248 
Fishery Bulletin 117(3) 
0 20 40 60 80 100 0 10 20 30 40 50 60 
Number of stomachs 
Figure 2 
Cumulative prey curves for sicklefin smoothhounds (Mustelus lunulatus ) 
caught in the southeastern Pacific Ocean between November 2003 and Octo¬ 
ber 2004. Graphs plot Shannon-Wiener diversity index values and coefficients 
of variation against the numbers of stomachs analyzed for (A) all samples 
combined (number of stomachs analyzed [n]=87), (B) females (n=58), (C) 
males (n= 75), (D) juvenile females (n= 51), (E) juvenile males (n= 44), (F) adult 
females (n=44), and (G) adult males (n=38). 
Dietary analyses 
The examination of stomachs revealed that the diet of 
sicklefin smoothhounds was composed mostly of crusta¬ 
ceans and, in a lower proportion, of mollusks and tele- 
osts (Table 1). The main prey were a swimming crab, 
Achelous iridescens, and crab species of the genus Iliacan¬ 
tha. (Table 1). Both sexes fed mostly on A. iridescens, but 
the females also consumed a small proportion of Panama 
mantis shrimp ( Squilla panamensis) 
and dart squid, Loiiiguncula (Loliolop- 
sis) diomedeae, and the males also con¬ 
sumed a small proportion of purse crabs 
(.Iliacantha spp.) and small arched box 
crab ( Calappula saussurei ) (Table 2). 
The dietary analysis by stage of sexual 
maturity revealed that the main prey of 
both juvenile and adult sicklefin smooth¬ 
hounds was A. iridescens. Adult females, 
however, incorporated in their diet the 
dart squid, the small arched box crab, 
and a swimming crab, Euphylax robus- 
tus, and adult males complemented their 
diet with prey such as the small arched 
box crab, Iliacantha spp., and the crab 
Acanthocarpus delsolari (Fig. 3). 
The dietary analysis of sicklefin 
smoothhounds also showed that Size-I 
sharks fed mostly on crustaceans: 
Achelous iridescens (PSIRI: 42.2%), 
Iliacantha spp. (4.8%), small arched 
box crab (3.9%), and Panama mantis 
shrimp (3.7%). In addition to A. irides¬ 
cens (26.6%), Size-II sharks ate Iliacan¬ 
tha spp. (7.7%), small arched box crab 
(5.7%), Panama mantis shrimp (3.8%), 
and dart squid (3.4%). Size-Ill sharks 
had a more varied diet composed of E. 
robustus (11.9%), dart squid (10.9%), 
Acanthocarpus delsolari (9.3%), Panama 
mantis shrimp (8.6%), and Achelous iri¬ 
descens (7.5%) (Fig. 4). 
The dietary analysis by trimester 
indicated that crustaceans were the 
principal prey consumed by sicklefin 
smoothhounds throughout the year. By 
trimester, the importance of some spe¬ 
cies changed. The importance of the 
crustacean A. iridiscens increased from 
Trimester I to Trimester IV; however, 
the second crustacean in importance, 
the Panama mantis shrimp, decreased 
in importance throughout the year. For 
other crustaceans and for cephalopods, 
changes were minimal (Fig. 5). 
Ontogenetic changes were identified 
in the diet of sicklefin smoothhounds, by 
stage of sexual maturity (global coeffi¬ 
cient of multiple correlation [7?]=0.035, 
P=0.002), because of dietary differences between female 
adults with respect to female juveniles and male adults 
(Benfferroni test, corrected: P= 0.02) as well as between 
female juveniles and male adults (Benfferoni test, cor¬ 
rected: P=0.01) (Fig. 6A). 
Likewise, ontogenetic changes were observed by size 
class (global i?=0.043, P=0.006; Figs. 4 and 6B). The results 
of the SIMPER analysis by stage of sexual maturity and 
size class are given in Table 3. 
