RICHARDSON and PEARCY: COASTAL AND OCEANIC FISH LARVAE 



Spring (March, April) and fall (September) are 

 usually periods of transition with variable winds 

 and currents. Since the predominant currents 

 are north-south (perhaps 10 times stronger 

 than east-west), transport of larvae is also pre- 

 dominantly north-south rather than inshore- 

 offshore. Thus, the greatest concentrations of 

 larvae spawned in the coastal and offshore areas 

 would be retained along zones parallel to the coast. 

 Perhaps the strong north or south flow (coastal jet) 

 reported to occur around 15 to 28 km offshore 

 serves as some kind of barrier to inshore or 

 offshore transport of larvae. The presence of an 

 actual persistent front in this region, which would 

 help explain the faunal break at 28 km, has not 

 been demonstrated. The strongest front that has 

 been observed in this region is associated with 

 Columbia River Plume water, which flows south 

 off Oregon in summer. However, its position is not 

 stable and it is not present off Oregon in winter. 

 The presence of a surface front around 28 km 

 offshore has been demonstrated during upwelling 

 when upward sloping isopycnals break the sur- 

 face. This occurs only during upwelling, usually in 

 summer. 



The extent of north-south transport is unknown. 

 However, evidence suggests that shoreward of 11 

 km, because of current reversals, the mean north- 

 south current velocity (alongshore flow) may be 

 approximately zero over the summer (Huyer 1974; 

 Huyer et al. 1975) and possibly also over the 

 winter (Huyer pers. commun.). Thus, at least in 

 the coastal zone, circulation patterns may explain 

 maintenance of larvae in specific areas with re- 

 spect to north-south as well as inshore-offshore. If 

 this apparent retention of coastal larvae in the 

 coastal area is persistent with respect to north- 

 south and east-west transport, it would seem that 

 other factors, most notably food, may be more 

 critical to early survival than transport away from 

 favorable areas (Hjort 1926). We have no evidence 

 that predators of fish eggs and larvae are con- 

 centrated at the 28-km station (Pearcy 1976). 



Comparison of Coastal Larvae 

 With Yaquina Bay Larvae 



Similarities exist between the species com- 

 position of fish larvae in the coastal area and in 

 Yaquina Bay (Pearcy and Myers 1974). The cot- 

 tids and the pleuronectids were the most speciose 

 families in both areas (not considering the po- 

 tential number of Sebastes spp.). Families in the 



Bay not represented offshore were Gobiesocidae, 

 Gasterosteidae, and Syngnathidae. Families from 

 the coastal region not represented in the Bay were 

 Myctophidae, Anoplopomatidae, Bathymas- 

 teridae, and Clinidae. 



Larval distributions described by Pearcy and 

 Myers (1974) as "bay" or "offshore" are generally 

 supported by the present study. Major differences 

 in dominant taxa were found between the Bay 

 fauna and the coastal assemblage in this paper. 

 The two most abundant Bay species, which ac- 

 counted for 90% of all larvae, were either not 

 taken in the coastal assemblage, i.e.,Lepidogobius 

 lepidus, or were relatively uncommon, i.e., Clupea 

 harengus pallasi. The only goby taken in the 

 coastal assemblage was Clevelandia ios, which 

 was designated Gobiidae type 1 from the Bay. Two 

 of the three taxa listed by Pearcy and Myers ( 1974) 

 as "bay only" types, Lumpenus sagitta and 

 Anoplarchus spp., were taken in the coastal 

 assemblage. The most abundant larvae in the 

 coastal assemblage, Osmeridae, Parophrys 

 vetulus, Isopsetta isolepis, and Microgadus proxi- 

 mus, did not contribute significantly to the larval 

 fish fauna of Yaquina Bay. 



Seasonal patterns of larval abundance were 

 similar in both areas with the peak occurring 

 February to June in the Bay and February to July 

 in the coastal area. The egg abundance peak of 

 July to October in the Bay, which was primarily 

 attributed to northern anchovy, Engraulis 

 mordax, corresponds somewhat with the peak 

 abundance of anchovy larvae offshore in this 

 study. The eggs may have been spawned in the 

 Bay or carried into the Bay from coastal areas. 

 Whichever is the case, the fact that anchovy lar- 

 vae were not abundant in the Bay indicates de- 

 velopment there was unsuccessful. Additional 

 evidence for the lack of developmental success of 

 anchovy eggs and larvae in northern estuarine 

 areas was given by Blackburn (1973). Anchovy 

 eggs were taken in plankton collections in Puget 

 Sound from May through August during a year- 

 long survey. Larvae were never captured in V2-m 

 plankton nets (0.5-mm mesh), but a few anchovy 

 larvae (presumably large) and juveniles were 

 captured in larger tow nets (3 x 6 m mouth 

 diameter, 6-mm mesh cod end and 1 x 2 m mouth 

 diameter, 3-mm mesh cod end). In another year- 

 long study in the Columbia River estuary (Misi- 

 tano 1977), only large (22-55 mm) anchovy larvae 

 were taken in low numbers from October through 

 March. Similarly, anchovy larvae were rare in 



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