densities were plotted by length interval the fol- 

 lowing September of each year, it was evident 

 that fish over 140 mm were not available in the 

 estuary and had probably emigrated to the open 

 coast. 



Discussion 



If there is an adaptive advantage in utilizing estu- 

 arine nursery grounds rather than the open coast, 

 there must exist a mechanism for 0-age fish to enter 

 estuarine systems. Although English sole larvae are 

 abundant in coastal waters (Richardson and Pearcy 

 1977), early stages have not been prevalent in estu- 

 arine larval surveys (Pearcy and Meyers 1974; 

 Misitano 1977). Large transforming larvae (18-23 

 mm) have been collected in Humboldt Bay and 

 Columbia River estuary (Misitano 1976, 1977), and 

 in Yaquina Bay (Boehlert and Mundy 1987). Immi- 

 gration of 0-age English sole to the Grays Harbor 

 estuary may be accomplished by direct settlement 

 of transforming larvae after simple advection by 

 ocean water into the bay, or by movements of new- 

 ly settled benthic juveniles. Such movement could 

 be accomplished either actively or by selective tidal 

 transport as noted for juvenile flatfishes in the 

 North Sea (DeVeen 1978). 



During the period of this study, newly trans- 

 formed English sole were found both within the 

 Grays Harbor estuary and along the adjacent open 

 coast. English sole have also been shown to enter 

 Yaquina Bay after settlement (Boehlert and Mundy 

 1987) so it is likely that both transforming larvae 

 and settled juvenile English sole may enter Grays 

 Harbor. Krygier and Pearcy (1986) found newly 

 transformed English sole to be more abundant in 

 open coastal areas and presumed movement into 

 Oregon estuaries to occur predominantly after 

 transformation. The occurrence of recently trans- 

 formed benthic juveniles in such high numbers 

 throughout Grays Harbor suggests direct settlement 

 of late stage larvae after advection into the estuary 

 may also be an important mode of entry. 



Emigration of the largest fish to the open coast 

 took place during late summer, and all fish larger 

 than 140 mm were found exclusively in the open 

 coast area by September. Studies of other estuarine 

 nursery areas have indicated that the emigration 

 process involves the larger size classes of 0-age fish 

 (Herke 1971; Weinstein 1983). Emigration from Ya- 

 quina Bay of the larger 0-age English sole has been 

 noted in the fall (Westrheim 1955; Olsen and Pratt 

 1973; Bayer 1981). Angell et al. (1975) observed a 



similar phenomenon for young English sole in a 

 Puget Sound nursery area. 



The departure of larger juveniles later in summer 

 may be in response to changing environmental con- 

 ditions and may be indicative of the limits of the 

 carrying capacity of estuaries being exceeded for 

 populations of juvenile fish (Krygier and Pearcy 

 1986). Alternatively, a change in dietary preferences 

 of larger 0-age fish may cause them to leave estu- 

 aries in search of prey items (Toole 1980), thus 

 reducing intraspecific competition. The advantage 

 in utilization of estuarine nurseries then, may be 

 more for protection of vulnerable sizes rather than 

 for accelerated growth (Rosenberg 1982). 



Even though our study found a great deal of inter- 

 annual variability, the Grays Harbor estuary and 

 other nearby estuaries (Shi 1987) clearly are impor- 

 tant nursery grounds for juvenile English sole, 

 which had similar size populations in the estuarine 

 and offshore study areas despite the greater geo- 

 graphic extent of the latter. Peak population esti- 

 mates for 0-age English sole for the month of May 

 show that 81% and 54% of 0-age fish in the Grays 

 Harbor area were found in the estuary in 1983 and 

 1984, respectively. This is probably an underesti- 

 mate of the degree of estuarine dependence, how- 

 ever, because some juveniles may move into the 

 estuary later in the summer. Nevertheless, our 

 results show that at least half of the 0-age English 

 sole in the Grays Harbor nearshore area make use 

 of an estuary during the first year of life. This kind 

 of information will prove useful in assessing the 

 economic impact on commercial fisheries from 

 navigation and industrial development projects, 

 which may contribute to habitat degradation in 

 Grays Harbor. 



Acknowledgments 



This note represents part of a Masters Thesis sub- 

 mitted to the University of Washington School of 

 Fisheries by C. W. Rogers. Work was supported 

 primarily by the Washington Sea Grant Program 

 (NOAA grant NA81AA-D00030, R/F-49). Data pro- 

 cessing assistance from the Northwest and Alaska 

 Fisheries Center is gratefully acknowledged. Logis- 

 tic support was provided by the U.S. Coast Guard 

 and the Washington Department of Fisheries. The 

 senior author also acknowledges the sponsors of the 

 Melvin G. Anderson Memorial Scholarship and the 

 Graduate School of the University of Washington 

 for support of portions of this work. We are grate- 

 fully indebted to all who assisted in field collections, 



830 



