The Gladstone Water Board Fish Hatchery in Queensland is one of the largest non-commercial breeders of barramundi fingerlings in Queensland, but also breeds mangrove jack and mullet. Most of the fish are released into Lake Awoonga, Gladstone’s principal water storage.
Hatchery manager Thomas Hayes admits that he and the other three hatchery staff are busy spawning and rearing the warm water species, (barra and jacks) in the summer, but the winter brings a welcome change of pace. Cooler temperatures provide an opportunity to do some maintenance on the hatchery, as well as concentrate on breeding sea mullet.
Hayes explains that as a cooler-water species sea mullet are more challenging to breed and rear.
“Barra and the jacks like to spawn in water about 28°C and upwards during our summer,” Hayes explained. “It’s once the water is below 25°C that the sea mullet will start.”
One of the difficulties with raising mullet is that they cannot tolerate being exposed to low salinity water and the area where the hatchery is located can have extended periods of heavy rainfall in winter.
Hayes also said he’s discovered that there’s not much information on spawning and raising sea mullet but the staff enjoy the challenges of breeding the species.
The mullet are released into the lake, where they tend to become fodder for the barramundi and jacks, but they also eat and reduce the weed and algal mats on the bed of the lake, helping to keep the lake healthy.
Hayes said the hatchery has a total of 41 tanks of various sizes ranging all the way from small larval and algae tanks up to the big 60,000-litre broodstock units and four 40,000-litre reservoir water containers.
“The rest are pretty much for larval rearing and live prey for the juvenile fish,” Hayes explained. “We use mainly rotifers and artemia but sometimes also run live algae and green-water – but we’re shifting more to use of algal pastes.”
– Quentin Dodd