In yellowfin, the percentage composition 

 of near-spawning fish (over 110 cm. , the size at 

 which most yellowfin reach first maturity) is no 

 more than 40 percent throughout the year inthe 

 entire equatorial Pacific. There appears to be 

 no tendency for the proportion of mature fish to 

 increase toward the east, as there is in the case 

 of the bigeye. Previously it was thought that the 

 main yellowfin spawning season changed grad- 

 ually from east to west, but presently it is con- 

 sidered that this change can be attributed to lati- 

 tudinal variations. 



King, Joseph E. , and Robert T. B. Iversen 



Midwater trawling for forage organisms 

 in the central Pacific. /Conference 



Paper VII - 1.7 (In press as _a U. S. 

 Fish and Wildlife Service Fishery 

 Bulletin, number unknown. ) 



Collections from 274 midwater trawl 

 hauls made in the central Pacific Ocean by the 

 Bureau of Commercial Fisheries inl951-56 were 

 quantitatively analyzedto obtain estimates of the 

 abundance and distribution of forage organisms. 

 Their occurrence in the trawl catches was com- 

 pared with the occurrence of similar organisms 

 in the stomachs of yellowfin, bigeye, skipjack, 

 and albacore tunas. Four trawls were utilized 

 (6-foot beam trawl, 1-meter ring trawl, and 6- 

 foot and 10-foot Isaacs-Kidd trawls) in double 

 oblique hauls between the surface and 400 

 meters. 



The largest catches by the Isaacs-Kidd 

 trawls were made in the Aleutian Current and in 

 the region of upwelling at the Equator, with the 

 poorest catches south of latitude 5° S. in the 

 North Equatorial Current between latitude 10° N. 

 and 18" N. , and in Hawaiian waters. The great- 

 est variety of organisms occurred in catches 

 made in the South Equatorial Current and in the 

 Counter cur rent. 



The re was a poor correspondence between 

 the composition of trawl catches and the contents 

 of tuna stomachs; this was not unexpected since 

 most hauls were made at night and tuna fishing 

 occurred in the daytime. There was marked di- 

 urnal variation in the trawl catches. Night hauls 

 produced catches larger in volumes, numbers, 

 and sizes of organisms. Diurnal differences in 

 the composition of the trawl catches were strik- 

 ing. 



The larger trawls generally produced the 

 largest catches, but in catch per unit of mouth 

 area the trawls were about equally efficient in 

 each geographic area. The largest catches and 



greatest variety of organisms were obtained in 

 the catches of the largest and most frequently 

 used trawls. All four trawls sampled about the 

 same phyla, classes, and orders; the major dif- 

 ferences occurred in the families and genera of 

 fishes. Only six juvenile tunas, from 18 to 60 

 mm. in length, were captured, although juvenile 

 tunas were known to be present in the area at the 

 time of the trawling. 



Trawl catch volumes were correlated 

 with various environmental factors and found to 

 be more closely related to zooplankton than to 

 inorganic phosphate or to the uptake of C by 

 phytoplankton. 



Checklists of the organisms captured 

 show the percent occurrence and average num - 

 bers per haul of members of a large number of 

 taxonomic categories according to six latitudinal 

 zones. A table of references useful in identi- 

 fying organisms captured by midwater trawling 

 was presented. 



Legand, M. 



Donnees biometriques sur les thons 

 anageoires jaunesenNouvelle- 

 Caledonie. /Conference Paper III - 

 1.7 (In Legand, M. and R. Desrosieres. 

 1960. Premieres donnees sur le thon 

 anageoires jaunesenNouvelle- 

 Caledonie. Office de la Recherche 

 Scientifique et Technique Outre-Mer, 

 Institut Francais d'Oceanie, Rapport 

 Scientifique No. 11, p. 33-54.) 



Data (16 morphometr ic and 2 meristic 

 characteristics) were collected on 504 yellowfin 

 tuna caught in the vicinity of New Caledonia. 

 The relationship of total length (L) to standard 

 length (L s ) was found to be L = 1.085 L s . In re- 

 gression analysis of morphometric data, regres- 

 sion equations of the form y = a+bx and y = ax b 

 were used, rather than polynomial equations. 

 Nevertheless, for each character it was neces- 

 sary to calculate two equations for the data; one 

 for fish above about 80 cm. total length and one 

 for fish below that size. The average number of 

 gill rakers was 28.96 + 0. 075. This is one of the 

 smallest values observed in the Pacific and is 

 in accord with the west (small) to east (large) 

 cline reported by Royce for yellowfin from the 

 equatorial Pacific. There is an indication of 

 sexual dimorphism in pectoral fin length. For 

 the larger fishes, the relative growth of fins and 

 middle and posterior parts of the body and 

 relative increase in weight tend to be faster 

 than for smaller fishes (less than 80 cm. ). For 

 the anterior parts, the reverse is true. Thus, 



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