Fish fauna of the Río San Pedro and Río La Pasión, Usumacinta River Basin, Guatemala / Ictiofauna del Río San Pedro y Río La Pasión, Usumacinta River Basin, Guatemala

Abstract The Río San Pedro and Río La Pasión lie within the Usumacinta River Basin, a globally significant center of freshwater fish diversity. Both rivers are listed among Central America's top 50 regions for conserving freshwater biodiversity. This study presents an updated checklist of 70 fish species, of which six are non-native to the Usumacinta River Basin. From these species, 69 are reported from the Río La Pasión and 56 reported from the Río San Pedro, representing higher species richness than previously reported. The checklist derives from a systematic survey of fishes conducted in 2019 and records available in public databases and published literature. Seventy-eight percent of the species were reported in both rivers, and Cichlidae and Poeciliidae had the most species. Secondary species represent 59% of the species reported, followed by peripheral species with 22% of the species. The species with highest fidelity in Río La Pasión were the armored catfish Pterygopichthys spp. and the livebearer Gambusia sexradiata; and the cichlids Thorichthys meeki and Oscura heterospila had highest fidelity in the Río San Pedro. Thorichthys helleri was widely distributed in both rivers. According to the IUCN Red List of Threatened Species, there are four species classified as Vulnerable in Río La Pasión. However, 62% of the species are of Least Concern, 25% of the species are Data Deficient, and 6% are listed as Not Evaluated. More research is needed to document the status of the fish fauna, and improved habitat protection is required to conserve stocks.

Resumen El río San Pedro y el río La Pasión se encuentran dentro de la cuenca del río Usumacinta, un centro de diversidad de peces de agua dulce de importancia mundial. Ambos ríos figuran entre las 50 regiones principales de América Central para conservar la biodiversidad de agua dulce. Este estudio presenta un listado actualizado de 70 especies de peces, de las cuales 6 son especies no nativas para la cuenca del Río Usumacinta. De estas especies, 69 se reportan para el Río La Pasión y 56 para el río San Pedro, lo que representa una riqueza de especies más alta que la reportada previamente. La lista de verificación se deriva de un muestreo sistemático de peces realizado en 2019 y registros disponibles en bases de datos públicas y literatura publicada. El 78% de las especies se reportan en ambos ríos, siendo Cichlidae y Poeciliidae las familias con mayor riqueza. Las especies con mayor fidelidad en Río La Pasión fueron el bagre acorazado Pterygopichthys spp. y el pez vivíparo Gambusia sexradiata; y los cíclidos Thorichthys meeki y Oscura heterospila tuvieron mayor fidelidad en el Río San Pedro. Thorichthys helleri se distribuyó ampliamente en ambos ríos. Según la Lista Roja de Especies Amenazadas de la UICN, existen cuatro especies clasificadas como Vulnerable en el Río La Pasión. Sin embargo, el 62 % de las especies son de Preocupación Menor, el 25 % de las especies tienen Datos Insuficientes y el 6 % se enumeran como No Evaluadas. Se necesita más investigación para documentar el estado de la fauna de peces, y se requiere una mejor protección del hábitat para conservar las poblaciones.

Water storage decisions will determine the distribution and persistence of imperiled river fishes.

Managing the world's freshwater supply to meet societal and environmental needs in a changing climate is one of the biggest challenges for the 21st century. Dams provide water security; however, the allocation of dwindling water supply among reservoirs could exacerbate or ameliorate the effects of climate change on aquatic communities. Here, we show that the relative sensitivity of river thermal regimes to direct impacts of climate change and societal decisions concerning water storage vary substantially throughout a river basin. In the absence of interspecific interactions, future Colorado River temperatures would appear to benefit both endemic and nonnative fish species. However, endemic species are already declining or extirpated in locations where their ranges overlap with warmwater nonnatives and changes in water storage may lead to warming in some of the coolest portions of the river basin, facilitating further nonnative expansion. Integrating environmental considerations into ongoing water storage negotiations may lead to better resource outcomes than mitigating nonnative species impacts after the fact.

Adaptive Radiation from a Chromosomal Perspective: Evidence of Chromosome Set Stability in Cichlid Fishes (Cichlidae: Teleostei) from the Barombi Mbo Lake, Cameroon.

Cichlid fishes are the subject of scientific interest because of their rapid adaptive radiation, resulting in extensive ecological and taxonomic diversity. In this study, we examined 11 morphologically distinct cichlid species endemic to Barombi Mbo, the largest crater lake in western Cameroon, namely Konia eisentrauti, Konia dikume, Myaka myaka, Pungu maclareni, Sarotherodon steinbachi, Sarotherodon lohbergeri, Sarotherodon linnellii, Sarotherodon caroli, Stomatepia mariae, Stomatepia pindu, and Stomatepia mongo. These species supposedly evolved via sympatric ecological speciation from a common ancestor, which colonized the lake no earlier than one million years ago. Here we present the first comparative cytogenetic analysis of cichlid species from Barombi Mbo Lake using both conventional (Giemsa staining, C-banding, and CMA3/DAPI staining) and molecular (fluorescence in situ hybridization with telomeric, 5S, and 28S rDNA probes) methods. We observed stability on both macro and micro-chromosomal levels. The diploid chromosome number was 2n = 44, and the karyotype was invariably composed of three pairs of meta/submetacentric and 19 pairs of subtelo/acrocentric chromosomes in all analysed species, with the same numbers of rDNA clusters and distribution of heterochromatin. The results suggest the evolutionary stability of chromosomal set; therefore, the large-scale chromosomal rearrangements seem to be unlikely associated with the sympatric speciation in Barombi Mbo.

Acoustic barriers as an acoustic deterrent for native potamodromous migratory fish species.

This study focused on the use of sound playbacks as acoustic deterrents to direct native potamodromous migratory species away from all kind of traps. The effects of two acoustic treatments, a repeated sine sweep up to 2 kHz (sweep-up stimulus) and an intermittent 140 Hz tone, were tested in three fish species native to Iberia: Salmo trutta, Pseudochondrostoma duriense and Luciobarbus bocagei. In contrast with S. trutta, the endemic cyprinids P. duriense and L. bocagei exhibited a strong repulse reaction to the frequency sweep-up sound. The 140 Hz stimulus did not seem to alter significantly the behaviour of any of the studied species. These results highlight the potential of acoustic stimuli as fish behavioural barriers and their application to in situ conservation measures of native Iberian fish populations, to protect them from hydropower dams. In addition, this study shows that acoustic deterrents can be used selectively on target species.

Evolving in the highlands: the case of the Neotropical Lerma live-bearing Poeciliopsis infans (Woolman, 1894) (Cyprinodontiformes: Poeciliidae) in Central Mexico.

BACKGROUND: Volcanic and tectonic activities in conjunction with Quaternary climate are the main events that shaped the geographical distribution of genetic variation of many lineages. Poeciliopsis infans is the only poeciliid species that was able to colonize the temperate highlands of central Mexico. We inferred the phylogenetic relationships, biogeographic history, and historical demography in the widespread Neotropical species P. infans and correlated this with geological events and the Quaternary glacial-interglacial climate in the highlands of central Mexico, using the mitochondrial genes Cytochrome b and Cytochrome oxidase I and two nuclear loci, Rhodopsin and ribosomal protein S7. RESULTS: Populations of P. infans were recovered in two well-differentiated clades. The maximum genetic distances between the two clades were 3.3% for cytb, and 1.9% for coxI. The divergence of the two clades occurred ca. 2.83 Myr. Ancestral area reconstruction revealed a complex biogeographical history for P. infans. The Bayesian Skyline Plot showed a demographic decline, although more visible for clade A, and more recently showed a population expansion in the last 0.025 Myr. Finally, the habitat suitability modelling showed that during the LIG, clade B had more areas with high probabilities of presence in comparison to clade A, whereas for the LGM, clade A showed more areas with high probabilities of presence in comparisons to clade B. CONCLUSIONS: Poeciliopsis infans has had a complex evolutionary and biogeographic history, which, as in other co-distributed freshwater fishes, seems to be linked to the volcanic and tectonic activities during the Pliocene or early Pleistocene. Populations of P. infans distributed in lowlands showed a higher level of genetic diversity than populations distributed in highlands, which could be linked to more stable and higher temperatures in lowland areas. The fluctuations in population size through time are in agreement with the continuous fluctuations of the climate of central Mexico.

Freshwater fish’s spatial patterns in isolated water springs in North-eastern Mexico

The Media Luna lake-spring was selected as representative of all thermal or no thermal springs in the zone of Valley of Rioverde, a semi-arid vegetation in the North-eastern of Mexico. This system is inhabited by 11 fish species, of which six are native. Four of the native species are endemic to the region and threatened due to touristic pressure and to the introduction of exotic species. The objectives were to determine the characteristics that influence the spatial distribution of the fish species, to analyze their spatial distribution patterns, and to describe the relationships between the different species. The general aim was to establish some basis for the conservation of these fish communities and their habitat. Several sessions were initiated in 1992 through direct observation. Later, between 1998 and 1999 five systematically seasonal sampling sessions were conducted (54 subaquatic transects/session). Finally, the data was updated by sampling in summer 2002 and winter 2006. Through the analysis was performed only for endemics of the region, like Ataeniobius toweri Meek, Cualac tessellatus Miller, Cichlasoma bartoni Bean and C. labridens Pellegrin, in at least one life stage, showed correlation with habitat variables or with other species. For these species, patterns of spatial aggregation and association with other species were observed. These results show a certain degree of specialization of endemic species to some microhabitat characteristics, as well as a significant interaction with other native species which they coexist. In addition, some significant relations between endemic and alien species suggest an antagonist relation. Management actions focused in the touristic use of the spring represent the main threat for these species, followed by an adequate management of exotic species. This study provides basis for future responsible management of these wetlands, where tourism and conservation can be combined. Rev. Biol. Trop. 58 (1): 413- 426. Epub 2010 March 01.

Este estudio se enfocó en los peces de un sistema dulceacuícola en el noreste de México, donde habitan seis especies nativas (cuatro endémicas amenazadas) y cinco exóticas. El objetivo fue establecer los patrones que determinan la distribución espacial, así como las interrelaciones de las especies. Los datos se basan en sesiones de observación directa desde 1992; entre 1998 y 1999 se llevó a cabo un muestreo sistematizado mediante transectos subacuáticos en cinco sesiones estacionales (54 transectos/ sesión), con sesiones adicionales en 2002 y 2006. Sólo las especies endémicas de la región: Ataeniobius toweri, Cualac tessellatus, Cichlasoma bartoni y C. labridens, en al menos un estadio de vida, mostraron correlación significativa con variables del hábitat o con otras especies. También mostraron patrones de agregación y asociación con otras especies nativas o introducidas. Existe especialización de los endémicos a las condiciones de su microhábitat, así como interacciones significativas con otras especies. Acciones inadecuadas para promover el turismo representaron la mayor amenaza por destrucción del hábitat, endémicos tales como A, toweri y C. bartoni enfrentan solapamiento con especies introducidas, sobre todo en sus sitios de crianza. Este estudio aporta bases para un manejo responsable de estos humedales, donde turismo y conservación pueden combinarse.