SWIMMING AND FEEDING BEHAVIOR OF LARVAL ANCHOVY 



ENGRAULIS MORDAX 



John R. Hunter^ 



ABSTRACT 



The swimming and feeding behavior of laboratory-reared larval anchovy, EngrauUs 

 mordax, was described over the first 30 days of larval life. Estimates were made of 

 cruising speed, proportion of time spent in rest, and burst speeds. Tail beat frequency, 

 tail beat amplitude, and speed of swimming larvae were measured from cine photographs 

 and the relationship between these variables determined. Complete and incomplete 

 feeding sequences were described in detail from cine photographs and the frequency of 

 feeding acts determined from visual observation. The extent of the reactive perceptive 

 field for prey was measured from cine photographs and expressed as a function of larval 

 length. Feeding success of larvae fed rotifers was determined for the first 21 days of 

 larval life. These estimates were combined to estimate the volume of water searched 

 by larvae per hour, and this estimate and others were used to calculate the density of 

 food required by larvae to meet metabolic requirements. These calculations indicated 

 that the density of food required by larvae just after yolk absorption was up to 37 times 

 that required by older larvae. 



In this report I describe the feeding and swim- 

 ming behavior of the larval anchovy, EngrauUs 

 mordax, during the first 30 days of larval life. 

 These observations will be combined with results 

 of other studies in a model for estimation of the 

 survival of larval anchovy in the sea. Similar 

 studies of feeding and locomotor behavior have 

 been made on other larval fishes (Blaxter, 1966; 

 Braum, 1967; Rosenthal and Hempel, 1970), 

 and the biology of larval fishes in general has 

 been reviewed by Blaxter (1969). 



APPARATUS AND METHODS 



Anchovy larvae were reared from the egg 

 using techniques described by Lasker, Feder, 

 Theilacker, and May (1970). The larvae were 

 kept in 500-liter black, fiber glass tanks in non- 

 circulated sea water at 17° to 18°C. They were 

 illuminated by fluorescent lamps and were given 

 a daily dark period of 10 hr with a half hour of 

 dim light preceding and following the dark pe- 

 riod. Larvae were fed a variety of organisms 

 ranging from wild plankton to laboratory-cul- 

 tured brine shrimp, Arteynia salina, the dinoflag- 



' National Marine Fisheries Service, Southwest Fish- 

 eries Center, P.O. Box 271, La Jolla, CA 92037. 



ellate, Gymnodinium splendens, the rotifer 

 Brachionus plicatilis, and the veligers of various 

 species of mollusks (Lasker et al., 1970; Thei- 

 lacker and McMaster, 1971). 



Most of the data in this report will be con- 

 cerned with larvae younger than 30 days and 

 15 mm or less in length because larvae in this 

 size range are more easily cultured than older 

 ones. Metamorphosis of EngrauUs occurs after 

 about 50 to 60 days at 17° to 18°C when the 

 larva is about 40 mm total length. 



Visual observations of the feeding and swim- 

 ming behavior of larvae were made in the 500- 

 liter rearing tanks throughout the 13-hr day. 

 A larva was chosen and all behavioral acts re- 

 corded continuously for 5 or more min. Be- 

 havioral acts were given a digital code, and the 

 occurrence, duration of acts, and elapsed time 

 were recorded on eight-channel paper tape by 

 operation of a keyboard. The keyboard con- 

 trolled a motorized paper-tape punch, and the 

 perforated paper tape was computer-processed. 

 Usually hundreds to thousands of larvae were 

 present; thus a different larva was probably ob- 

 served during each 5-min observation period and 

 consequently each period was treated as an in- 

 dependent set of observations. A total of 447 



Manuscript accepted February 1972. 



FISHERY BULLETIN: VOL. 70, NO. 3, 1972. 



821 



