In meat cooking, the critical temperature is 140°F/60°C, when the connective-tissue collagen sheath around each muscle cell collapses, shrinks, and puts the squeeze on the fluid-filled insides, forcing juice out of the meat. But fish collagen doesn’t play the same critical role, because its squeezing power is relatively weak and it collapses before coagulation and fluid flow are well underway. Instead, it’s mainly the fiber protein myosin and its coagulation that determine fish texture. Fish myosin and its fellow fiber proteins are more sensitive to heat than their land-animal counterparts. Where meats begin to shrink from coagulation and major fluid loss at 140°F/60°C and are dry by 160°F/70°C, most fish shrink at 120°F/50°C and begin to become dry around 140°F/60°C. (Compare the behaviors of meat and fish proteins in the boxes).