BOEHLERT ET AL.: VERTICAL DISTRIBUTION OF ICHTHYOPLANKTON 



water samples at 5 to 10 m intervals or using a self- 

 contained Applied Microsystems CTD-12. The 

 salinities of water bottle samples were determined 

 in the laboratory using a Guideline 8400 autosali- 

 nometer. The CTD salinities from 13 July were not 

 used because of suspected machine malfunction. The 

 CTD temperatures from 13 July agreed with sur- 

 face bucket temperatures and were used in our study. 

 Plankton samples were preserved at sea in 10% 

 buffered Formalin. Samples were sorted for fish lar- 

 vae in the laboratory using a dissecting microscope. 

 Larvae were identified to the lowest possible taxon, 



measured (standard length), and stored in 5% buf- 

 fered Formalin. 



Larval abundances were calculated as number per 

 1,000 m'* for each tow. The six sampling series were 

 combined into three data sets, spring daytime 

 samples (30 April and 14 May, NHIO), summer day- 

 time (2 and 13 July, NHS), and summer nighttime 

 (2 and 6-7 July NHS). In April and May the salinity 

 profiles closely paralleled each other, with lower 

 salinity at the surface, 30.S-31.0"/„o, than in deeper 

 water, where salinities gradually increased to about 

 33-34°/oo (Fig. 2a). Water temperatures above 50 m 



April 30 



3iO 



33J 



34.0 





 5 

 10 



20- 



30- 



■C 40- 

 o. 



SO- 



SO 



70- 



April 30 



May 14 



Salinity (%o) 



"~1 1 1 1 1 1 1 1 



7.0 e.O 9.0 10.0 1 1.0 12.0 13.0 14.0 15.0 



Temperature ('O 



Q. 

 O 



0- 

 5- 

 10- 



20' 



30- 



40- 



50- 



60- 



70- 



July 13 



'\ 7 July 2 



30^ 



I 



31/) 



T 



-r 



31.5 32.0 32.5 



Salinity (%o) 



I 



33.0 



— I 



3i5 



—I 

 34.0 



o^ 



5 

 10 



20 



30 



^ 40 

 Q. 



50- 



60 



70- 



~1 1 1 1 1 1 1 1 



7.0 8.0 9.0 10.0 II.O I2X) liO 14.0 liO 



Temperature CO 



Figure 2.— Salinity and temperature profiles during the collections, a. Salinity profiles during the spring collections, b. Spring temperature 



profiles, c Summer salinity profiles, d. Summer temperature profiles. 



613 



