Crabtree et al.: Feeding habits of Albula vulpes 
757 
could have been avoided, not preferred, or only inci- 
dentally ingested by bonefish. Alternatively, taxa that 
were not selected could have been preferred, but were 
able to evade capture. 
Results 
Stomachs of 385 bonefish that ranged in length from 
228 to 702 mm contained prey (Fig. 1) consisting 
mostly of small benthic and epibenthic organisms 
(Table 2). Stomachs of 67 of the bonefish we exam- 
ined were empty. Decapods and teleosts dominated 
the diet by weight, but gastropods and bivalves were 
among the most speciose prey categories. Relatively 
few prey species made up most of the diet by weight; 
xanthid crabs ( W=29.9%), the gulf toadfish, Opsanus 
beta (W=17.2%), portunid crabs (W=10.9%), alpheid 
shrimp ( W=9.2%), and penaeid shrimp (W=7.7%) to- 
gether made up 74.9% of the diet. At least 17 fami- 
lies and 24 species of gastropods and 9 families and 
16 species of bivalves were recognized, but gastro- 
pods made up only 2.7% of the diet by weight and 
bivalves made up only 2.5%. Polychaetes, represented 
by at least seven families, were important numerically 
(Af=37. 1%) but made up only 1.4% of the diet by weight. 
Both the cluster analysis and the MDS ordination 
grouped bonefish stomach contents according to fish 
length (Fig. 2). Cluster analysis organized the 23 
length groups into two principal clusters that were 
linked at a level of similarity greater than 20% and 
one outlying group of bonefish 280-299 mm long 
(group 2) that was linked to the other clusters at a 
Fork length (mm) 
Figure 1 
Length-frequency distribution of 384 bonefish, Albula 
vulpes, whose stomachs contained recognizable prey. The 
tail of one of the 385 bonefish whose stomach contents were 
examined was eaten by a shark during capture, so that 
fish was not measured. 
level of similarity less than 10%. One principal clus- 
ter contained bonefish 260 to 439 mm long, and a 
second principal cluster contained mostly larger fish 
400 to 702 mm long. Bonefish in the 400-419 mm 
length interval (group 8) were classified with larger 
fish, and bonefish in the 420-439 mm length inter- 
val (group 9) were classified with smaller bonefish. 
In Table 3, stomach contents are summarized sepa- 
rately for small bonefish (<440 mm) and large bone- 
fish (>439 mm) on the basis of cluster analysis, but 
we reassigned bonefish stomachs in the 400-419 mm 
length interval (group 8) into the <440 mm group to 
avoid any overlap in the table between lengths of 
small (<440 mm) and large (>439 mm) bonefish. In 
the SIMPER analysis (Table 4), bonefish stomachs 
were grouped according to the cluster analysis shown 
in Figure 2, and no groups were reassigned. Levels 
of similarity among stomach contents of the 20-mm 
length groups within the 260-439 mm cluster were 
less overall than the levels of similarity of stomach 
contents of the 20-mm length groups of bonefish in 
the 400-699 mm cluster. Stomach contents of bone- 
fish length groups ranging from 480 to 699 mm had 
a high level of similarity (>55%) and were tightly 
grouped in the MDS; we chose this length group as 
the basis for all other statistical comparisons. 
SIMPER analysis suggested that much of the dis- 
similarity between the two principal length clusters 
was due to xanthid crabs, penaeid shrimp, alpheid 
shrimp, and O. beta (Table 4). The large values of 
the ratios (5 ; /SD(5 ; )) between the mean contribution 
(S-) to the overall level of dissimilarity and the stan- 
dard deviation (SD) of the 5 ( values across all stom- 
achs suggest that these taxa consistently contributed 
to the level of dissimilarity, and so they are probably 
reliable discriminating prey taxa characteristic of one 
or the other length clusters. Bonefish longer than 
439 mm consumed more decapods (alpheid shrimp, 
xanthid crabs, and Callinectes spp.) and teleosts than 
smaller bonefish (Tables 3 and 4). The most striking 
difference was in the consumption of teleosts, prin- 
cipally O. beta, which was not eaten by bonefish 
shorter than 440 mm but made up 17.8% of the diet 
of bonefish longer than 439 mm. Penaeid shrimp 
made up a larger proportion of the diet of small bone- 
fish (W=40.5) than large bonefish (W=6.7), but they 
were eaten by bonefish of all sizes. Portunid crabs 
were eaten in nearly equal amounts by both length 
groups of bonefish, but this finding is misleading 
because all the Portunus spp. eaten by small bone- 
fish were eaten by a single individual collected in 
Florida Bay; thus the importance of portunid crabs 
in the diet of small bonefish is probably less than 
what is suggested in Table 3. No crabs of the genus 
Callinectes were eaten by small bonefish. 
