Flathead grey mullet fish growing in aquaculture
Photo of flathead grey mullet fish in the sea
The flathead grey mullet fish is one of the most common fish from the flathead grey mullet family, a valuable commercial fish, an object of catch for amateur fishermen, and also an interesting object for growing in aquaculture. Let's take a closer look at what kind of fish flathead grey mullet is, what flathead grey mullet looks like, where it lives, how flathead grey mullet is grown in aquaculture and much more.
Content
- Description of flathead grey mullet fish
- Where does the flathead grey mullet fish live?
- What does flathead grey mullet fish look like?
- What does flathead grey mullet fish eat?
- Lifestyle of flathead grey mullet fish
- How flathead grey mullet fish spawn
- Breeding flathead grey mullet in aquaculture
- Breeding flathead grey mullet and obtaining flathead grey mullet fish seed material
Description of flathead grey mullet fish
The flathead grey mullet fish, Latin name Mugil cephalus, is a fish from the family Mugilidae. The flathead grey mullet fish is the largest of the flathead grey mullet fish family.
Where does the flathead grey mullet fish live?
The flathead grey mullet fish prefers warm waters, so the flathead grey mullet lives in the Atlantic Ocean, where it can be found from Cape Cod to Brazil, as well as from the mouth of the Loire to Cape Town. The flathead grey mullet lives in the Mediterranean, Marmara, Red, Aegean, Black and Azov seas, and can be found in the Indian Ocean. In the Pacific Ocean, flathead grey mullet fish is distributed from Aleksandrovsk on Sakhalin to Australia and New Zealand; but in the Sea of Japan flathead grey mullet is very rare, but along the American Pacific coast it is often found from California to Chile. As you can see, the flathead grey mullet is widely distributed in the World Ocean.
What does flathead grey mullet fish look like?
What does flathead grey mullet fish look like? One of the characteristic features of flathead grey mullet is the presence of fatty eyelids reaching to the pupils. There is an elongated lobe above the base of the pectoral fin of the flathead grey mullet. The scales on the fish's head begin in front of the front nostrils.
What color is the flathead grey mullet? The top of the head and back of the flathead grey mullet are dark in color with a silver tint, the sides of the fish are silvery, with approximately 12 brownish longitudinal stripes on them. There is a blue spot above the base of the pectoral fin of the fish. Its dorsal and caudal fins are gray-black, the anal fin is gray, and the ventral fins are light-colored. The maximum length of the flathead grey mullet reaches 75 cm, it is the largest fish of the flathead grey mullet family.
What does flathead grey mullet fish eat?
What does flathead grey mullet eat? The flathead grey mullet is a fish with a low trophic level diet. The flathead grey mullet larvae feed on zooplankton, but a month after hatching they gradually switch to the type of feeding typical for adult fish, eating organic detritus, fouling, benthic crustaceans, and worms. The flathead grey mullet does not feed during migrations (spawning, spring and autumn). In warm winters, the flathead grey mullet feeds poorly and stops feeding in cold winters.
Lifestyle of flathead grey mullet fish
The flathead grey mullet is a sea coastal fish that lives in schools. Juvenile flathead grey mullet often live in the estuaries and middle reaches of coastal rivers, and can also live in desalinated lakes that still have a connection with the sea.
Fingerlings of flathead grey mullet winter in bays and bays. In the Black Sea, flathead grey mullet forms aggregations of wintering adults annually in two different places on the Caucasian coast: one near the cities of Novorossiysk - Gelendzhik and the second in the Sochi - Gagra region. Rarely found in Crimean bays in winter. To feed, the flathead grey mullet goes to the Sea of Azov. From June to August in the Kerch Strait you can simultaneously find flathead grey mullet migrating in opposite directions. Mature individuals go to spawn in the Black Sea, and those that spawn return to the Sea of Azov to continue feeding. As a rule, young fish return to the Azov Sea for post-spawning feeding, while older fish feed in the salty areas of the Black Sea. From mid-September and in October - November, the flathead grey mullet leaves the Sea of Azov and returns to the shores of the Black Sea for the winter.
How flathead grey mullet fish spawn
How does flathead grey mullet spawning take place? The spawning season of flathead grey mullet in the Black Sea lasts from the end of May - June to the end of August. During spawning, flathead grey mullet fish keep in schools, in which there are several fish (one female and several (3–7) males).
The fertility of flathead grey mullet is very high and reaches 3–13 million eggs per female. The caviar of flathead grey mullet is pelagic and has a spherical shape. Development, depending on temperature, lasts from 1.5 to 5 days. Prelarvae hatch at a length of 2.4 mm. Fingerlings of flathead grey mullet in July have a length of 1–3 cm, by September they reach a length of 2–6 cm. By spring, yearlings of flathead grey mullet grow to 5.6–5.7 cm, sometimes up to 10 cm. Female flathead grey mullet of the same age are always larger than males. Male flathead grey mullet mature in the third year of life, female flathead grey mullet mature in the fourth year.
The flathead grey mullet fish attracts the attention of fish farmers with its rapid growth. If conditions are favorable, then already in the second year of life the flathead grey mullet reaches a length of 45-50 cm and a weight of 450-600 g.
Breeding flathead grey mullet in aquaculture
The flathead grey mullet is the fastest growing and most promising for fish farming in brackish water bodies. It can be used
- as an object of polycultures in carp fish ponds,
- in reservoirs for complex purposes,
- for cultivation in pasture aquaculture in estuaries and bays,
- for growing in cages and fenced off areas of estuaries,
Breeding flathead grey mullet and obtaining flathead grey mullet fish seed material
Previously, to raise flathead grey mullet, its juveniles were caught in the sea and released into nursery reservoirs, but the natural population of flathead grey mullet has been undermined and currently there are few juvenile flathead grey mullet in the sea, so catching them for stocking ponds is ineffective, and therefore it is necessary to obtain flathead grey mullet planting material artificially.
Method for obtaining mullein planting material
If the enterprise does not have its own broodstock of flathead grey mullet, then the spawners are caught in the sea in June-August, during its spawning run, in a net cage the caught spawners are delivered to the base, where they are sorted, selecting uninjured individuals with stage IV gonad maturity.
Caught flathead grey mullet producers are kept in pools measuring 2x2x0.7 m, at a water temperature of 24-26 C in running water with a salinity of 16-17%.
To stimulate maturation, pituitary injections (gonadotropin or flathead grey mullet pituitary gland) are used in the first 24 hours after catching. One female flathead grey mullet weighing 2.5-3 kg consumes 90 mg of pituitary gland. Females are injected intramuscularly in two doses: the first time 1/3 of the dose and after 16 hours 2/3 of the dose. Male flathead grey mullet is administered 1/2 dose once.
After the second injection, the producers are placed in tanks with a capacity of 2-3 m3 and from 2 to 8 breeding males are added to each female. Maturation of females at a temperature of 24-26 C lasts 32-40 hours.
The caviar of flathead grey mullet is pelagic; it is collected and incubated in aquariums, basins, cages and other containers.
Sometimes caviar is obtained by straining. In this case, insemination is carried out using dry and semi-dry methods.
For incubation, eggs with a high percentage of fertilization (above 60%) are selected; they float if placed in water with a salinity of 17%. The eggs are incubated in VNIIPRH apparatus with weak aeration or flow, or in flat 100-150-liter containers with only aeration for about 35 hours at a water temperature of 23-24°C.
Hatched larvae, about 2 mm long, are placed in small pools with a capacity of 2 m3, into which unicellular algae (single-celled algae, chlorella or monochrysus) are added 1-2 days before, so that by the time the larvae are planted, the algae density is 0.5- 0.7 million cells in 1 ml of water. The larvae are pre-adapted to the conditions of the pool.
Due to the photosynthetic activity of algae in the pool, the water saturation with oxygen is maintained at least 70%. On the 13-14th day, the nursery tanks are switched to flow mode.
The larvae switch to external feeding on the 5th day. From this moment until the age of 9-13 days, the larvae are fed with mussel trochophores and rotifers. Their numbers are constantly monitored 2-3 times a day, maintaining the concentration: trochophore - 5-15, rotifers - 3-5 pcs/ml.
On the 10-12th day after hatching, the larvae begin to be fed with one-day-old Artemia nauplii, adding them in concentrations of up to 1 piece/ml.
And after another 2 days, the larvae can already take the grown juveniles of Artemia and zooplankton caught in the coastal areas of the sea - (nauplial, copepodite and adult forms of Acarcia, Harpacticoids and Diaptomus, in concentrations of up to 1-2 pcs/ml.
Metamorphosis in flathead grey mullet usually occurs on the 24th day after hatching. The survival rate of larvae during the metamorphosis period is approximately 15%.
On the 30th day, the larvae can be gradually transferred to artificial food - minced mussel and fish meat, at the rate of 20-30% of the average weight of the fish.
Viable juvenile flathead grey mullet are transplanted into brackish-water ponds or coastal pools with additional feeding with artificial food. The juveniles are raised in drainage and non-drainage ponds with a depth of 30-40 cm, an area of 0.1-0.5 hectares, rich in detritus and silt. Before release into the pond, the juveniles are first adapted to the conditions of the pond and raised until the onset of autumn cooling and the water temperature drops to 12-13°C.
To transplant juveniles for wintering, they are caught with a 20-meter fry drag net or the pond is drained.
If the wintering of flathead grey mullet is organized in a wintering hut with artificially heated water or water is supplied from a spring or artesian well with a temperature of 5-10 ° C, then the juveniles are fed, minced fish or mussels, soy or fish meal, grain flour, and mixed feed are used as food.
After wintering, yearling flathead grey mullet are released by gravity (using a flow of warm water) into the estuary or used for growing in polyculture together with carp or herbivorous fish in brackish and freshwater feeding ponds with an area of 0.5-1 ha. Its main food is detritus, but the flathead grey mullet can eat zooplankton and zoobenthos. Mixed feed is used (for feeding carp) at the rate of 2-5% of the body weight of the fish.
In the autumn, after the water temperature has dropped to 6-7°C, the pond is drained and flathead grey mullet is caught with drag nets or in a catcher.