370 
Fishery Bulletin 96(2), 1 998 
For all prey species, average individual length was 
smaller than 20 cm. 
Average individual wet weights of Argentine 
shortfm squid, Patagonian squid, Argentine hake, 
and Argentine anchovy ranged from 4 to 92 g. The 
Argentine anchovy, Argentine hake, and Argentine 
shortfm squid had an average individual wet weight 
(± standard deviation) of 21.34 ±7.49, 92.17 ±121.62, 
and 12.39 ±33.62 g, respectively. 
Discussion 
Patagonian dusky dolphins fed mostly on pelagic 
species or pelagic stages of dem- 
ersal species. Argentine anchovy 
is typically a pelagic species 
(Brandhorst et al., 1974; Ange- 
lescu, 1982; Angelescu and Anga- 
nuzzi, 1986; UNESCO, 1990), 
and Argentine shortfin squid, 
Patagonian squid, Argentine 
hake, and “pampanito” are dem- 
ersal-pelagic species (FAO, 1983; 
Angelescu and Prenski, 1987; 
Nigmatullin, 1989; Hatfield et al., 
1990; Rodhouse and Hatfield, 
1990; Brunetti and Ivanovic, 
1992). The sepiolid and southern 
cod are demersal-benthic species, 
whereas common octopus is ben- 
thic (Roper et al., 1984; Angelescu 
and Prenski, 1987). 
Anchovies are the main food 
item for dusky dolphins in Argen- 
tine and Peruvian waters. Engrau- 
lis ringens was found to be the 
principal prey species for dusky 
dolphins in waters off Peru (Mc- 
Kinnon, 1994), and this study 
shows that E. anchoita is the 
most important prey species in 
Argentine waters. Furthermore, 
squids were the second prey by 
numbers (I. argentinus and L. 
gahi in Argentine waters, and L. 
gahi and Dosidicas gigas in Pe- 
ruvian waters) and hakes were 
rated second by weight (M. hub- 
bsi and Merluccius gayi in Argen- 
tine and Peruvian waters respec- 
tively) (McKinnon, 1994). More- 
over, the number of commonly 
eaten and important prey species 
(by weight) was quite similar be- 
tween Argentine and Peruvian 
dusky dolphins (4 and 6 prey spe- 
cies respectively), considering the 
difference in the sample size in 
this work (n= 25) and that in 
McKinnon’s (1994) study (n=136). 
Both populations of the dusky 
