Salvador Contreras-Balderas

The fishes of northern and central Veracruz, Mexico

AbstractThe northern and central part of Veracruz, México, as herein delimited, is inhabited by 121 species of fish, in 83 genera and 47 families. Four species and 3 families are Nearctic, 28 species and 6 families are Neotropical, and 1 species is circumtropical. Ecologically, 8 species and 4 families are primary, 25 species and 6 families are secondary, 30 families are peripheral, and 7 families are marine, many of them marine accidentals. A mountainous area near Punta del Morro almost reaches the sea, and acts as a filter for primary and secondary species. Its importance had not been described in detail. From the north, the following species range to Punta del Morro or less:astyanax mexicanus, Dionda ipni, Ictalurus cf.furcatus, I. cf.punctatus, Lucania parva, Cyprinodon variegatus, Gambusia affinis, G. vittata, Heterandria sp.,Poecilia formosa, P. latipinna, Xiphophorus birchmani, X. variatus, Cichlasoma cyanoguttatum, C. labridens andC. sp.. From the south, the species that approach or reach Punta del Morro are:Astyanax aeneus, Hyphessobrycon compressus, Rhamdia guatemalensis, R. laticauda, Rivulus cf.robustus, Belonesox belizanus, Poeciliopsis gracilis, Xiphophorus andersi, X. maculatus, andOphisternon aenigmaticum. Eight species including one peripheral are present on both sides and constitute short penetrations across the barrier. At least nine species represent introductions, purposeful or accidental. Gambusia regani andG. panuco are nominal species of the same form: by first reviser,G. regani is regarded as senior synonym.

Freshwater fish at risk or extinct in México

The Mexican freshwater fish that are at risk orextinct are listed by family, state,basin/region, and causes of risk. Of the 506known species, 168 are at some level of risk,and 25 are believed to be extinct. States withthe most reports are: Chihuahua (46); Coahuila(35); Nuevo León (20); Sonora (19); Durango(18); and Tamaulipas (15). With the exceptionof Sonora, these states are largely located inthe Río Bravo region, and are all arid orsemiarid. Most extinctions have occurred inNuevo León (8) and Coahuila (7). The maincauses of risk reported are: habitat reductionor alteration (86); water depletion (83);presence of exotics (76); small or decliningpopulation (73); and small habitat (57). Allof which result in very local endemism. Thesecauses of risk develop easily when thedistribution is small. The critical factor isaridity, which is associated withdesertization. Water conflicts were to beexpected, and the result is resource nonsustainability.

An annotated distributional checklist of the freshwater fish from Baja California Sur, México

An annotated distributional checklist of thefreshwater fish recorded historically andrecently in Baja California Sur, México, isprovided. This checklist is supported with4,857 specimens collected at freshwaterlocalities during the period of May 1991 toApril 2002, and complemented with a review ofspecimens in museums and in the literature. Thenative ichthyofauna is represented by 19species belonging to 16 genera and 12 families,with only two cases of endemism (Funduluslima and Gobiesox juniperoserrai). Thefirst occurrence of Centropomus viridisin freshwater environments of Baja Californiapeninsula is reported here. The familiesEleotridae and Mugilidae are the most diversewith 3 species each. Zoogeographically, most ofthe species are of tropical affinity(panamanian 63%, tropical amphiamerican 16%and circumtropical 5%) and of marineecological derivation (sporadic 53%,complementary 26%, vicarious 16% anddiadromous 5%). Six species are exotic in thisregion, of which Cyprinus carpio, Xiphophorus helleri and Tilapia cf. zilli are of recent introduction. The currentstatus of the endemic killifish (Funduluslima) is determined as endangered due tocompetition with Tilapia cf. zilliand other exotic fish.An annotated distributional checklist of thefreshwater fish recorded historically andrecently in Baja California Sur, Mexico, isprovided. This checklist is supported with4,857 specimens collected at freshwaterlocalities during the period of May 1991 toApril 2002, and complemented with a review ofspecimens in museums and in the literature. Thenative ichthyofauna is represented by 19species belonging to 16 genera and 12 families,with only two cases of endemism (Funduluslima and Gobiesox juniperoserrai). Thefirst occurrence of Centropomus viridisin freshwater environments of Baja Californiapeninsula is reported here. The familiesEleotridae and Mugilidae are the most diversewith 3 species each. Zoogeographically, most ofthe species are of tropical affinity(panamanian 63%, tropical amphiamerican 16%and circumtropical 5%) and of marineecological derivation (sporadic 53%,complementary 26%, vicarious 16% anddiadromous 5%). Six species are exotic in thisregion, of which Cyprinus carpio, Xiphophorus helleri and Tilapia cf. zilli are of recent introduction. The currentstatus of the endemic killifish (Funduluslima) is determined as endangered due tocompetition with Tilapia cf. zilliand other exotic fish.

Fish biodiversity changes in the Lower Rio Grande/Rio Bravo, 1953–1996

Clearly defined changes in the fishesof the Lower Rio Grande/Rio Bravo, Texas andMexico, have been documented since 1953. Morerecent surveys show that the originalfreshwater fish fauna has been retreating fromthe lower reaches and is being replaced bybrackish and marine invaders. A total of 13localities between Colombia (Nuevo León,México) and the delta (580 km) weresurveyed, with a total fish fauna of 142species, which include native, exotic, andintruding species. Changes were analysed bylocality. These changes show a loss of themajority of freshwater species, replacement oflow to higher salinity forms. This shift isvery clear in marine invaders, with somespecies penetrating the whole areainvestigated. Those changes are morenoticeable in the lower-most localities, anddiminish upstream. Data suggest that thechanges in the basin, reflecting shifts inwhole-basin ecology, include elevatedtemperature, salinity, turbidity, and lowerrunoff levels. There are indications of higherlevels of pollution as well. Informationobtained in this study is being incorporated inan Index of Biological Integrity to appearelsewhere.