PELAGIC AND BENTHIC FISHES, SWIMBLADDER, ECONOMY OF DEEP-SEA LIFE 105 



Table 8. The relative developments of tissue in two assemblages of bathypelagic fishes 



Lyomeri and Ceratoidea 1 



Gonostomatidae (most species), 

 Sternoptychidae, Astronesthes 

 spp. Myctophidae (most species) 



1000-4000 m. 



Absent 



Reduced, particularly in Lyomeri and poorly 



ossified 

 Reduced, particularly in Lyomeri 

 Relatively small (except in certain male cera- 



tioids) 

 Present only on female ceratioids and on tail of 



Lyomeri 

 Small 

 Much reduced 



Text-fig. 46. Filaments from the second gill arch of (a) Neocer alias spinifer; (b) Melanocetns murrayi; (c) Danaphryne sp. 



(a, X40; B, X20; c, X40.) 



may be found in Foxton's (1956) paper. Reference to his table 7 will show that in tropical and sub- 

 tropical waters the mean volume of zooplankton between the surface and 150 m. is more than twenty- 

 times that between 1000 and 1500 m. In the Kurile-Kamchatka area, the biomass (mg./m. 3 ) of 

 plankton between the surface and 100 m. is about forty times the value measured between 1000 and 

 2000 m., (and about ninety times greater than that between 2000 and 4000 m.) (Zenkevitch and 

 Birstein, 1956). 



Extra data on the biomass of zooplankton in the North-western Pacific are given by Bogorov 

 (1958). In the surface-zone (0-200 m.) the biomass is 1000 mg./m. 3 or more, while in the 'transition 

 zone ' (200-500 m.), which is generally richer in species than the surface-zone, the biomass falls to 

 about 350 mg./m. 3 Below this comes a 'deep-sea zone' (500-6000 m.) in which the biomass varies 

 from 2-64 to 78 mg./m. 3 Between 6000 m. and the deep-sea floor the zooplankton-content is less than 

 1 mg./m. 3 Finally some indication of the paucity of life in deeper waters is also given by measure- 

 ments of the oxygen consumption and phosphate regeneration (Riley, 195 1). Over the Atlantic 

 (between 45 N. and 54 S.) the curves of oxygen consumption (ml./l./year) fall sharply below depths 

 ranging from about 250 to 800 m. (see Riley's fig. 25) and Text-fig. 47 of this Report. 



1 The Giganturoidea could also be placed in this assemblage. Nearly all the sizeable specimens in the Dana collections 

 have been taken by nets fishing below a depth of 1000 m., and, apart from their large tubular eyes, they have a low level 

 of tissue development, much like that described under the Lyomeri and Ceratioidea. The giganturoids also have very small 

 kidneys. 



