RICHARDSON: LARVAL FISHES OFF OREGON 



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Comments on Major Families 



Discussion is limited to the most important 

 families. Numbers of larvae refer to total num- 

 bers taken during the sampling period. Com- 

 ments on distribution focus on inshore-offshore 

 aspects as no north-south differences were evi- 

 dent except for E. mordax. Trends in seasonality 

 can be determined from Tables 2 and 5. 



Engraulidae (43,191 larvae in 110 samples) 



E. mordax larvae were taken first on the 

 June cruise. At that time, larval lengths ranged 

 from 3 to 12 mm with a median at 8 mm (Figure 

 2A). Some were newly hatched. Spawning prob- 

 ably occurred from June until August in 1969 

 if growth rates (to 10.2 mm in 20 days after 

 fertilization) given by Lasker et al. (1970) are 

 comparable for this area. Surface water tem- 

 peratures were cooler (14°-17°C) than the 17.5 °C 

 temperature used in their experiments and 

 would result in a longer development time. The 

 smallest larvae collected after August were 18 

 mm which suggests the spawning period was 

 limited. Larval growth throughout the study 

 period is indicated in Figure 2. Ranges of SL 

 overlapped considerably in July-August and 

 August, probably because of continued spawn- 

 ing into August. By September spawning ap- 

 peared to be over and a marked increase in 

 median length was shown from September to 

 October. 



Ranges, medians, and median quartiles of SL 

 of larvae differed somewhat according to gear 

 type for each cruise (Figure 2A). Some of the 

 apparent differences may be a result of small 

 numbers of larvae measured. The IKMT did not 

 catch any anchovies until July-August when 

 larvae were larger. The MN did not catch any 

 after August probably because the larger forms 

 avoided the net. By October, only the IKMT 

 took anchovies (except for one specimen taken 

 by the bongos) which had a median length of 

 43 mm. 



Anchovy larvae were most abundant in 

 Columbia River plume waters in June and July- 

 August. Larvae were not taken north of the 

 Columbia River or south of the major influence 

 of plume waters. They were not abundant near 



705 



