Oxygen Dissociation Curves of the Blood of the Tench, Tinca Tinca

Oxygen dissociation curves of tench (Tinca tinca) blood were constructed for fish which had been acclimated to 5, 13 or 20 °C for at least 3 weeks. Compared to the blood of an active fish such as the rainbow trout tench blood, has a high affinity for oxygen; at 13 °C and a of 2–3 mmHg the blood was half saturated with oxygen at a of 4 mmHg. Increasing temperature, increasing and increasing hydrogen ion concentration decreased the oxygen affinity of the blood. At low temperatures the blood had an elevated pH value compared to blood at high temperatures. This is discussed in terms of the temperature dependence of ionization constants, in particular that of water. The Bohr effect and the factors influencing the loading and unloading tensions of oxygen in tench blood are discussed. The role of the blood in respiration and some properties of fish haemoglobins are also discussed.