WALTERS: ECOLOGY OF HAWAIIAN SERGESTID SHRIMPS 



eaten-larval bivalves, small cyclopoid copepods, 

 and foraminifera commonly occurring in the diet. 

 Sergia bigemmea was the only species in which 

 chaetognath spines were found. Other food items 

 included the large cyclopoid copepod Sapph iriua, a 

 single larval decapod, and unidentified fibrous 

 matter. 



Sergia inequalis (Bur ken road 1940) 



Vertical Distribution (Figure 25) 



As with S. bigemmea, S. inequalis may have 

 avoided the trawl. The few daytime captures were 

 nearly all below 750 m; the peak near 550 m 

 resulted from a tow in June 1971 that dipped to 760 

 m. Maximum daytime depth appeared to be 1,100- 

 1,200 m. The December 1970 cruise took S. in- 

 equalis in open tows between 800 and 1,250 m- 

 seven in a 950- to 1,000-m tow and four in a 1,150- 

 to 1,250-m tow. The nighttime distribution varied 

 with size. Small shrimp less than 12 mm CL were 

 found in the upper 100 m; larger shrimp occurred 

 between 100 and 250 m. Moonlight did not 

 significantly affect the adults; there were no 

 captures of small shrimp under these conditions. 

 The Teuthis series showed no evidence of full 

 moon nonmigration, but the December 1970 cruise 



200 

 400 

 600 

 800 

 1000 

 1200 



200 

 400 

 600 

 800 

 1000 

 1200 



200 

 400 

 600 

 800 

 1000 

 1200 



Figure 25.- Vertical distribution of Sergia inequalis. 



took five specimens at night between 550 and 

 800 m. 



Population Size, Growth, and 

 Reproduction (Figure 26) 



Sergia inequalis was not abundant in Hawaiian 

 waters; the average population density estimated 

 from all horizontal tows was only 0.55 per 100 m^, 

 less than any other regularly occurring all-red 

 sergestid. The largest catch of adults was only 

 seven, from an open tow in December 1970. The 

 oblique series of September 1972 and May 1973 

 gave estimates of 0.94 and 0.31 per 100 m-, 

 respectively. 



In spite of its relative rarity, S. inequalis 

 showed a clear seasonal cycle of growth, although 

 because of the small sample size, the differences 

 among histograms are only marginally significant 

 statistically (Kolmogorov-Smirnov test, II dif- 

 ferent from III, 0.10 >P>0.05). Recruitment was 

 greatest in the second quarter (April-June), and 



SERGIA INEQUALIS 



c5 o 



rH i H 



4 8 12 16 20 

 APR - JUN 



4= 



\ 



I  1 r 



4 e 12 l« 20 



P 



■II 



^ 



-| r— — 1 1 r— 



4 8 12 16 20 20 



8 - JUL- SEP 



-1 1 1 1 r 



4 8 12 16 20 



/3 



■•— ^ 1 I I 



-1 1 r 



4 8 12 lb 20 24 



-AA 



-1 — I I 



4 8 12 '6 20 24 



CARAPACE LENGTH (mm) 



Figure 26.-Quarterly size-frequency distribution of Sergia 



inequalis. 



821 



