题目选项分析

First discovered several years ago in North American lakes and rivers, the northern snakehead is a nonnative fish with no local predators. To keep the northern snakehead's population from growing, for the past three years wildlife officials have been paying recreational fishers for each northern snakehead they catch. In this way, the officials hope to stop the northern snakeheads from eliminating rare native fish species.

To evaluate the likelihood that the wildlife officials' plan will succeed, it would be most useful to determine which of the following?

【选项】Whether the fish species on which the northern snakehead preys in regions to which it is native and in which it is abundant have become significantly depleted in recent decades