FISHERY BULLETIN: VOL. 77, NO 4 



3). Centrobranchus andrae and C. brevirostris 

 were represented by single specimens. The five C. 

 choerocephalus individuals (3.4-7.1 mm) occurred 

 in three samples. All specimens were early photo- 

 phore stage larvae. 



DIOGENICHTHYS ATLANTICUS. —The 12 D. 

 atlanticus larvae (all early photophore stage lar- 

 vae) were caught between 75 and 350 m; 8 came 

 from 75-100 m (Table 2). During other central gyre 

 cruises, D. atlanticus was abundant in IKPT sam- 

 ples, and developmental stages from early larvae 

 to transformation (11.3-12.8 mm) were found. 



HYGOPHUM SPP. —Hygophum proximum was 

 the most numerous larval myctophine (Table 2). It 

 occurred from 25 to 100 m, with maximum abun- 

 dance and significantly larger catches in replicate 

 tows (P<0.01) at 50-75 m (Table 3). Median stan- 

 dard length increased with depth (Table 3) and 

 25-50 m and 50-100 m size-frequency curves were 

 significantly different from each other. The 

 largest larva (10.0 mm, from 75-100 m) was in 

 early photophore development. No late-stage H. 

 proximum larvae have been found among the 490 

 examined from 0-300 m IKPT samples. 



Hygophum reinhardti larvae were more deeply 

 distributed than those off/, proximum, occurring 

 from 50 to 225 m. As with its congener, maximum 

 estimated water column abundance and signi- 

 ficantly larger catches (Ps0.05) were at 50-75 m, 

 but the larvae were also frequently taken (7 of 10 

 samples) at 75-100 m (Figure 7c). There were no 

 apparent trends in size with depth (Table 3). No 

 late photophore development larvae were caught, 

 but two recently transformed individuals (12.3- 

 13.3 mm) were found in 0-300 m IKPT samples 

 from other cruises. 



MYCTOPHUM SPP.— Four Myctophum species 

 were caught (Table 2). The 58 M. lychnobium lar- 

 vae occurred between 25 and 100 m, with 

 maximum abundance at 25-50 m; M. brachy- 

 gnathum had a similar distribution. All five M. 

 selenops were caught at 50-75 m, and six of the 

 seven M. nitidulum at 75-100 m. All of the larvae 

 were small (<8.0 mm) and in early photophore 

 development; only those of M. brachygnathum ap- 

 peared to have increased size with depth (Table 3). 

 A total of 393 Myctophum larvae, of all four 

 species, have been examined from central gyre 

 IKPT samples; none exceeded 10.0 mm or were in 

 advanced stages of photophore development. 



SYMBOLOPHORUS EVERMANNl.—Symbolo- 

 phorus evermanni occurred from 25 to 225 m; over 

 90% of the estimated water column abundance 

 was between 50 and 100 m; abundances in repli- 

 cate samples within the 50-75 m interval were 

 significantly greater (P<0. 05) than in other inter- 

 vals (Table 3). Although the largest larva (10.5 

 mm) was from 75-100 m, the median standard 

 length was smaller there than at shallower depths 

 (Table 3). The 25-50 m and 50-75 m cumulative 

 size-frequency curves were significantly different 

 from each other, indicating decreased size with 

 increased depth. Only early photophore develop- 

 ment stages were caught by stratified tows. This 

 was also the case for all 0-300 m IKPT samples 

 examined, where the largest prejuvenile (15.5 

 mm) of 369 individuals was in the earliest stages 

 of photophore development. 



Other Larvae 



Other families contributed only 9% of the iden- 

 tified larvae and included a wide assortment of 

 mesopelagic fishes; only 3 of the 33 families iden- 

 tified were epipelagic. These "other larvae" were 

 found in samples taken from to 350 m ( Figure 2), 

 Total abundance was low in the upper 75 m, but 

 increased greatly below 75 m (due primarily to 

 peak abundances of two families), and made up 

 25% and 19% of the ichthyoplankton in 75-100 m 

 and 100-350 m samples, respectively. Maximum 

 diversity occurred at 25-50 m. 



None of these "other" species was abundant. Of 

 the 49 kinds of larvae represented only 3 were 

 caught in even moderate numbers: Bregmaceros 

 spp. (Bregmacerotidae), Odontostomops nor- 

 malops (Evermannellidae), and Howella sp. 

 (Aponogonidae). Only Bregmaceros spp. is abun- 

 dant in the central gyre ichthyoplankton on a 

 year-round basis (Loeb 1979bl. Together these 

 three kinds made up 39% of the other larvae; the 

 remaining 61% was contributed by 1 order and 30 

 families (42 species). Catch information on the 

 other larvae is presented in Table 2; more detailed 

 distributional data is provided in Loeb (1979a). 



DISCUSSION AND CONCLUSIONS 



The overall vertical distribution pattern of cen- 

 tral gyre ichthyoplankton conforms to that de- 

 scribed by Ahlstrom (1959) for the California Cur- 

 rent. Most species and individuals were in the 

 upper 100 m, with maximum abundance and di- 



790 



