I will find time to read the paper linked in post #9, so for the moment my comments do not take into account any data from this paper.
As for the article linked by Nick in post #8 I have some concerns. First, I decide whether to accept or disregard data on any internet fish site when the author identifies him/herself and provided this individual is knowledgeable. Anyone can set up web sites and pose as "experts" with no reliable basis. I am not saying the "Joseph" who seems to administer that Endler site is not knowledgeable, but I do question the "salt" information.
Schories et al. (2009) determined that Endler's Livebearer is the species
Poecilia wingei is now unequivocally defined by the molecular phylogeny as a valid distinct species from the guppy,
P. reticulata. A third distinct "guppy" species is described from Trinidad (Schories et al, 2009). The three guppy species have been placed in the sub-genus
Acanthophacelus that is considered to be generically different from all other taxa in the Poeciliinae subfamily.
It was not until 2005 that the species was scientifically described as a distinct species by F.N. Poeser, M. Kempkes & I.J.H. Isbrucker. The genus name
Poecilia comes from the Greek poikilos meaning "with different colours" and the species epithet honours the ichthyologist Dr. Ojvind Winge. Poeser et al. (2005) proposed re-establishing the genus name
Acanthophacelus, originally erected by Eigenmann in 1907 and subsequently deemed a synonym for
Poecilia, as a sub-genus of
Poecilia. As mentioned above, Schories et al. (2009) have followed this provisional sub-classification for the (now) three guppy species on the basis of generic differences from the other species in the subfamily.
The common name "Endler's Guppy" honours John Endler who "discovered" the species in 1975, although it was actually first discovered in 1937 by Franklin Bond. The species is feared to be extinct in the habitat lake in which it was discovered due to pollution from garbage. A second possible site was mentioned by Dr. Endler but he was unable to find it. Schories et al. (2009) document this species occurring in the Cumana region.
Seriously Fish accepts this species to be endemic to Campoma and Buena Vista coastal lagoons in NE Venezuela. The source for the type specimens is a warm freshwater lake with hard, alkaline water on the Paria Peninsula. This paragraph is from the profile of the Endler on Seriously Fish, a site owned and run by a trained ichthytologist, and to which biologists contribute:
Laguna de Patos (the
type locality for the
species) was originally a
brackish lake which was formed by being cut off from the ocean by a sandbar. Over time the water has been altered by
runoff and is now
freshwater. When
P. wingei was rediscovered the lake contained very warm,
hard water which was very green due to high concentrations of
algae. The fish are now thought to be
extinct here as a garbage dump has been built adjacent to the lake and the water has since become polluted.
Occurs in fresh waters in the Campoma and Buena Vista lagoons unto Carupano, in northeastern Venezuela.
I believe both lagoons are now cut off from the ocean, and water is solely rain runoff. I would like someone to explain how an influx of sea water (bringing salt) can occur to land-locked lagoons?
Regardless of all that, most of the Endlers today are commercially raised; the original species may even be extinct in its habitat. I cannot be certain, but I suspect the commercial breeders are using fresh, not brackish, water.
The fact that any species can "manage" with certain water chemistry does not mean it would not be better if not forced into such water. Thrive rather than survive. There is no question that salt does impact all freshwater species, as I pointed out in my article I linked previously. Making life more difficult, however minimally, for our fish should not be our aim. There is no reason mollies should ever be kept in brackish or full marine water, even though they appear to at least "manage." I guess the bottom line is that it is not necessary to provide salt for these fish to have them in good health, and if not necessary, then better avoided.
