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

REPORTS VOLUME XI, 1 JULY 1963 TO 30 JUNE 1966 61FIGURE 3. Embryonic development of the anchovy (Engraulis anchoita). 1. Formation of the first cell; 2. Two-blastomere stage; 3. Formation of theblastula; 4. Blastula; 5. Gastrulation; 6. Neurula, a) frontal and b) lateral view of same; 7. Commencement of the separation of the caudalregion from the vitelline sac; 8. Embryo immediately prior to hatching (from Dz. de Ciechomki 1965).approach the coast in the area near Mar del Plata,where they appear forming great schools from Septemberonwards. The schools stay in the area untilthe beginning of Summer, when they start movingtowards the open sea. A similar migration occurs withthe adult individuals of the Autumn population thatalso migrate for reproduction in the period fromFebruary to March. After spawning, they return tothe open sea.The problem of the reproduction and embryonic andlarval development of Engraulis anchoita has beenstudied in greater detail by the present author, whohas incorporated the results in the papers presentlyin press. It has been possible to determine the exactperiod of reproduction of this species on the basis ofappearance and disappearance of the eggs, larvae andjuveniles of the anchovy in the sea. This has been accomplishedby a systematic collection of the materialand the use of quantitative methods.The intensity of spawning was related to changes insea temperature. The reproduction of the anchovystarts in September, very close to the coast, at atemperature of about 10" C, and reaches its peak inOctober at a temperature of about 11"-13 "C. FromNovember onwards the anchovy continues its reproductionin a more or less intensive form, and apparently,more towards the open sea. In February, thespawning intensity reaches a slight peak. In March,the intensity of spawning seems to decline and apparentlytakes place more towards the open sea. Spawningcontinues in this manner until September. Theexistence of two periods (October and February) ofgreater intensity agrees with the results given byFuster de Plaza (1964) on the basis of an examinationof adult individuals.There occurs in the anchovy a daily spawningrhythm, ranging from 8 pm until 12 pm. The determinationof this daily rhythm by the present author