Popular as aquarium fish, armored catfishes from South America (Pterygoplichthys spp.) have been introduced and become invasive in tropical and subtropical regions worldwide. These ecosystem engineers can deplete basal resources (e.g., periphyton and detritus), with potential negative effects for native fauna. We studied the trophic ecology of fishes in the Usumacinta River Basin, Guatemala, where Pterygoplichthys is now widespread and locally abundant. We analyzed stable isotopes (δ¹³C, δ¹⁵N) in fish tissues and basal resources to assess the potential impact of Pterygoplichthys on the trophic ecology of six co‐occurring native fishes that feed at a similar trophic level (Astyanax aeneus, Dorosoma petenense, Thorichthys pasionis, Oscura heterospila, Poecilia mexicana, and Gambusia sexradiata). The study was conducted during the dry season in the La Pasion (LPR; high invasion) and San Pedro (SPR; low invasion) rivers. We compared isotopic spaces occupied by native fish and Pterygoplichthys, estimated isotopic overlap, and evaluated the trophic displacement of native species. We also evaluated the relationships of environmental factors, including the relative biomass of the invasive catfish, with δ¹³C and δ¹⁵N signatures. Except for P. mexicana, native species had lower isotopic overlap with the catfish in LPR. Native fish isotopic spaces were compressed and shifted toward higher trophic positions in LPR relative to SPR. Benthic food resources were important for Pterygoplichthys in both rivers, and water‐column resources had greater relative importance (RI) for native species in LPR. Native fish δ¹³C was significantly associated with Pterygoplichthys biomass, conductivity, and water flow velocity; and water depth and sedimentation had a significant association with native fish δ¹⁵N. Findings provide evidence that invasive Pterygoplichthys, along with environmental factors, impact the trophic ecology of native fish in the Usumacinta Basin. Additional field research conducted over longer time periods and mesocosm experiments that account for fish assemblage and environmental variation could elucidate Pterygoplichthys impacts via food resource depletion or habitat alteration.

Central America contains a rich diversity of freshwater habitats that support more than 600 species of freshwater fishes. However, despite several perceived threats to the integrity of the freshwater habitats throughout the region, a formal analysis of extinction risk for the region’s ichthyofauna is lacking. In this manuscript, we report an updated checklist of species and a novel comprehensive assessment of the conservation status of Central American freshwater fishes by applying the IUCN Red List Categories and Criteria to species at the global level. We also analyze the distribution of freshwater fishes across Central America and generate baseline geospatial data that can be used in multi-species conservation planning processes, which is available through the Red List Website. Our results indicate that between 15 and 28% of freshwater fishes in the region are threatened with extinction, with considerable uncertainty resulting from elevated data deficiency. We identify major and widespread threats in the region, including pollution, agriculture, aquaculture, biological resource use, natural system modifications, invasive species, and land development. This analysis represents an important first step in formulating effective conservation planning and action initiatives for a taxonomic group that historically has received few protections and can be used to inform conservation priorities of freshwater ecosystems at both national and regional scales.

La ictiofauna nativa de la cuenca del río Usumacinta se documentó en el noroeste de Guatemala para conocer la composición de los peces nativos en 20 sitios y su importancia en la pesca artesanal. El estudio incluyó recolecta de las especies con diversas artes de pesca, evaluación de abundancia de las especies mediante muestreos en transectos e identificación de las mismas en los mercados de venta, y en entrevistas con pescadores. Se identificó un total de 54 especies, 38 géneros, 18 familias y 8 órdenes. Las familias más abundantes fueron Characidae (3 especies), Poeciliidae (12 especies) y Cichlidae (22 especies), y en términos de riqueza el 68% de las especies corresponden a las familiasCichlidae y Poeciliidae. Al menos 38 especies nativas y 7 exóticas fueron identificadas en la pesca artesanal, de las cuales Centropomus undecimalis., Megalops atlanticus y Atractosteus tropicus son de alto valor comercial. Entre las 7 especies exóticas identificadas solo las especies del género Pterygoplichthys no son parte de la pesca artesanal. Los peces del área se dividen en 2 grandes grupos, uno en las zonas bajas de Petén y otro en las zonas altas de Las Verapaces y la pesca artesanal varía de acuerdo con este patrón. Según el estudio, a pesar de las especies exóticas, la pesca en la cuenca del Usumacinta está basada principalmente en especies nativas. Se requieren medidas de control delpez diablo exótico Pterygoplichthys spp. para evitar la propagación de sus poblaciones y mitigar los efectos negativos en la comunidad íctica nativa.

Non-native freshwater fishes have been introduced to Guatemalan freshwater ecosystems since the beginning of the last century without prior risk assessment or subsequent evaluation of their impacts. We synthesized historical records, and distributional data from a literature review, online databases and museum records of non-native freshwater fishes in Guatemala. We found records for 22 non-native freshwater fishes with the oldest records dating back to 1926. Non-native freshwater fishes were recorded in 64% of the river sub-basins in Guatemala and we identified that at least 12 species have established populations. The Jaguar guapote (Parachromis managuensis) and Tilapias (Oreochromis spp.) are the most widespread non-native fishes. The species of non-native freshwater fishes introduced indicates that they are human selected (e.g., for farming purposes). Our work shows that aquaculture has been the major driver of introductions in the country, but aquarium release has become an important source in the last 20 years. Given the potential impact of non-native freshwater fishes on native fauna and ecosystems, we highlight an urgent need to assess their ecological effects, as well as to establish a fish fauna monitoring program in Guatemala to detect new introductions. Government and non-governmental agencies should promote the use of native species to supply fish demands in alignment with environmental policies and the objectives of the fishing agency in Guatemala.