400 
Fishery Bulletin 106(4) 
1 
^ % mean prevalence B % prevalence per sighting 
5 10 15 20 25 30 35 40 
5 10 15 20 25 30 35 40 
* • 'Blue Whale (24) 
Killer Whale (68) • 
Blue Whale (17) . 
Killer Whale (354) 
• Fin Whale (4) 
— 1 Bryde's Whale (64) 
• Pilot Whale (34) 
-•-i Long-beaked Common Dolphin (69) 
• Dusky Dolphin (11) 
» Striped Dolphin (319) 
• Striped Dolphin (51) 
" Dusky Dolphin (68) 
• Risso’s Dolphin (12) 
- Pilot Whale (297) 
• Humpback Whale (12) 
• Pantropical Spotted Dolphin (326) 
• Spinner Dolphin (38) 
w Humpback Whale (34) 
• Long-beaked Common Dolphin (13) 
« Short-beaked Common Dolphin (287) 
• Short-beaked Common Dolphin (48) 
■ Bottlenose Dolphin (284) 
• Bottlenose Dolphin (70) 
» Risso’s Dolphin (58) 
• Pantropical Spotted Dolphin (76) 
< Spinner Dolphin (271) 
• Bryde's Whale (38) 
Figure 3 
Prevalence of Xenobalanus on cetaceans in the eastern tropical Pacific Ocean in 2003 as deter- 
mined from cetacean identification photographs; (A) percent mean prevalence of Xenobalanus ±2 
standard errors, and (B) percent prevalence of Xenobalanus per sighting (number of sightings 
with barnacles/total number of sightings of a species; 
. The number in parentheses (n) represents 
the total number of individuals and sightings, respectively, observed for each cetacean species 
on which Xenobalanus was observed. 
rough-toothed dolphin, and Indo-Pacific bottlenose dol- 
phin (Tursiops aduncus). 
Discussion 
Prevalence and intensity of the barnacle 
We describe four new host species for the cetacean-spe- 
cific phoretic barnacle Xenobalanus and document that 
the barnacle is present on cetaceans far offshore as well 
as in coastal areas. The fact that Xenobalanus has now 
been reported on 34 species of cetaceans in both coastal 
and offshore waters, from the Arctic to Antarctic, either 
1) indicates that the barnacle is extremely cosmopolitan 
(Newman and Ross, 1976; Spivey, 1981), or 2) may sug- 
gest that more than one species of the genus Xenobala- 
nus is involved. 
Mean prevalence results from this study were lower 
than those from previous published accounts: 0.2% vs. 
4-19% for short-beaked common dolphins ( Delphinus 
delphis) (Pilleri, 1970; Dailey and Walker, 1978), 0.2% 
vs. 43-56% for bottlenose dolphins ( Tursiops truncatus) 
(Di Beneditto and Ramos, 2004; Toth-Brown and Hohn, 
2007), and 0.7% vs. 33-43% for striped dolphins ( Stenel - 
la coeruleoalba) (Pilleri, 1970; Aznar et ah, 2005). Two 
striped dolphins have been reported with an intensity 
of more than 100 Xenobalanus (Aznar et al., 2005), but 
the greatest intensity observed in our study was seven, 
on killer whales. 
Although some differences in prevalence are due to 
previous reports of maximum, rather than mean, rates, 
the prevalence of Xenobalanus infestation reported in 
this study is underestimated because not all barnacles 
present on the animals were visible in our photographs. 
Only one side of the animal was photographed, and 
often part of the body was in the water. On the other 
hand, prevalence reported in many previous studies 
may have been overestimated when rates were based on 
mortality events and strandings. Because stranded ani- 
mals are not usually healthy, the reported rates could 
represent an abnormal presence of the barnacle, as was 
observed in Aznar et al. (2005). Differences may also 
be related to habitat. Moreover, previous reports have 
