WALTERS: ECOLOGY OF HAWAIIAN SERGESTID SHRIMPS 



Sergestes consobrinus Milne 1 968 



Vertical Distribution (Figure 1 1) 



Nearly two-thirds of the captures during the 

 Teuthis series were from shallow night tows 

 during the May 1973 cruise (Teuthis XXI); it was 

 also fairly abundant in the oblique series of 

 September 1972 and May 1973 (Teuthis XXII). 



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-fer^ 



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<s> 



^ 



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 CRRHPRCE LENGTH (MMl 



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 NO. PER 10^ m3 



Figure IL-Vertical distribution of Sergestes consobrinus. 



Sergestes consobrinus was broadly distributed 

 during the daytime, from 450 to 725 m. The 

 population maximum appeared to be around 600 

 m, but most daytime catches were small. A few 

 captures were made between 800 and 950 m; these 

 may have been contaminants. The nighttime 

 distribution showed a broad peak from the surface 

 to 75 m, with lesser numbers to 125 m. These 

 numbers were strongly influenced by the May 1973 

 captures. Moonlight depressed most of the 

 population to 100-150 m, with a substantial 

 number remaining at the daytime depth. The 

 December 1970 cruise took S. consobrinus near full 

 moon in tows between 140 and 180 m, and also in a 

 700- to 800-m tow. Later catches when the moon 

 was waning were in the upper 120 m, with a large 

 catch at 30 m. 



Population Size, Growth, and 

 Reproduction (Figure 12) 



Like S. vigilax, S. consobrinus appears to have 

 been undersampled by the MT. The average 

 population size estimated by all horizontal tows 

 was 1.05 per 100 m'-. The figure for only the night 

 tows was 1.99 per 100 m-, reflecting the large night 

 catches of the May 1973 cruise (Teuthis XXI)-up 

 to 76 in a single 3-h tow. The oblique IKMT series 

 of September 1972 and May 1973 (Teuthis XXII) 

 yielded higher figures of 5.42 and 2.08 per 100 m-, 

 respectively, presumably because the finer mesh of 

 the IKMT retained more of the small shrimp. 



The seasonal size-frequency histograms show a 

 maximum proportion of small individuals in the 

 third quarter (July-September). The largest 

 shrimp were taken in the first and second quarters, 

 although first quarter catches were small. 



Diet was not examined, since none were taken 

 during DSB III. 



Sergestes sargassi Ortmznn 1893 



Vertical Distribution (Figure 13) 



With the possible exception of S. cornutus, 



SERGESTES CONSOBRINUS 



15- 

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9 



JAN -MAR 



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- JUL-SEP 

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CARAPACE LENGTH (mm) 



Figure 12.-Quarterly size-frequency distribution of Sergestes 

 consobrinus. 



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