thought that almost nothing can be cxpoctcd from the uso of polo fishing 

 and trolling methods. 



As was also reported in last year's report, it is thoi-'^ht th^^.t bettor 

 results can be obtained in the future by adopting the mobhcrohlp syctom for 

 operations in Axoa I because, this area being the farthest from the base, a 

 great deal of time and money are consumed in going to anf. from the groun5v'5 

 and the operating efficiency for the vjholo season is thereby lo-,jored. The 

 above conclusions were reached after operating nothing? "cut louglines every 

 day on the fishing grounds and using only one or two trcllinj^ linos on the 

 way to and from the operating area, but naturally if largo schools of fish 

 were discovered in the surface layer, whichever of these methods v/ould 

 produce the biggest catch would bo selected. 



(d) Fishing Grounds, Fishing Seasons 



From the results of this investigation it appears that during the summor 

 the designated area of the albacore gr-ounds should on the whole be shifted 

 somewhat to the north. At the bcgianiing of the rsearon the grounds wore in 

 areas having surface water temperatures of around 18 _, that is in the vicinity 

 of 34.-35° north latitude, while at tho end of tho season they vi/ere in areas 

 having surface temperatures of around 16° in tho vicinity of 4.4.-4-6° north 

 latitude. Thus it appears that the suitable water temperature changes 

 regularly v/ith the season. The fishing grounds of the first cruise can be 

 considered to have been in zones of water tomperaturos suitable for tho 

 season. '^I'hen, on the third cruise, the vessel was following tho lines of 

 discontinuity at the northernmost extremes of Areas II and III, it aprxjarod 

 that there wore suitable viator zones even farther north; tho first half of 

 the operations in Area I seem to have been fairly near the center of a 

 suitable water zone. On the first cruise the fishing grounds appear to have 

 been roughly at the center of a group of schools in motion, but the second 

 cruise was at the season v/hen the schools are moving fastest and it is most 

 difficult to discover their center. Consequently tho concentration of the 

 schools was sparse and the fish were not of uniform size. On the third 

 cruisG, as v^as notort above, the first half of the operations was near tho 

 center, apparently somewhat to the south, but at the end of the cruise the 

 schools appeared to have changed their direction of migration and headed 

 south again. 



This year the vessel was absent from tho fishing grounds for about 50 

 days due to its participation in the North Pacific Simultaneous Ocoauographic 

 Observations between the second and third cruises, and consequently it was 

 not possible to gain a detailed knowledge of the movements of tho schools. 

 If these investigations wore carried on continuously or in relays it is 

 believed that they would be even more effective. 



12. Other particulars considered essential 



(a) Ecological Investigations 



The results of the ecological observations aro shovm in Table 3. In 

 studies of the stomach contents small squids, Euphausia sp. (including 

 Stylocheiron carinrtun), Isopoda sp., i\nisopoda sp., Carinaria sp., and small 



5A 



