FISHERY BULLETIN; VOL. 78, NO. 2 



Figure l. — Occurrence of northern 

 and southern forms of Euphausia 

 eximia in plankton samples from the 

 eastern Pacific Ocean; Krill Expedition 

 station numbers locate samples in 

 which vertical distribution and growth 

 of larvae were studied. 



30' 



20' 



- 10' 



- 0° 



10° 



20° 



120° 



110° 



100° 



90° 



80° 



raphy Expeditions Krill, Aries, and Muddauber, 

 and CalCOFI Cruise 5804. They were identified 

 from an area off western Baja California in which 

 E. eximia is consistently abundant and where 

 closely related species {E. mutica and£'. recurva), 

 whose larvae we have identified, are rarely, if 

 ever, present (Brinton 1967). At three locations 

 (Stations 6, 10, and 21) larvae were counted as 

 well in separate day and night series of tows taken 

 across eight strata above 500 m on Krill Expedi- 

 tion (Brinton 1979) to investigate patterns of ver- 

 tical distribution. 



Larvae from each sample were grouped by size, 

 information from length-frequency histograms, 

 and degree of morphological differentiation into 

 developmental stages which, to furcilia IV, were 

 discrete and assumed to be separated by one molt. 

 Furcilia V-VI and juvenile I were also presumed to 

 be one intermolt although individual variation in 

 growth and morphogenesis made boundaries less 

 distinct. Altogether 2,210 individuals were mea- 



sured and 347 dissected for study of appendages. 

 Measurements were made with an ocular mi- 

 crometer; the method was the same as that used in 

 studies of species of the E. gibboides group 

 (Knight 1975, 1978). In the comparison of growth 

 rate between areas within each population larvae 

 from Stations 1520 and 1604 were treated as one 

 sample. Larvae were dissected in glycerine and at 

 least 10 specimens of each stage were examined in 

 detail . In the description of larval stages, the usual 

 setation or condition noted is given in parentheses 

 following the range observed. Drawings were pre- 

 pared with the drawing attachment of a Wild M20 

 Microscope.^ 



The nomenclature used to describe larval mor- 

 phology was modified from the studies cited above 

 with respect to the mandible. It appears appro- 

 priate to refer to the dentate process near incisor 



^Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



314 



