218 



Fishery Bulletin 89(2). 1991 



JAN 



Ll_j^^ 



FEB 



MAR 



APR 



MAY 



JUN 



JUL 



AUG 



SEP 



OCT 



NOV 



DEC 



YS 15 30 40 



100 120 



SL(mm) 



Figure 6 



Length-frequency distribution of Sagamichthys abei in SIO 

 collections, 1949-79, presented by month of capture. 



o 



100 

 200 

 300 



m too 



| 500- 



g 



Jc 600- 



Q. 

 03 



O 700 



800 - 



900 - 



1000- 



1280 ^ — 

 16 



"I 



J-S 



H S 



Lw\A-Lw^ 



20 22 24 26 28 133 217 



YOLK SAC 



JUVENILE 

 Body Length (mm) 



ADULT 



Figure 7 



Sampling depths of opening-closing plankton net tows which 

 captured Holtbyrnia latifrons (H) and Sagamichthys abei (S). 



either of these species. Samples of H. latifrons were 

 from nets that had sampled depths of 290-860 m, and 

 S. abei of 330-860 m (Fig. 7). All of these individuals 

 were 20 mm and smaller, providing evidence that young 

 stages occur over the entire depth range of the species. 

 Large larval size and early appearance of presumed 

 swimming and foraging capabilities, noted in this 

 study, are apparent specializations for developing at 

 these nutrient-poor depths. 



Absence of day and night differences in depth of cap- 

 ture (Tables 5, 6) add to the previous evidence (Matsui 

 and Rosenblatt 1987) suggesting the absence of diel 

 migration in platytroctids. Hart (1973) and Fitch and 

 Lavenberg (1968) mention the migration of young 

 5. abei to within 200 m of the surface at night, but did 

 not give the source of their information. However, 

 records of platytroctids from depths 200 m and shal- 

 lower are extremely rare and the single record from 

 the Pacific Ocean may be an error (Matsui and Rosen- 

 blatt 1987). 



Hydrographic data (Fig. 8) taken in an area where 

 most Leavitt net tows were made show that samples 

 represented in Figure 7 were taken below the thermo- 

 cline at depths where the temperature range was 

 ~4-8°C. CalCOFI (California Cooperative Oceanic 



