30G: 30−40 cm, 40G: 40−50 cm). Results indicate that the blood parameters of the juveniles were relatively stable in the three body length groups. K⁺, Ca²⁺, Cl⁻, H⁺, pH, glucose and hematocrit were not significantly different between groups (P>0.05). The content of lactic acid and total hemoglobin concentration in the 20G group was significantly higher than the other two groups (P<0.05). The standardized calcium ion in the 30G group was significantly higher than the other two groups (P<0.05). The sodium ion content decreased with the increase of body length gradually, and the difference between the adjacent two groups was not significant (P>0.05). The results show that the juveniles had a small difference between the 30G and 40G groups. The 20G group was relatively different from the other two groups. As body length increased, blood indicators tended to be more stable.