In early spring, the skies of Japan get decorated with Koinobori, multicolored windsocks that come along with the celebrations of Children´s Day. They are inspired by koi carps (Cyprinus sp.), which are ornamental fish that have been part of the Asian aquaculture for centuries. Their symbolism comes from an old legend, were a group of koi swam upstream for years, fighting with strong currents and an endless waterfall. The gods recognized their effort turning them into dragons, symbol of strength and perseverance. Alongside the great colors, their tolerance to cooler temperatures, adaptability and omnivorous diet allowed them to grow worldwide popularity in the pond hobby. However, people did not realized at that time of the risk that could be that an adaptable exotic fish reached the native freshwater systems.
Sadly, this happened when flooding of private ponds and intentional introductions released koi into the wild. It´s presence has potentially leaded to reduced water quality, algal blooms, uprooting of aquatic plants and overall loss of native biodiversity. This was proven in New Zealand, were implicated in the process of eliminating the aquatic plants that covered 80% of a lake in just 10 years, fostering the growth of algae and radically changing the ecosystem dynamic. Additionally, the koi herpesvirus (KHV) originated from them and can be transmitted to other carps, leading to mortality rates of up to 80%.
Fortunately, efforts have been taken to study them and create better strategies to reduce their populations. Hopefully, in a not so distant future, we will be able to appreciate them flying in the wind in the shape of Koinobori and not in the wild rivers and lakes throughout the world.
