Male pufferfish attract females through the design of intricate sand patterns on the ocean floor. This behavior is particularly well-documented in the white-spotted pufferfish (Torquigener albomaculosus), found in the waters around Japan. Here's how the process works: 

Building the Nest

The male pufferfish spends days, sometimes even up to a week, creating large and symmetrical circular patterns in the sand, often called "mystery circles." These circles can be up to 2 meters (about 6.5 feet) in diameter and feature complex ridges and valleys. 

Design and Decoration

The male uses his fins to carefully carve out these patterns, often adding finer details and decorations like shells and coral fragments to make the structure more appealing. Attracting 

Females

The finished pattern serves as a visual display to attract females. The more intricate and symmetrical the pattern, the more likely it is to attract a female. 

Spawning Site

Once a female is attracted to the pattern, she will enter the circle to inspect it. If she is impressed, she will mate with the male in the center of the circle, where she lays her eggs. The male then fertilizes the eggs. 

Egg Protection

After mating, the male continues to protect the eggs until they hatch, ensuring they remain safe from predators and are aerated properly. These sand patterns serve as a demonstration of the male's fitness, showcasing his ability to invest time and energy into creating and maintaining the structure, which in turn suggests he would be a good mate.