Trophic overlap of lionfish (Pterois volitans) and two native predators (Lutjanus apodus and Cephalopholis cruentata) in the western Caribbean / Traslape trófico del pez león (Pterois volitans) y dos depredadores nativos (Lutjanus apodus y Cephalopholis cruentata) en el Caribe occidental

Abstract Impact of invasive species on native biota may be due to predation, competition for space or food, or indirect effects. Lionfish (Pterois volitans), invasive in the western Atlantic, is a voracious generalist predator, so it is expected to have a significant trophic overlap with native fishes of comparable size and habits. The goal of this study was to determine the diets of potential competitors of the lionfish, in particular a grouper, Cephalopholis cruentata (Graysby), and a snapper, Lutjanus apodus (Schoolmaster), and to compare them to the diet of lionfish in Xcalak, southern Mexican Caribbean. Stomach contents were analyzed and electivity and diet overlap were estimated. The trophic overlap between the lionfish and the two putative competitors, especially the grouper, was high, including prey that was consumed by the predators in higher proportion than the relative abundance of the prey in the environment, and probably at the same time of day. Lionfish and grouper shared as important diet items Stegastes sp., Halichoeres sp., Brachyura, and Palaemonidae, and most full stomachs were found during the early morning. The hypothesis of competition between them for particular prey is supported, so we advise to continue the culling programs of lionfish and also to monitor the abundance of the possible native competitors.

Resumo El impacto de las especies invasoras sobre la biota nativa puede deberse a depredación, competencia por espacio o alimento, o efectos indirectos. El pez león (Pterois volitans), invasor en el Atlántico occidental, es un voraz depredador generalista, de modo que se espera que tenga un notable sobrelape trófico con peces nativos de tamaño y hábitos comparables. El objetivo de este estudio fue determinar las dietas de competidores potenciales del pez león, en particular un mero, Cephalopholis cruentata (payaso), y un pargo, Lutjanus apodus (canchix), y compararlas con la dieta del pez león en Xcalak, sur del Caribe mexicano. Se analizaron los contenidos estomacales y se estimó la selectividad y el traslape de dietas. El traslape trófico entre el pez león y los dos posibles competidores, sobre todo el mero, fue amplio, incluidas presas consumidas por los depredadores en proporción mayor a la abundancia relativa de éstas en el ambiente, y probablemente a la misma hora del día. El león y el mero compartieron como presas importantes Stegastes sp., Halichoeres sp., Brachyura, y Palaemonidae, y la mayoría de los estómagos llenos se encontraron en horas tempranas de la mañana. Se apoya entonces la hipótesis de competencia entre ellos por presas específicas, de modo que recomendamos continuar el programa de extracción de pez león y también el monitoreo de la abundancia de los posibles competidores nativos.

Ictiofauna de sistemas cárstico-palustres con impacto antrópico: los petenes de Campeche, México

Ichthyofauna of karstic wetlands under anthropic impact: the "petenes" of Campeche, Mexico. "Petenes" are small springs and associated streams that drain into wetlands near the coast in karstic areas. We studied composition, distribution, and abundance of the ichthyofauna in Los Petenes region (northwest Campeche). Two petenes displaying different degrees and types of anthropic impact were selected, Hampolol and El Remate. Hampolol has a smaller area but a longer derived stream; it is located within a protected area, but has been invaded by tilapia. El Remate is a popular spa, with no tilapia; it has a larger area but a shorter derived stream. At each "petén", several sites in the main spring, the associated stream, and secondary (temporary) springs were sampled in the rainy and dry seasons. Fishing gear was variable (throw net, gill net, small and large seine nets), but effort was uniform. We recorded temperature, dissolved oxygen, salinity, and depth at each site and season; also, we noted the different types and intensities of anthropic impact (channelization, presence of exotic species, recreational use, etc.) at each petén. We compared the petenes in terms of their environmental quality and fish fauna (composition, distribution, abundance, biomass); we also tested for effects of season and site within each petén. The study found 27 species of fishes, included in 18 genera and eight families, 24 species in Hampolol and 20 in El Remate. The geographical range of ‘Cichlasoma’ salvini, Rivulus tenuis, Phallichthys fairweatheri, Xiphophorus hellerii, and X. maculatus is extended. The dominant species in both seasons was Astyanax (probable hybrids A. aeneus × altior at Hampolol, pure A. altior at El Remate), which contributed most of the abundance and biomass, together with Vieja synspila and Poecilia velifera. A significantly greater overall diversity (H’n=3.31) was recorded in Hampolol compared to El Remate (H’n=2.10). Cluster analysis of sites by species presence allowed distinction of two groupings within each petén: permanent waters (i.e., main spring, stream) vs. temporary sites (secondary springs, which dry out in winter). Environmental parameters (except salinity) presented significant differences by site and season; a canonical correspondence analysis indicated that the distribution of fish assemblages was influenced by the environmental parameters in both seasons. In terms of composition, historical factors play a role in the differences between the fish assemblages of the two petenes, especially concerning the presence of Astyanax hybrids and Xiphophorus spp. in the southern petén (Hampolol) and Poecilia velifera in the northern petén (El Remate). Rev. Biol. Trop. 57 (1-2): 141-157. Epub 2009 June 30.

Los petenes son pequeños manantiales y arroyos asociados que drenan a sistemas palustres en áreas cársticas costeras. Se estudió la composición, distribución y abundancia de la ictiofauna en dos petenes del noroeste de Campeche, en el manantial principal, el arroyo asociado, y pequeños ojos de agua secundarios (temporales), en dos épocas del año. Se registraron variables ambientales y tipos de impacto antrópico en cada petén. Se encontraron en total 27 especies de peces, con extensiones de ámbito de ‘Cichlasoma’ salvini, Rivulus tenuis, Phallichthys fairweatheri, Xiphophorus hellerii y X. maculatus. La especie dominante en ambas épocas fue Astyanax (probables híbridos A. aeneus × altior en Hampolol, A. altior en El Remate). Hubo diferencia significativa en diversidad entre ambos petenes. El análisis de conglomerados diferenció dos agrupaciones dentro de cada petén: aguas permanentes y sitios temporales. Las variables ambientales (excepto salinidad) presentaron diferencias significativas por sitio y época; un análisis de correspondencia canónica indicó que la distribución de los conjuntos de peces tuvo influencia de las variables ambientales en ambas temporadas. En términos de composición, los factores históricos juegan un papel en las diferencias ictiológicas entre ambos petenes, sobre todo por lo que concierne a la presencia de híbridos de Astyanax, así como Xiphophorus hellerii en el petén del sur (Hampolol) y de Poecilia velifera en el petén del norte (El Remate).