| Main Ref. | Allardi, J. and P. Keith, 1991 |
| Mode | dioecism |
| Fertilization | external |
| Mating type | |
| Spawning frequency | one clear seasonal peak per year |
| Spawning aggregation | Ref. |
| Batch spawner | Yes. Ref. |
| Reproductive guild |
nonguarders open water/substratum egg scatterers |
| Parental Care | none |
| Description of life cycle and mating behavior | Adults in the sea begin to congregate near mouths of estuaries in April. Enter estuaries and ascend rivers in May and June when water temperature is between 10-14 °C (Refs. 188, 51442, 59043, 89636). Males begin such movements at 2-3 years, females at 3-4 years (Ref. 59043). Although movement upstream is usually limited to a few kilometres above the brackish zone (Refs. 59043, 89486), spawning has also been reported in non-tidal freshwater areas up to 400 km upstream (Ref. 89637). Gametogenesis occurs in the estuaries. Early arrivals in the rivers are mostly males, with the sex ratio becoming more equal with the later arrivals (Ref. 42360). Spawning movements occur with spring tides and peak when river discharge levels are high (Refs. 89636, 89638). However, when flows are too high, movements upstream become limited (Refs. 89636, 89639). Spawn when water temperature is anywhere between 12-22 °C (Ref. 10541). Move to riverine spawning grounds at night; spawn in large, very noisy schools near surface and leave these areas before daybreak (Ref. 10541). Spawning sites consist of sand and gravel areas with flowing water (Ref. 10541). Spent adults return to the sea and may spawn for 3-4 seasons throughout their lifetime (Refs. 30578, 51442, 59043). Most individuals will have lost 22 % of their body weight after spawning (Ref. 89640). There is some evidence that most individuals return to their natal rivers to spawn (Refs. 10541, 59043). Eggs either drift with the current or sink to the bottom (Ref. 59043, 89641). Eggs hatch after 2-8 days, depending on water temperature (optimal 15-25 °C) (Refs. 35387, 41851). Larvae and juveniles move towards the estuaries and river mouths during their first summer and to the sea at the end of their second year (Ref. 59043). Males mature mainly between the ages of 2-5 years, females between 3-7 years (Ref. 188, 2163, 10541). Length at maturity is between 30-40 cm total length (Ref. 88187). |
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