Discovery reports (1937) Discovery reports discoveryreports14inst Year: 1937 STATfON 637 620 618 647 W5 197 638 636 TIME 1907-2026 2214-2359 2225-0100 0059-0328 0530-0915 0537-0730 0935-1230 Fig. 33. Diagram showing the vertical distribution of the Metanauplius and later stages of development at the stations indicated. Areas shown in outline represent the Metanauplius, areas in black represent later stages. 50 m. In the remaining seven stations, as shown in Fig. 33, the Metanauplii are con- centrated in the lowest nets fished. With the exception of two individuals all are in the 750-500 m. a
Discovery reports (1937) Discovery reports discoveryreports14inst Year: 1937 STATfON 637 620 618 647 W5 197 638 636 TIME 1907-2026 2214-2359 2225-0100 0059-0328 0530-0915 0537-0730 0935-1230 Fig. 33. Diagram showing the vertical distribution of the Metanauplius and later stages of development at the stations indicated. Areas shown in outline represent the Metanauplius, areas in black represent later stages. 50 m. In the remaining seven stations, as shown in Fig. 33, the Metanauplii are con- centrated in the lowest nets fished. With the exception of two individuals all are in the 750-500 m. and 1000-750 m. nets. It will be seen that there is considerable variation in the vertical distribution of the older larvae and that this can be connected with the time of day at which the net hauls were made. The stations have been arranged in a sequence from midday to midday, the first starting at 1907 and the last finishing just after midday. The figure shows that in the larvae of E. siiperba subsequent to the Meta- nauplius stage there is a definite diurnal migration, so that during the hours of darkness they are concentrated between the surface and 100 m., whereas at other times they are massed at 500-250 m. The vertical migration of larvae will be referred to more fully later; it is sufficient here to mark the contrast between the behaviour of the Metanauplius and subsequent larval stages.
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