FISHERY BULLETIN: VOL, 69, NO. 3 



in the laboratory. Zooplankters in general and 

 copepods in particular have been seen to devour 

 marine fish larvae. For example, in an early 

 study on the rearing of marine fish, Garstang 

 (1900) noted that the harpacticoid copepod Idya 

 furcata (= Tisbe furcata) was a larval-fish 

 predator. Subsequently Lebour (1925) from 

 her examination of living marine plankton, 

 concluded that a variety of zooplankters eat fish 

 larvae and noted that "many jellyfishes and 

 Pleurobrachia besides Sagitta and Tomopteris 

 will readily eat small fishes." Lebour also il- 

 lustrated the capture of an anglerfish larva 

 (Lophius piscatorius) by the copepod Anomalo- 

 cera Patterson i (family Pontellidae). 



Despite this information on the predatory be- 

 havior of copepods, there is virtually no behav- 

 ioral information available on the ability of ma- 

 rine copepods to capture and ingest or fatally 

 injure fish larvae, although many marine cope- 

 pods are known to be carnivorous (Gauld, 1966) 

 and other incidental reports of copepods preda- 

 tory on marine fish larvae have been made 

 (Wickstead, 1965; Petipa, 1965). Furthermore, 

 the possible importance of predation on fish lar- 

 vae as it affects the determination of year class 

 strength through larval fish mortality has been 

 generally ignored, probably because of the lack 

 of pertinent quantitative laboratory and field 

 information. 



In this study we present the results of exper- 

 iments designed to measure quantitatively the 

 ability of three jiontellid marine copepods, La- 

 hidocera trispi7iosa, L. jollae, and Pontellopsis 

 occidentalis, to capture or fatally injure larvae 

 of the northern anchovy, EngrauUs mordax, an 

 important commercial fish of the California Cur- 

 rent. The behavior of copepods and larvae 

 which bears on the susceptibility of the latter to 

 predation is also described in detail. 



METHODS 



Copepods and anchovy eggs were captured 

 with a 0.5-m-mouth-diameter plankton net 

 (0.333-mm mesh) towed at the surface in coastal 

 water off' San Diego, Calif., between March and 

 August 1970. The copepods were separated 



from other plankton with a large bore pipette on 

 shipboard, diluted with surface water in liter 

 jars, and kept at sea water temiierature (about 

 15° C) in an insulated chest until returned to 

 the laboratory. 



All experiments were ])erformed in 3500-ml 

 beakers in the dark because Lnbidocera were 

 ]3hototactic and attracted to the light source and 

 Pontellojjsifi was inhibited in its attacks on lar- 

 vae in the light. In an earlier study on fresh- 

 water cyclopoid cope]5ods, Lillelund (1967) used 

 a constant level, continuous flow device which 

 we used also for maintaining marine copepods 

 in good condition in the laboratory (Figure 1). 

 However, it was more convenient to do all pre- 

 dation experiments in static water over a 20- to 

 24-hr period, since the copepods we investigated 

 swim continuously throughout the small volume 

 (3500 ml), obviating the need for continuously 

 circulated water. A constant temjjerature of 

 18° C was maintained in the beakers by placing 

 them in a running seawater bath. 



Mortality of the larvae was measured by 

 taking the difference between the number of 

 larvae at the beginning of the experiment and 

 those remaining alive at the end. Some mor- 

 tality not associated with predation always oc- 

 curred, hence control vessels containing larvae 

 alone were always provided and the results of 

 experiments corrected for larvae dead of other 

 causes. In all experiments, this natural mor- 

 tality never exceeded 10';;. 



Anchovy eggs were sorted in the laboratory 

 according to their stage of development and 

 newly hatched larvae were used as prey in the 

 predation experiments. When older larvae were 

 required they were reared according to the meth- 

 od of Lasker et al. ( 1970) , except that the rotifer 

 Brachionus plicatilis was substituted for snail 

 veligers as larval-fish food (Theilacker and Mc- 

 Master, in press). 



Oxygen consumi>tion measurements were 

 made by Warburg manometry. Usually 18 to 22 

 copepods were put into 3 ml of seawater in a 

 Warburg flask and oxygen uptake monitored for 

 8 hr at 18° C. Dry weight of individual cojie- 

 ])()ds was measured with an electrobalance 



to ± 2 jLtg. 



656 



