Author: Fernando de la Gándara / Planet Tuna

Scientific name: Thunnus thynnus

Place of photography: Mazarrón marine crop plant of the Oceanographic Center of Murcia (IEO-CSIC)


Bluefin tuna lays eggs in the Mediterranean in the months of June and July. These occur around 4 in the morning. Two or three males chase a female that is releasing the eggs, which are fertilized by the sperm that the males are expelling. These eggs (once fertilized), carry the embryo developing for about 30 hours (time depends on temperature) until hatching occurs. Both the egg and the larva in their first days, feed on the nutritious reserves consisting of the yolk sac and the drop of fat (equivalent to the white and yolk of a chicken egg). The heartbeat can be seen at the stage of development in which the embryos in the photo are located.