LASKER: FIELD CRITERIA FOR SURVIVAL 



AREA OF STUDY 



This investigation was conducted in the Los 

 Angeles Bight along the southern California 

 coastline from Malibu to San Onofre, between 18 

 and 21 March 1974. All the stations occupied were 

 over the 20-fathom line except for the Laguna 

 Beach station which was over the 270-f athom con- 

 tour. Table 1 gives the coordinate positions and 

 Figure 2 shows the relative location of the sta- 

 tions. The San Onofre station was reoccupied on 8 

 April 1974 to determine the persistence of the 

 chlorophyll maximum layer which earlier had con- 

 tained relatively large numbers of G. splendens. 

 The station was occupied again on 10 April, after a 

 violent wind storm and later on 22-23 April after a 

 period of no storms. 



Figure 2.-Stations in the Los Angeles Bight. 



RESULTS AND DISCUSSION 



Shipboard Experiments with 

 First-Feeding Anchovy Larvae 



Table 1 provides a summary of the results of 

 feeding experiments with first-feeding anchovy 

 larvae in water from the surface and from the 

 chlorophyll maximum layer or from a depth of 

 about 15 m if no clear chlorophyll maximum was 

 observed. The dominant phytoplankter in the 

 chlorophyll maximum layers was G. splendens. For 

 details about G. splendens blooms from Baja 

 California, Mexico, and the Los Angeles Bight see 

 Kiefer and Lasker (1975); as reported earlier, 

 Lasker et al. (1970) had demonstrated that 

 anchovy larvae will grow when fed on G. splen- 

 dens. 



Also given in Table 1 are the results of a feeding 

 experiment at the San Onofre station on 8 April 

 1974, 18 days after a chlorophyll maximum layer 

 containing G. splendens as the dominant phy- 

 toplankter was found. The chlorophyll maximum 

 layer was still present and heavily populated with 

 G. splendens. A violent wind storm on 9 April 

 obliterated the chlorophyll maximum layer and no 

 G. splendens were seen at this station when it was 

 reoccupied on 10 and 11 April. A comparison of 

 chlorophyll a profiles taken before and after the 9 

 April storm is shown in Figure 3. The results of 

 control feeding experiments are given in Table 2. 



SAN ONOFRE 

 SS^'IS.S' N., II7''35.3' W. 



April 8, 1974 1500 



-—April 10, 1974 1710 

 April II, 1974 0830 



UJ 



Q 



0.5 1.0 1.5 20 2.5 



CHLOROPHYLL-a (pg/ liter) 



Figure 3.-Chlorophyll maximum layers before (8 April 1974) and 

 after (10 and 11 April 1974) a violent wind storm near San 

 Onofre, Calif. 



Some anchovy larvae capture a few particles in 

 any concentration of 20- to 100-/Am particles over 

 an 8-h period, but experience in the laboratory has 

 shown that feeding on less than 1 particle/h will 

 not sustain a first-feeding larva which becomes 

 weak and dies. Thus, in Tables 1 and 2, two feeding 

 categories are indicated: larvae observed with 

 food organisms packed into the intestine, and 



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