GARTNER ET AL.; LANTERNFISHES 



oligotrophic regime in the eastern Gulf, with an 

 annual primary production of <50 to 75 g C yr"^ 

 (El-Sayed 1972; Hopkins 1982, unpub. data). 



Species Data 



A total of 13,369 myctophids were examined from 

 all stations, with all but 77 (0.6%) identifiable to 

 species. Table 3 lists all taxa, along with the number 

 of individuals captured from each sampling region, 

 their distribution pattern (from Backus et al. 1977), 

 diel distribution ranges, and overall size ranges. The 

 identified material comprised 17 genera and 49 

 species. 



The distribution ranges and estimates of abun- 

 dance and standing stock of the abundant species 

 in the following species accounts were limited to 

 data collected during the three Columbus Iselin 

 cruises to Standard Station (EC). Too few collections 

 were made in the other two areas (NE, SE) to allow 

 for comparable analyses. 



Based on frequency of capture and total number 

 of specimens from EC, seven species were con- 

 sidered abundant, i.e., dominant, (>500 specimens 

 total captured) in the eastern Gulf. In decreasing 

 order of abundance these were Ceratoscopelus 

 warmingii, Notolychnus valdiviae, Lepidophanes 

 guentheri, Lampanyctus alatus, Diaphus dumerilii, 

 Benthosema suborbitale, and Myctophum affine. 

 Together they comprised approximately 75% of the 

 total number of specimens collected from EC 

 (74.4%). Table 4 Usts the dominant species along 

 with their percentage composition among the domi- 

 nant species and overall. 



From all collections, 42 additional species were 

 divided into the following abundance categories: 

 common (101-500 specimens; 10 species); uncommon 

 (10-100 specimens; 26 species), and rare (<10 speci- 

 mens; 6 species). 



Abundant Species 



Ceratoscopelus warmingii: N = 2,267, 

 14-65 mm SL, Juvenile-Mature Adult 



The vertical distribution profile shows this species 

 to be a strong migrator with a broad diel depth 

 range (Fig. 3a). During the day, it occurred from 

 650 to 1,000 m (recent deep mesopelagic daytime 

 tows in the Gulf of Mexico have taken C. warmingii 

 below 1,000 m, J. V. Gartner unpub. data). Night 

 captures were mainly between 75 and 125 m, with 

 a maximum abundance of 95 individuals/lO'* m^ at 

 125 m. Abundance was bimodally distributed with 



some small juveniles apparently remaining near day- 

 time depths at night (Fig. 3a, Table 5). 



Notolychnus valdiviae: N = 1,780, 

 9-22 mm SL, Postlarvae-Mature Adult 



Peak daytime distribution was mainly between 

 400 and 500 m (Fig. 3b). Some night captures were 

 made as shallow as 50 m, but abundance maxima 

 were found at 75 and 155 m, with the peak at 75 

 m (>72 individuals/lO"^ m^). The distribution pattern 

 was discontinuous, with no specimens taken at 

 125 m. There was no evidence for a nonmigratory 

 portion of the population as was found for C. 

 warmingii. 



Analysis of the size vs. depth for N. valdiviae 

 showed an increase in mean size with increasing 

 depth at night (Table 5). No trend was apparent dur- 

 ing the day because of small sample size. 



Lepidophanes guentheri: N = 1,610, 

 13-64 mm SL, Juvenile-Mature Adult 



This species was a moderate to strong vertical 

 migrator. Although daytime captures were recorded 

 as shallow as 400 m, this species was most abun- 

 dant between 650 and 800 m and recent discrete 

 depth hauls in the Gulf of Mexico have also taken 

 L. guentheri from below 1,000 m (J. V. Gartner un- 

 pub. data). Nighttime abundance was highest at 75 

 m (38.1 individuals/lO"* m^) and sharply decreased 

 below this depth (Fig. 3c). Differences in day-night 

 abundances were not as pronounced as in Cerato- 

 scopelus or Notolychnus. At 650 m during the day, 

 catch abundance was approximately the same as at 

 105 and 125 m at night. 



Lepidophanes guentheri was the only abundant 

 species for which lunar influence on depth of cap- 

 ture was apparent. During a new moon cruise (Dan 

 Braman), L. guentheri measuring 27 to 37 mm SL 

 were captured as shallow as 10 m. 



Nonmigration of members of the population was 

 noted, mostly among juveniles measuring from 13 

 to 25 mm SL. Because of sample size, no other clear 

 size-depth patterns were discernible. 



Lampanyctus alatus: N = 1,418, 

 15-48 mm SL, Juvenile-Mature Adult 



The daytime vertical profile extended from 350 

 to 900 m, with a peak at 650 m (Fig. 3d). This species 

 was found between 75 and 155 m at night (maximum 

 24.2 individuals/lO"* m^ at 125 m). Some estimated 

 daytime abundances for L. alatus were as large as 



85 



