“…Because both hypoxia and elevated temperature induce gill remodelling, it has been suggested that the signal for gill remodelling may be related to changes in the ambient oxygen supply or oxygen demand of the fish. An increase in ([Hb]) and blood oxygen-carrying capacity (Wood and Johansen, 1972;Tetens and Lykkeboe, 1981;Randall, 1982;Saint-Paul, 1984;Wells et al, 1989;Val et al, 1995;Silkin and Silkina, 2005), an increase in the number of muscle mitochondria and muscle myoglobin concentration, and a higher capillarization of muscle, which improves the extraction and utilization of circulating oxygen stores at low P O2 (Johnston and Bernard, 1984;Sänger, 1993). At the same time, fish may down-regulate energy turnover and improve the efficiency of ATP production (Hochachka et al, 1996), resulting in a lower maintenance metabolism.…”