Salt tolerance in Xiphophorus species:



April 1, 2010. After consulting the late Robert Rush Miller’s book Freshwater Fishes of Mexico, I can report than none of the Xiphophorus species found in Mexico naturally occur in brackish environments. The ancestors of the aquarium platy, X. maculatus and X. variatus, are found near the coasts and, as such, might occasionally venture into brackish waters, but I could not find any record of this in the aforementioned book. The closest brackish-inhabiting Xiphophorus I could find was X. andersi (the Spiketail Platy), inhabiting waters with 0.3 ppt salinity, but this is technically still considered freshwater (according to my reading). So, while this doesn’t rule out the Xiphophorus species south of Mexico, it does suggest that this particular grouping of fish species do not naturally inhabit brackish waters.

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