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yolk stage
y
year class the fish hatched in a given year.
yellow substance -tGelbstoff.
yolk the reserve food for developing embryos in eggs. Yolk consists in dry
weight of approximately 60 to 70 % protein and 30 to 20 % lipid. During
development, yolk is transformed into embryo tissue with a conversion efficiency of about 60 to 90 %, depending on the rate of development and the
amount of yolk utilized for metabolism of the embryo. In many fish species
the hatching larvae still contain a considerable amount of yolk in the yolk
sac, which is used by the larvae for further development and as an energy
source during early life (yolk sac resorption).
yolk stage life stage during which larvae do not eat, but still live on the yolk.