Their methods do not attempt to estimate the actual biomass (the amount of living biological matter) of fish species in particular parts of the ocean, but rather changes in that biomass over time.

• 他们的方法并不试图估量在海洋中特定区域的鱼类的确切生物总量（活着的生物的总量），却是那生物总量随时间的变化量。