The most endangered group of fish in the world.

Mexican goodeids – or splitfins – are one of the most popular groups of fish in the aquaria trade and yet in the wild many are very close to extinction. These tiny fish live in the small pockets of water in some of the driest of places on Earth, including Death Valley. This unique project brings together well organised and passionate ex situ breeders (at home and in public aquaria) with simple, direct action on the ground with Mexican experts and landowners.


Goodeids, generally referred to as splitfins, are some of the rarest fish in the world. These tiny jewels are often confined to the smallest pools of water in the Mexican and American deserts. Because of their beauty they are frequently kept in aquaria, including many public zoos and aquaria. They have a strong following of passionate supporters but until now there has been limited action for these highly threatened species.

There are approximately 50 species of goodeid. Three are found in Nevada in the US (there were four but one is extinct) and the rest are found in the Mexican Plateau. Many of the species are only found at a single location and confined to a single body of water. Two species are already extinct and three are extinct in the wild. More than 90% of the fishes are threatened with extinction, making it the most endangered group of fish in the world.

The first Mexican goodeid SHOAL is working on is the critically endangered blackspot goodeid Allotoca maculata. This species is endemic to the Lago de Magdalena basin near Guadalajara in Jalisco, Mexico and was first described in 1980. The project will focus on restoring and protecting habitat in the upper Ameca River watershed, where the first individuals were found and described as a new species.

The blackspot goodeid Allotoca maculata

This tiny fish grows to a maximum size of 48mm. As its name suggests it is distinguished by a black spot on its side. It is now only found in one area in two places in small ditches, pools and small muddy ponds close to the Laguna Magdalena. It is threatened by the loss of its habitat (even though it can survive massive reductions in the ponds during the dry season), pollution, and non-native species.

© Wolfgang Gessl

© Günther Hulla

What the project will do

The primary objective of the project is to restore and create new habitat that is free from pollution and invasive species. The team will also work closely with the Goodeid Working Group to investigate possibilities of releasing captive bred fish into this new habitat. The long-term success of the project will depend on the support and engagement of the local community and landowners.