Eduardo Soto-Galera

Development of a preliminary index of biotic integrity (IBI) based on fish assemblages to assess ecosystem condition in the lakes of central Mexico

The lakes of central Mexico have great cultural, economic, and biological value, but they are being degraded at an accelerating rate. We employed historical data on fish communities from 19 of these lakes and case studies of community responses to environmental degradation from four of the best-studied, Xochimilco, Cuitzeo, Chapala, and Pátzcuaro, to construct a preliminary index of biotic integrity (IBI). This IBI was designed to be an easily applied method for assessing lake ecosystem health and evaluating restoration efforts. The IBI had 10 metrics: number of total native species, number of common native species, number of native Goodeidae species, number of native Chirostoma species, number of native sensitive species, percent of biomass as tolerant species, percent of biomass as exotic species, percent of biomass as native carnivorous species, maximum standard length of native species, and percent of exotic invertebrate parasite species on or in native fishes. Initial applications of the index showed promise, accurately ranking the relative degradation of the four case-study lakes. Further tests of the index are warranted, and more data are needed to standardize sampling procedures, improve species classifications, and refine metric scoring criteria.

Fish as indicators of environmental quality in the Rı́o Lerma Basin, México

Abstract The Rio Lerma basin, one of the most important hydrographic regions of Mexico, has a distinctive fish fauna. In recent years, the basin has experienced major increases in human populations and industrial and agricultural development. To assess the health of aquatic ecosystems in the Lerma basin, we analyzed the current status and long-term trends in fish species occurrence at 116 widely distributed sites in relation to water quality and land use information. Our results reveal a staggering and unprecedented level of environmental degradation. Over 50% of our sites are no longer capable of supporting fish life. Many sites have completely disappeared because of groundwater extraction, water diversions, or urbanization. The Alto Lerma subprovince has experienced the greatest negative impacts, but no region of the basin has escaped significant damage. Only 15% of our sites currently support species that we classify as sensitive to environmental degradation, and most of these sites are on small headwa...

Helminth parasites in freshwater fish from the Papaloapan river basin, Mexico

A checklist based on previously published records and original data is presented for the helminth parasites reported in 35 fish species from nine families from the Río Papaloapan basin, east Mexico. The checklist contains 85 taxa from 39 helminth families. Trematodes and nematodes were the most abundant taxonomic groups. The helminth fauna in the fish of the Papaloapan River basin predominantly consists of Neotropical species that are largely autogenic. The introduced species Centrocestus formosanus was the most widely distributed helminth, infecting 16 host species. Ten of the recorded helminth species have only been found in fish from the Papaloapan. This inventory contributes 157 new host records, and reports the presence of 30 helminth species in the Papaloapan for the first time . This inventory shows the richness of helminth parasite species in the fish of the Papaloapan River basin in comparison with the other hydrological basins in Mexico. It also demonstrates that this fauna is typically Neotropical and quite similar to that from the neighboring basins of the Grijalva–Usumacinta system and the Yucatan Peninsula. The data also suggest highly effective transmission between environments within the same basin and that the regional parasite fauna is strongly influenced by fish community composition.

Decline of Freshwater Fishes and Fisheries in Selected Drainages of West-Central Mexico

Abstract The unique freshwater fishes and fisheries of west-central Mexico are sharply declining because of environmental degradation. In the Lerma River basin, half of the localities that once supported fish communities either no longer have water or are so polluted that fish cannot survive. Of 44 native fishes, 3 are now extinct, and 23 are greatly reduced in range or abundance. In Lake Chapala, total fisheries production has actually increased despite major declines in water quantity and quality, but the fisheries for several valuable native species have declined or collapsed, and exotics now constitute a substantial portion of the catch. In the Ayuquila River, several species have been locally extirpated, and major untreated industrial and municipal discharges, coupled with substantial water withdrawals for irrigation, preclude fish life during the dry season in 20 km of river that once supported an important subsistence fishery. Conservation priorities include protecting localities that still retain ...

Helminth Parasites of Freshwater Fishes of the Pánuco River Basin, East Central Mexico

Abstract This study presents results from a survey of helminth parasites of fishes in the Pánuco River basin, in the states of San Luis Potosí, Hidalgo, Querétaro and Guanajuato, all in east central Mexico. Seventeen freshwater fish species (n = 1,019) were examined for helminths between May 1997 and September 1998. Thirty-one helminth species were collected: 11 allogenic species, mostly Nearctic in origin, and 20 autogenic species. Two anthropogenically introduced species were recorded. The most prevalent and widespread helminth taxon was Posthodiplostomum minimum (metacercariae). The helminth fauna of fishes of the Pánuco River is dominated by trematodes (12 species) and nematodes (11 species) accompanied by a few monogenean (4 species), cestode (3 species), and acanthocephalan (1 species) taxa. Most of the helminth taxa reported have been reported from other regions of Mexico. Thus, the helminth parasite fauna of fishes of the Pánuco River basin are not exclusive, including a primordially autogenic Neotropical species component mixed with a mainly allogenic, globally distributed Nearctic species component. The regional freshwater fish helminth fauna is associated with the ichthyofaunanal composition of the basin. The nematode family Rhabdochonidae displays high species richness in this hydrological basin of Mexico.

Helminth parasites of freshwater fish in Chiapas, Mexico.

An inventory based on previously published records and original data is presented for the helminth parasites reported in 54 fish species from 17 families from the state of Chiapas, southeast Mexico. This survey reports the presence of 43 helminth species in Chiapas for the first time. The actualized inventory of helminth parasites of freshwater fish from Chiapas contains 88 species from 67 genera and 40 helminth families. Trematodes and nematodes were the most abundant taxonomic groups. The helminth fauna in freshwater fishes from Chiapas consists of Central American species. All the helminth species recorded in Chiapas have also been collected from bodies of freshwater between the Isthmus of Tehuantepec and the Isthmus of Panama. This inventory shows that this fauna is quite similar to that from the neighboring basins of the lower Grijalva–Usumacinta system and the Yucatan Peninsula. The taxonomic composition and distribution data reported here for the helminth fauna of Chiapas’ freshwater fish, contribute to a better understanding of this faunal component in Central America.

DNA barcoding reveals taxonomic conflicts in the Herichthys bartoni species group (Pisces: Cichlidae)

Fishes of the genus Herichthys are the only representatives of the family Cichlidae to have colonized the Neartic region. In this study, we used DNA barcode of 64 individuals of the Herichthys bartoni species group to test the monophyly of the species and the efficiency of this tool to discriminate among species. The Bayesian phylogenetic tree and the neighbour joining (NJ) tree obtained from the Kimura two‐parameter model (K2P) give similar topologies. DNA barcoding resolution was very poor (25%). Additionally, the low levels of genetic divergence among taxa preclude the use of threshold values as has been suggested in earlier studies.

DNA barcoding of the ichthyofauna of Pánuco-Tamesí complex: evidence for taxonomic conflicts in some groups.

The Pánuco–Tamesí complex in eastern Mexico is globally recognized as an important ecoregion due to its high level of endemism. In this study, DNA barcodes were generated for 152 individuals of 31 species. Additionally, 170 DNA barcodes for the related species available in the Barcode of Life Database (BOLD) system were included to test the ability of barcoding technique to discriminate between the closely related species. DNA barcoding allowed the discrimination of 79.2% of the analyzed species; poor resolution was observed in four genera in which the levels of resolution ranged from 16.6% in the genus Herichthys to 77.7% in the genus Xiphophorus. The results of this study demonstrate that DNA barcoding is a useful exploratory tool but fails to discriminate between closely related species.

Morphometric variation of the Herichthys bartoni (Bean, 1892) species group (Teleostei: Cichlidae): How many species comprise H. labridens (Pellegrin, 1903)?

Cichlids of the tribe Heroini have long been a source of taxonomical conflict. In particular, the species included in the Herichthys bartoni group have failed to be recovered as monophyletic in different molecular studies. In this paper we use traditional and geometric morphometrics to evaluate morphological variation in the species included in the H. bartoni complex in order to evaluate the number of species it contains. An update of a previously published DNA barcoding study suggests the existence of three genetic clusters that included the six recognized species analyzed in this study, none of them recovered as monophyletic. On the other hand, geometric morphometrics arise as a useful tool to discriminate species due that traditional morphometrics showed a high overlap in the characters analyzed that prevents the proposal of diagnostic characters.

Threatened fishes of the world: Chirostoma riojai (Solorzano and López, 1965) (Atherinopsidae)

Common name: Charal de Santiago, Toluca silverside. Conservation status: Endemic, endangered (DOF 2002). Identification: Maximum length about 83 mm SL; body relatively deep; snout blunt equal to or included by lower jaw; teeth in bands, outer teeth not enlarged, none on vomer or palatines; lateral scales with pores; predorsal scales not crowded; pectoral fins small, rounded. Gill rakers, 12–18; anal rays 10–16; snout to origin of first dorsal fin, 45.2– 48.4% of standard length (SL); eye length, 5.1–6.0% (Barbour 1973). Distribution: Endemic to Valley of Toluca, State of México (Barbour 1973). Habitat and ecology: Clear to turbid (9–332 UFT), spring-fed lakes and streams, inhabiting relatively shallow, vegetated areas. Found in alkaline (pH 7.4–9.7) and well oxygenated (5–9 mg l) waters of low to moderate conductivity (20–340 μs.cm). Carnivorous, feeding primarily on zooplankton, fish less than 50 mm SL consume mainly Bosmina coregoni, Paracyclops sp. y Diaphanosoma leuchtenbergianum; larger individuals eat mostly Daphnia, especially D. catawba. Lifespan probably does not exceed two years in nature (Méndez-Sánchez and Soto-Galera 1996). Reproduction: Individuals mature within one year (30 mm SL), and spawning females deposit up 900 eggs in vegetation between January and October (Méndez-Sánchez and Soto-Galera 1996). Threats: Historically know from nine localities but now only found in two, Ignacio Ramírez reservoir and Santiago Tilapa lake (Méndez-Sánchez and Soto-Galera 1996). Declines have been caused by industrial and urban pollution and loss of habitat from excessive water extraction for potable, agricultural and industrial uses (Soto-Galera et al. 1991). Conservation action: This species is listed as endangered by the Mexican Government (DOF 2002). It has been reared in the laboratory with excellent results (Figueroa-Lucero et al. 2004). Conservation recommendations: Implement population monitoring programs and protect the two remaining habitats. Establish refuge populations, and re-introduce into historical habitats that have suitable environmental conditions. Environ Biol Fish (2008) 83:343–344 DOI 10.1007/s10641-008-9346-6