Lavaniegos: Vertical distribution of euphausnd life stages 



305 



whereas E. pacifica larvae were advanced furcilias. 

 Though the larvae of nighttime epipelagic species (E. 

 recurva, E. eximia, and E. pacifica) occupied upper 

 strata during both day and night, larvae of E. gib- 

 boides showed the same tendency as TV. difficilis in 

 avoiding the surface layer. 



Few postlarvae (juveniles and adults) of epipelagic 

 species were caught during daytime, particularly of 

 E. gibboides, making it difficult to compare day and 

 night vertical distributions. However, the other 

 Euphausia species (Fig. 7) may have been migrating 

 daily, on the basis of specimens found between 200 

 and 400 m during daytime, compared with their 

 nighttime presence near the surface (Tables 3 and 



4). Thysanoessa gregaria and Stylocheiron affine did 

 not appear to migrate; they were not present in the 

 upper 100 m during day and night (Fig 8). 



The main part of the population of the three meso- 

 pelagic species did not occur above 100 m (Fig. 8). 

 Larvae of Stylocheiron longicorne and S. maximum 

 were at 100 m (except at st. 120.60 during the day) 

 and of Thysanopoda orientalis at 200 m (Table 3). 

 Off Point Eugenia and in Guaymas Basin virtually 

 no euphausiids were found below 400 m depth. At 

 those depths, dissolved oxygen was <1 mL/L at both 

 locations (Fig. 2). In Salsipuedes Channel, oxygen 

 values below 400 m was >2 mL/L, and some postlarvae 

 of TV. difficilis were found as deep as 700-800 m. 



