Table 10 Numbers of Tarletonbeania crenularls collected at different depths at stations 8 and 



17 during the 2'i-hour sampling periods, spring 1963 



Number 



Number 



SUMMARY 



1. Plankton samples from the upper 150 m, 

 of the water column were collected in coastal 

 waters off Vancouver Island, British Columbia, 

 and the State of Washington in spring and fall 

 1963, by towing a 0.9-nn. Isaacs-Kiddmidwater 

 trawl. 



2. The biomass was composed of about 90 

 percent euphausiids, of which 76 percent, by- 

 number, were Euphausia pacifica and 14 per- 

 cent were Thysanoessa spinifera . 



3. Biomass was generally lowest near 

 shore, reached a maximum at or near the outer 

 edge of the continental shelf, and decreased 

 again farther offshore. 



4. Biomass was significantly higher in the 

 southern part of the region than in the northern 

 part. 



5. Macrozooplanktonic and small nektonic 

 organisms were much more abundant in the 

 spring than in the fall. The change in biomass 

 resulted principally from the large decrease 

 in nunnbers of Euphausia pacifica and the de- 

 crease in size of E. pacifica and Thysanoessa 

 spinifera from spring to fall. 



6. Mesopelagic fishes were numerous over 

 the continental slope but were found only oc- 

 casionally at the edge of the shelf. None were 

 caught over the continental shelf. 



7. Most of the macrozooplanktonic and small 

 nektonic organisms appeared to undergo a di- 

 urnal vertical migration of at least 150 m. at 

 the two stations where horizontal tows were 

 made. All the euphausiid species showed 

 greatly diminished numbers or were com- 

 pletely absent from the surface to 150 m. dur- 

 ing the day at these two stations except 

 Thysanoessa longipes , which was found in the 

 upper 150 m. during daylight only at the sta- 

 tion with a sharp thermocline and well-mixed 

 layer. Most of the macrozooplankton and sn-iall 

 nekton were in the surface to 30-m. rather 

 than the 30- to 150-m. interval at night. 



8. Large concentrations of crab larvae and 

 postlarval benthic fishes were taken at the sur- 

 face and 75 m., but euphausiids were not abun- 

 dant at these depths. The mesopelagic fish, 

 Tarletonbeania crenularis , was caught pri- 

 marily at the surface. 



LITERATURE CITED 



ARON, WILLIAM. 



1959. Midwater trawling studies in the 

 North Pacific. Limnol. Oceanogr. 4: 

 409-418. 



1962, The distribution of animals in the 

 eastern North Pacific and its relation- 

 ship to physical and chemical condi- 

 tions. J. Fish. Res. Bd. Can. 19: 271- 

 314. 

 ARON, WILLIAM, NEWELL RAXTER, ROY 

 NOEL, and WILLIAM ANDREWS. 



1964. A description of a discrete depth 

 plankton sampler with some notes 

 on the towing behavior of a 6 -foot 

 Isaacs -Kidd mid-water trawl and a 



one-meter ring net. Limnol. Oceanogr. 

 9: 324-333. 

 BANNER, ALBERT H. 



1947. A taxonomic study of the Mysidacea 

 and Euphausiacea (Crustacea) of the 

 North Pacific. Part I, Mysidacea. 

 Trans. Roy. Can. Inst. 26: 345-414. 



1948. A taxonomic study of the Mysidacea 

 and Euphausiacea (Crustacea) of the 

 North Pacific. Part n, Mysidacea. 

 Trans. Roy. Can. Inst. 27: 65-125. 



1949. A taxonomic study of the Mysidacea 

 and Euphausiacea (Crustacea) of the 

 North Pacific. Part ni, Euphausiacea. 

 Trans. Roy. Can. Inst. 28: 2-49. 



23 



