CONTENTS 



Introduction 1 



Materials and methods 2 



Results 3 



Vertebrate forage (fishes) ' 3 



Thunnus albacares 3 



Thunnus alalunga 4 



Thunnus thynnus 4 



Thunnus obesus 4 



Alepisaurus 4 



Invertebrate forage 5 



Thunnus 5 



Alepisaurus 5 



Discussion 6 



Acknowledgments 9 



Literature cited 9 



Figures 



1. Area sampled (crosshatched) for Thunnus and Alepisaurus by longline in the western North Atlantic ... 2 



2. Relative importance of families of fishes present in more than 1% of the stomachs of western North At- 

 lantic Thunnus albacares. Percent frequency of occurrence is on the horizontal axis, mean length (mm 

 SL) of forage family on the vertical axis, and mean number of individuals in a forage family on the third 

 axis. The most important families are those that occur more frequently (to the right on the horizontal 

 axis), average larger in size (lines coming up from the horizontal axis), and are the most numerous (dis- 

 placed back into page on third axis) 4 



3. Frequency of occurrence of the 20 most frequently occurring families of fishes in the stomachs of Thun- 

 nus and Alepisaurus. Families are separated into three categories: Sargassum -associates, near-surface, 



and midwater 7 



4. Frequency of occurrence of invertebrate forage categories in the stomachs of Thunnus and Alepisaurus. 

 Categories are separated by their general location in the water column: near-surface or midwater ... 8 



Table 



1. Numbers, size ranges, and mean sizes of Thunnus spp. and A lepisaurus examined 2 



Appendix Tables 



1. Forage components of Thunnus and Alepisaurus. (A) eaten by Alepisaurus; (T) eaten by Thunnus; 

 (A*) addition to forage list of Haedrich (1964); (T*) addition to forage list of Dragovich (1969) ... 11 



2. Percent frequency of occurrence of food fish categories identified from 266 stomachs of western North 

 Atlantic Thunnus albacares by size range 14 



3. Percent frequency of occurrence of food fish categories in 38 stomachs of western North Atlantic Thun- 

 nus alalunga by size range 16 



4. Percent frequency of occurrence of food fish categories in 38 western North Atlantic Thunnus thynnus 17 



5. Percent frequency of occurrence of food fish categories in 81 western North Atlantic Alepisaurus . . 17 



6. Percent frequency of occurrence of principal invertebrate groups in 215 stomachs of western North At- 

 lantic Thunnus albacares by size range 18 



7. Percent frequency of occurrence of principal invertebrate groups in 34 stomachs of western North At- 

 lantic Thunnus alalunga by size range 18 



8. Percent frequency of occurrence of principal invertebrate groups in 27 stomachs of western North At- 

 lantic Thunnus thynnus by size range 18 



9. Percent frequency of occurrence of principal invertebrate groups in 81 stomachs of western North At- 

 lantic Alepisaurus spp 19 



10. Occurrence and co-occurrence of crustaceans and cephalopods in the stomachs of western North At- 

 lantic Thunnus and Alepisaurus species 19 



11. Percent frequency of occurrence of cephalopod groups in stomachs of western North Atlantic Thunnus 



and Alepisaurus species 19 



iii 



