the day, larvae were distributed throughout the 

 water column and were most abundant in the 0- to 

 10-m depth interval. A trend of increasing age 

 with depth was evident. Early juveniles were 

 present in low numbers in the 51- to 100-m and 

 101- to 150-m intervals. The sled tows revealed a 

 very high concentration of early juveniles (284 and 

 290/1,000 m^) on the bottom during midday. 



At night larval shrimp were still distributed 

 throughout the entire water column. The younger 

 stages (V and VI), found in some abundance in the 

 0- to 10-m interval during the day, were not 

 collected at night. Furthermore, an age gradient 

 with depth was no longer present. This was due, in 

 part, to the presence of late larvae at all depths in 

 the water column. The most dramatic feature of 

 the night distribution was the vertical migration 

 of the early juveniles as indicated by their virtual 

 absence on the bottom (0 and 4/1,000 m-') in the 

 sled samples. Juveniles were again present in the 

 lower portion of the water column (101-150 m) and 

 had migrated into the upper 100 m, including the 

 top 10 m. There was no evidence that larvae 

 younger than Stage XIII migrated to any extent. 

 Vertical migratory behavior starts late in the 

 larval phase, before the molt to juvenile and 

 recruitment to the bottom. 



Acknowledgments 



We thank R. Mesecar for suggestions on the 

 design and T. Nolan for the fabrication of the 

 epibenthic sampling device. C. B. Miller gave 

 advice on aspects of the research and critically 

 read an early draft of the manuscript. W. T. 

 Peterson, D. 0. Elvin, B. Sullivan, the captain and 

 crew of the RV Cayuse were patient and helpful 

 during the sea trials and sampling. 



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Peter C. Rothlisberg 



Marine Science Center 



Oregon State University 



Newport. OR 97365 



Present address: 



CSIRO 



Division of Fisheries and Oceanography 



North Eastern Regional Laboratory 



Cleveland, Queensland, il63, Australia 



School of Oceanography 

 Oregon State University 

 Corvallis, OR 97331 



William G. Pearcy 



997 



