CalCOFI Reports, Vol. 11, 1967 - California Cooperative Oceanic ...

80 CALIFORNIA COOPERATIVE OCEA&’IC FISHERIES ISTESTIGATIOKSof the anchovy which live in v-aters which are not deephave some tendency to look for their food near thebottom. These iliof agous tendencies are more markedduring the winter.SELECTION OF FOODIn connection with the problem of the selection offood by the Argentine anchovy, only some generalconsiderations can be made. The lack of exact quantitativedata on the composition of the plankton collectedwith the fishes studied precludes a more detailedanalysis of this subject. Kevertheless, the availabledata allow some general conclusions 011 this problem.The species of copepods from the group of the Calanoidaand Euterpinn acu tifrons, which are frequentlyand abundantly found in the diet of the larvae andjuveniles of the anchovy are also the most abuiidaiitspecies in the plankton. The great quantity of Cladocerain the intestinal content, especially during somewinter and summer months, coincides with the abundanceof this microcrustacean in the plankton. Again,the presence of fish eggs in the food supply, especiallyduring the spring and summer, coincides with thcappearance of these eggs in the plankton. In somecases, remains of fish niusclps were found in the food.which in all probability was part of the bait used bythe fishermen to attract the fishes, as was mentionedearlier.All of the information obtained suggests that thelarvae and juveniles of the anchovy do not select muchof their food, and that they feed upon the food whichis present in greater abundance. as a consequence,their diet may be quite dependent upon the patternsof plankton dispersal. Another very important factoris the accessibility of the food as determined by thesize of the prey and the dimensions of the mouth ofthe fish. Only more detailed quantitative data on thecomposition of the plankton and experimental studieson the feeding habits of the larvae of the anchorycan clarify this interesting problem.OTHER CONSIDERATIONSAnother interesting fact in the study of the larvaeand juveniles of the anchovy is that the quantity offood found in their intestinal tracts was generallysmall. In many cases the ingestion coefficient was lowerthan 0.01. It was believed, as a consequence, that anyanalysis based on the calculation of these coefficientsas,for instance, in the case of the juveniles of A.ilzcisa which were studied simultaneously (Ciechomski,in press), could lead to erroneous conclusions.In respect to the problem of feeding competitionbetween the larvae and juveniles of the anchovy withthose of A. incisa, it can be assumed that, in spite ofthe great similitude between their diets, there is noreal chance that these species should compete fortheir food. This is based on the abundance of theplanktonic organisms and on the fact that all of theindividuals studied were apparently in good condition.SUMMARYThe subject of the present paper has been the foodand feeding habits of the larvae and juveniles of3.0-90.0 mm of length of E. anckoita from coastalwaters off Mar del Plata, Argentina. The followingresults hare been obtained.The incidence of feeding found varies with the sizeof the larvae and juveniles. The lowest values arefourid in larvae of 5.0-30 mm in length. The assumptionis made that this plieiiomenon can be likely relatedto the structure of the digestive tract of thelarvae at this stage of deuelopinent.The argentine anchovy is almost exclusively zooplanktofagousfrom its earlier life stages. The maincomponent of the diet of both larrae and juveniles isCopepoda in all of their dewlopmental stages. Amongthem the Calnnoida are the most abundant group.Phytoplanktonic organisms were found in greatestabundance in the diet of juueniles of 38.0 mni oflength and larger. This phenoiiienon is related to thechangcs which take place in the filtering net of thelarvae along with the derelopnieiit of the gill-rakers.The comparisons betn-een larvae and juveniles ofthe Argentine anchovy E. mchoita and those of thePeruvian “anchoveta ” E. rillgens has been made.The juveniles of the ancliorp show some iliofagoustendencies, especially diiring winter.The assumption is made that the larvae and juvenilesof the anchovy do not choose their prey muchand that they ingest the food that they find in greaterabundance.It is assumed that there is no chance of feeding competitionbetmeen the larvae and juveniles of the anchovyand those of A. incisaREFERENCESAndreo, B. 1960. Sobre la aparicion de las branquispinas enlas formas juvrniles de sardina (Sardina pilchai-dus Walb.) .Real SOC. Espaiiola Hist. Nut., Bol., Sec. Biol. 58: 199-216.Angelescu, V., and M. B. Coussean. 1%6. Distribuci6n espacialy cronolngica de la anchofta en el Mar Epicontinental Argentino.Relacioiies con el desarrollo de las pesquerias pelhgicas.C.A.R.P.A.S., 3, Doc. Tec. 1 :1-30.Bayliff, W. H. 1963. The food and feeding habits of the anchovetaCeteitgraulis inusticetus, in the Gulf of Panama.Inter-Anzer. !Prop. Tuiia Comm., Bull., 7 (6): 3W32.Berner, L., .Tr. 1959. The food of the larvae of the northernanchovy, Engraulis niordax.Inter-Anzer. Trop. Tuna Comru., Bull., 4 (1): 1-22.Blaxter. J. H. S., 1965. The feeding of herring larvae and theirecology in relation to feeding. Calif. Coop. Ocean. Fish.Invest., Rept., 10 :79-88.Ciechomski, .J. Dz., de. In press. La alimentacion del cornalito,Ausfroatherina incisa en la zona de Xar del Plata.Dulta, 1,. A. 1961. Food of anchovy larvae in the Black Sea(in Rnssinn). Sevastopol Biol. Sla., Trudy, 14: 244-25s.Ekegovie, A. 1940. The food of sardines (Clupea pilchardusWalb.) in the metamorphosic stage. Transl. from Serbo-Croatian, 1962. Godisn jak Oceanogr. Inst., Ann. 1939-1940,2: 4144.Fuster de Plaza, Ill. L., and E. E. Boschi, 1958. Estudio bio-1Bgico pesquero de la ancholta (Engraulis anchoita) de Mardel Plata. Sew. Agric. Ganad., Dept. Inaest. Pesquer. Puhl.(7): 1-19.