series sampled only to 1,200 m, they may have 

 missed the deeper portion of the population. 



The seasonal size-frequency histograms are not 

 significantly different from one another. 



Diet (Table 5) 



DSB III took only three specimens, all with 

 empty stomachs. 



Sergia laminata (Burkenroad 1940) 



Vertical Distribution 



Only four individuals were captured in closing 

 tows, all in daytime tows during the November 

 1972 cruise. A tow at 650-725 m took three shrimp, 

 and a tow at about 750-800 m took one shrimp. At 

 night oblique tows in the upper 400 m took single 

 shrimp during the September 1972 and May 1973 

 cruises, suggesting that S. laminata may be a 

 vertical migrator. On the other hand, the 

 December 1970 cruise captured one shrimp in an 

 open horizontal tow at 550-600 m at night, sug- 

 gesting that S. laminata may not migrate near 

 full moon. 



The small sample size did not allow studies of 

 growth, reproduction, or diet. 



Petalidium suspiriosum Burkenroad 1937 



Vertical Distribution (Figure 31) 



A deep-living nonmigrator, P. suspiriosum 

 generally stayed below 800 m day and night. The 

 shallowest captures came during the June 1972 

 cruise, which took six in a 750- to 800-m day tow 

 and five in two night tow^s between 630 and 720 m. 

 Maximum depth appeared to be at least 1,500 m; as 

 with 5. tenuiremis, limited trawling below 1,500 m 

 did not catch any P. suspiriosum. 



Population Size, Growth, and 

 Reproduction (Figure 32) 



Petalidium suspiriostim is more abundant than 

 its small numbers in our collection would seem to 

 indicate, since the depths below 800 m where it 

 lives were not as thoroughly sampled as the shal- 

 lower waters. The average population density 

 estimated from all horizontal tows was 1.84 per 100 

 m-, making it the second most abundant all-red 

 sergestid. Like S. tenuiremis, the oblique series 



FISHERY BULLETIN: VOL. 74, NO. 4 



10 12 14 16 



U 6 8 10 12 14 16 

 CmfiPfiCE LENGTH (MM) 



NO. PER 10=' M 



5 m3 



Figure 31. -Vertical distribution of Petalidium suspiriosum. 

 NIGHT and MOON data combined. 



PETALIDIUM SUSPIRIOSUM 



^^il 



9 



I — I 



^ 



ih 



(/> 



< 4 - 



O 



2 - 



UJ 



V) 



n , nn 



n 



rm 



4 



Z 



2- 







JZL-Q. 



__L oJ , n . I h n I . In 



^ 



^^i^ 



10 12 



CARAPACE LENGTH (mm) 



Figure 32.— Quarterly size-frequency distribution of Petalidium 

 suspiriosum. 



gave lower numbers, 1.21 per 100 m- in September 

 1972 and 1.31 in May 1973, probably because some 

 of the population was below the 1,200 m maximum 

 of the oblique tows. 



Because of its susceptibility to damage, it was 

 possible to make accurate measurements of car- 

 apace length on only about two-thirds of the 

 specimens in the collection. There was no 



824 



