The ovarian fluid properties of the three‐spined stickleback Gasterosteus aculeatus were studied in overripe and non‐overripe ovulated female sticklebacks and in females that were implanted with Silastic capsules containing testosterone (T), oestradiol (E2), 17,20 β ‐dihydroxypregn‐4‐en‐3‐one (17,20 β ‐P) or progesterone (P4) into the abdominal cavity. Overripe females had less ovarian fluid than non‐overripe females, but with...