Tab. 2. List of species classified according with their tolerance to salinity, abundance, standard length (maximum, minimum, average and standard deviation) and occurrence by elevation; High (352-519), Medium (185-351), and Low (19-184) meters above the sea level in the main rivers of the Río Acahuapa basin, San Vicente, El Salvador, 2011-2012. Shaded data represents the month of occurrence, the black circles represent occurrence by elevation. a Considered amphidromous or catadromous species by different authors based on direct or indirect evidence (Cruz 1987; Ribeiro & Villalobos 2010; Lorion et al. 2011; Smith & Kwak 2014b, 2014a). b Considered diadromous or amphidromous species by different authors based on direct or indirect evidence (Lorion et al. 2011; Smith & Kwak 2014b). c Considered diadromous or amphidromous species by different authors based on direct or indirect evidence (Lyons 2005; Smith & Kwak 2014b).FamilySpeciesNClassification tolerance an originStandard length (cm) minimum/ maximumAverage size/ standard deviationSamplesJuneAugustNovemberFebruaryMayHMLHMLHMLHMLHMLCharacidaeAstyanax aeneus (Günther, 1860) Roeboides bouchellei Fowler, 1923439 8Primary Primary4.22-9.00 5.00-6.506.38±1.41 5.93±0.81●●● ●●●●●●● ●●●●●●● ●HeptapteridaeRhamdia guatemalensis (Günther, 1864)62Primary3.37-14.508.81±3.48●●●●●Rhamdia laticauda (Kner, 1858)65Primary3.50-19.7211.14±4.26●●●●●AriidaeCathorops steindachneri (Gilbert & Starks, 1904)18Marine-estuarine6.06-9.427.74±2.38●●MugilidaeAgonostomus monticola (Bancroft, 1834)222Diadromousa4.64-25.507.95±1.49●●●●●●●Mugil curema Valenciennes, 18368Marine-estuarine3.71-4.003.86±0.21●●AnablepidaeAnableps dowei Gill, 18618Secondary7.00-16.5010.41±2.43●●Poecilia gillii (Kner, 1863)55Secondary4.00-10.256.77±1.81●●●●●Poecilia marcellinoi Poeser, 1995768Secondary3.00-6.804.24±0.94●●●●●●●●●●●●●●PoeciliidaePoecilia butleri Jordan, 1889802Secondary2.92-5.503.56±1.31●●●●●Poecilia salvatoris Regan, 19072721Secondary1.70-9.754.92±1.48●●●●●●●●●●●●●●●Poeciliopsis pleurospilus (Günther, 1866)741Secondary2.00-6.003.56±0.88●●●●●●●●●●●●●●●Poeciliopsis turrubarensis (Meek, 1912)107Secondary2.44-7.003.86±1.64●●●●SynbranchidaeSynbranchus marmoratus Bloch, 17952Secondary25.00-40.0032.50±10.61●●Centropomus medius Günther, 18641Marine-estuarine33.00---●CentropomidaeCentropomus nigrescens Günther, 18645Marine-estuarine14.20---●Centropomus robalito Jordan & Gilbert 18821Marine-estuarine17.00---●SciaenidaeBairdiella armata Gill, 18631Marine-estuarine9.00---●Amatitlania nigrofasciata (Günther, 1867)446Secondary1.50-10.005.93±1.65●●●●●●●●●●●●●●●Amphilophus longimanus (Günther, 1867)1Secondary5.50---●Amphilophus trimaculatus (Günther, 1867)1Secondary13.00---●CichlidaeAmphilophus macracanthus (Günther, 1864)1Secondary23.00---●Oreochromis niloticus (Linneaus, 1758)1Secondary: Exotic9.00---●Parachromis managuensis (Günther, 1867)1Secondary: Exotic25.00---●Parachromis motaguensis (Günther, 1867)8Secondary5.33-8.006.02±1.53●●●Dormitator latifrons (Richardson, 1844)36Marine-estuarine6.00-12.008.28±2.53●●●●EleotridaeEleotris picta Kner, 18631Marine-estuarine37.00---●Gobiomorus maculatus (Günther, 1859)23Marine-estuarine7.00-17.009.62±3.71●●●●●GobiidaeAwaous banana (Valenciennes, 1837)3Diadromousb9.00-13.1010.05±1.48●●Sicydium multipunctatum Regan, 1906183Diadromousc6.12-19.258.98±2.28●●●●●●●AchiridaeTrinectes fonsecensis (Günther, 1862)1Marine-estuarine9.00---●ParalichthyidaeCyclopsetta panamensis (Steindachner, 1876)2Marine-estuarine10.00---●Total6,742Total species5915411145101458155821Primary124132123121122Secondary465377477457469Marine-estuarine004002002005007Diadromous012013012012003