Diet shift of Red Belly Pacu Piaractus brachypomus (Cuvier, 1818) (Characiformes: Serrasalmidae), a Neotropical fish, in the Sepik-Ramu River Basin, Papua New Guinea

Introduction of fish species is a globally widespread practice that causes losses of native species and homogenization of diversity within and across continents. Diet assessments are important tools to depict the ecological function of species introduced into novel ecosystem and possible direct and indirect ecological effects. In this study, we compare the diet of Piaractus brachypomus, a mainly frugivorous Neotropical fish, introduced into the Sepik-Ramu River Basin (Papua New Guinea) nearly two decades ago, to that of similar size individuals from Neotropical populations in the Amazon and Orinoco River basins (South America). In contrast to native populations that feed mainly on terrestrial plants and invertebrates, the diet of introduced P. brachypomus is mainly composed of fish remains and aquatic plants, while terrestrial plants are frequently consumed but in relatively smaller amounts. These findings show that P. brachypomus has an inherently plastic diet that can be adjusted when displaced to a novel geographic area. While trophic plasticity increases the likelihood of a species to establish breeding populations after its introduction, it also reduces our ability to predict negative effects on native species.

La introducción de peces es una práctica que se extiende globalmente y que causa perdida de especies nativas y homogenización de la diversidad dentro y entre continentes. Los estudios de dieta son herramientas útiles para definir la función ecológica de una especie introducida en un ecosistema nuevo y los posibles efectos directos e indirectos. En este estudio describimos la dieta de Piaractus brachypomus, una especie de pez Neotropical principalmente frugívora, que fue introducida en el río Sepik (Papua Nueva Guinea) hace casi dos décadas; y la comparamos con aquella de individuos de tamaño corporal similar de poblaciones nativas en las cuencas de los ríos Amazonas y Orinoco (América del Sur). En contraste con las poblaciones nativas que se alimentan principalmente de frutas y semillas, plantas e invertebrados terrestres, la dieta de individuos de P. brachypomus introducidos se compone principalmente de restos de peces y plantas acuáticas, mientras que plantas terrestres son consumidas frecuentemente pero en pequeñas cantidades. Estos resultados indican que P. brachypomus tiene una dieta plástica que puede adaptarse cuando la especie se desplaza a un área geográfica nueva. A pesar de que la plasticidad trófica aumenta la probabilidad de que una especie establezca poblaciones reproductivas después de la introducción, también reduce nuestra habilidad de predecir los efectos negativos sobre especies nativas.

Revision of the species of the genus Cathorops (Siluriformes: Ariidae) from Mesoamerica and the Central American Caribbean, with description of three new species

The ariid genus Cathorops includes species that occur mainly in estuarine and freshwater habitats of the eastern and western coasts of southern Mexico, Central and South America. The species of Cathorops from the Mesoamerica (Atlantic slope) and Caribbean Central America are revised, and three new species are described: C. belizensis from mangrove areas in Belize; C. higuchii from shallow coastal areas and coastal rivers in the Central American Caribbean, from Honduras to Panama; and C. kailolae from río Usumacinta and lago Izabal basins in Mexico and Guatemala. Additionally, C. aguadulce, from the río Papaloapan basin in Mexico, and C. melanopus from the río Motagua basin in Guatemala and Honduras, are redescribed and their geographic distributions are revised.

O gênero de ariídeos Cathorops inclui espécies que habitam principalmente águas doces e estuarinas das plataformas orientais e ocidentais do sul do México, Américas do Sul e Central. Neste estudo, se apresenta uma revisão das espécies de Cathorops da Mesoamérica (bacias do Atlântico) e Caribe centroamericano, incluindo a descrição de três espécies novas: C. belizensis, de áreas de manglar em Belice; C. higuchii, de águas costeiras rasas e rios costeiros do Caribe centroamericano, desde Honduras até o Panamá; e C. kailolae, das bacias do rio Usumacinta e lago Izabal no México e Guatemala. Adicionalmente, se redescrevem C. aguadulce, da bacia do rio Papaloapan no México, e C. melanopus, da bacia do rio Motagua na Guatemala e Honduras, apresentando-se uma revisão de suas distribuições geográficas.