FISHERY BULLETIN: VOL, 77. NO, :) 



egg dormancy is maintained by low oxygen levels 

 (Kasahara, Onbe, and Kaniigaki 1975; Uye and 

 Fleminger 1976). Light is also required to break 

 dormancy in at least one species, A . clan si ( Landry 

 1975a; Uye and Fleminger 1976). 



Further work is required to fully demonstrate 

 the factors regulating dormancy in coastal 

 calanoids. A localized summer-fall population of 

 A. californiensis in Yaquina Bay, Oreg., affords an 

 excellent opportunity to examine this phenome- 

 non, since the entire winter-spring period is 

 passed in the resting egg stage. A field research 

 program provided data for the correlation of popu- 

 lation dynamics with temperature and salinity. 

 Laboratory experiments were carried out to de- 

 termine the relative importance of temperature 

 and salinity in the formation and subsequent 

 hatching of dormant eggs of A. californiensis . 

 Analysis of the data provides additional informa- 

 tion on the role of the female versus that of the egg 

 in development of dormancy. 



Acartia californiensis , a newly described species 

 (Trinast 1976), is useful for comparative studies in 

 egg dormancy since it displays close affinities to A . 

 tonsa in both physiological and morphological fea- 



tures. Earlier studies in Yaquina Bay (Zimmer- 

 man 1972; Frolander et al. 1973; Johnson and 

 Miller 1974; Miller et al. 1977) identified the 

 species as A. tonsa in the belief that it represented 

 a smaller, ecophenotypic variant of the larger, 

 offshore, A. tonsa present in the northerly David- 

 son Current during the winter months. Further- 

 more, the unidentified "Acartia sp. I" discussed by 

 Uye and Fleminger ( 1976) has been recently iden- 

 tified as A. californiensis Trinast by A. 

 Fleminger,^ thus permitting comparison of egg 

 dormancy in northern and southern populations. 



METHODS 



The seasonal population cycle of A. californien- 

 sis in Yaquina Bay was determined by the collec- 

 tion of plankton samples twice weekly at Stations 

 21, 29, 39, 45, and 57 (Figure 1). Sampling was 

 done from June to November in 1972-74 with a 

 Clark-Bumpus sampler (mouth diameter 12.5 cm) 

 fitted with a 112 ;um mesh net which quantita- 



^Abraham Fleminger, Scripps Institution of Oceanography. 

 University of California, La JoUa. CA 92037, pers. commun. 

 June 1978. 



I24<'00'W 



FK,:l:RE 1, — Sampling stations for Acartia caltforntrnsis in Yaquina Bay estuary. Oreg. 



568 



