Alejandro Varela-Romero

1. Summary: We conducted field surveys over two consecutive years (2022 and 2023) of freshwater habitats in the Rio De La Concepcion (several tributaries and sites) and one site in the Rio Santa Cruz (tributary of the Gila River) in the state of Sonora, Mexico. Our primary goal was to detect the presence of the Rio Concepcion Topminnow ( Poeciliopsis jackschultzi ), an endangered microendemic livebearing desert fish whose external morphology is indistinguishable from several sympatric congeners. Using an environmental DNA (eDNA) metabarcoding approach (“MiFish” locus), we failed to detect evidence of P. jackschultzi , implying that it is extinct or present at abundances below our detection ability. Applying a collective evidence approach including visual/eDNA surveys and past records, we discuss the strengths and limitations of the eDNA metabarcoding approach. In the Rio De La Concepcion, we confirm the presence of the other known native and previously reported introduced teleosts, and reveal more recent introductions. In the Rio Santa Cruz site, we detect three putative non-natives (Asexual Hybrid Topminnow, Yaqui Sucker, and Mexican Roundtail Chub). We recommend further monitoring of habitats and fish taxa, and implementation of practices that improve groundwater recharge and the quality and quantity of treated wastewater in the study area.

El berrendo sonorense es una prioridad de conservación por acuerdos estatales, federales e internacionales. Para determinar las unidades de hábitat apropiadas para su manejo y conservación, se requiere información sobre los sitios preferidos por esta subespecie de berrendo. El estudio se realizó en la Reserva de la Biosfera El Pinacate y Gran Desierto de Altar. El conteo de grupos fecales sirvió como indicador de la abundancia de berrendos y, se identificaron sitios y características ecológicas relacionadas con la abundancia de berrendos en varias épocas del año. Se reconocieron nueve sitios de observación en las áreas críticas de distribución del berrendo para recolectar muestras fecales por temporada. Se recolectaron 244 grupos fecales, de los cuales en 234 fue posible extraer ADN. Utilizando el gen citocromo b, se verificó que 182 de los grupos fecales eran de berrendo, el resto correspondían a venado bura. Los sitios de observación se caracterizaron por cinco asociaciones de plantas y cuatro tipos de suelo asociados. Se determinó la abundancia de grupos fecales por sitio y estación anual. El berrendo prefirió las asociaciones de Larrea-Encelia, Larrea-Ambrosia y Cylindropuntia-Krameria. Se concluyó que el berrendo utilizó las asociaciones vegetales de manera diferente a su disponibilidad.

The Sonoyta pupfish (Cyprinodon eremus) is an endangered species endemic to the Sonoyta River basin in northwestern Mexico and southwestern United States. To assist the conservation efforts for this species in Mexico, a refuge population was established in an artificial pond in 1988 at Centro Ecológico de Sonora in Hermosillo, Sonora by translocating individuals from the Sonoyta River population. We used multivariate morphometric methods to delineate body shape variations in the refuge population after 29 years of isolation in comparison with wild individuals collected from the same sample. Significant variations were observed in the body shape between the refuge and wild populations. These variations are potentially attributable to different environmental conditions that influenced the refuge and wild populations. El pez cachorrito de Sonoyta (Cyprinodon eremus) es una especie en peligro de extinción endémica de la cuenca del Río Sonoyta en el noroeste de México y el suroeste de Estados Unidos. Para ayudar en los esfuerzos de conservación de esta especie en México, se estableció una población de refugio en un estanque artificial en 1988 en el Centro Ecológico de Sonora en Hermosillo, Sonora mediante la translocación de individuos de la población del Río Sonoyta. Usamos métodos morfométricos multivariados para delinear las variaciones en la forma del cuerpo en la población del refugio después de 29 años de aislamiento en comparación con individuos silvestres recolectados de la misma muestra. Se observaron variaciones significativas en la forma del cuerpo entre las poblaciones del refugio y las silvestres. Estas variaciones son potencialmente atribuibles a diferentes condiciones ambientales que influyeron en las poblaciones silvestres y del refugio.

Cyprinodon eremus is endemic to the Sonoyta River system, where wild populations comprise two conservation management units, one in Quitobaquito Springs, Arizona, and another small segment of the Sonoyta River, Sonora. Declining habitat from overmining of groundwater threatens both populations. Because of concern for the Sonoyta River population, refuges were built in Sonora and stocked with individuals from the river. Using seven microsatellite loci, we evaluated the genetic diversity of the wild population and three refuge populations. Comparison with earlier results for the wild population suggests that diversity changed little over the 12 years between collections. Two refuge populations established in 2007–2008 had levels of diversity comparable to that of the wild population. This reflects the relatively recent origins and exchange with the wild population. Notably lower measures of diversity occurred in an older refuge population that was established in 1988 and has no history of exchange with other populations. Suggestions for a program of genetic exchange are presented to inform future management.

Cyprinodon eremus is endemic to the Sonoyta River system, where wild populations comprise two conservation management units, one in Quitobaquito Springs, Arizona, and another small segment of the Sonoyta River, Sonora. Declining habitat from overmining of groundwater threatens both populations. Because of concern for the Sonoyta River population, refuges were built in Sonora and stocked with individuals from the river. Using seven microsatellite loci, we evaluated the genetic diversity of the wild population and three refuge populations. Comparison with earlier results for the wild population suggests that diversity changed little over the 12 years between collections. Two refuge populations established in 2007–2008 had levels of diversity comparable to that of the wild population. This reflects the relatively recent origins and exchange with the wild population. Notably lower measures of diversity occurred in an older refuge population that was established in 1988 and has no history of exchange with other populations. Suggestions for a program of genetic exchange are presented to inform future management.

We present here a post-impact assessment approach to address the challenges of measuring the quality of evidence from uncertain expert judgments, in accordance with the precautionary principle. This approach addresses the contentious issues regarding the different positions of experts, regulatory agencies, and academic institutions commonly referred to as “politically induced uncertainty.” To determine the best explanation of environmental damage, our approach combines two decision theory techniques: Weight of Evidence (WoE) and Clairvoyance Analysis (CA). We present the post-event assessment of the Buenavista del Cobre mine spill to illustrate our approach. In this case, experts stated candidate hypotheses and mechanisms linking the spill to environmental damage. The use of WoE and CA allowed us to ascertain the degree of scientific uncertainty of the causal mechanisms and to determine the pertinence of reversal of proof postulated by the precautionary principle. Our approach provided a sound basis to determine the validity of claims of environmental harm within a contested and uncertain context, which enhanced the process of adjudication.

The Yaqui catfish, Ictalurus pricei, is the only native ictalurid species described from north‐west México and south‐west USA. It is an endangered species owing to the decline and loss of most of its historical populations, mainly because of competition and hybridization with the non‐native channel catfish, Ictalurus punctatus. The Arroyo Cajón Bonito is one of the few remnant populations of Yaqui catfish in the Yaqui River basin, and it is threatened by the presence of channel catfish that escaped from private culture facilities. Phylogenetic analysis of two mitochondrial and two nuclear genes was used to detect evidence of hybridization with channel catfish in a collection of 20 catfish from Arroyo Cajón Bonito. Fourteen putatively pure Yaqui catfishes, five hybrids and one channel catfish were detected. This study further highlights hybridization between channel and Yaqui catfish as the main threat to the remaining Yaqui catfish populations. We recommend urgent evaluation of the remnant populations of native catfish elsewhere and their current conservation status.