GMAT 逻辑考题
In 1992 outlaw fishing boats began illegally harvesting lobsters from the
territorial waters of the country of Belukia. Soon after, the annual tonnage
of lobster legally harvested in Belukian waters began declining; in 1996,
despite there being no reduction in the level of legal lobster fishing
activity, the local catch was 9,000 tons below pre-1992 levels. It is
therefore highly likely that the outlaw fishing boats harvested about 9,000
tons of lobster illegally that year.
Which of the following is an assumption on which the argument depends?
其中一选项：
The illegal lobster harvesting was not so extensive that the population of
catchable lobsters in Belukia's territorial waters had sharply declined by
1996.
未免涉及背景理解，我把题目也贴上来，
不过我的问题单纯在于上面选项这句话我看不懂，想要针对这个句子，请教前辈们该怎么
理解才对，谢谢。
我自己看这个句子是觉得时态很怪：一件事提及程度、但却是造成另一件“过去事情”的
发生？另一问题是觉得句子的因果也兜不太拢。
粗糙的直译的意思是：非法渔船之前的龙虾捕获量不是那么大，以至于1996年在B海域的龙
虾产量大减。(?)
既然非法渔船渔获量不大、为何会造成可捕到的数量大减呢？
想请教前辈不知道这句话是怎么想岔了、是否句意上理解有误，或有什么逻辑没有厘清。
PS 此选项正好为正解。