FISHERY BULLETIN: VOL. 69, NO. 3 



Further comparisons of respiration rates were 

 made only between newly caught and larval- 

 fish fed L. jollae females, males, and L. tris- 

 pinosa males and females (Figure 15). In 

 each instance there was an increase in res- 

 piratory rate after feeding on anchovy larvae. 

 The caloric requirement of Lubidocera jollae and 

 L. trispinosa was calculated from oxygen con- 



sumption data to estimate the number of larvae 

 which could sustain the copepod in a healthy 

 condition at 18° C (Table 1). In spite of La- 

 hklocera's ability to kill large numbers of fish 

 larvae or Artemia in a day, actual caloric re- 

 quirements may be met by ingestion of only a 

 few (1-4) larvae or nauplii (4-16). 



2.5 



•=> 2.0 

 O 



1.5 



cr 



UJ 



a. 



o 

 o 



Q. 

 UJ 

 Q. 



o 

 o 



CM 



O 0.5 



0.0 



 

 



J .^ 





,f(5P ,f,5P 



Figure 15. — Oxygen consumption by newly caught (open 

 symbols) and larval-fish fed (closed symbols) labidocer- 

 ans at 18° C. 



PREDATION ON FISH LARVAE AND 

 Labidocera BY Potitellopsis occidetitalis 



Poiitellopsis adults and copepodites stages IV 

 and V can kill by biting or capture and ingestion 

 of anchovy larvae; older larvae (up to 3.5 days 

 old in our test) were killed by this copepod as 

 easily as yolk-sac larvae. Each stage V copepo- 

 dite killed three larvae per day on the average 

 and each adult female killed about 11 per day 

 (Figure 16) . We observed also that Pontelloijsis 

 attacked and ate Labidocera spp. when they were 

 confined to the same beaker. 



CO-OCCURRENCES OF PREDATORY 

 COPEPODS AND FISH LARVAE IN THE SEA 



In the laboratory we noted that 30 to 40% 

 of the Labidocera individuals resided in the up- 

 per 5 to 25 cm of 140-cm-deep, 17.5-cm-diameter 

 tanks — both in darkness and in the light. Yolk- 

 sac anchovy larvae occupied a similar stratum 

 because they are slightly buoyant. In the sea, 

 spawning by anchovies occurs mostly in the 

 upper 10 m but occasionally may occur relatively 

 deeply (Ahlstrom, 1959). This prompted us to 



Table 1. — Oxygen consumption and the calculated number of 

 anchovy larvae required to sustain the respiratory requirements of 

 Labidocera jollae and L. trispinosa per day at 18° C. The oxycal- 

 orific equivalent of 1 jaliter of oxygen is 0.005 calorie. Yolk-sac 

 anchovy larvae weigh 0.01 mg dry weight and contain 0.054 calorie. 

 These data assume 100% digestive assimilation and an RQ ^ 0.8 

 for each copepod. Approximately four Artemia nauplii are cal- 

 orimetrically equivalent to one anchovy larva. 



Species 

 and sex 



Q Oj 



/tliter/mg dry 

 weight/nr 



Oa consumption 

 ^liter/copepod/hr 



Average dry weight 

 per copepod 



Anchovy 



larvae 



required/day 



Labodocera jollae . 

 /.. jollat 

 L. trijpinosa '• 

 L. trispinosa 



11 



II 

 7.7 

 4.3 



2.0 

 1.0 

 0.94 

 0.40 



0.19 

 0.095 

 0.12 

 0.092 



664 



