Castillo et al .: Recruitment variation in Eopsetta jordani 



487 



Pacific high and Aleutian low pressure systems 

 (Huyer, 1983). Large negative correlations between 

 YCS and winter sea surface atmospheric pressure 

 were evident in both areas (Fig. 5H). However, fil- 

 tered series suggested that this index was spuriously 

 correlated with recruitment strength (Fig. 6H). 



Effects of the spring transition on YCS Correlations 

 between YCS and the week of the spring transition 

 from 1967 to 1977 were not significant (Area 2B: 

 r=0.27, Area 3A: r=0.22; P>0.20; Fig. 7A). Moreover, 

 correlations for attendant filtered series were nega- 

 tive (Area 2B: r=-0.18, Area 3A: r=-0.32; Fig. 7B). 

 However, onshore transport during early spring can 

 affect YCS as recruitment strength was correlated 

 with mean onshore Ekman transport during March 

 in both study areas (Area 2B: r=0.55, Area 3A: r=0.50; 

 P<0.05). Such correlations were also supported by 

 the attendant filtered series (Area 2B: ;-=0.58, Area 

 3B:r=0.42). 



Environmental- YCS series Based on exploratory cor- 

 relation analyses for original and filtered series, win- 



I? 



2 



o 



z _ 



Ei 



| E 

 § O 



is 



su 



So 1 



u 



o 



z 





CO 



< 



-J 

 u 

 cr 

 < 



8 10 12 14 16 18 



SPRING TRANSITION (JULIAN-WEEK) 



Figure 7 



Variation of year-class strength for petrale sole, Eopsetta jordani, in Pacific 

 States Marine Fisheries Commission areas 2B and 3A in relation to the week 

 of the year in which the spring transition occurred. Comparison is shown for 

 (A) original and (B) filtered series. Year classes are considered hatched be- 

 tween 1967 and 1977 and are identified by the last two digits. 



ter offshore Ekman transport seemed to be the main 

 factor affecting YCS of petrale sole in areas 2B and 

 3A. In subsequent analyses, the period January- 

 March was chosen for describing the association be- 

 tween YCS and offshore/onshore Ekman transport. 

 This period was selected because of the importance 

 of onshore transport on YCS during March. More- 

 over, correlations between offshore Ekman transport 

 and YCS tended to be higher during January-March 

 (original and filtered series respectively: Area 2B, r=- 

 0.48 and -0.67; Area 3A: r=-0.52 and -0.65; P<0.05) 

 than December-February (original and filtered se- 

 ries respectively: Area 2B, r=-0.46 and -0.53; Area 

 3A: r=-0.52 and -0.42; P<0.05). 



Comparing onshore Ekman transport with YCS, 

 we found that two periods of reduced onshore Ek- 

 man transport ( 1962-65 and 1974-77) coincided with 

 weak year classes of petrale sole (Fig. 8). The years 

 1958, 1961, and 1968 showed the largest positive 

 anomalies in onshore Ekman transport from 1958 to 

 1977. However, unlike 1961 and 1968, the 1958 El 

 Nino produced weak YCS in Area 2B and near-aver- 

 age YCS in Area 3A. Other anomalies for indices such 

 as winter and spring sea surface temperature and win- 

 ter sea level height showed some 

 correspondence with YCS 

 anomalies in Area 3A. In Area 

 2B, only onshore Ekman trans- 

 port and sea level height sug- 

 gested some association with 

 YCS (Figs. 8 and 9). 



Percentage of YCS variation ex- 

 plained by environmental fac- 

 tors The relationship between 

 YCS and January-March off- 

 shore Ekman transport anoma- 

 lies was best described by sec- 

 ond-order polynomial regres- 

 sions (Fig. 10, Table 3). Associa- 

 tions between YCS and winter 

 sea level height anomalies in 

 areas 2B and 3A, were also de- 

 scribed by second-order poly- 

 nomials (Fig. 11, Table 3). Al- 

 though the association between 

 YCS and winter sea surface tem- 

 perature in Area 3A was better 

 described by a second-order 

 polynomial than by a linear re- 

 gression, only the latter was sig- 

 nificant (Fig. 12, Table 3). Ex- 

 cept for the year 1958, and for 

 the years with large anomalies 

 in offshore Ekman transport 



8-6-4-2 2 4 6 

 FILTERED SPRING TRANSITION 



