Abstract. -The larvae and juve- 

 niles of two platytroctid species, Holt- 

 byrnia latifrons and Sagamichthys 

 abei, from the northeastern Pacific 

 are described. Young individuals 

 were collected at a broad range of 

 mesopelagic depths, indicating that 

 they occupy similar depths as adults. 

 The relatively large larvae (~15mm) 

 have well-developed teeth and fins 

 while carrying the yolksac. Presence 

 of <20mm sizes from most months 

 of the year may indicate year-round 

 spawning. 



Description of Young of 

 the Mesopelagic Platytroctids 

 Holtbyrnia latifrons and 

 Sagamichthys abei (Pisces, 

 Alepocephaloidea) from 

 the Northeastern Pacific Ocean 



Tetsuo Matsui 



Marine Life Research Group 



Scnpps Institution of Oceanography A-027 



La Jolla, California 92093 



Manuscript accepted 10 January 1991. 

 Fishery Bulletin, U.S. 89:209-219 (1991). 



The only published description of 

 larval platytroctids is that of Beebe 

 (1933). However, Parr (1960) in his 

 review of the family (then known as 

 Searsidae) believed larval platytroc- 

 tids of 11- 17 mm could not be iden- 

 tified even to genus, and showed that 

 Beebe's detailed description of the 

 larvae identified as Bathytroctes ros- 

 tratus was based on several species. 

 In a recent revision of the family, 

 Matsui and Rosenblatt (1987) recog- 

 nized five species off California. None 

 are congeners. The earliest larvae of 

 the two commonest species, Holtbyr- 

 nia latifrons * and Sagamichthys abei, 

 are identifiable by their photophores. 

 This report describes the young of H. 

 latifrons and S. abei and presents 

 catch data from the Scripps Institu- 

 tion of Oceanography (SIO) Fish Col- 

 lection and depth of capture data 

 from a series of opening-closing net 

 tows. 



Material and methods 



Material used in this study is from 

 the SIO Fish Collection and from 

 samples collected on seven cruises 

 sponsored by the Marine Life Re- 



* Holtbyrnia latifrons may be a junior synonym 

 of//, baucoti Mayer and Nalbant 1972. How- 

 ever//, baucoti was inadequately described, 

 and I have failed to gain additional informa- 

 tion on the holotype. 



search Group (MLRG) of SIO. Most 

 SIO Fish Collection samples and 

 some from the MLRG cruises were 

 captured in 3-m Isaacs-Kidd mid- 

 water trawls (IKMT). Other MLRG 

 collections were made with 2-m Stra- 

 min nets and 1-m plankton nets. The 

 1-m nets were attached to modified 

 Leavitt devices (Leavitt 1938) that 

 allowed the nets to be opened and 

 closed by messengers to sample dis- 

 crete depth intervals. Their sampling 

 depths were either recorded by TSK 

 depth-distance recorders on the nets 

 and activated when the nets were 

 sampling, or estimated from records 

 taken on a Benthos time-depth re- 

 corder attached to the bottom net in 

 the cast. Eight depth intervals from 

 surface to nearbottom were sampled 

 at stations 850-1350 m deep, and 12 

 depth intervals at stations of 1370 m 

 to ~1800m. Two samples in the Fish 

 Collection were taken in opening- 

 closing Bongo nets (McGowan and 

 Brown 1966). 



A total of 167 (young and adult) H. 

 latifrons and 220 5. abei were ex- 

 amined in the study. The description 

 of H. latifrons is based on measure- 

 ments and counts of 157 individuals 

 (1 larva, 12 transitional specimens, 

 and 144 juveniles). For S. abei, 1 lar- 

 va, 4 transitional specimens, and 37 

 juveniles were measured and counted. 

 Samples of H. latifrons were gener- 



209 



