PEARCY and MYERS: LARVAL FISHES OF YAQUINA BAY 



1967) contention that estuaries of the Pacific 

 coast may be less important as nursery grounds 

 than eastern seaboard estuaries. But such a 

 conclusion is unwarranted without a comparison 

 of larval abundances within the estuary with 

 those in adjoining open ocean to learn if larvae 

 are restricted to or concentrated in estuaries. 

 High numbers of larvae within the estuary are 

 not necessarily pi-oof of estuarine dependance, 

 as they may be more abundant in the ocean. 

 Conversely, low densities of a species inside the 

 estuary may indicate importance if it is absent 

 elsewhere. A comparison of larval catches in 

 Yaquina Bay with the open ocean is possible 

 since we collected fish larvae at stations 1, 3, 5, 

 and 10 miles off Yaquina Bay, using the same 

 bongo nets during the same sampling period 

 as the bay sampling. The results of this compari- 

 son (Table 4) corroborate our earlier suggestion: 

 with the exception of the Pacific herring the 

 estuary does not appear to be important to the 

 pelagic larvae of commercial fishes. Most of 

 the larvae that were restricted to or were most 

 common in the estuary were of small, non-food 

 species of cottids, stichaeids, and gobies. Larvae 

 of all the pleuronectids collected were more 

 common offshore than inside the estuary. 



Thus the Pacific herring was the only species 

 of commercial interest that appeared to use the 

 estuary extensively as both a spawning and a 

 nursery ground. In California, herring spawn in 

 bays and estuaries (Hardwick, 1973). Since 

 Pacific herring are known to comprise more or 

 less distinct populations with adults returning 

 to the same bay to spawn (Stevenson, 1955; 

 Rounsefell, 1930), estuaries may be vital to the 

 maintenance of herring along some portions of 

 the west coast. 



Feeding conditions for herring are undoubt- 

 edly related to their use of estuaries as nurs- 

 eries. Russell (1964) found that Yaquina Bay 

 is used as a feeding ground for 1 to 4 yr-old 

 herring which fed mainly on the copepods 

 Acartia clausii and Pseudocalaiiui< sp., both 

 abundant within the bay. A. clausii, which is 

 thought to maintain indigenous populations 

 in Yaquina Bay, is especially abundant in the 

 upper estuary (Buoys 21 and 29) early in the 

 spring when densities of adults and immatures 

 exceed 30,OOOm-5 (Zimmerman, 1972 Froland- 

 er et al.. 1973). The numbers of copepod eggs, 

 nauplii, and copepodites, important food for 

 Atlantic herring larvae, probably exceed this 



100 



X 



10 



o 



cr 



UJ 

 Q. 



CLARKE-BUMPUS 233 



-^ BONGO 233 

 -a BONGO 571 



0. 



o'^ 



J L 



00 O oo 



ID 



^ '^ ?° 9 C\J ^ liJ 



I , 7 I I f^ c\j c\j (\j 



~ 00 C\J (\J 



LENGTH OF LARVAE (mm) 



Figure 6. — Catches of different lengths of herring larvi 

 at Buoy 29 expressed as a percentage of the total catc 

 for each of the Clarke-Bumpus and bongo nets with 0.2J 

 mm mesh and the bongo net with 0.571 mm mesl 

 February 10-March 13, 1970. 



density during the early spring and provid 

 adequate food for larval herring (Blaxter, 196c 

 Bainbridge and Forsyth, 1971; Sherman an 

 Honey, 1971). 



Our planktonic survey of fish larvae was n( 

 adequate to assess completely the estuary as 

 nursery ground. First, plankton nets are sele( 

 five and only weakly swimming pelagic larv£ 

 were effectively sampled. Other young stag( 

 may not have been fully susceptible to captui 

 because they actively avoid the nets. Secondl; 

 the young of some species may have been preser 

 but simply unavailable for sampling because ( 

 their distributions. These may include youn 

 that migi'ate into the estuary after metamo: 

 phosis, benthic forms, or young that reside i 

 shallow areas of the estuary. 



For example, viviparous embiotocids (PJiai 

 erudoii furcatus, Rhacochilus vacca, an 

 Embiotoca lateralis) are common species i 

 Yaquina Bay. Mature females of all these specif 

 are numerous in the middle and upper estuar 



201 



