 In Kattegat the amount of empty stomachs has been observed in the months of January to April and is described as “very high, close to 100% in some month”.⁠⁠⁠
Those findings may be due to the lower water temperature of around 12 to 13 °C and the therefore lowered metabolism and feeding activity respectively.⁠
Aquarium experiments with stable light, temperature, salinity and sustained food supply on the contrary suggest an endogenous feeding pattern because even under such conditions the fishes refused to eat in the time from January to April and from October to March.⁠

The reproduction period of "T. draco" seems to lasts from June to October.⁠ This very broad range is limited by the observations of Ole Bagge (2004) who states that his findings strongly indicate that the spawning time of "T. draco" is indeed restricted to the period between June and August with a peak in July.Bagge also says that there have been no findings of greater weever in spawning condition from September to May.⁠
"T. draco" is an oviparous spawning fish that lays its eggs into the pelagic zone.⁠The larvae have a size of about 4.8 mm to 6.8 mm ⁠ and hatch after approximately three months.