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yellow in the ventral and in the entire caudal 
region. 
In still another respect young threadfin caught 
in the pelagic situation exhibit marks of that 
habitat. Young P. opercularis collected off the 
Tres Marias Islands, Mexico, were infested with 
juvenile stages of the parasitic copepod Caligus 
coryphaene (Shiino, 1959). The regular hosts 
of this parasite are usually such pelagic fishes 
as the dolphin, various tunas, and the bonito, to 
mention a few. 
Numerous predators, besides man, take ad- 
vantage of the aggregations of threadfin found 
offshore. Skipjack ( Katsuwonus pelamis ) , yel- 
lowfin tuna ( Thunnus macropterus ) , sailfish, 
sharks, and oceanic birds were observed (by 
W.L.K.) feeding on the threadfin some 50 miles 
off San Jose, Guatemala, in April 1957. We 
have been informed that the crew of the clipper 
M/V "Commander” observed whales feeding on 
schools of threadfin 40 miles WSW of Cape 
Corrientes, Mexico, in August 1957. 
Fig. 2. Locations of capture of bobo by scientific personnel. 
