Final answer:
The main idea is that fish with certain markings make fishermen happy as they try to catch many fish. Selective fishing practices like keeping colorful fish and throwing back dull ones can lead to changes in the genetic makeup of the population, an example of natural selection.
Step-by-step explanation:
The main idea of the sentence is that this particular type of green fish with dark spots and a dark stripe is desirable to fishermen trying to catch a lot of fish.
However, if we consider how the fishing practices mentioned could influence the fish population in a lake, a single event of selective fishing could have a significant impact on the make-up of the fish population. If a fisherman catches and keeps colorful fish for an aquarium while throwing back dull-colored fish, over time, this could lead to a shift in the population genetics.
The dull-colored fish will have a better chance to survive and reproduce, leading to an increase in the frequency of genes for dull coloration in the population. This is a demonstration of natural selection, whereby the less colorful individuals have a survival advantage and become more common in the fish population as a result of human activity.
This sentence is referring to a specific fish species that has certain characteristics, such as green color, dark spots, and dark stripes on its body. These features make the fish visually appealing to fishermen, who are trying to catch as many and as colorful fish as possible.
By catching the colorful fish and throwing back the dull colored ones, the fisherman's actions can potentially change the overall makeup of the fish population, favoring the survival and reproduction of the colorful fish in the long run.