Rio - 



? 4- 



2 - 



50 60 70 80 90 



SIZE CLASS (LBJ 



100 



Figure I. — Weight-frequency histogram of white marlin, 

 Tetraptiirus alhidiis, from the eastern North Atlantic 

 Ocean. Sohd color = females, cross-hatching = m^es. 



grams respectively. None was in ripe or near ripe 

 condition. All females were in a refractory state 

 with no developed eggs except that EATL-6 had 

 relatively large ovaries with very small eggs. How- 

 ever, it, too, was nowhere near reproductive state. 

 These data agree with the suggestion that the 

 white marlin concentrations are postspawning af- 

 fairs. Also, Ueyanagi et al. (1970) demonstrate 

 convincingly that white marlin spawn early in the 

 summer and they further suggest that the post- 

 spawning feeding migration to temperate waters 

 then occurs. The Japanese have done little work in 

 the eastern Atlantic north of lat. 30°N and east of 

 long. 30°W. Why there should be a preponderance 

 of females is unknown but de Sylva and Davis 

 ( 1963: 87) also noted a significantly large percentage 

 of female marlins in the Middle American Bight in 

 1959 though not in 1960. There is nothing in our 

 limited data nor in the much larger samples of de 

 Sylva and Davis to suggest a time difference in the 

 peak abundance of males and females. 



Food 



All stomachs were examined but the stomach 

 acid of marlins is strong and the time from trap to 

 freezer uncertain. Also marlins taken on hooks fre- 

 quently void the contents of their stomach. In any 

 event only well digested remains, some of it fish in 

 origin, were found. 



Weight 



Weight in pounds is given for each specimen in 

 Appendix Tables 1 and 2 with equivalent weights in 



kilograms in Appendix Table 1 . These weights are 

 of the frozen or partly thawed fish but they proba- 

 bly do not vary in any meaningful way from the 

 original weights. To facilitate comparison with the 

 data of de Sylva and Davis (1963: Figures 4 and 5) a 

 histogram of weights in 5-lb (2.27-kg) units is pre- 

 sented in Figure 1. 



Although data are few the first peak in the 55-59 

 lb (24.9-26. 8-kg) range agrees remarkably with the 

 weight frequency data for American Bight speci- 

 mens. There are more large fish off Gibraltar and 

 the lower peaks at 75-79 (34.0-35. 8-kg) and 95-99 lb 

 (43.1-44.9-kg) probably represent successive year 

 classes. If so, the data suggest that older year clas- 

 ses of white marlin along the Atlantic coast of the 

 United States do not participate in the migration or 

 that they are fished out in that population. A wider 

 range in weights is seen in white marlins in southern 

 Florida (personal observations) which might sup- 

 port the first of these suggestions but more likely 

 indicates that the large Florida and Bahamas fishes 

 are not part of the population that congregates in 

 the Middle American Bight. Mather's (1968) chart 

 of migration trends based on 34 tag returns shows 

 the pivotal nature of the Florida-Bahama region rel- 

 ative to the three stocks and that at least some 

 marlin from this area participate in the summer 

 concentration off the Mississippi Delta. Possibly 

 fishes of the Gulf and northwestern Atlantic stocks 

 pass through the Straits of Florida. Determination 

 of minor morphometric differences between these 

 stocks would be invaluable in analyzing the catch in 

 the Straits of Florida but data available are inade- 

 quate and no such study has yet been undertaken. 

 The Venezuela stock may be confined to northern 

 South America. 



Population Structure 



No clear picture yet emerges with regard to the 

 population structure of the white marlin. Specimens 

 from the eastern and western Atlantic are not 

 meristically distinct (Table 1). The detailed analysis 

 of the Atlantic longline operations of the Japanese 

 fishing fleet by Ueyanagi et al. (1970) shows a 

 summer peak in the western Atlantic consistent 

 with the late summer concentrations off Louisiana 

 and Maryland-New Jersey. Their data however 

 give no real indication of a Venezuelan concentra- 

 tion and they have virtually no data on the species 

 from the eastern Atlantic north of lat. 25° or 30°N. 

 Their data definitely indicate a dense population 



166 



