求分析这个长难句

孤云vs蓝天

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 size.

来自Android客户端

TwoGenTwoGen

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 size.

of what is in the sea 作定语修饰 proportion,句子主干成分是  a higher proportion is being caught.
between present and past 修饰 the real difference.句子主干成分是 the real difference is likely to be worse than the one.后面的recorded by changes in catch size修饰the one.
整句话直译：这意味着更高比例(的生物)正在被逮捕，所以现在和过去真正的差异，可能比已捕获记录的差别更大。

个人拙见，有不对的地方欢迎指教