Table 6. — Catch rates (numbers of fish/1,000 hooks) for white marlin of the Japanese Atlantic longline fishery, 1956-70, by years 

 and areas. Note: 0.00 =-=0.005 but=»0; = effort but no catch; - = no effort. Data furnished by J. P. Wise (pers. commun.). See 

 Figure 13 for areas. 



Figure 13.— Division of the Atlantic Ocean. (From Wise and 

 Davis, 1973, Fig. 1 and caption.) 



No information was found on the effects of food 

 competition, predation, and natural fluctuations on 

 the abundance of the species. 



4.23 Average density 



No information was found in the literature. 



4.24 Changes in density 



Seasonal and areal variations in density, as in- 

 dicated by longline catch rates, are shown in Figures 

 4, 5, and 7. 



Some indications of seasonal changes in density 

 with depth are given by the relative success of longline 

 and rod and reel fishing, and also by the availability 

 of white marlin to longline fishing in situations in 

 which they are not seen on the surface. Off the U.S. 

 coast between Cape Hatteras and Cape Cod, surface 

 trolling is effective in summer, when white marlin are 

 concentrated on or at the edge of the continental shelf, 

 and longline fishing is poor. In late September and 

 October, the fish have left the shelf (Mather et al., 

 1972) and longline catches in the adjacent deep waters 

 are at their peak (Fig. 5). A similar situation exists off 

 Venezuela, where surface (sport) fishing is at its peak 

 from August-October, while longline results are 

 relatively poor. Longline fishing, on the other hand, is 

 good in the area in December and February when few 

 white marlin are taken on rod and reel (Fig. 5, for 

 longline catch rates; Jaen, 1964, for sport fishing 

 success). 



A generally deeper distribution in oceanic than in 

 coastal waters is indicated by the lack of visual obser- 

 vations of white marlin in deep, oceanic waters, even 

 in areas and seasons in which longline fishing 

 produces good catches. 



4.3 Natality and Recruitment 



4.31 Reproduction rates 

 Nothing found in the literature. 



4.32 Factors affecting reproduction 

 Nothing in the literature. 



80 



