ROTHLISBERC. and MILLER: LARVAL PANDALl 'S JORDANI OFF OREGON 



•- 60 



C 



0) 



\— 



o 



o 



<D 

 u 



c 

 o 



50 



40 

 35 

 30 



25 

 20 

 15 

 10 



^ 5, 



o 9 



)co Q 

 o o 



U U 



< 



to 

 o 



U U U 



< Q 



U3 co 

 o o 



u 



r- r~ r- 



r^co 



22 

 r^r~ 



UU 



o 



in 

 O 



CD 



o 





u u 



nil 



u 



u 



CM 



U 



< Q 



CM CO 



o o 



<N CN 



r- r- 



U U 



o 



CO 



o 

 U 



O 



O 



< LU I 



in co id 



o o o 



N « N 



r-- r- r*- 



U 



CO 

 CO 



O 



Dec I Jon I Feb Mor [Apr |May | June | July |Auq 



Jan 



Feb |Mor 



Apr May | June| July Aug 



Oct 



Nov 



1971 



Time 



1972 



FIGURE 2.— Date and offshore extent of 32 cruises sampling larval Pandalus jordani from January 1971 to August 1972. 



term perspective. These monthly indices (Bakun 

 1973, footnote 4) estimate the magnitude of the off- 

 shore component of Ekman transport mtons/s per 

 100 m coast) from mean monthly sea surface, geo- 

 strophic winds based on pressure fields. Deviations 

 from the long-term mean (Table 1) imply that surface 

 flow onshore in the first quarter of 1971 was below 

 average, while that of 1972 was near normal. Upwell- 

 ing in 1971 was less than normal, while that of 1972 

 was close to the long-term mean. 



The northward Davidson Current was well demon- 

 strated by the drift of bottles released in March and 

 early April. There was also an onshore component 

 which produced high return rates in those months 

 (mean for March and early April = 47%; Fig. 4). By 

 late April currents acquired a large southward com- 

 ponent, and an offshore component reduced return 

 rates (19.8% for late April through August; Fig. 4). 

 Surprisingly, a considerable northward component 

 remained in all months in the zone very close to the 

 coast, as implied by returns from the 1 to 5 nmi 

 stations in all periods except late May and early 

 August. 



In February through April 1971, temperatures 

 varied between 8° and 10°C inside 20 nmi (Fig. 5). 

 From late April through July they increased to be- 

 tween 14° and 15°C due to increased sunshine and 

 lack of strong upwelling. The sharp, temporary de- 

 crease of early June corresponded to a pulse of up- 

 welling in late May 1971 (Fig. 3). Nearshore tem- 

 peratures in 1972 were more constant and warmer in 



Table 1. — Upwelling indices by year and quarter for 1971 and 1972 

 along with the anomalies from a 2 5-yr average ( from Bakun 1973, see 

 text footnote 4). 



4 A. Bakun, Pacific Environmental Group, Southwest Fisheries 

 Center, NMFS, NOAA, c/o Fleet Numerical Oceanography Center, 

 Monterey, Calif., pers. commun. February 1982. 



the early part of the larval season than in 1 97 1 , rang- 

 ing between 10° and 12° C. We attribute that to the 

 strong onshore flow of late winter in that year. Tem- 

 peratures rose slightly in spring but were held below 

 the highs reached in late June of 197 1 by the stronger 

 upwelling conditions of 1972. 



Larval Distribution and Abundance of 

 Pandalus jordani in 1971 



Zoeae I, II, and III were found first on 16 February. 

 They were widely distributed but most abundant at 

 5, 10, and 15 nmi (Fig. 6). In early March all larvae 

 were within 20 nmi with highest density at 5 nmi; 

 most were recently hatched, but there were some 

 Zoeae II' s, Ill's, and IV's. The cruise of 20 March ap- 

 peared to coincide with the peak of larval hatching, 

 Zoea I predominating and most abundant within 20 

 nmi of shore. The late March cruise was abbreviated 

 because of bad weather. However, all larvae found 

 at the 3 and 5 nmi stations were Zoea I. By 22 April 

 the P. jordani were dispersed as far as 50 nmi 

 offshore, but the peak of abundance was still at 5 nmi 

 and consisted mostly of Zoeae II' s and Ill's. A few 



457 



