Pachypanchax Killifish

Pachypanchax killifish are suitable for a small, species-specific aquarium, where they may even breed.

Pachypanchax are robust killifish native to Madagascar and the Seychelles. They are superficially similar to representatives of the Asian genus Aplocheilus, to which they are closely related, as well as the West African genus Epiplatys, to which they are not related. They differ superficially from their Asian and African relatives in their generally chunkier build — indeed the generic name Pachypanchax means “thick panchax.” “Panchax” is a catchall term for a number of colorful Old World fish in multiple genera. These differences extend to a number of skeletal features and the possession of a heavily scaled caudal fin.


Chunky Killies
Somewhat paradoxically, though it is a Malagasy species, P. omalonotus was the first member of the genus to be formally named, yet it is not the type species (a type species anchors a genus to its formal name; it is that which is most representative of its genus). That distinction belongs to P. playfairii (named after British naturalist Robert Lambert Playfair), a congener endemic to the Seychelles, a cluster of granitic islands located several hundred kilometers north of Madagascar that are, like P. playfairii, a remnant of the ancient southern super-continent of Gondwanaland.

Notable for the slightly raised scales of large males (suggestive of a case of dropsy), this colorful but rather belligerent killifish has remained available to hobbyists since 1924 (Sterba, 1966). I suspect that the availability of both live and preserved material was a factor influencing George S. Myer’s selection of this species as the type species of Pachypanchax when he erected the genus in 1933. As he himself admitted that he had not examined specimens of the three nominal Malagasy species (P. omalonotus, P. nuchisquamulatus or P. sakaramyi), geographical proximity seems to have been his rationale for including them within the new genus.

As noted, P. playfairii has been known to killifish fanciers for 80 years. Its Malagasy congeners, by way of contrast, are relative newcomers to the aquarium hobby. In 1953, Jacques Arnoult, a fisheries biologist and enthusiastic aquarist working in Madagascar, sent several pairs of a robust Pachypanchax he collected from the tributaries of the Betsiboka River, near the town of Maevatanana, to France.

While Arnoult’s killifish was both attractive and gratifyingly hardy, it made less of a splash among hobbyists than Bedotia madagascariensis, the first Malagasy species he exported to France. While the Madagascar rainbowfish is still commercially bred in the Far East, by 1980 the Malagasy killifish could no longer to be found in either Europe or North America. The reasons for its nearly simultaneous disappearance on both sides of the Atlantic will probably never be known. However, the observation that the final generation of this Malagasy Pachypanchax consisted exclusively of a single sex strongly suggests that inbreeding (which may lead to reduced fertility or sterility) may have played a role in the loss of the captive population.

When Arnoult collected his fish, the prevailing view among ichthyologists was that P. omalonotus was widely distributed along the western slope of Madagascar (Pellegrin, 1933; Kiener, 1963). It was thus perfectly reasonable for him to assume that the founders he exported to France were indeed this species (Arnoult, 1955). He thus introduced the fish to hobbyists as P. omalonotus. However, the type specimens of P. omalonotus were not collected on Madagascar proper but rather from Nosy Be, a large volcanic island located just off the coast of northwestern Madagascar.

Pachypanchax Bonanza
As I discovered when I visited the island in 1994 in the hope of reintroducing P. omalonotus to American hobbyists, representatives of the type population of this species resembled their distant Indian cousin Aplocheilus lineatus rather than the fish Arnoult collected from the Betsiboka drainage. The fish I collected from the Djabala River were polymorphic, with both red and yellow male color forms. Fish collected a few years earlier from streams near the town of Ambato-zavavy by German hobbyists in 1989 (Schaller, 1991) came in both red and blue morphs; these fish frequently sport broad black submarginal bands in their dorsal, caudal and anal fins.

This was the first surprise the genus Pachypanchax had in store for me. It wasn’t the last. Subsequent fieldwork undertaken in Madagascar by Patrick de Rham, John Sparks and myself has turned up seven additional undescribed species. Madagascar is now known to be home to 11 Pachypanchax, and exploration of yet-unsurveyed rivers on the western slope of the island will probably turn up a few more. Table 1 presents a current synopsis of Malagasy Pachypanchax species and their status in the hobby.

Malagasy Killie
Natural History With the exception of P. varatraza, Pachypanchax on Madagascar are restricted to rivers draining the northern and western slopes of the island. These killies occur in a broad range of habitats, from streams flowing 2,600 feet above sea level to lakes at sea level. Surprisingly dense populations can be found in the shallow lakes characteristic of the western lowlands of Madagascar (de Rham, 2000), as well as in the planted shallows of much larger bodies of water, such as Lake Kinkony (Kiener and Thérezien, 1963).

However, as the island’s climate over the past several millennia has been characterized by alternating periods of extreme drought followed by wetter conditions (Burney, 1999), shallow lakes are relatively ephemeral fish habitats. The persistence of Pachypanchax over a span of 65 million years argues that these killies are basically inhabitants of the small to mid-sized tributaries of the rivers that have been much more permanent features of the Malagasy landscape. However, their life history characteristics allow them to successfully colonize lakes and swamps when the opportunity presents itself.

Killie Care
Captive fish appreciate some degree of water movement. The waters of western Madagascar range from very soft and acidic to moderately hard and slightly alkaline. Both pH and hardness vary on a seasonal basis. It is thus hardly surprising that these killies can cope successfully with a wide range of water chemistries. In captivity, they seem to do best in moderately hard (DH 3 to 7), neutral to slightly alkaline water. They will breed in softer, slightly acidic water, but I have found both adults and fry to be much more susceptible to velvet disease when maintained in these water conditions.

As one might expect in fish native to flowing water, Pachypanchax do not appreciate elevated nitrite or nitrate levels. A regular program of partial water changes should be an integral part of their maintenance regime. These killies can tolerate therapeutic concentrations of salt in captivity; they are never found in brackish conditions in nature and do not respond positively when salt is added to their water. Unlike their south Asian and West African cousins, Pachypanchax are not compulsive jumpers. However, on three occasions, the addition of very small amounts of salt (1 tablespoon per 5 gallons of water) to their holding aquarium triggered a mass exodus of recently collected specimens.

Pachypanchax can also tolerate a wide range of water temperatures. They are able to deal with temperatures as high as 95 degrees Fahrenheit, but a range of 74 to 82 degrees is optimal for the day-to-day maintenance of most species, with a rise to 86 degrees for breeding.

The one exception to this rule is P. sakaramyi. This species is less vigorous and more prone to skin diseases if it is maintained at temperatures higher than 72 degrees year-round. Males are much less vividly colored, and the production of viable eggs also diminishes in such temperatures. I deal with this problem by unplugging the heater in the aquarium housing my colony in early January, and I do not plug it back in until the beginning of March. As the air temperature in my basement never drops below 60 degrees, this gives my fish three months of water temperatures close to those they would experience in the upper reaches of the Sakaramy during the austral winter. Plugging the heater back in results in the males lighting up like neon signs, spawnings and fry appearing about three weeks later.

In nature, Pachypanchax feed primarily on insects. Pachypanchax consume substantial quantities of aquatic insect nymphs and larvae taken from the bottom. Adult P. sakaramyi spend as much time picking at the substratum, submerged twigs and branches as they do investigating objects that have fallen into the water (Loiselle and Ferdenzi, 1997). Examination of the freshly expelled feces of newly collected specimens reveals comparable percentages of terrestrial and aquatic insects in the diets of the other Malagasy representatives of the genus.

Captive specimens eat any fish food small enough to be easily swallowed. I have had specimens of P. patriciae and P. varatraza take flake food within 15 minutes of their capture and have found that all of these fish learn to “beg” for food within a day of being brought into captivity.

I offer my fish a light feeding of high-protein flake food in the morning, and a much more substantial meal of frozen freshwater Mysis shrimp and bloodworms in the evening. I have found that a twice-weekly feeding of frozen subarctic copepods brings out the red and orange coloration of male Pachypanchax. I also offer my fish occasional feedings of live vestigial-winged fruit flies. I am not a great fan of Tubifex worms as fish food, but other breeders have found them an effective conditioning food for boosting the egg output of Pachypanchax females.

Most killifish fanciers house their fish in single-species aquariums, which works quite well for Pachypanchax. Most Malagasy Pachypanchax are surprisingly tolerant of male conspecifics even when housed together with females.

The undescribed species from the Doroa, a tributary of the Loza River, is the only exception to this rule. Larger specimens housed in holding quarters in the field were so aggressive toward one another that I had to bag them individually to put a stop to losses.

All the Malagasy species seem quite capable of holding their own in a community aquarium setting. These killies get along nicely with platies and swordtails. The smaller barbs and less “nippy” tetras also make suitable companions. I have even housed large specimens of P. varatraza with young adult Malagasy cichlids without difficulty. The killies were effectively ignored by their Ptychochromis and Paretroplus tankmates. Surprisingly, these killifish shove cichlids aside during feeding to be the first to grab a mouthful of frozen bloodworms! In any event, it would probably not be prudent to expect the same sort of amiable cohabitation between Pachypanchax and Paratilapia, as these Malagasy cichlids do prey on smaller fish in the wild.

It is not a good idea to house Pachypanchax with Bedotia rainbowfishes either. The more active rainbowfish react quite strongly to the killies and will force them to hide in the floating aquatic plants. As both genera feed on stranded terrestrial insects, this might be a case of the Bedotia reacting to the presence of a perceived competitor. However, as the present distributions of these two genera do not overlap, it remains something of a mystery how such behavior could have evolved.

Do Pachypanchax Have a Future?
Madagascar’s freshwater fish have the dubious distinction of being the Red Island’s most endangered vertebrates. Nearly two-thirds of the island’s 105 known endemic freshwater species are classified as endangered, threatened or vulnerable. To put this into perspective, compare the situation of Malagasy freshwater fish with that of lemurs, the “poster children” of conservation efforts in Madagascar. While the future prospects of many of these primates are far from promising, every species of lemur known to science at the beginning of the 19th century is still extant. However, since 1950, six fish species have gone “missing in action” and are feared extinct.

Like all of Madagascar’s freshwater fish, Pachypanchax must confront the paired threats of habitat loss and invasive exotic species. Table 2 summarizes the conservation status of the island’s 10 most important families. While the Aplocheilidae appear to have thus far dealt with these challenges more effectively than other families of endemic Malagasy fishes, it would be unwise to infer that these killies face an untroubled future.

Due to the interaction of habitat loss and exotic predators and competitors, P. sakaramyi is critically endangered and may become extinct in the wild within the decade. Given the rate of forest loss in the watershed of the Menambery River, a similar fate seems all too likely for the northernmost population of P. varatraza, while the remaining populations must confront the threat of the spotted snakehead (Channa maculata).

Pachypanchax sparksorum and the undescribed species native to the Loza and Sofia basins are also menaced by ongoing deforestation, while pressures from introduced poeciliids continues to push P. arnoulti into fragile marginal habitats. The relatively secure status of the remaining species of the genus is due in large measure to the absence of exotic predators, such as mosquitofish and the spotted snakehead from the Sambirano region of northwestern Madagascar. As there are no mechanisms to prevent the translocation of Gambusia holbrooki or Channa maculata from regions where they are solidly entrenched, the situation of P. omalonotus, P. patriciae, Pachypanchax sp. ‘Analalava’ and Pachypanchax sp. ‘Mahamasina’ could deteriorate abruptly.

In light of this constellation of present and future threats, it seems only prudent to maintain captive populations of these killies as insurance against their possible global extinction. Pachypanchax are certainly candidates for inclusion in existing institutional captive-breeding programs for endangered species. However, these and other endangered freshwater fish must compete with often more charismatic animals for the resources available to zoos and public aquaria, while the number of candidate species for captive management continues to increase. Given their common interest in preserving the world’s amazing diversity of freshwater fish, partnership between conservation biologists and serious aquarium hobbyists represents a logical response to this situation.

In view of the small number of species in question, no less than their extreme hardiness, any of the many specialist killifish groups operating in North America and Europe could easily organize and manage captive-breeding programs for the Malagasy Pachypanchax. The regulatory obstacles that have inhibited hobbyist involve-ment in efforts to save endangered North American killifish are not an issue in this case; securing founder stocks is not an insurmountable obstacle, either.

Several Pachypanchax species are already in the hobby, and most of the remainder hopefully soon will be. I invite serious killifish enthusiasts on both sides of the Atlantic to join zoos and public aquaria in the effort to assure a future for the killifishes of the Red Island.

Article Categories:
Fish · Freshwater Fish