What percentage of body weight does blood volume approximately constitute in fish?

In fish, blood volume typically accounts for approximately 4-8% of their body weight. This percentage is influenced by factors such as species, size, and environmental conditions.

Blood in fish serves crucial functions, including the transportation of oxygen, nutrients, and waste products, as well as playing a role in immune responses and temperature regulation. The relatively lower blood volume percentage in fish compared to terrestrial animals reflects their aquatic adaptation, where the buoyancy of water reduces the need for a larger volume of blood to maintain circulation and support bodily functions.

The other provided options do not align with the known physiological characteristics of fish. For instance, higher percentages would suggest a different circulatory or physiological demand that is not observed in fish, given their unique adaptations to their aquatic environment. The 4-8% range is a well-established figure in comparative physiology, emphasizing the efficiency of fish circulatory systems in relation to their overall body structure and environmental context.