VARIOUS SPECIES OF PHYTOPLANKTON AS FOOD FOR LARVAL 



NORTHERN ANCHOVY, ENGRAULIS MORDAX, AND RELATIVE 



NUTRITIONAL VALUE OF THE DINOFLAGELLATES 



GYMNODINIUM SPLENDENS AND GONYAULAX POLYEDRA 



Edward D. Scura 1 and Charles W. Jerde 2 



ABSTRACT 



First feeding northern anchovy larvae were presented with a variety of phytoplankters common to 

 coastal waters of southern California to determine which species are acceptable as food. Most of 

 the larvae ate the four species of dinofiagellates tested in feeding experiments but did not feed on 

 diatoms or small flagellates. Larval rearing experiments were conducted to compare the nutritional 

 value of Gymnodinium splendens and Gonyaulax polyedra, two species of dinofiagellates readily 

 eaten by anchovy larvae and known to predominate in the chlorphyll maximum layers off the 

 southern California coast. Gymnodinium splendens was a nutritional food for the first 10 days of 

 larval life, but Gonyaulax polyedra was judged to be inadequate. Supplementing the G. polyedra 

 diet with microzooplankton increased larval survival comparable to survival on a microzooplankton 

 diet alone. When the Gymnodinium splendens diet was supplemented with microzooplankton, 

 the larvae grew faster but survival did not increase. Results are discussed in relation to studies on 

 larval survival in the Southern California Bight during 1974 and 1975. 



The strength of a year class offish may depend on 

 availability of food organisms during the early 

 larval stages (May 1974). Consequently, there 

 have been attempts to assess the abundance of 

 planktonic organisms in larval feeding areas as 

 a step towards predicting year class success (Shel- 

 bourne 1957; Bainbridge and Forsyth 1971; 

 Lasker 1975, in press). For this approach to be suc- 

 cessful, additional information is also necessary 

 concerning: 1) selection of prey by the fish larvae, 



2) concentration and size of food organisms nec- 

 essary to initiate feeding by the fish larvae, 



3) nutritional value of the food that the larvae 

 select, and 4) temporal and spatial distribution of 

 the food organisms in the feeding area. 



The northern anchovy, Engraulis mordax, 

 larva has been studied in the laboratory and many 

 criteria for successful feeding have been deter- 

 mined (Lasker et al. 1970; O'Connell and Ray- 

 mond 1970; Hunter 1972, 1976; Hunter and 

 Thomas 1974). Results of these studies indicate 

 that first feeding anchovy larvae require small 

 particles (<100 /xm in smallest dimension) at 



'Southwest Fisheries Center, National Marine Fisheries 

 Service, NOAA, P.O. Box 271, La Jolla, CA 92038. 



2 San Diego Mesa College, 7250 Mesa College Drive, San 

 Diego, CA 92111. 



relatively high densities to initiate feeding and 

 to insure moderate survival. O'Connell and Ray- 

 mond ( 1970) found in laboratory experiments that 

 anchovy larvae reared in seawater containing 

 1 copepod nauplius/ml or less experienced heavy 

 mortalities during the sixth and seventh days 

 after hatching. To date such a high concentration 

 has not been found in the nearshore region of the 

 California Current (Beers and Stewart 1967, 

 1969). However, the possibility does exist that 

 anchovy larvae could survive on some of the larger 

 phytoplankters during early stages of develop- 

 ment (Hunter and Thomas 1974). Lasker et al. 

 (1970) found that anchovy larvae would feed and 

 grow to a length of 5 to 6 mm in the laboratory 

 on a diet of the naked dinoflagellate, Gymno- 

 dinium splendens. With this in mind, Lasker 

 (1975) used laboratory-spawned anchovy larvae 

 to test for feeding activity in seawater pumped 

 from the surface and chlorophyll maximum layer 

 in the nearshore region of the Southern California 

 Bight. Lasker found that during March and April 

 1974 there were sufficient numbers of G. splen- 

 dens (>20 organisms/ml) in the chlorophyll max- 

 imum layer for initiation of feeding by anchovy 

 larvae. During 1974 and 1975, Lasker (in press) 

 monitored the plankton distribution off the south- 

 ern California coast in an effort to establish a 



Manuscript accepted February 1977. 

 FISHERY BULLETIN: VOL. 75, NO. 3, 1977. 



577 



