OMORI and GLUCK: LIFE HISTORY OF SERGESTES SIMIUS 



130° 125° 120° 



ESTIMATED ABUNDANCE UNDER 

 I m2 OF SEA SURFACE 



M 



60+ 



no 



40° 



Figure 3. — Distribution and abundance of Sergestes smiths larvae from January to February 1964, Estimated abundance is expressed 

 as number of mdividuals beneath 1 m^ of sea surface m depths between and 100 m. 



Table 3. — Experimental data on sinking velocity of eggs of 

 Sergestes simihs in water of salinity 33.72%o. Difference in sink- 

 ing rates is not significant at the S'J level. 



Spawning Season 



The highest spawning of S. similis took place 

 from late December to early April. Protozoea lar- 

 vae occurred most abundantly between January 

 and April at Stn. 90.37 (Figure 7), but were not 

 found in samples collected in November and De- 

 cember. During 1951-54, a number of PZ2 and PZ3 

 appeared each year between January and July, 

 but the occurrence of PZl was restricted to 



January- April, except for August 1952 and July 

 1954. Although one-third of the autumn months 

 were not represented by samples, these months 

 were scattered enough to make the data sig- 

 nificant. Seasonal abundance of zoeal stages dup- 

 licated that of PZl. Early postlarvae were found in 

 plankton from February to early July. Consider- 

 able numbers of PZl and PZ2 (<1.3 mm BL) ap- 

 parently passed through the mesh of the CalCOFI 

 net, as their measured population densities were 

 almost always lower than those measured for PZ3. 

 The optimum temperature range for larval de- 

 velopment is 10'-15°C(Omori 1979), and the high- 

 est temperature at which adult S. similis occur is 

 13°C. Thus, the best temperature for the larvae is 

 close to the upper temperature limit of the adult's 

 habitat. Furthermore, comparison of the repro- 

 ductive activity of S. similis with physical and 



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