1028 



Fishery Bulletin 97(4), 1999 



Dusk tows 



Jordan station ni-62 



1,5 2 6 3,5 4.5 5 5 6.5 7 5 8 5 



Night tows 



B 



5 t 5 2.5 3 5 4 5 5 5 6 6 7,5 8.5 



Jordan station rV-05 



D 



5 15 2.5 3.5 4.5 5 5 6.6 T b 8 5 



Mantle length (mm) 



Figure 4 



Size-frequency distributions for ommastrephid paralai-vae. All specimens were measured from samples 

 that collected <100 rhynchoteuthions. A subsample of 100 specimens was measured from samples 

 containing >100: (A) pooled distribution for all dusk tows (samples collected <1 h after local sunset); 

 (Bl pooled distribution for all night tows (samples collected >1 h after local sunset); (C) lengths of 100 

 specimens from the station that collected maximum abundance; (D) example of size-frequency distri- 

 bution expected from a station that sampled a recent hatching event. 



state. The low variability of flow meter counts in(di- 

 cates that observed abundances did not result from 

 sampling artifacts. 



Discussion 



Aside from the band of high rhynchoteuthion abun- 

 dance parallel to the coast and coincident with the 

 29°C isotherm, these collections are not unusual for 

 surface samples of cephalopod paralarvae. The abun- 

 dance of other cephalopods with paralarvae typically 

 found at the surface, such as Argonauta, was not 

 exceptional. Unusually high abundances in these 

 samples were found only in the paralarvae of 

 ommastrephid squids. 



The Humboldt squid, Doscidicus gigas, is an 

 ommastrephid sufficiently abundant in this area to 

 support commercial fisheries, but descriptions of the 

 paralar\'ae of this species are not adequate to iden- 

 tify them with confidence. However, the general mor- 

 phology, morphometries, and chromatophore patterns 

 of the paralarvae reported here are consistent with 



those of another widely distributed and abundant 

 ommastrephid, Stheiwteiithis oualaniensis, whose 

 paralarvae have been described from off Hawaii 

 (Harman and Young, 1985). It is not possible at this 

 time to be certain which of these species composed 

 the high abundances reported here. Although natu- 

 ral spawning has not been observed directly for ei- 

 ther of these species, ommastrephids are known to 

 spawn large egg masses that are gelatinous and pe- 

 lagic and are very difficult to collect with nets. 

 Spawning aggregations of S. oualaniensis and other 

 ommastrephids have been located in other areas. It 

 seems reasonable to assume that either species may 

 aggregate in the study area to produce egg masses. 

 No information is available on the abundance of 

 these squid paralarvae in subsurface waters of this 

 region. The highest abundance of S. oualaniensis in 

 Hawaiian waters is found in the mixed layer from 

 the surface to 20 m depth (Young and Hirota, 1998). 

 Surface abundance therefore appears to be a reason- 

 able indication of overall paralarval distribution of 

 this species. Furthermore, the depth of maximum 

 zooplankton abundance in the eastern tropical 



I 



