One of the Zoo’s most beautiful exhibits is one that most guests don’t notice on initial glance. The Zoo is home to a group of stunning koi fish that swim among the ponds that weave throughout Bamboo Trail. Known for their beautiful markings and calm demeanor, koi fish typically get along very well with little to no competitiveness or aggression toward each other. However, over the last few weeks, our group of koi were making it a little bit harder to go unnoticed with swift chasing and splashing.
The chasing and splashing were a result of the koi spawning. Spawning season usually takes place in the early mornings during May and June. As the koi prepare to spawn, the males will start following and showing interest to the most receptive and fertile female. When it’s time for the female to lay her eggs, the males will start frantically chasing her around the shoreline of the ponds and nudging her side with their mouths.
Like most fish, koi are egg layers. A mature female can produce up to 100,000 eggs. Once the female sheds the eggs, they will stick to whatever they come in contact with. As the eggs are shed, they are immediately fertilized by the males that are following her.
While females lay thousands of eggs during spawning, most of the eggs are eaten by other koi in the pond. In attempts to save some of the eggs, Nashville Zoo’s aquatic team placed green filters inside the ponds so we could collect the eggs and move them to an isolated area of the pond for hatching.
While they are admired for their unique colors and markings, the history of koi fish is not commonly known but is very elaborate. koi, or Nishikigoi (Cyprinus carpio), are descendants of the common carp. In nature, they are brown, but through selective breeding by the Japanese, numerous colors and patterns were developed.
The beautiful coloring of the koi is actually a mutated form of carp. Although the Japanese specialized in the selective breeding, the true beginning of koi fish originates in China when the carp started to develop patches of colors (like white, red, and blue) in their natural habitats in the Black, Caspian, and Aral seas in Asia.