DAILEY and RALSTON: BIOLOGICAL DEVELOPMENT OF HETEROCARPUS LAEVIGATUS 



Table 5.— Sex ratio and size of Heterocarpus laevigatas by depth 

 (M is for males, F0 for females without eggs, and FE for females 

 with eggs). S p is the standard error of the proportion. 



The results presented in Table 5 also show the 

 distribution of mean size (CL mm) by depth (m) for 

 all H. laevigatus caught, and for the M, F0, and 

 FE subgroups. For all shrimp combined, average 

 size decreases slightly with increasing depth fished. 

 The trend for decrease in size with increasing depth 

 is not evident in the M subgroup. However, the F0 

 class demonstrates a strong relationship of decreas- 

 ing mean CL with depth. For the FE category the 

 decline is much less apparent, if at all. Thus the 

 overall decline in mean CL of all shrimp combined, 

 is clearly due to an overriding influence of females 

 without eggs. We interpret these trends, or lack 

 thereof, to indicate that young (i.e., small) females 

 may move from deep to shallow water as they 

 mature. 



There is some evidence that the depth distribu- 

 tion of H. laevigatus changes with reproductive 

 activity (i.e, season). Figure 5 presents the depth 

 distributions for reproductively competent (>40 mm 

 CL) male and female shrimp, classified into samples 

 taken outside (March- July) and during the reproduc- 

 tive season (August-February). Note that depth 

 distributions of both male and female shrimp are 



60 



40- 



20- 



> 



- 40 



« 



cc 



20- 



M ALE S 



> 40 mm CL 



400 



FEMALES 

 > 40 mm CL 



800 



Depth 



Figure 5.— Seasonal distributions of large (>40 mm) male and female Heterocarpus 

 laevigatus by depth. The dashed line represents the spawning season distribution (May- 

 February) and the solid line represents the distribution during the nonspawning season 

 (March-July). 



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