Final answer:
Fish age can be estimated by counting the growth rings, known as circuli, on their scales. The protective and overlapping nature of these scales provides streamlined swimming and reduces friction. Each ring generally corresponds to a period of slowed growth, typically associated with seasonal changes.
Step-by-step explanation:
Scales can be utilized to determine a fish's age in a similar way that trees can be aged by their rings. Although the process of determining age by scales is not as readily possible through direct observation, fish scales have growth rings, known as circuli, which appear as concentric lines. Each ring generally represents a period of slowed growth, which usually correlates with a change in season. Thus, by counting these rings, much like counting a tree's rings, scientists can estimate the age of the fish. Scales are a critical aspect of a fish's anatomy, providing protection and aiding in streamlined swimming. This protective feature not only shields them from predators and parasites but also reduces friction when moving through water. The overlapping nature of scales offers flexibility that is crucial for efficient swimming.