Feeding ecology of <i>Bathyraja macloviana</i> (Rajiformes, Arhynchobatidae): a polychaete-feeding skate from the South-west Atlantic

Abstract

SUMMARY: The present paper analyses the diet, feeding strategy and niche width of B. macloviana in a sector of the Argentinean Continental Shelf (ACS). Individuals (n = 147) were collected from 43 sampling stations in late summer and autumn 2001. Thirty one alimentary items in the gut contents were found, with a clear dominance of polychaetes. Crustaceans were secondary alimentary items. The polychaete Travisia kerguelensis was the main food item ingested, followed by Nepthyidae, Sabellidae and Lumbrineridae, while Gammaridae and Cirolanidae were the main items among crustaceans. The niche width and feeding strategy displayed by B. macloviana support the specialisation towards polychaetes throughout this study. Slow motile and infaunal species constitute major preys. The results suggest that this skate actively selects worms, reflecting, in some sense, the composition of the polychaete assemblage, and allowing a low dietary overlap with other sympatric skates of the ACS.Keywords: skates, feeding strategy, polychaetes, niche width, specialist, Argentina. RESUMEN: ECOLOGÍA ALIMENTARIA DE BATHYRAJA MACLOVIANA (RAJIFORMES, ARHYNCHOBATIDAE): UNA RAYA CONSUMIDORA DE POLIQUETOS DEL ATLÁNTICO SUDOCCIDENTAL. -En el presente trabajo se analiza la dieta, estrategia alimentaria y amplitud del nicho trófico de Bathyraja macloviana en un sector de la Plataforma Continental Argentina (ACS). Los individuos (n = 147), fueron colectados en 43 estaciones de muestreo a fines de verano y otoño de 2001. Fueron encontrados 31 ítems en los contenidos estomacales con una clara dominancia de poliquetos. Los crustáceos constituyeron ítems secundarios. El poliqueto Travisia kerguelensis fue el principal ítem consumido seguido por Nepthyidae, Sabellidae y Lumbrineridae, mientras que Gammaridea y Cirolanidae fueron los ítems principales entre los crustáceos. En este estudio, la amplitud de nicho y la estrategia alimentaria de esta especie muestran su especialización hacia poliquetos. Especies de baja motilidad e infaunales constituyeron las presas fundamentales. Los resultados sugieren que esta raya selecciona activamente poliquetos, reflejando de algún modo las asociaciones de poliquetos, lo que permite un bajo solapamiento con otras especies de rayas simpátricas del Atlántico Sudoccidental.Palabras clave: rayas, estrategia alimentaria, poliquetos, amplitud de nicho, especialista, Argentina.

Hábitos alimentarios de la raya de cola corta, <i>Bathyraja brachyurops</i> (Chondrichthyes, Rajidae), en el Atlántico Sudoccidental

“…Bathyraja brachyurops occurs sympatrically with B. macloviana and B. albomaculata along the Argentinean continental shelf (Cousseau et al, 2000), which have been reported to be polychaete consumers (Sánchez and Mabragaña, 2002;Mabragaña et al, 2005;Scenna et al, 2006). Species that share the same habitat may rely on differences in the utilization of food resources to avoid competition (Schoener, 1974).…”

“…The diet of five species of Bathyraja have been briefly described on the Argentinean continental shelf (Sánchez and Mabragaña, 2002), and only the feeding habits of the Patagonian skate B. macloviana have been thoroughly studied (Mabragaña et al, 2005;Scenna et al, 2006). Brickle et al (2003) provided some data on diet composition of B. albomaculata, B. brachyurops and B. griseocauda around the Malvinas Islands.…”

“…Brickle et al (2003) provided some data on diet composition of B. albomaculata, B. brachyurops and B. griseocauda around the Malvinas Islands. The diet composition of skate species of other genera have been studied in the region (Lucifora et al, 2000;Koen Alonso et al, 2001;Sánchez and Mabragaña, 2002;Braccini and Perez, 2005;Mabragaña et al, 2005;Mabragaña and Gilberto, 2007;San Martín et al, 2007). Although understanding a predator's trophic interactions is crucial for developing sustainable management strategies (Robinson et al, 2007), trophic relationships among skate species in Argentinean waters remain unknown.…”

Food habits of the sandpaper skate, Bathyraja kincaidii (Garman, 1908) off central California: seasonal variation in diet linked to oceanographic conditions

“…Crustaceans were by far the most important prey taxa to the overall diet of B. kincaidii from central California, comprising >72% of the prey by % N and % IRI and more than 47 % M. This is a trait shared with many other nearshore and offshore, small bodied (<700 mm TL) benthic skates (McEachran et al 1976;Berestovskiy 1990;Ebert et al 1991;Smale and Cowley 1992;Pedersen 1995;Ellis et al 1996;Orlov 1998a;Muto et al 2001;Braccini and Perez 2005;Dolgov 2005;Mabragañ a et al 2005). The most important lower taxon of this category was euphausiids, which are known to be an important, and often primary, prey for cetaceans, birds and fishes (Schoenherr 1991;Brodeur and Pearcy 1992;Ainley et al 1996;Croll et al 1998Croll et al , 2005Yamamura et al 1998).…”

From coexistence to competitive exclusion: can overfishing change the outcome of competition in skates (Chondrichthyes, Rajidae)?

“…On the other hand, B. macloviana is the smallest species of the genus in the southwestern Atlantic, reaching 67 cm in total length and matures at 5-6 years (Bücker, 2006). Both species are specialized feeders, being polychaetes their dominant prey (Mabragaña et al, 2005;Scenna et al, 2006;Ruocco et al, 2009), which results in a high dietary overlap suggestive of a potential competitive interaction between them (Brickle et al, 2003). Thus, B. albomaculata and B. macloviana are a good model system to study the competitive release hypothesis in skates because both species suffer a similar fishing pressure, potentially overlap in the use of some resource (i.e.…”