NOTE Cherel et al.: Importance of Hyaloteuthis pelagico in the epipelagic cephalopod community of the tropical Atlantic Ocean 



The ommastrephid Sthenoteuthis pteropus, usually 

 abundant in the tropical Atlantic Ocean, was surpris- 

 ingly absent in fish diets in the present study. Two 

 hypotheses may account for that apparent absence: 

 either fish selected H. pelagica rather than S. pteropus, 

 or S. pteropus was not an important and available nek- 

 tonic prey organism at the time of sampling. The latter 

 hypothesis is likely to be the best explanation because 

 tunas and billfishes are known to be opportunistic 

 predators. Moreover, the geographical distribution of S. 

 pteropus shows that juvenile squids are not abundant in 

 the central Atlantic Ocean where cruises of the present 

 investigation took place (Warneke-Cremer, 1986; Zuev 

 and Nikolsky, 1993). Instead, our study underlines the 

 numerical importance of H. pelagica. together with O. 

 antillarum (Vaske et al., 2004), in the area, and our 

 numbers are in agreement with the large catches of 

 the species with nets between 20°S and 31°S off Brazil 

 during 1966 and 1968 (Warneke-Cremer, 1986). 



The present study documents the largest number 

 of H. pelagica ever reported, thus emphasizing the 

 usefulness of marine predators to gain valuable in- 

 formation on the biology of their prey (Clarke, 1980; 

 Cherel et al., 2004). Other ommastrephid species are 

 important food items of various fishes, seabirds, and 

 marine mammals (Clarke, 1996; Cherel and Klages, 

 1998), but H. pelagica was previously found only as 

 a rare prey of squids (Shchetinnikov, 1992), fishes 

 (Matthews et al., 1977; Okutani and Tsukada, 1988; 

 Vaske et al., 2004). birds (Harrison et al., 1983), and 

 cetaceans (Robertson and Chivers, 1997). In the same 

 way, the squid Grimalditeuthis bonplandi and the pe- 

 lagic octopods T. violaceus and J. diaphana were rarely 

 found in significant numbers in the diet of cephalopod 

 predators (Okutani and Tsukada, 1988; Le Corre et 

 al., 2003), but we commonly found them as fish prey. 

 Consequently, our study shows that these poorly known 

 cephalopods, together with adults of//, pelagica, con- 

 stitute a link in the transfer of energy from lower 

 trophic levels (most likely mesozooplankton) to higher 

 trophic levels (including tunas and billfishes) in the 

 tropical Atlantic Ocean). 



Acknowledgments 



The authors thank P. Borsa, P. Dewals, and O. Maury 

 for their help to collect scientific samples on board, and 

 the captain and crew of the RV Shoyo-Maru. 



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