NO. 3583 COPEPODS — GRICE AND HULSEMANN 7 



cubic meter and generally the densities were considerably smaller, 

 especially below a depth of 2000 m. The single exception referred to 

 above, where small numbers of copepods were fomid in the 2000- 

 1000 m interval, was at station 334. Interestingly, the volume of 

 zooplankton at this station exceeded that of all other stations. A 

 large number of contaminant specimens (i.e., copepods that inhabit 

 shallower depths) were noted in this sample. It thus appears that a 

 considerable quantity of zooplankton from the upper 1000 m might 

 have entered the net and was then retained durmg its descent to 

 2000 m; or, possibly, material from the 1000-500 m interval, collected 

 just prior to the collection of the 2000-1000 m sample, may have re- 

 mained attached to the meshes of the net due to incomplete washing 

 of the net. These animals may have been washed into the plankton 

 during the washing of the net after the 2000-1000 m collection. 

 The volume of zooplankton and number of copepods obtained in the 

 3000-2000 m collection at station 334 does not appear to be unusual. 

 The number of adult copepods foimd in the depth intervals below 

 1000 m in the Indian Ocean are comparable to that previously found 

 by us between 30° and 40°N in the northeastern Atlantic Ocean (Grice 

 and Hulsemann, 1965). 



Vertical Occurrence of Copepods 



Population mean size. — We have measiu"ed the total length of 

 1277 adult copepods from the NV samples amd computed the mean 

 size of the animals, excluding the "contaminant" species, collected 

 within each depth interval. The 4000-3000 m interval will not be 

 considered as only 19 adults were found in the three samples obtained 

 from this mterval. 



The mean size of the adult copepods between 2000 and 1000 m was 

 2.36 mm and between 3000 and 2000 in, 2.19 mm. The range of 

 mean sizes in these same intervals at fom* stations between 30° and 

 40°N in the northeastern Atlantic (Grice and Hulsemann, 1965) 

 was 2.26-3.04 mm (2000-1000 m) and 1.71-2.38 mm (3000-2000 m). 

 The size of the Indian Ocean copepods living between 1000 and 3000 

 m are quite comparable to those of the Atlantic. 



Species vertical distribution. — Since the present study is 

 based on the analyses of only those NV samples collected in depths 

 below 1000 m, the shallow living species and families are poorly 

 represented. There were present 153 species, excluding contaminants, 

 in 13 families. 



The predominantly shallow living families Eucalanidae and 

 Pseudocalanidae were together represented by only seven species. 

 No species, excepting those considered contaminants, of Calanidae, 

 Paracalanidae, Centropagidae, Pontellidae, or Acartiidae, also epi- 



