FISHERY BULLETIN: VOL. 74, NO. 4 



200 

 MOO 

 600 

 800 

 1000 

 1200 



200 

 MOO 

 600 

 800 

 1000 

 1200 



200 

 400 

 600 

 800 

 1000 

 1200 



SERGESTES SAR0AS3 



M 6 8 10 12 14 16 6 12 

 CRRHPfiCE LENGTH (MMl NO. PER 10= M^ 



Figure 13.- Vertical distribution of Sergestex xargaasi. 



which is very rare in Hawaiian waters, S. sargastii 

 had the shallowest daytime range of the local 

 species: 450-575 m, with a maximum around 475 m. 

 No significant variation of depth with size was 

 noted, perhaps because of the small number 

 caught. One immature shrimp was captured 

 between 340 and 425 m, and oblique tows from the 

 surface to about 350 m took a few immature 

 specimens in September 1972. There was a pro- 

 nounced variation of size with depth at night. 

 Immature individuals less than 6 mm CL occurred 

 between 100 and 200 m, mostly in the 125- to 150-m 

 range. Larger shrimp were found from 125 to 300 

 m, mostly from 225 to 275 m. Most of the adults 

 captured at night were males; the few females 

 were mostly taken between 125 and 175 m. This 

 apparent segregation by sex was probably a 

 sampling artifact, since the December 1970 cruise 

 took both males and females in tows from 250 to 

 300 m. Moonlight had little effect on the depth 

 range of adults; immature individuals were 

 depressed to about 150-200 m. The peak in the 

 upper 25 m is a sampling artifact. There was no 

 evidence of full moon nonmigration. 



Population Size, Growth, and Reproduction (Figure 14) 

 Sergestes sargassi was not very abundant in the 



^^^ 



^^[\ 



(J " T I [ 



2 20. 



CARAPACE LENGTH (mm) 



Figure 14. -Quarterly size-frequency distribution of Sergestes 



sargassi. 



horizontal collections, the estimated average 

 population density being only 0.70 per 100 m-. The 

 night tows gave a higher total than the daytime 

 tows, 1.07 and 0.64 per 100 m-, respectively. The 

 two IKMT oblique series of September 1972 and 

 May 1973 produced higher estimates, 5.84 and 1.74 

 per 100 m-', respectively; the daytime figure of 

 10.37 per 100 m- in September was the third 

 highest such total for that cruise. These higher 

 figures for the IKMT tows were not the result of 

 more eflRcient filtering, as appears to be the case 

 for the smaller species, since S. sargassi is a 

 moderately large species, about the same size as 

 Sergia scintillans and Sergia gardineri, neither of 

 which showed any signs of significant undersam- 

 pling by the MT. 



Recruitment was highest during the second 

 quarter (April-June), when nearly 70% of the 

 population was immature. Growth during the 

 summer was about 1.0-1.3 mm CL per month, 

 slowing during the third and fourth quarters to 

 0.2-0.5 mm CL per month. Maximum sizes were 

 attained in December and the first quarter 

 (January-March). 



Diet (Table 5) 



DSB III took 10 S. sargassi. Three had empty 

 stomachs. The rest had eaten zooplanktonic 



814 



