Taxonomy & naming
Paratherina wolterecki was described by Aurich in 1935 and is recognised by Eschmeyer's Catalog of Fishes as a valid species in the genus Paratherina, family Telmatherinidae. The Telmatherinidae — the sailfin silversides — sit within the order Atheriniformes, the silversides and rainbowfishes, and reach their greatest diversity in the Malili Lake system of central Sulawesi, where Paratherina is one of the endemic genera.
The genus name Paratherina combines the Greek para, meaning near or beside, with atherina, the classical Greek name for the smelt or sand-smelt — a nod to the fish's silverside affinities. The specific epithet wolterecki is a patronym honouring Professor Dr Richard Woltereck (1877–1944), the German zoologist and philosopher whose work on Sulawesi's lakes and their fauna helped bring this endemic radiation to scientific attention.
Paratherina is one of a small cluster of telmatherinid genera confined to the Malili Lakes. Within a genus of otherwise similar slender silvery fishes, P. wolterecki is told apart by a suite of characters reported in the literature: an upward-directed mouth, 35 to 38 scales in the longitudinal row, an elongate ethmoid, and 13 to 14 branched anal rays.
Morphology
A small, slender, laterally compressed silverside, P. wolterecki reaches about 6 in in total length — one of the larger sailfin silversides of the Malili system. The body is elongate, the overall impression that of a typical open-water silverside: streamlined, pale, built for sustained swimming in clear pelagic water rather than for cover among structure.
Meristic counts recorded for the species include 9 to 10 soft dorsal rays, a single anal spine, and 13 to 14 soft anal rays, with 35 to 38 scales along the longitudinal row. The mouth is directed upwards, a feature noted as diagnostic against its congeners and consistent with feeding at or near the surface. The ethmoid bone is described as elongate.
Detailed published descriptions of live colour are sparse, and this atlas does not assert a colour pattern beyond what the sources support. As in many sailfin silversides, the common name refers to the enlarged or sail-like fins developed by some telmatherinids; the degree of fin elaboration and any sexual difference in P. wolterecki specifically is not well documented in the accessible literature, so it is left unstated here rather than guessed.
Habitat
The species is endemic to the Malili Lakes of central Sulawesi, Indonesia — specifically Lakes Towuti and Mahalona — within a latitude band of roughly 2 to 3 degrees south. The Malili Lakes are an ancient tectonic system, geologically old and long isolated, and that deep history is what let a distinctive flora and fauna — including the Paratherina sailfin silversides — evolve in place.
FishBase characterises P. wolterecki as a freshwater, pelagic, non-migratory tropical fish. In practical terms it is an open-water species of the lakes rather than a fish of marginal vegetation or inflowing streams, swimming in the clear water column above the lake bed. Its congener and the wider telmatherinid assemblage share this lake system, so P. wolterecki lives as part of an endemic species flock unique to these waters.
Towuti and Mahalona are connected within the Malili drainage, and genetic work on Paratherina has examined how populations are structured within and among these lakes. The restricted, lake-bound distribution is the single most important fact of the species' ecology: it exists nowhere else on Earth.
Feeding
Specific dietary studies of Paratherina wolterecki are not available in the cached sources, but its general ecology points to a diet of small invertebrates taken in open water. FishBase places the species at a trophic level of about 3.2, which is consistent with a carnivore or omnivore feeding chiefly on small animal prey rather than on plant material or detritus.
The upward-directed mouth noted in its description points to feeding at or near the surface, where small crustaceans, insect larvae, and other drifting invertebrates would be available to a pelagic silverside — the usual feeding mode of open-water atheriniform fishes, which pick small prey from the water column.
Because the species is essentially absent from the aquarium hobby, there are no established captive-feeding notes to report. Any keeper would have to extrapolate from the husbandry of other small, surface-oriented silversides — small live and frozen foods such as Daphnia, brine shrimp, and finely sized prepared foods — but this atlas flags that captive data for the species is genuinely sparse.
Mating
Reproductive behaviour specific to Paratherina wolterecki is poorly documented in the accessible literature, and this atlas declines to fabricate courtship detail. What can be said comes from its place in the sailfin silverside family — a group in which males of several genera develop enlarged fins for display and in which spawning generally involves adhesive eggs.
Genetic research on Paratherina sailfin silversides has focused on population structure and connectivity among the Malili Lakes rather than on mating systems directly, but that work bears on reproduction in an indirect way: the degree to which populations in Towuti and Mahalona exchange individuals shapes how the species' gene pool is maintained, which in turn is relevant to any breeding or conservation programme.
In the absence of published observations of pair formation, display, or spawning site choice for this species, the honest position is that the mating system is not well described. The wider telmatherinid literature offers analogues, but extending them to P. wolterecki specifically would be speculation, and the editorial standard here favours saying less.
Breeding
There are no detailed published breeding accounts for Paratherina wolterecki in the cached sources, and the species is not established in captivity, so a step-by-step breeding protocol cannot be given without fabrication. Sailfin silversides as a family are egg-layers that produce adhesive eggs attached to substrate or vegetation, and P. wolterecki can reasonably be assumed to share this broad reproductive mode, but clutch size, incubation period, and fry development for this species are not documented.
What the literature does provide is a conservation-genetics frame. Herder and colleagues, in a 2011 study in Conservation Genetics, examined genetic structure and connectivity among lake populations of the threatened Paratherina sailfin silversides of Sulawesi, covering two Paratherina species across Lakes Towuti and Mahalona. Their work treats the reproductive isolation and connectivity of populations as central to the group's long-term persistence.
The practical implication is that the species' reproductive future is tied to the health of two specific lakes. Narrowly endemic fishes with no outlying populations have little buffer against local breeding failure, which is exactly why connectivity and population structure within the Malili system are of conservation interest.
In the aquarium
Paratherina wolterecki is essentially an ichthyological subject rather than an aquarium fish. Targeted searches of rainbowfish and ANGFA-style hobby sources turned up no dedicated care, water-parameter, or breeding pages for the species, and sailfin silversides from the Malili Lakes are only very rarely kept. Captive data for this species is sparse, and this atlas reports that plainly rather than inventing husbandry figures.
What little can be inferred comes from the wild setting. A pelagic fish from a warm tropical lake would want a long tank with open swimming space, clear well-filtered water, stable tropical temperatures, and the company of its own kind rather than solitude. With an upturned mouth, it would take small live and frozen foods presented in the upper water column.
Prospective keepers should also weigh provenance. As a narrowly endemic, Near Threatened species with no captive-breeding base, P. wolterecki is not a fish to remove casually from the wild, and anyone encountering it should prioritise its conservation status over its novelty in the hobby.
Conservation
Paratherina wolterecki is assessed by the IUCN Red List as Near Threatened (NT). The assessment (Lumbantobing), dated 29 June 2018 and published in 2019, applies criteria relating to a restricted range and a continuing decline in habitat quality — the species is confined to the Malili Lakes and faces ongoing pressure on the quality of that habitat, with high sedimentation flagged as the leading threat.
The underlying vulnerability is geographic. Endemism to a single ancient lake system means there is no large outlying population to absorb local declines, and narrow distributions leave such species prone to extinction through habitat loss. The Malili Lakes face the pressures common to economically important lake systems — changes in water quality, introduced species, catchment disturbance — and any of these can erode habitat for an open-water endemic.
Conservation work on the genus has emphasised understanding how the Towuti and Mahalona populations are connected, information that helps target protection where it matters most. For an aquarist atlas the message is straightforward: P. wolterecki is a fish whose long-term survival depends on the integrity of two specific Indonesian lakes, and it should be regarded first as a conservation subject and only secondarily, if at all, as a fish for the home aquarium.