Vertical Distributions 



Vertical distribution data for all dives were lumped 

 together because there were insufficient data to determine if it 

 varied among submarine canyons or from year to year. 



The medusae were mostly found at depths in excess of 600 m 

 (Fig. 3). Only a single macro-medusa ( >2 cm diameter) species 

 i.e. Pelagia noctiluca was found above 300 m and only three 

 species occurred above 600 m while 15 species were found below 

 this depth. There were no eurybathyl species. Pantachoqon 

 haeckeli occurred over the greatest depth range (425-800 m). The 

 medusae as a group showed no evidence of a diel vertical 

 migration. 



Siphonophores were somewhat more eurybathyl than medusae. 

 Two species i.e., Forskalia sp. and Nanomia cara, were found at 

 depths of 100-170 m to 800 m. Nine species occurred above 600 m 

 and only four species were not found above this depth. N. cara 

 apparently showed a diel vertical migration of about 150 m. 



During the day the mean depth of minimum occurrence was 480 

 m but at night it was only 330 m. 



Ctenophores showed a somewhat different depth distribution. 

 Two species i.e., Beroe cucumis and Bolinopsis infundibulum were 

 eurybathyl, occurring from near the surface to 800 m. Four 

 species were observed above 450 m and five species were only seen 

 at greater depths. Ctenophores did not vertically migrate to any 

 extent. 



The only mollusc species for which we have depth data is 

 Limacina helicoides a dark-purple pteropod which was seen below 

 580 m. A number of squids were seen at depths of greater than 

 150 m, most were seen below 300 m. 



The three common macro-crustaceans mostly occurred over a 

 broad depth range but were not seen at the surface. 

 Meganyctiphanes norvegica was observed from 75 to 800 m but was 

 most numerous below 200 m. Themisto gaudichaudii and Sergestes 

 sp. were present below 150 m but were most common at depths 

 greater than 300 m. The mean day depths of the sometime dense 

 layers of euphausiids was 290 m but at night it had decreased to 

 200 m (Table 2). Themisto populations moved from an upper limit 

 during the day of 500 m to 370 m at night and Sergestes moved 

 from 470 m during the day to 340 m at night. Thus, these species 

 showed a 90 to 130 m upward movement at night. 



Most of the fishes occurred below 450 m (Fig. 4). Only a few 

 species were found above this depth by day but some migrated into 

 surface waters at night. Hatchet fishes ( Sternoptychidae ) , 

 myctophids, paralepidids and snipe eels showed some evidence of a 



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