What effect does increased water temperature have on fish gill function?

Increased water temperature leads to a rise in the metabolic rate of fish. This is largely due to the fact that temperature influences the kinetic energy of molecules; as the temperature increases, molecular movement accelerates. In fish, higher temperatures can enhance the rate of biochemical reactions, including those involved in respiration and metabolic processes.

As the metabolism increases, fish require more oxygen for cellular respiration to meet their heightened energy demands. However, warmer water holds less dissolved oxygen compared to cooler water, which can create a challenge for fish in terms of oxygen availability. This increased metabolic activity often leads to a higher respiration rate, contrary to the notion that it would decrease.

In contrast, other options present interpretations that do not align with the physiological responses of fish to elevated water temperatures. For instance, slow movement would not generally result from increased metabolism; rather, fish may exhibit increased activity as they seek more oxygen to match their metabolic needs. Thus, the correct answer highlights the significant link between elevated water temperature and increased metabolic demands in fish.