The allis shad (alosa alosa) is a species of herring that comes upriver to spawn – generally as far as the barbel region. The spawning fish are between 40 and 70 cm long, and may attain to a weight of 3 or 4 kg. Allis shad spawn at night on flat gravel banks. When their sexual encounters are turbulent, they can be seen and heard gyrating through the water in a wild pursuit of courtship. The young fish probably pass downstream again to the brackish water zone in the first year of life, moving on to the sea at a later stage. After two or three years the sexually mature fish return to the river to spawn. In earlier times there were hundreds of thousands of allis shad migrating upriver – they were the daily bread of professional fishermen. Today the species has practically died out, apart from a few lone survivors. There are plans for obtaining young fish for resettlement from France, where there is still a large population of the species in the Gironde.
