Answer:
If all fish caught under 60cm are required to be thrown back, the fish population will likely increase over time. This is because the smaller fish that are thrown back will have a chance to grow and reproduce, leading to a larger population of fish in the future. Additionally, the larger fish that are caught and kept will have a chance to breed and produce more offspring, further contributing to the growth of the population. However, this also depends on other factors such as the availability of food, water quality, and other environmental factors that affect the fish population.