Feeding habits of delphinids (Mammalia: Cetacea) from Rio de Janeiro State, Brazil

Abstract

Stomach content analyses were performed in 28 dolphins stranded between 1994 and 2007 on the beaches of Rio de Janeiro State (23°06′S 44°18′W/22°14′S 41°54′W), Brazil, comprising six delphinid species: Stenella frontalis (N = 10), Steno bredanensis (N = 7), Tursiops truncatus (N = 4), Delphinus delphis (N = 5), Lagenodelphis hosei (N = 1) and Stenella coeruleoalba (N = 1). Fish otoliths and cephalopod beaks were used to identify the prey species and to estimate the original length and weight. Seven different cephalopod species from six families and 15 fish species belonging to 10 families were identified. Although the fish contribution could be underestimated, cephalopods constituted the group of higher importance, revealing that these invertebrates may represent an important source of energy for delphinids in the region. In this context, the squid Loligo plei should be highlighted due to its important contribution. Most preys were coastal and demersal, and such consumption could indicate coastal foraging habits of the quoted dolphin species. Although dolphins consumed many species of prey in common, they fed on different size-classes of prey. The foraging area of the dolphins could be the same region used by fishing operations, which would represent a risk for incidental capture.

High accumulation of PCDD, PCDF, and PCB congeners in marine mammals from Brazil: A serious PCB problem

“…Finding high concentrations of persistent accumulative toxicants in this dolphin population is not surprising. Rough-toothed dolphins from RJ feed on top-predator fish (Bisi et al, 2012;Melo et al, 2010), thus they are more likely to take in high amounts of contaminants that have accumulated in the bodies of the prey.…”

“…Rough-toothed dolphins can occasionally reach more than 2.8 m of total length (Jefferson, 2009). Taking into consideration that this continental shelf (CS) delphinid has many prey species in common with estuarine dolphin species, such as the Guiana dolphin (Melo et al, 2010, submitted for publication), the greater size of rough-toothed dolphins means that these CS delphinids have anatomical characteristics that enable them to feed on larger fish, and hence, on prey specimens that had a longer exposure time to pollutants than those consumed by Guiana dolphins. Although it is still controversial whether or not false killer whales feed on other cetacean species, they are known to prey on large and long-lived fish such as tunas and swordfish (Baird et al, 2008).…”

“…The latter approach is based on the fact that many fish species are consumed by humans in Rio de Janeiro at the size preyed on by the delphinid species analyzed in our study (Melo et al, 2010, submitted for publication). In addition, it is also of great interest to investigate if accumulation of persistent bioaccumulative toxicants can pose an additional threat to these cetacean species.…”

Bottlenose dolphins (Tursiops truncatus, Montagu 1821) in central-northern coast of Rio de Janeiro State, Brazil: stranding patterns and insights into feeding habits

“…On the other hand, studies carried out in the Gulf of Mexico have demonstrated that cephalopods are also important part of the diet for this species, though principally for offshore populations (Barros and Odell, 1990). Table 2 shows the prey species detected in stomach contents of bottlenose dolphins in the study area from previous works (Di Beneditto et al, 2001;Melo et al, 2010). In general, cutlass fish followed by midshipman fish and Atlantic spade fish seem to represent significant prey species.…”

“…and life stage. Previous studies conducted in RJ indicate that the bottlenose dolphin feeds preferentially on coastal fish (Di Beneditto et al, 2001;Melo et al, 2010).…”