In the Philippine fishey, floating objects 

 are used to help "lure" or guide skipjack toward 

 the mouth of large traps. This practice appears 

 to be associated with the presence of deep, nar- 

 row channels between islands. 



Techniques of observation must be re- 

 lated to whether the investigator is studying the 

 behavior of individual fish or the behavior of 

 schools offish. For the former, direct obser- 

 vation of a detailed image is necessary; the use 

 of movies appears to be the best technique be- 

 cause it allows more detailed analyses. For 

 studying fast-moving tuna, fast shutter speeds 

 and fast film are required to prevent blurring. 

 The desirability of securing much more footage 

 of movies of tuna was pointed out. Vessels hav- 

 ing underwater viewing facilities are particularly 

 useful in this work. 



In the observations of fish schools, sonar 

 instruments are useful. Other possibilities in- 

 clude the use of aerial observations with movies 

 of schools being fished. Airplanes are standard 

 equipment in the North American west coast 

 fisheries. In Hawaii, attempts to use aircraft 

 for scouting have not been successful because of 



sea surface glitter and rough seas. In the At- 

 lantic, movies of tuna schools have been taken 

 from a slow-flying aircraft flying at 20 feet and 

 at 30 - 35 miles per hour. 



Relating the studies of anatomy and be- 

 havior appears to be a useful approach, particu- 

 larly in the case of fishes that are difficult to 

 observe directly . Examples mentioned included 

 the hypothesis that the ratio of rods and cones 

 in the retina may be related to the amount of 

 light in the usual environment; that the presence 

 or absence of a swim bladder may be related to 

 diving behavior; and that the presence of vascu- 

 lar anastomoses may be a mechanism of blood 

 flow control related to diving behavior. 



Studies of the internal body temperature 

 taken in live tuna indicate that it is consistently 

 1 to 5° C. higher than the water temperature. 

 Just what part of this difference is associated 

 with the unusual exertions of being caught and 

 what part is normal has not been determined. 

 Because it is difficult to take thermometer ob- 

 servations of "normal" fish, the use of infrared 

 heat detection was suggested as a useful tool. 



Subpopulations 



Discussion Leader - Lucian M. Sprague 

 Rapporteur - Richard N. Uchida 



Reference: Papers No. 



Ill - 1. Legand, M. - Biometric data on yellowtin tuna in New Caledonia 



2. Suzuki, A. - Blood types in tuna 



3. Fujii, Y., K. Mimoto, andS. Higasa -Biochemical studies on the races of tuna 



base composition of testis deoxyribonucleic acid (DNA) 



4. Marr, J. C, and L. M. Sprague - The use of blood group characteristics in 



studying subpopulations of fishes 



5. Ridgway, G. J. - Distinction of tuna species by immunochemical methods 



6. Royce, W. F. - A morphometric study of yellowfin tuna Thunnus albacares 



(Bonnaterre) 



7. Hiyama, Y., and K. Kurogane - Morphometrical comparisons of tuna from areas 



in the Pacific and Indian Oceans 



8. Sprague, L. M. , and L. I. Nakashima - A comparative study of the erythrocyte 



antigens of certain tuna species (Abstract) 



9. Sprague, L. M. , and L. I. Nakashima -Studies on the erythrocyte antigens of 



the skipjack tuna (Katsuwonus pelamis) 



10. Sprague, L. M. - Blood group studies of albacore (Germo alalunga) tuna from 

 the Pacific Ocean 



