The breeding program implemented by scientists involved artificial selection, focusing on increasing the growth rate of the fish population. By selectively breeding fish with desirable traits, such as rapid growth, and interbreeding them over multiple generations, the scientists successfully shifted the distribution curve towards larger fish sizes. The graph displays this shift, which resulted in more fish achieving larger body sizes compared to the initial population before the breeding program. Through consistent selection and controlled breeding, artificial selection was effectively used to enhance the growth potential of the fish population.