SMILES and PEARC\- : GROWTH RATE OF Eupham,a pa„fica 



(1932), Bargmann (1945), and Marr (1962) 

 for Euphausia superba; and by Baker (1959) 

 for Enphau^ia triacantha. Most of these species 

 have a maximum life expectancy of 2 years, 

 reproduce each year, and grow slowly during 

 the winter. Other species are known to have 

 a life expectancy of 1 year (Mauchline and 

 Fisher, 1969). 



Development, growth, and sexual maturity of 

 the same species of euphausiid are known to 

 vary among geographic iropulations (Einarsson, 

 1945; Nemoto, 1957; Ponomareva, 1963; 

 Mauchline and Fisher, 1969). Mauchline and 

 Fisher (1969) stress that this variability is 

 probably directly related to differences in food 

 and temperature. Hence, the rapid growth of 

 E. pacifica off Oregon may be related to the high 

 productivity of the region and the lack of large 

 seasonal temperature fluctuations in nearshore 

 waters. 



Small, Curl, and Glooschenko' report high 

 values for primary productivity in the coastal 

 waters off Oregon. Curl and Small' found that 

 standing stocks of chlorophyll-n averaged high- 

 est inshore and steadily decreased offshore. 

 High production and stocks persist through the 

 summer, the upwelling season, in inshore waters, 

 whereas offshore waters have a tyijical summer 

 productivity minimum (Anderson, 1964). Note 

 that those seasonal and inshore-offshore gradi- 

 ents in phytoplankton are correlated in time and 

 place with the spawning of E. pacifica off Ore- 

 gon, mostly inshore and protracted over the 

 summer and fall months. Ponomareva (196?.) 

 believes that phytoplankton is not only im- 

 portant as food for euphausiid larvae, but also 

 may be necessary in the diet for development 

 of reproductive products of E. pacifica. 



Water temperatures along the Oregon coast 

 are fairly uniform throughout the year and lack 

 the extremes found along the eastern coasts of 

 continents at similar latitudes. Advection of 

 cool water to the surface (upwelling) during 

 the summer and warm water toward shore dur- 



* L. F. Small, H. Curl, Jr., and W. A. Glooschenko. 

 Seasonal primary production in a region of upwelling. 

 III. Effects of solar radiation and upwelling on daily 

 production. Unpublished MS. 



^ H. Curl, Jr., and L. F. Small. MS. 



ing the winter moderates the usual seasonal 

 variations. Pattullo, Burt, and Kulm (1969) 

 observed that the seasonal range of heat con- 

 tent was twice as large offshore as inshore (with- 

 in 65 miles) of the Oregon coast. The absence 

 of severe winter temperatures may help to ex- 

 plain the rapid growth of E. pacifica through- 

 out the year off Oregon. Conversely the slow 

 and seasonally variable growth of E. pacifica 

 found by Ponomareva (1963) was in the Far 

 Eastern Seas of Asia where temperatures are 

 often lower and where thermal variations are 

 greater. The fact that E. pacifica is the only 

 widespread euphausiid that spawns in the sum- 

 mer, when the phytoplankton bloom was almost 

 over, indicates that this boreal species may be 

 poorly adapted to the cold marginal Far Eastern 

 Seas (Ponomareva, 1963). 



The main pulses of larvae, hence spawning, 

 of E. pacifica were in the fall, and not in the 

 spring and summer as found by Ponomareva 

 (1963), Nemoto (1957) off Japan, and Barham 

 (1957) in Monterey Bay, Calif. Brinton (per- 

 sonal communication) notes larval recruitment 

 throughout the year off Southern California. 

 The later spawning off Oregon, like the rapid 

 growth, may again be related to the prolonged 

 production cycle caused by upwelling off Oregon 

 and the moderate fall and winter water temper- 

 atures. 



ACKNOWLEDGMENTS 



We are grateful to J. Mauchline for his sug- 

 gestions and to T. Nemoto for providing his 

 growth curve for E. pacifica. 



LITERATURE CITED 



Anderson, George C. 



1964. The seasonal and geographic distribution of 

 primary productivity off the Washington and 

 Oregon coasts. Limnol. Oceanogr. 9(3) : 284-302. 

 Baker, A. de C. 



1959. The distribution and life history of Euphaus- 

 ia triacantha Holt and Tatersall. Discovery Rep 

 29: 309-340. 

 Bargmann, Helens E. 



194.5. The development and life-history of ado- 

 lescent and adult krill, Euphausia superba. Dis- 

 covery Rep. 23: 10,3-176. 



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