Bower Paralarval drift of and inferred hatching sites for Ommastrephes bartramii 



403 



a unidirectional flow away from the islands. Table 2 

 shows the estimated percentage of paralarvae taken 

 at each sampling station that could not have been 

 spawned within 10 km of the archipelago. The pro- 

 jected spawning grounds of individuals collected dur- 

 ing the five surveys are shown in Figures 7—11. 



Discussion 



New information was obtained on the estimated 

 spawning areas of the squid Ommastrephes bartramii 

 with respect to the Hawaiian Archipelago over the 

 1991-93 winter spawning seasons. The objective of 

 the study was to determine whether a spatial rela- 

 tionship exists between the Hawaiian Archipelago 

 and O. bartramii spawning grounds. The results pre- 



sented here suggest that although estimated spawn- 

 ing of O. bartramii did often occur along the island 

 chain, spawning was not limited to nearshore wa- 

 ters; on the basis of estimated current speeds, some 

 animals hatched at least 646 kilometers away from 

 the archipelago. For a minimum of 72% of all 

 paralarvae from the five surveys, projected hatch- 

 ing sites were located at least 10 kilometers from 

 shore. 



Statolith analysis is the most effective method for 

 estimating age in many natural squid populations, 

 yet preparing statoliths for counting growth incre- 

 ments is time-consuming, and frequently increments 

 prove unreadable. This study showed that when a 

 sample size is large, analysis of paralarval mantle 

 lengths measured from a representative subsample 

 can be used as an alternate, easier, and faster method 



7 ( 



0.1 - 

 0.05 



ii 



■,  



M 



IUI1L 



Townsend Cromwell 1991 



» = 98 



mean = 3.5 mm 



SD= 1.4 mm 



I I I I I I 



,1, , ,1, 



,1,1, 



i i i I i i [ i i i i i i 



0- 



0.1 • 



05  



ii 



IIA^^A 



Hokusei Maru IW 



n = 2lh 



mean = 2.5 mm 



SD = 0.8mm 



II I I I II I I III I I I I I I I I I I i i i i 



A 



Townsend Cromwell 1 992 



n = 550 



mean = 2.5 mm 



SD = 7 mm 



ii i i i i i i i i i i i i i ii i i i i i i i i i i i 



Mantle length (mm) 



Figure 3 



Size-frequency distribution of Ommastrephes bartramii 

 paralarvae captured during each cruise. 



