Vecchione: Abundance of squid paralarvae during El Niiio of 1987 



1027 



set) and night tows to determine the contribution of 

 diel variabiHty, from either visual avoidance of the 

 net or vertical migration by larger animals, to the 

 size distribution. The overall size distribution was 

 skewed toward the size of newly hatched animals, 

 with the model length 1.0-1.5 mm DML. The size 

 range in dusk samples was 0.5-3.5 mm DML (Fig. 

 4A). A small second group of larger squid 3.5-8.5 mm 

 DML (modal length ca. 6.0-6.5 mm DML) not present 

 in dusk tows was collected at night in addition to the 

 smaller paralarvae (Fig. 4B). Some stations, such as 

 Jordan station IV-05 (Fig. 4D), included only very 

 small squid 1-2 mm DML, as might be expected from 

 a hatching event. The greatest abundance, however, 

 at station III-62, was characterized by a broader 

 range of lengths (Fig. 4C) with a larger modal size of 

 2.0-2.5 mm DML. On the basis of analysis of growth 

 rings in statoliths from Hawaiian S. oualaniensis, a 

 2.5-mm-ML paralarva is ca. 20 days old (Bigelow, 

 1991 ). I therefore conclude that this very high abun- 

 dance did not result from the net happening upon 

 an egg mass, either just before or just after hatch- 

 ing, but instead an aggregating mechanism must be 

 responsible for this patch. 



I examined the second alternative by calculating 

 the variability in flow meter revolutions among tows. 

 The mean and standard deviation for this estimate 

 of sampling efficiency were 2771 and 645, respec- 

 tively. None of the three outliers from this distribu- 



24 25 26 27 28 29 30 31 32 

 Surface temperature 



Figure 2 



Rhynchoteuthion squid paralarval abun- 

 dance plotted against surface temperature 

 for NOAA Ship D.S. Jordan cruise 8710. 

 Vertical arrows represent samples with 

 maximum numbers of paralarvae. 





32 



S 30 

 |- 29 

 a 28 

 S 27 

 ^ 26 

 ^ 25 

 24 



220 240 260 280 300 320 340 

 140 

 I 120 

 S100 

 S" 80 

 I 60 

 S 40 



Q. 



^ 20 

 



220 240 260 280 300 320 340 

 .lulian date 



Figure 3 



Relationships among water temperature, 

 squid abundance, and date for NOAA Ship 

 D.S. Jordan cruise 8710: (A) surface tem- 

 perature plotted against Julian date; (B) 

 rhynchoteuthion squid paralarval abun- 

 dance plotted against Julian date. Verti- 

 cal arrows represent samples with maxi- 

 mum numbers of paralarvae. 



Hi 



tion (one high and two very low) collected >20 

 rhynchoteuthions. All of the samples with abun- 

 dances >40 rhynchoteuthions came from tows with 

 2612-2947 revolutions. Although this parameter can 

 be used to estimate the volume of water filtered by 

 the sample, I did not do this because assumptions 

 about the orientation of the net mouth with respect 

 to the sea surface are required for surface samples 

 and this orientation can change greatly with sea 



