Fish Net Species

Anatolian killifish, Aphanius transgrediens

Only found in the spring inlets to Acigöl Lake in the Anatolian lakes region of south-western Turkey which is shrinking fast. In 2010 ZSL teamed up with Vienna Zoo, Hacettepe University, and Doğa Derneği to conduct surveys in this area of Turkey to try and find the Anatolian killifish and other threatened species. As recently as 2005 the Anatolian killifish was located in six springs feeding into the lake but in 2010 only three springs still contained small numbers of the fish. For this reason, along with the continued pressures on Acigöl Lake’s water supply, competition with introduced mosquitofish and climate change, the Anatolian killifish is classified as critically endangered. Like other FishNet species, ZSL Aquarium keeps two populations of this killifish, just in case one population develops a disease or a disaster strikes. Like most Aphanius killifish, the Anatolian killifish shows distinctive sexual differences. Males are slate blue with vertical white bars whereas females are silvery grey with black dots. Males spend most of the warmer months courting females and chasing rival males from a small territory. When a female is ready to spawn she will enter the male’s territory and lay her eggs, which are quickly fertilised by the male. At ZSL we collect the eggs and hatch them separately in order to prevent adult fish from eating them.

Azraq killifish, Aphanius sirhani

The tiny Azraq Oasis in the Kingdom of Jordan is the only place this fish lives in the wild. The oasis is also the only wetland in Jordan. What was once a vast and very important wetland for wildlife and people is now less than 10% of its former size. As the city of Amman got bigger the Azraq Oasis shrunk, with the water being used for people. That means the population of Azraq killifish has also shrunk since the habitat couldn’t support many fish. To add to the problem non-native species of fish were introduced to the oasis which predated or out-competed the unique native killifish. Now the Azraq killifish is considered critically endangered. There is still some hope though. In 2000 two Austrian scientists discovered a few remaining fish and rescued them, creating captive breeding programmes in Jordan and at Vienna Zoo. These offspring of these fish formed the stock for repopulating the Azraq Oasis. Also a stone pool was built that contains permanent water and no alien species; it acts as a refuge for the Azraq killifish. ZSL is keeping a population of these fish, along with Vienna Zoo and a few dedicated hobbyists. There is now a proposal to make the Azraq killifish Jordan’s national fish. If this happens it is hoped that additional conservation work will be initiated in Jordan.

Bluetail goodea, Ataeniobius toweri

This Mexican goodeid comes from a small sulphurous spring with water that emanates from underground caves. The area is called the Media Luna and its waters are used increasingly by the nearby human population. As a result the habitat is under threat as are Bluetail goodeas. They are now classified as endangered. At ZSL London Zoo we keep two colonies of this species and they breed quite readily. The parents take no notice of their offspring so very little manipulation of the animals is needed to ensure good population management. Between six and twenty fry are born after a two month gestation period and they can take most aquarium foods almost immediately. This species is much more slender than most goodeids and is considered a more primitive species than most. Male Bluetail goodeas give the species its name; during the courtship and breeding period males develop a metallic baby blue colour over their body which intensifies nearest to the tail. Females are more blandly coloured with a brownish-grey background colour and two horizontal stripes on the side. Only a very few zoos and aquariums maintain this species, along with a few hobbyists. Besides London Zoo the only other collection to keep Bluetail goodeas in the UK is Bristol Zoo.

Butterfly goodeid, Ameca splendens

The first Butterfly goodeids arrived at London Zoo from Mexico in 1970; six fish quickly turned into hundreds and the species was distributed to many other zoos and aquariums throughout Europe. It is now one of the most common live-bearing fish found in aquariums. The situation back in Mexico is quite the opposite. Butterfly goodieds are classified as extinct in the wild. Formerly found in the Rio Teuchitlan watershed in Jalisco, along with other endemic species, they are now confined to a tiny swimming pool that was created by local people who built a small impoundment near the stream. Somehow a few Butterfly goodieds survive here, despite the large number of people that use the pool for swimming and washing in. ZSL participated in an expedition to Mexico in 1998 that found the last remaining fish surviving in the pool. Unfortunately the Rio Teuchitlan itself is severely degraded though pollution and the introduction of alien species. For this reason even though Butterfly goodeids are common in captivity, it is essential that stocks are well managed to prevent them from becoming extinct. Like many other goodeids, this species shows distinctive sexual dimorphism. Males have a characteristic yellow and black banded tail, whereas females have a mottled tail without the banding.

Chapultepec splitfin, Girardinichthys viviparus

The critically endangered Chapultepec splitfin is only found in Lake Tecoco in the centre of Mexico City! Due to this urban location the habitat is under constant threat from human activities and it may seem surprising that the splitfin survives in the wild at all. Pollution in the lake along with introduced species has nearly wiped out the remaining Chapultepec splitfins in the wild. Most of the time this fish is an unassuming grey colour but during the breeding season males will develop jet black fins to attract the attention of females. Unlike most other goodeid livebearers, this splitfin requires much cooler water year-round, having evolved at the lower temperatures found in the higher elevations around Mexico City. This species was the first goodeid to be described by science way back in 1837. At that time the species was abundant in the lakes around Mexico City. The Chapultepec splitfin is one of the most difficult of the goodeids to maintain in an aquarium. Its requirement for cool water all year can be difficult to provide during a hot summer. Additionally this species is prone to mycobacterium infections and stressors often cause an outbreak. Very few other public aquariums hold this species so here at ZSL London Zoo we try to manage our population very carefully.

Corfu toothcarp, Valencia letourneuxi

This critically endangered species can only be found in Western Greece and Lake Butrint in Albania. It can no longer be found at the spring where it was first discovered because the spring is now a tap supplying water to the people of Corfu! ZSL Aquarium keeps populations that are considered genetically distinct from two locations – Albania in the north and the Pinios River in the south. This killifish has quite specific habitat requirements; it needs clean spring water that stays a fairly constant year-round temperature between 17-24C and contains floating aquatic plants on which to lay its eggs. It is very intolerant to the invasive mosquitofish and in places where the mosquitofish has been introduced, the Corfu toothcarp eventually disappears. In 2005 ZSL teamed up with the Hellenic Centre for Marine Research to conduct a rapid survey in Greece of all the known habitats in which the toothcarp was thought to be found. Alarmingly the survey results showed this species’ range has contracted considerably in the last few years. Now ZSL and HCMR are working together to try and save this species from extinction. Through monitoring, captive breeding, research and a trial translocation, we hope to stabilise the remaining populations of the Corfu toothcarp and prevent their extinction in the wild.

Crescent zoe, Zoogoneticus tequila

This species was only described by scientists in 1998, having been discovered a few years earlier. By the early 1990’s attempts to find the fish in the wild failed and it was thought to be extinct in the wild. In 2003 however a small population of less than 500 individuals was discovered in a small pool; it therefore is considered critically endangered. The Crescent zoe has met a similar fate to other goodeids from the Rio Teuchitlan region in Mexico after a dam was built, alien species introduced and humans polluting the water. There are now more individuals surviving and reproducing in captivity than in the wild. ZSL London Zoo has two colonies of Crescent zoe that are doing well and breeding regularly. Like other FishNet programme species we will continue to maintain and breed this species should a habitat restoration plan be implemented in the future. The live-bearing Crescent zoe can be predatory on its own offspring so for this reason we often isolate pregnant females from the rest of the group to ensure good fry survival. Males are distinctive with a bright yellow crescent on their tail fin and a deep slate grey body colour. Females lack this band and are paler grey.

Dead Sea killifish, Aphanius richardsoni

Only found in a few springs and tiny creeks that lead into the Dead Sea, this killifish could soon be dead itself if the situation continues to worsen. Already critically endangered this fish barely clings onto life in the wild. Although the Dead Sea no longer contains fish it is thought that before becoming too salty these killifish lived in the shallow waters along its shores. Fortunately a few zoos and aquariums and dedicated hobbyists have kept safety net populations in captivity should further disasters occur in the wild. Jerusalem Zoo is keeping and breeding the Dead Sea killifish and now ZSL also maintains a group of fish. Jerusalem Zoo is actively monitoring the remaining sites in Israel and trying to provide some protection for the fish in the wild. With increasing desertification, remaining water supplies in high demand and the growing threat from climate change the future of the remaining wild fish is uncertain. Like other Aphanius killifish, the Dead Sea killifish female lays eggs that are rapidly fertilised by the male. Here at ZSL we remove the eggs quickly to avoid them being eaten and then hatch the eggs and rear the fry in a separate tank until they are old enough to rejoin their parents.

Golden skiffia, Skiffia francesae

The Golden skiffia is extinct in the wild. This species shared a similar fate to the other species that made the Rio Teuchitlan their home after the river was dammed and non-native fish species were introduced. Its sympatric species: Butterfly goodeid and Crescent zoe still barely exist in tiny swimming pools near the river that humans created. The Golden skiffia wasn’t so lucky and completely died out in Mexico. Fortunately a few dedicated hobbyists caught some fish before the habitat was degraded and had luck breeding them. Zoos and aquariums now have populations of Golden skiffia that are being maintained as well. ZSL London Zoo has two colonies of Golden skiffia and Chester Zoo also keeps a group. This species is less robust than the other goodeids from the Rio Teuchitlan and requires excellent water quality, frequent feeding with small live foods and warm water year-round. Like other goodeids this species is a livebearer and produces around twenty fry with each birth. The fry must be fed on small high protein food to survive but generally their parents avoid predating them, unlike some other goodeids. Golden skiffia are susceptible to mycobacterium, an untreatable and contagious disease. For this reason we must keep a careful watch on our fish, immediately culling any individuals that show symptoms to prevent spread to the rest of the colony.

Polka-dot splitfin, Chapalichthys pardalis

The Polka-dot splitfin is another Mexican goodeid species under threat. Although the species hasn’t yet been evaluated by IUCN it is likely that it will be considered critically endangered when it is. The reasons for its decline include the usual problems: introduced species, pollution and water abstraction. Like the more commonly kept and similar looking Butterfly goodeid, the Polka-dot splitfin is now confined to a single human made pool. The concrete pool was created by diverting water from the stream and is used for people to bathe in. This precarious existence in Mexico makes the populations held in captivity very important for the survival of the species. ZSL London Zoo keeps three colonies of Polka-dot splitfins. We are currently doing behavioural studies on this species to determine the optimal stocking density for a given aquarium. Unlike many other goodeids this species behaves more territorially with males and females claiming a small space and chasing any rivals from it. We have also found them to be highly predatory on their own young. For this reason we separate females into isolated birthing chambers and return them to the colony when they have given birth. The fry then rejoin their parents and other adults when they are old enough to defend their own territory.

Potosi pupfish, Cyprinodon alvarezi

This Mexican killifish was once found in a clear spring that was a remnant of a much larger lake. Sadly the spring is no more and therefore the Potosi pupfish has no home left in the wild. Like many other small springs and pools in arid countries, human demand for their limited water supply has caused the Potosi spring to dry up. Fortunately dedicated aquarium enthusiasts collected some Potosi pupfish before the spring dried completely and the descendents of these fish now survive in a few private collections and a handful of zoos and aquariums. This pupfish is distinctive – males are metallic cobalt blue with a black band on their tail fin; females a silvery grey. Like other pupfish species, a male will fiercely defend a territory against other males. Battles between males rarely last for long but the winner gains a territory and with it a chance of enticing females to breed with them. The stress of defending a territory means that a dominant male rarely stays in the top position for long; younger males are always ready to challenge them for the space. Due to this territorial behaviour, ZSL London Zoo maintains three colonies of Potosi pupfish and tries to give them plenty of space for natural courtship and territory holding behaviour. You can see one of the colonies in our breeding room in Hall 3 of the Aquarium.

Rainbow characodon, Characodon lateralis

This stocky goodeid looks almost like a pupfish and shows the relationship between these two familes, despite the fact that goodeids are livebearers and pupfish are egg layers. Males of the rainbow characodon are bright red, especially during breeding time. Females stay an olive green colour with some black spots, perhaps to help stay camouflaged among the aquatic plants and stones in their habitat in the wild. Rainbow characodons are found in only a few springs with clear water in Durango, Mexico. The habitats in this area are under threat from pollution and introduced species; this makes the Rainbow characodon classified as endangered. Only a few public aquariums hold this species in Europe, although it is often kept in small numbers by hobbyists. This species can be problematic in captivity, being very disease prone if kept in water that is too warm for too long. For this reason ZSL London Zoo keeps them below 24C even in summer. In winter we drop their temperature to as low as 15C. In the hot summers of 2005 and 2006 we lost many individuals of this species but fortunately now we have built the numbers back up again.

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