The swimming crab Charybdis smithii: distribution, biology and trophic role in the pelagic ecosystem of the western Indian Ocean

Feeding ecology and consumption rates of yellowfin tuna (Thunnus albacares) in the eastern Arabian Sea

“…Low value for the diet breadth index (Levin's Standardised index, B i ) for yellowfin tuna in our study (0.106) indicated that, although this species consumed a wide variety of prey items, maximum contribution to the diet was by few prey items including oceanic squids, swimming crabs and teleosts (bigeye cigarfish and flying fishes), which are available in high density in the Arabian Sea (Trotsenko and Pinchukov, 1994;Couwelaar et al, 1997;Chesalin and Zuyev, 2002;Potier et al, 2008;Romanov et al, 2009), that could restrict yellowfin's feeding to most frequently available prey items in this area. Yellowfin tuna of Arabian Sea may be feeding mainly on these prey species, leading to low value for diet breadth index and hence showing an opportunistic feeding strategy.…”

Feeding ecology of silky sharks Carcharhinus falciformis associated with floating objects in the western Indian Ocean

“…falciformis in this region. Previously, Romanov et al () found a lower occurrence ( O % = 11·8) of C . smithii in a small sample of C .…”

“…The latter appears to be a highly important food resource for C. falciformis in this region. Previously, Romanov et al (2009) found a lower occurrence (O% = 11·8) of C. smithii in a small sample of C. falciformis (21 individuals) caught during tuna purse-seine operations around floating objects in the western Indian Ocean. They noted, however, that the species was more common (O% = 28·2) in the stomachs of C. falciformis (n = 113) caught on longlines.…”

“…smithii was higher (39·9%) than previously reported for either gear type. Romanov et al () suggested that this species represents an important prey resource for a multitude of pelagic predators within this region and was consistently the main prey of T . albacares and lancet fish Alepisaurus ferox Lowe 1833.…”

“…The occurrence of epipelagic and mesopelagic cephalopods and some mesopelagic fish species in the stomachs sampled here, probably reflect feeding activity during these nocturnal excursions when these species migrate to the surface layers (Galván‐Magaña et al , ; Ménard et al , ). Furthermore, Romanov et al () found that the swimming crab, C . smithii , which was a principle component of the diet of the sharks in this study, also undertake diel vertical migrations and are significantly more abundant in the upper 100 m of the water column between dusk and dawn than during the day.…”