FISHERY BULLETIN: VOL. 75. NO. 1 



Humboldt Bay (Eldridge and Bryan 1972). Data 

 from this study and Richardson (1973; unpubl. 

 data) provide evidence that at least off Oregon 

 major anchovy spawning occurs and early de- 

 velopment is successful offshore beyond 28 km 

 rather than in coastal areas. 



Pearcy and Myers (1974) reported Yaquina Bay 

 was an important spawning area only for Clupea 

 harengus pallasi and numerous cottids, gobies, 

 and stichaeids. It was, however, an important 

 nursery area for juvenile Parophrys vetulus, 

 Hypomesus pretiosus, Platichthys stellatus, 

 Citharichthys stigmaeus, and embiotocids. The 

 present study has shown that the coastal area 2 to 

 28 km offshore is important as a spawning area for 

 P. stellatus and Parophrys vetulus which utilize 

 Yaquina Bay estuary during part of their early 

 life. 



Comparison With 

 Other Planktonic Components 



Results from studies on zooplankton (Peterson 

 and Miller 1975, see footnote 2), pink shrimp, 

 Pandalus jordani, larvae (Rothlisberg 1975), and 

 crab larvae (Lough 1975) off Oregon indicate that 

 trends in seasonality and inshore-offshore dis- 

 tribution do not always correspond with those 

 found for fish larvae. These planktonic compo- 

 nents were all studied from the same sets of 

 samples (70- and 20-cm bongos, 0.571- and 

 0.233-mm mesh nets, collected from June 1969 to 

 August 1972 off Newport). 



Seasonal abundance peaks of certain compo- 

 nents of the meroplankton, i.e., larvae of shrimp, 

 crabs, and fishes, appear to be similar but do not 

 correspond as well with those of zooplankton. 

 Total zooplankton (predominantly copepods) 

 abundance in the coastal zone is high in summer 

 during upwelling, with peaks usually in late June 

 and July, and low in winter (November-January). 

 A secondary winter-spring peak may develop 

 around February-April, but it is an order of 

 magnitude lower than the summer peak. Larvae 

 of the pink shrimp first occur in March and are in 

 the plankton through June. Larvae of most species 

 of crabs occur between February and July with 

 peak abundances in May and June, although a few 

 species are present all year; lowest abundances 

 are in December and January. Fish larvae are 

 most abundant between February and July. Those 

 larvae that are present during the summer 



zooplankton peaks tend to be of advanced de- 

 velopmental stages. Since the 0.233-mm mesh 

 used for zooplankton did not adequately sample 

 smaller animals such as copepod nauplii, it may be 

 that peak abundances of such potential food items 

 actually coincide with larval abundance peaks. 



Inshore-offshore distribution trends appear to 

 differ among the various planktonic constituents 

 with crab larvae being most similar to fish larvae. 

 Total zooplankton abundance, which is influenced 

 mainly by copepods, is consistently greatest (often 

 by an order of magnitude) in both summer and 

 winter at the 2-km station, grades to lows at 18 

 km; and according to Cross (1964), copepod 

 abundances continue to decrease farther from 

 shore. However, within the coastal zone (2-18 km) 

 abundance of individual species may not follow 

 that pattern, e.g., some may be more abundant 

 offshore of 2 km. Larvae of the pink shrimp first 

 occur (March) within 37 km of shore with greatest 

 concentrations at 9 to 28 km. Later (April-May) 

 the larvae are much more widely dispersed, oc- 

 curring from 2 to 111 km; abundance peaks may 

 occur coastally at 9 km as well as offshore at 93 

 km. Later in the season (June) when they are 

 ready to settle, peak abundances occur around 28 

 to 46 km offshore, apparently over favorable 

 settling areas. Larvae of most species of crabs 

 which are coastal forms as adults occur within 18 

 km of the coast. Highest densities are at 2 and 6 

 km with a dramatic decrease between 9 and 18 

 km. Larvae of slope species occur primarily in the 

 offshore area beyond 28 km. These distributions 

 are similar to the coastal and offshore distribu- 

 tions of larval fishes. However, larvae of a few crab 

 species which are coastal as adults are found at all 

 stations from 2 to 1 1 1 km and are abundant in the 

 coastal area as well as offshore. Larvae of at least 

 one of these species, Cancer oregonensis, have 

 been found in great abundance ( — 11 liters of 

 megalopa in one 15-min night surface tow) in the 

 neuston 65 km offshore (Richardson unpubl. data). 

 This type of distribution is similar to that found for 

 larvae of the fish Hemilepidotus spinosus, which 

 are also neustonic. This apparent offshore 

 transport of larvae spawned in the coastal zone 

 inside 28 km suggests that those which spend at 

 least part of their early life in surface waters may 

 be subjected to different dispersal mechanisms 

 than those which do not occur in the neuston. 

 Offshore flow of surface waters occurs during the 

 upwelling season, providing a mechanism of 

 transport. 



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