Lucania interioris
Cuatrociénegas killifish / sardinilla de Cuatrociénegas

FUNDULIDAE - killifishes




20-30 mm SL as adults, rarely >35 mm

Conservation Status

Listed as Endangered by the American Fisheries Society in 1989, and as ------------- by the Mexican Government in 1994.


Restricted to margins of saline lakes and pools, marshes, springs, and their outflows, throughout much of the central and southwestern Cuatro Ciénegas basin, Coahuila, México.


Generally rare in collections, sometimes frequent in restricted, local areas.

Habitat & Ecology

Little is known of the ecology and behavior of this diminutive fish, which is likely more common than indicated by collections because of it's habitat and an evasive and secretive behavior. Cuatro Ciénegas killifish have been taken in habitats varying from seasonally hot, hypersaline, shallow and otherwise severe lake and pool margins through marshlands, to quiet, constant-temperature springs. They tolerate temperatures >44°C and total dissolved solids >95 gm/l. Occurrences are solitary or in small groups in water 5-30 mm deep along and within clumps of terrestrial and aquatic plants, vegetative debris, or even in livestock hoofprints. Individuals do not hesitate to force their way through water < 5 mm deep to attain such places or to flee when disturbed. Based on 10 stomachs analyzed they feed on detritus and algae. They are invariably associated with flocculent bottoms into which they abruptly dive to disappear when disturbed. Fish diving into the substrate remain there, invisible, for times often exceeding the patience of an observer. Such bottoms are often reducing in nature, yielding toxic gasses (e.g., hydrogen sulfide) when disturbed by collecting, which, along with presumably reduced dissolved oxygen, may result in death of fishes not otherwise captured.


Reproductive behavior of Cuatro Ciénegas killifish has yet to be reported. Breeding males are spectacularly colored, with pearl-like pigment spots on each lateral scale, yellow to orange fins with darkened margins, and iridescent blue eyes. The tiny young are locally common along shorelines in spring, summer and autumn in water a few millimeters deep.


Reduced volumes of flow during drought results in vast reductions of shallow, marginal habitats, which must be reflected in reduced populations of killifish. Some springs have further been canalized, resulting in reduced water levels and in some instances desiccation, both of springheads and downflow marshes. Groundwater extraction within and adjacent to springs clearly exacerbates these conditions. Anticipated detrimental impacts of non-indigenous crayfish, molluscs, and perhaps fishes (none yet confirmed as naturalized) may be far less severe on this species than others because of it's special habitats and behaviors.

Conservation Actions

A substantial proportion of the Cuatro Ciénegas basin, including many springs their outflows, marshes, and other habitats inhabited by this killifish, were set aside in 1994 as a biological preserve. Specific conservation actions are, however, yet to be proposed or implemented.

Conservation Recommendations

Devise and implement conservation actions preventing further loss and change of habitat and prohibit introductions of non-indigenous organisms. Especially needed are provisions to maintain marshes, which are quickly and permanently drained by canalization.

Important References


W. L. Minckley, Department of Zoology, Arizona State University, Tempe, Arizona 85287-1501

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