LARVAL FISHES OF YAQUINA BAY, OREGON: 

 A NURSERY GROUND FOR MARINE FISHES? 



WiLUAM G. Pearcy and Sharon S. Myers' 



ABSTRACT 



Based on a survey of planktonic fish larvae, the Yaquina Bay estuary appears important as a 

 spawning or rearing ground only for Cliipea harengus pallasi (Pacific herring) and a variety of 

 small cottids, gobies, and stichaeids. Other investigators, however, have found an abundance 

 of juvenile Paroplirys vctiihis (English sole), Citharichihys stigiuaeus (sanddab), HyponicsHs 

 pretiosus (surf smelt), Plutichthys siellatiis (starry flounder) and embiotocids (surf perches), 

 indicating that the bay is an important nursery area for these species. 



Of the 44 types of larval fishes found in the bay, C. h. pallasi and Lepidogobius lepidits 

 (bay goby) were co-dominants each year, 1960-1970, comprising 90% of all larvae collected. 

 There was no evidence of trends in abundances or species composition during the 11-yr study. 



Maxima of planktonic fish eggs and L. gobiiis larvae occurred in the summer: maxima of all 

 larvae combined and most species of larvae occurred in the winter and spring. High densities 

 of larval herring were found in February and March, and peak numbers appeared earlier 

 in the lower than the upper estuary. 



Larvae of C. h. pallasi, L. lepidus, and Cotius asper were common at all stations from 0.5 

 to 8 nautical miles up the estuary, but not in the adjacent open ocean. Larvae of many species 

 that were found in the estuary in small numbers were more abundant in offshore waters. 

 Although English sole and sanddab were rare in the bay as larvae, juveniles were numerous. 



This is a study of the species composition, 

 relative abundance, seasonal and annual occur- 

 rence and distribution of larval fishes in an 

 Oregon estuary. It was undertaken to increase 

 the extremely limited knowledge of fish larvae 

 in estuaries of the Pacific Northwest and to 

 evaluate the role of these estuaries as spawning 

 and nursery grounds. 



According to Clark (1967) and McHugh 

 (1966, 1967) the young of up to 70% of the eco- 

 nomically important Atlantic species of fishes 

 inhabit estuaries during part of their early life. 

 Many species spawn offshore and young stages 

 subsequently move into brackish estuaries. 

 Although the Pacific coast is known for its runs 

 of anadromous salmonids which migrate 

 through estuaries, "There is no counterpart on 

 the Pacific coast of the mass inshore movement 

 of larvae and young of offshore-spawning nek- 

 tonic species into brackish nursery grounds 

 that is such a striking feature of the ecology of 

 most Atlantic coast and Gulf of Mexico 

 estuaries." (McHugh, 1967). Thus the number 

 of species that are dependent on estuaries may 



' School of Oceanography, Oregon Stale University, Cor- 

 vallis, OR 97.131. 



not be as great on the Pacific as the Atlantic 

 coast. 



Oregon's estuaries are few in number and 

 include but a small area. For this reason man's 

 infringement on them for recreation, land 

 development, harbors, agriculture, and waste 

 disposal will be intense. This study evaluates 

 some long-term trends of the relative abundance 

 of larval fishes. Hopefully it will facilitate future 

 comparisons of faunal changes within this 

 estuarine habitat. 



THE ESTUARY 



Yaquina Bay (Figure 1) is a small tidal 

 estuary on the central Oregon Coast. It extends 

 inland about 37 km and has an area of about 

 11.6 km-. A channel is dredged to a depth of 7.9 

 m to McLean Point and to 3.7 m to the town of 

 Toledo. Tides are mixed, semidiurnal with a 

 mean tidal range of 1.7 m (Kulm and Byrne, 

 1967). According to Zimmerman (1972) the bay 

 has an exchange ratio of 52% and a flushing time 

 of 13.3 tidal cycles during the summer. The 

 estuary is well-mixed with little vertical strati- 

 fication in the summer when freshwater runoff 

 is low, and is partially mi.xed (4-19"/on salinity 



Manuscript accepted June. 1973. 



FISHERY BULLETIN, VOL. 72, NO. 1, W74 



201 



