La abundancia y la ecología del comportamiento del blenny Ophioblennius trinitatis (Teleostei: Blenniidae) en un archipiélago oceánico de Brasil (Atlántico)

Local patterns of fish density, microhabitat use, feeding behaviour, bite rate, territory area and agonistic interactions were recorded for Ophioblennius trinitatis at an oceanic archipelago (southwestern Atlantic). Rugosity, number of crevices and benthic diversity positively predicted the distribution of O. trinitatis. Turf algae was the preferred food item at all sites, but given its high availability inside and outside territory boundaries, it did not seem to be a limiting factor on the density of this blenny, as opposed to substrate heterogeneity. Bite rate was higher in the afternoon and for smaller individuals (juveniles). Territory size showed local variation and, although larger territories may be an effect of density-dependent conditions (more available space in low-density areas), we propose that individuals expand territories to compensate for residing in areas of lower quality (i.e. of low structural complexity). Larger individuals defended larger territories and residents responded differently to intruders, with higher rates of agonistic interactions towards potential competitors. Higher agonistic rates were also observed in larger territories and at low-complexity sites.En este trabajo se han estudiado las pautas en la densidad, la utilización del micro hábitat, el comportamiento alimentario, las tasas de mordisqueo, la superficie del territorio y las interacciones agonísticas de Ophioblennius trinitatis en un archipiélago oceánico del SO Atlántico. Los mejores predictores de la distribución de O. trinitatus fueron la rugosidad, el número de grietas y la diversidad bentónica. El turf algal es el alimento preferido de este pez en todos los lugares, pero dada su elevada disponibilidad, dentro y fuera de los territorios, no pareció ser un factor limitante para este blénido como lo fue la heterogeneidad del substrato. La tasa de mordisqueo resultó ser más elevada entre los peces pequeños (juveniles) y especialmente por la tarde. La superficie del territorio presentó notables variaciones locales y, a pesar de que los territorios mayores pueden ser el resultado de un efecto denso-dependiente (al haber más espacio disponible en la zonas con densidades bajas), proponemos que los individuos expanden su territorio para compensar la baja calidad ambiental de ciertas zonas (una baja complejidad estructural). Los ejemplares mayores defendían territorios más extensos y respondían de manera diferente ante los intrusos, con una mayor tasa de interacciones agonísticas hacia los potenciales intrusos. Las interacciones agonísticas también fueron más elevadas en los territorios más amplios y con una baja complejidad

Abundance and behavioural ecology of the blenny <em>Ophioblennius trinitatis</em> (Teleostei: Blenniidae) at an oceanic archipelago of Brazil (Atlantic)

Local patterns of fish density, microhabitat use, feeding behaviour, bite rate, territory area and agonistic interactions were recorded for Ophioblennius trinitatis at an oceanic archipelago (southwestern Atlantic). Rugosity, number of crevices and benthic diversity positively predicted the distribution of O. trinitatis. Turf algae was the preferred food item at all sites, but given its high availability inside and outside territory boundaries, it did not seem to be a limiting factor on the density of this blenny, as opposed to substrate heterogeneity. Bite rate was higher in the afternoon and for smaller individuals (juveniles). Territory size showed local variation and, although larger territories may be an effect of density-dependent conditions (more available space in low-density areas), we propose that individuals expand territories to compensate for residing in areas of lower quality (i.e. of low structural complexity). Larger individuals defended larger territories and residents responded differently to intruders, with higher rates of agonistic interactions towards potential competitors. Higher agonistic rates were also observed in larger territories and at low-complexity sites

Necrophagy of a nurse shark (Ginglymostoma cirratum) by tiger sharks (Galeocerdo cuvier)

The aim of this study is to report a scavenging event, involving the consumption of a nurse shark, Ginglymostoma cirratum, by tiger sharks, Galeocerdo cuvier, at Fernando de Noronha archipelago, Brazil. Recreational divers found and photographed a bitten nurse shark carcass, just after sighting two tiger sharks near of the site. We estimated the sharks total lengths and discussed aspects of this feeding interaction using of images of forensic analysis. A straight cut on the nurse shark caudal fin, whose total lenght was estimated as 200 cm, suggest that it was caught by illegal fishing. A skin peeling process on the nurse shark fins indicates that the tiger sharks consumed it after its death, in a scavenging event. This is the first published report of a scavenging event involving the consumption ofan elasmobranch by tiger sharks, allowing a better comprehension of tiger sharks’ alimentary biology

Necrophagy of a nurse shark (Ginglymostoma cirratum) by tiger sharks (Galeocerdo cuvier)

The aim of this study is to report a scavenging event, involving the consumption of a nurse shark, Ginglymostoma cirratum, by tiger sharks, Galeocerdo cuvier, at Fernando de Noronha archipelago, Brazil. Recreational divers found and photographed a bitten nurse shark carcass, just after sighting two tiger sharks near of the site. We estimated the sharks total lengths and discussed aspects of this feeding interaction using of images of forensic analysis. A straight cut on the nurse shark caudal fin, whose total lenght was estimated as 200 cm, suggest that it was caught by illegal fishing. A skin peeling process on the nurse shark fins indicates that the tiger sharks consumed it after its death, in a scavenging event. This is the first published report of a scavenging event involving the consumption ofan elasmobranch by tiger sharks, allowing a better comprehension of tiger sharks’ alimentary biology