That means a higher proportion of what is in the sea is being caught,so the real difference between present and past is likely to be worse than the one recorded by changes in catch sizes.

这意味着更高比例的海洋生物正在被捕杀，因此介于现在和过去这一段时间，海洋生物量的真正差别可能比捕获量所记录的变化更要糟糕。