FISHERY BULLETIN: VOL. 78, NO. 2 



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Figure 13. — Temporal variations in number of crustacean indi- 

 viduals along the southern transect in Monterey Bay, Calif, 

 (means and 95% confidence limits). 



creases, to zero in some cases, were at the shal- 

 lowest station (Figure 12; M-1, 6 m). Because of 

 the shallow water depth, wave-induced substrate 

 motions were most severe at this station (see En- 

 vironmental Setting). Furthermore, seasonal sub- 

 strate movements were greatest during the late 

 fall and winter, when wave heights were large and 

 wave periods short (Figure 3). Therefore, the low- 

 est polychaete numbers were found during that 

 time (late fall and winter) and at the water depth 

 (6 m) corresponding to the greatest substrate 

 motions. 



Many environmental factors had a general 

 seasonal trend similar to wave activity. Water 

 temperature, river runoff, and phytoplankton 

 standing stocks also had marked winter-summer 

 variations in Monterey Bay (Oliver et al.'*). How- 

 ever, wave-induced sediment motion was one of 

 the only seasonal factors that changed with water 

 depth and was, thus, coincident with the depth and 

 seasonal changes in polychaete abundance. The 

 depth-dependent changes in resuspended particu- 

 late material are treated in the discussion. 



Prionospio pygmaea, Armandia brevis, and 

 Magelona sacculata settled into the crustacean 

 zone (M-1 and M-2), but rarely survived to adult 

 size. Their frequency of occurrence at the shal- 



"Oliver, J. S., P. N. Slattery, L. W. Hulberg, and J. W. Nybak- 

 ken. 1977. Patterns of benthic succession after dredging and 

 dredge material disposal in Monterey Bay, California. U.S. 

 Army Corps Eng. Waterways Exp. Stn., Tech. Rep. 0-77-27, 

 186 p. 



lower stations was much lower than it was in 

 deeper water (Table 2). Moreover, the low popula- 

 tion abundance during the winter was not simply 

 a result of seasonal changes in larval availability. 

 Although some polychaete species appeared to 

 have a relatively seasonal pattern of larval avail- 

 ability (e.g., M. sacculata), the larvae of other 

 species (e.g., N. elegans and P. cirrifera) were 

 present throughout the year (Figure 14). 



The seasonal peaks in polychaete abundance in 

 deeper water (M-4, 18 m) were largely due to the 



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Prionospio pygmaea 



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YEARS 



Figure 14. — Abundant sandflat polychaetes collected in larval 

 settling jars at the 18 m station (M-4) in Monterey Bay, Calif. 



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