Two species of stickleback fish live in an isolated glacial lake in Canada. One species dwells in the open water and the other dwells near the lake bottom. These stickleback species can mate and produce a hybrid species. In 1958, a river flowing into the lake was dammed. The graph shows the population change in each stickleback species before and after the dam was built.
Which is the best conclusion from the data shown in the graph?
The damming of the river caused a decline in the population of hybrid sticklebacks.
The decline in open-water sticklebacks caused an increase in bottom-dwelling sticklebacks.
The number of hybrid sticklebacks has increased since the dam was built.
The populations of both open-water and bottom-dwelling sticklebacks rose after the dam was built.