82 DISCOVERY REPORTS 



Order Iniomi. Suborder Alepisauroidea. Suborder Myctophoidea : Scopelosauridae ; Mycto- 

 phidae : while most species have a swimbladder, the following species lack this organ : Lampanyctus 

 braneri, Ctenobranchus nigro-ocellatus, Gonichthys coccoi, Diaphns coeraleus. In Electrona antarctica, 

 the swim bladder regresses during the adult phase and as already mentioned (p. 65), the swim- 

 bladders of Lampanyctus leucopsarus and Diaphus theta are reduced and invested with fat. 



Order Cetunculi, Order Miripinnati, Order Giganturoidea, Order Lyomeri. Order Allotriognathi: 

 Stylophorus chordatus. Order Berycomorphi, Suborder Anoplogastroidea : Anoplogaster longidens, 

 Melamphaes mizolepis. Order Percomorphi, Chiasmodontidae: Pseudoscopelus scriptus, Dysalotus 

 alcocki. Order Pediculati, Suborder Ceratioidea. 



VERTICAL DISTRIBUTION AND THE SWIMBLADDER 



In his ' Challenger' Report, Giinther (1887, p. xxxiii) has written: ' I formerly assumed that the fishes 

 of the open sea were living either near to the surface or at the bottom, but I think now that Mr Murray 

 is right in supposing that certain fishes live habitually in intermediate strata, without ever coming to 

 the surface or descending to the bottom.' The biologists of the ' Valdivia' Expedition (1898-9) were 

 the first, however, to give close consideration to the fact that deep-sea fishes live at different levels in 

 the ocean. After distinguishing between benthic and bathypelagic species, Brauer (1906) proceeded 

 to discuss this problem and the difficulties involved with the use of open-nets. But the expedition 

 did fish some closing-nets and Brauer gave examples of species taken with this gear (e.g. St. 120, 

 Cyclothone microdot!, 1500-900 m. ; St. 227, Sternoptyx diaphana, 800-600 m.; St. 229, Lampanyctus 

 nigrescens, 1000-800 m.). The Deutsche Sudpolar Expedition (1901-3) used open vertical and hori- 

 zontal nets, and some details are given of the apparent vertical distributions of the deep-sea fishes that 

 were taken (Pappenheim, 1914). 



Since these earlier expeditions, our knowledge of the depth distribution of bathypelagic fishes has 

 been largely due to the 'Michael Sars' Expedition in 1910 (Murray and Hjort, 19 12); the Danish 

 Oceanographic Expeditions in the Mediterranean and adjacent Atlantic waters during 1908-10 

 Uespersen, 1915; Taning, 1918 and Jespersen and Taning, 1926); the Discovery Investigations 

 (Norman, 1929, 1930); the Dana Expeditions (Regan and Trewavas, 1929, 1930; Bertin, 1934, 1937; 

 Ege, x 934> : 948> 1953; Bruun, 1937, Bertelsen, 1951 and Bertelsen and Marshall, 1956) and the 

 Bermuda Oceanographic Expeditions (Beebe, 1937). From these and other publications, Grey (1956) 

 has compiled a valuable and detailed survey of the bathypelagic and benthic fishes found below 

 a depth of 2000 m. A more general appreciation of vertical distribution may be found in Marshall ( 1 954). 



Besides tangible evidence from the nets, underwater observations are now beginning to play their 

 part. Since Beebe's (1934) dives in a bathysphere, a number of observers have been down in bathy- 

 scaphes. To take but one account (Peres, 1958), it is clear that an experienced observer can both 

 enlarge and corroborate present knowledge. During three dives off Cap Side, Peres found that the 

 schools of lantern fishes not only occurred in a mid-water layer (mainly from 400 to 700 m.), but were 

 also clustered close to the bottom (about 10 m. above 1500 m.). He also saw that Argyropelecus 

 hemigymnus is found between 250 and 600 m. (with a maximum at 350-400 m.), which is a striking 

 confirmation of Jespersen's (191 5) estimates from open-nets. 



These findings, so far as they concern the fishes dealt with in this report, may now be summarized: 

 A. Fishes with centres of concentration between depths of about 200 and 1000 m. 



Reference to the papers cited earlier will show that any species may have a considerable vertical 

 range about its centre of concentration. And, apart from diurnal migrations, the main depths of 



