Recovery from exhausting exercise in an Antarctic fish,Pagothenia borchgrevinki

Summary Pagothenia borchgrevinki, an Antarctic teleost fish was swum to exhaustion and changes in lactic acid levels and blood haematocrit were monitored during recovery. The fish did not perform well at high swimming speeds due to an inability of the white myotomal muscle to produce ATP by anaerobic glycolysis. Consequently, low levels of lactic acid were produced which were fairly rapidly broken down. Haematocrit values were low in non-exercised fish, and these increased by over 100% during exercise, falling back to control levels over many hours. This is probably related to the increased oxygen demand during exercise.