America in the second quarter — in all other 

 cases the contour of 6 fish per 100 hooks does 

 not enclose values of much above 6. 



SWORDFISH 



The plots of swordfish apparent abundance 

 shown in Figure 8 for the four quarters ap- 

 pear on cursory examination to be among the 

 most complex of all the species and groups 

 of species. In fact, they are among the sim- 

 plest, since they demonstrate little difference 

 in distribution with reference to longitude, 

 latitude, land masses, open ocean areas, or 

 even with season. In the first, third, and fourth 

 quarters, the northern limit of distribution 

 at the lowest level shown, 2 fish per 10,000 

 hooks, extends beyond the limits of the fishery. 



The highest average catch per unit of 

 effort is about 27 fish per 10,000 hooks, at the 

 northern limit in the fourth quarter — in other 

 quarters it runs about 12-19 fish per 10,000 

 hooks, either at the northern limit or near 

 lat 10 °N on the coast of west Africa. 



The catch-per-unit-of-effort figures given 

 are for swordfish caught incidental to daytime 

 longline fisheries primarily for other species 

 — commercial longline fisheries for swordfish 

 operate primarily at night, since catches are 

 considerably higher than they are in daylight 

 hours. This fact, together with the increase 

 in apparent abundance of swordfish through 

 the 1956-63 period (Figure 2) means that the 

 values in Figure 8 must be interpreted with 

 considerable caution. 



WHITE MARLIN 



Figure 9 shows catch rates for white marlin 

 for the four quarters of the year. The major 

 concentrations of white marlin occur in the 

 western Atlantic. There is a concentration 

 along the east coast of South America in each 

 quarter except the second and another which 

 appears to move along the north coast of South 

 America, through the Caribbean, and into the 

 northern Gulf of Mexico, starting in the first 

 quarter. Mather et al. (1972), after studying 

 65 tag returns, mostly from the commercial 

 fishery, state that these shifts may be attrib- 

 uted to seasonal migration. They hypothesize 

 that there are probably no major migrations 



of white marlin between the two western At- 

 lantic concentrations and that they may be 

 separate populations. 



Average catch rates reach 30 or more white 

 marlin per 1,000 hooks in the Gulf of Mexico 

 and Caribbean in the second quarter and nearly 

 that rate off eastern South America in the 

 first and fourth quarters. 



Figure 2 shows that the catch rate of white 

 marlin tended to increase during the 1956-68 

 period, with rates of about 1 fish per 1,000 

 hooks or below in 1956-60 and rates generally 

 over 2 fish per 1,000 hooks in 1961-68, ap- 

 proaching 3 fish per 1,000 hooks in 1966-68. 



BLUE MARLIN 



Figure 10 shows catch rates for blue marlin 

 for the four quarters of the year. Catch rates 

 in the areas where most of the blue marlin 

 have been caught have decreased markedly 

 (Figure 2), with rates near or above 2 fish 

 per 1,000 hooks in 1956-63, but only 0.6 fish 

 or less per 1,000 hooks in 1965-68. 



The most striking features of Figure 10 are 

 two major concentrations, both in the western 

 Atlantic. (The apparent concentration off 

 Africa in the first quarter is based on very 

 little fishing.) One of the western Atlantic 

 concentrations lies off the easternmost part 

 of South America in the first and second 

 quarters, with a suggestion of its existence in 

 the fourth quarter. The other lies in the Gulf 

 of Mexico and Caribbean, centered around 

 Cuba, in the second and third quarters. Mather 

 et al. (1972) have hypothesized on the basis 

 of spawning information that these two widely 

 separated concentrations represent separate 

 populations although Ueyanagi et al. (1970) 

 believe there is mixing in equatorial areas. 



Highest average catch rates in both con- 

 centrations reach over 13 fish per 1,000 hooks 

 in the second quarter. 



BLACK MARLIN 



Black marlin had not been reported in the 

 Atlantic until the first statistical report on 

 the Japanese longline fishery (Shiohama et al., 

 1965). Its existence in the Atlantic still has 

 not been confirmed by examination of speci- 

 mens by a qualified ichthyologist. Nonetheless, 



16 



