Table 13. — Percentage laxonomic composition of micronek- 

 lon in area 6 of figure 5, from net hauls and tuna stomachs 



(5 standard night net hauls of 1.6-m. net (1,365 ml. ) ; 204 stomachs ol yellowfin 

 tuna (15.698 ml.); 617 stomachs o( skipjack tuna (26,583 ml.); asterisk means 

 <0.05 percent] 



Group of animals 



Myctophidae. 



Leptocephali... -. 



Sternoptychidae 



Gonostomatidae lyinciguerria) . 



Nemichthyidae 



Bathylasidae -. 



Stomiatidae 



Scopelarchidae 



Scombridae 



Thunnidae... --. 



Gadidae.. 



Exocoetidae 



Carangidae, 



Trichinridae 



Other fish 



Total fish. 



Euphausiidae 



Penaeidae 



Sergestidae 



Squillidae (larvae). 



Portunidae 



Other crustaceans.. 



Total crustaceans.. 



Source of material 



Percent 



33.2 



7.0 



3.4 



2.4 



1.5 



1.0 



.7 



.5 



.1 

 .4 

 1.3 



51.6 



32.0 

 3.7 

 2.9 

 2.3 



4.0 



Enoploteuthidae 



Cranchiidae 



Ommastrephidae. -. 

 Other cephalopods.. 



Total cephalopods. 

 Grand total 



44.9 



2.0 

 1.0 



3.5 



Yellowfin 

 tuna 



Percent 

 1.4 



(•) 



(•) 



4.7 



25.0 

 16.0 

 4.7 

 .7 

 3.2 

 1.2 

 20.1 



77.0 



(•) 



.4 



10.2 



.5 



1.4 



10.6 



Skipjack 

 tuna 



Percent 

 6.7 



(•) 



13.4 



.3 



4.9 

 .2 

 6 4 

 4.1 



35.0 



.2 



60. i 



1.6 



.2 



2.4 



4.2 



100.0 



net catches, in areas where they were significant 

 in tuna stomachs, may reflect the fact that only 

 five or six net liaiils were made in each of those 

 areas. The other major differences in representa- 

 tion of families in net catches and tima stomach 

 contents probably indicate real differences between 

 the catching performance of the net and of the 

 tunas, discussed below. Carangidae are possibly 

 underrepresented in the net material of area 4; 

 some hauls taken in that area on cruise TO-62-1, 

 which are neglected in most parts of this paper for 

 reasons given elsewhere, were moderately rich in 

 carangids (table 2) . 



A similar situation is suggested by the cepha- 

 lopod data of tables 8 to 14, which show the main 

 families in net catches little represented in tuna 

 stomachs and vice versa; but the component "other 

 cephalopods" (which is mainly material that was 

 too much digested for identification) was rela- 

 tively large in the tuna stomach contents, and the 

 principal components of the net catches (En- 

 oploteuthidae and Cranchiidae) might have oc- 

 curred in it. 



Table 14. — Percentage taxonomic composition of micro- 

 nekton in areas 11 and 12 of figure 5, from net hauls 

 and tuna stomachs 



(6 standard night net hauls of 1.5-m. net (1,138 ml.); 72 stomachs of yellowfin 

 tuna (4,880 ml.); 37 stomacas of s.v.^.ack tuna (2,321 ml.); asterisk means 

 <0.0o percent] 



The crustacean components were much more 

 alike than the fish and cephalopod components, 

 qualitatively and quantitatively, in the micronek- 

 ton from nets and in the stomachs of yellowfin 

 and skipjack tunas. The galatheids were repre- 

 sented by large and somewhat comparable per- 

 centages in all three series in areas 1 and 2, where 

 the material was mostly Pleuroncodes planipes. 

 Percentages of similar material were very differ- 

 ent in area 3 (very low in net catches, high in 

 stomachs of yellowfin tuna, nil in the scanty ma- 

 terial from skipjack tima), but the percentage in 

 net catches would have been higher if a special 

 group of hauls from the Cape San Lucas front 

 had been included (see Griffiths, 1965). Per- 

 centages of galatheids in areas 4 and 5 were small 

 and similar for net catches and yellowfin tuna, 

 and this material consists mainly of juveniles. 

 Percentages of euphausiids in net micronekton 

 were comparable with tliose in stomachs of skip- 

 jack tuna in some areas (especially 1 and 6) but 

 the percentages were uniformly very low, or nil, 

 in yellowfin tuna. Squillid larvae occurred in net 



MICRONEKTON OF THE EASTERN TROPICAL PACIFIC OCEAN 



105 



