Table 16. — Measurements of Indian Ocean juvenile ^uxm thazard (specimen Nos. 1-12, 14) and A. rochei (specimen Nob. 17, 

 19-26) in millimeters and the gill raker counts in the upper and lower limbs (Jones 1961). 



Table 17. — Various fish species usually taken with frigate and bullet 

 tunas and presumably in competition with them, by type of gear 

 (Yokota et al. 1961). 



Albacore. Thunnus alalunga 

 Bigeye tuna, Thunnus obesus 

 Bluefin tuna. Thunnus thynnus 

 Indo-Pacific bonito, Sardn orientaiis 

 Kawakawa. Euthynnus affinis 

 Mahimahi, Coryphaena hippurus 

 Sailfish. Istiophorus orientaiis 

 Scad. Decapterus maruadsi 

 Skipjack tuna. Katsuwonus pelamU 

 Japanese Spanish mackerel. 



Scorn beromorus nipkonius 

 .Spotted mackerel. Scomber austratasicus 

 Striped marlin, Makaira mitsukurii 

 Swordfish. Xiphias gladius 

 Yetlowfin tuna, Thunnus albacares 

 Yellowtail. Seriola aureovittata and 



S. purpurascens 



peting for available food. Competitors of Auxis in Afri- 

 can waters include yellowfin tuna, bluefin tuna, alba- 

 core, and bigeye tuna (de Jager et al. 1963). Other possi- 

 ble competitors mentioned by de Jager et al. are listed 

 below. 



Blue shark, Prionace glauca 

 Mako shark, hurus oxyrinchus 

 Brown shark, Carcharhinus obscurus 

 Thresher shark, Alopias vulpinus 

 Moonfish, Lampris regius 

 Angelfish, Brama rail 

 Mackerel, Scomber japonicus 

 Lancetfish, Alepisaurus ferox 



Stockfish, Merluccius capensis 

 Snoek, Thyrsites atun 

 Yellowtail, Seriola lalandii 

 Skipjack tuna, Katsuwonus pelamis 

 Gannet, Moms capensis 

 Cormorant, Phalacrocorax capensis 

 Cape penguin, Spheniscus demersus 

 Wandering albatross, Diomedia exulans 

 Cape fur seal, Arctocephalus pusillus 

 Sperm whale, Physeter catodon 

 Sei whale, Balaenoptera borealis 



In Indian waters, A. rochei and A. thazard, and other 

 competitors such as Megalaspos cordyla, Stromateus 

 niger, and E. affinis are frequently caught together in 

 gill nets (Jones 1963). In the hook-and-line fishery, 

 Jones observed that A. rochei, carangids, seerfishes, 

 thunnids, and perches (includes lethrinids, lutjanids, 

 and serranids) all appear in the catches. 



3.34 Predators 



Auxis, according to several studies, constitute a sig- 

 nificant part of the food of adult tunas £md billfishes. 

 Predators listed by several investigators are as follows: 



Tunas 



Albacore, Thunnus alalunga (Kishinouye 1917, Japan; 

 de Jager et al. 1963, South Africa; Dragovich 1969, 

 Atlantic; Matthews et al. 1977, North Atlantic) 



Bigeye tuna, T. obesus (Kishinouye 1917; King and 

 Ikehara 1956, central Pacific; Yokota et al. 1961, 

 Japan; de Jager et al. 1963; Watanabe 1964, 

 Japan) 



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