What does So-iuy mullet look like and how to grow it in aquaculture

 

So-iuy mullet or So-iuy mullet is one of the valuable commercial mullet fish. The inhabitant of the Far East was acclimatized in the Black and Azov Seas, where it became a favorite object of fishermen and fish farmers. So-iuy mullet turned out to be a very flexible species that can be grown in aquaculture. It is necessary to consider in more detail the So-iuy mullet fish, where it lives, what the So-iuy mullet looks like, what it eats and, of course, how the So-iuy mullet are raised.

 

Content

• The appearance of sawfish on the Black Sea
  
• Description of So-iuy mullet fish
  
• Where is the So-iuy mullet found?
  
• What does So-iuy mullet look like?
  
• What does So-iuy mullet eat?
  
• Spawning of the sawfish
  
• How to grow So-iuy mullet in aquaculture
  

 

   

 

The appearance of sawfish on the Black Sea

 

For many centuries, people in the Mediterranean have raised fish in pasture-based aquaculture. The Black and Azov Seas also have great opportunities for growing fish in aquaculture. In recent years, both the number of valuable fish species and their structure in the sea have changed dramatically, which has reduced the efficiency of mariculture farms, especially in the Northwestern Black Sea region.

 

There are 5 species of mullet in the Black Sea, of which 3 - flathead grey mullet (Latin name Mugil cephalus L.), Leaping mullet (Latin name Liza saliens Risso) and Golden grey mullet (Latin name L.aurata Risso) - are of commercial importance, but their numbers have greatly decreased . In the Far East, So-iuy mullet (Latin name Mugil soiuy Basilewsky) lived in river mouths. It was the So-iuy mullet that managed to acclimatize in the 70-80s in the Azov-Black Sea basin, where it took root and reached high numbers, but what kind of fish is So-iuy mullet?

Description of So-iuy mullet fish

Where is the So-iuy mullet found?

 

Is So-iuy mullet a sea or river fish? So-iuy mullet fish is a sea fish that comes in summer and autumn (before laying down in pits) in desalinated areas of estuaries and bays and in river mouths. So-iuy mullet quite often lives in old, stagnant river beds and in lakes where the water is almost completely fresh. 

The historical range of the So-iuy mullet covers the Sea of Japan and the Yellow Sea. 

Where is So-iuy mullet found within Russia? So-iuy mullet lives in the Sea of Japan, from Peter the Great Bay to the Amur Estuary. In addition to the sea, So-iuy mullet is also found in rivers, where it enters in summer and autumn. But in addition to its Far Eastern range, the sawfish was acclimatized in the Black and Azov Seas, thus ending up in European seas.

What does So-iuy mullet look like?

 

The fatty eyelid is poorly developed. There is no elongated lobe above the base of the pectoral fin. The scales begin in front of the nostrils. The pectoral fins do not reach the vertical line of the beginning of the dorsal fin. The caudal peduncle has more than 20 longitudinal rows of scales. Plengas length reaches 60 cm and weight up to 2–3 kg.

What does So-iuy mullet eat?

 

What does So-iuy mullet eat? The sawfish feeds on organisms that live in the mud. Juvenile fry feed mostly on plankton, the main part of which is copepods and rotifers. Juveniles reaching a length of over 8 cm switch to feeding on detritus, the basis of which is bottom algae and organic remains.

Spawning of the sawfish

 

How does sawfish spawn? Spawning of the sawfish lasts from the second half of May to the first half of July at a water temperature of 16–17° C. During spawning, the sawfish stays in schools near the shore. In a flock, one or two females are followed by several males of different sizes, and when the female lays eggs, they take turns participating in her insemination. So-iuy mullet caviar is pelagic, spherical in shape, with a large fat drop. The eggs of the sawfish develop in the surface layer of water. The length of newly hatched larvae is 1.6 mm. Juvenile fry, 0.5 to 5 cm long, are found mainly in the surface layer of water near the shore, in estuaries and river mouths. Yearlings of the So-iuy mullet are 10–12 cm long. Two-year-olds of the So-iuy mullet reach a length of 18–20 cm. Females of the So-iuy mullet first mature at the age of five, males of the So-iuy mullet mature at four years. 

 

 

 

 

How to grow So-iuy mullet in aquaculture

 

Growing the Far Eastern mullet can be very effective and even more effective than other mullet fish, since the fish can winter in brackish water bodies and in fish ponds located in temperate climate zones.

 

Table - Growth rate of sawfish in various reservoirs, g

body of water habitat	Age of fish, years
	1+	2+	3+	4+	5+	6+	7+	8+	9+
Far East	-	60	300	580	620	650	800	1000	1200
Milky Estuary (Sea of Azov)	150	600	800	1200	3500	-	-	-	-
Dairy estuary (cages)	100	420	935	1158	1365	1470	-	-	-
Milk estuary (ponds)	120	550	1100	1300	-	-	-	-	-
Kherson region (ponds)	430	1167	2172	-	-	-	-	-	-
Shabolat (Black Sea)	190	820	2600	-	-	-	-	-	-

 

 

In 1979 and later, 4060 fingerlings, 5-7 cm long and weighing 4-5 g, were brought into cages on the Molochny Estuary of the Sea of Azov.

In the Dairy Estuary, successful experiments were carried out on the creation of broodstock and artificial breeding of sawfish. The area of the Dairy Estuary is 22 thousand hectares, fish productivity is only 10-13 kg/ha with detritus reserves only in the surface layer 3 cm thick, with leaving 374 thousand tons, and its accumulation causes death. Water salinity ranges from 11 to 20%o, water temperature - from 32°C in summer to 0°C in winter, dissolved oxygen content - from 8 to 2 kg/l, occasionally reaching 14 mg/l.

The formation of the broodstock of the sawfish began with the 1979 generation, brought by fingerlings from the Amur Bay. The fish were kept in cages installed on pontoon sections in artificial quarry ponds with a depth of 2.5-3.0 m and an area of about 1 hectare. Cages measuring 2x3x5 m, made of knotless wire with a mesh size of 3.6 for fingerlings and from 6 to 16 mm for older juveniles. In the summer, the fish are transplanted monthly (if necessary, 2 times a month), and the cages are cleaned of fouling.

The fish are fed with paste-like food, consisting of 90% minced fish and 10% mealy feed for farm animals, as well as granulated carp and trout feed. From November to April, the sawfish does not feed; start and finish feeding at a temperature of 8-10°C. In spring and autumn, fish are fed 1-2 times a day in an amount of 10% of body weight; in summer, the diet of juveniles is increased:

4-5 times a day, feed is given to juveniles - up to 30%, to adults - up to 20% of body weight. When the water temperature rises to 25°C and the oxygen content drops to 3 mg/l, feeding is stopped.

For the winter, the feeding holes are closed, and the cages are deepened 70-100 cm below the water level, making holes in the ice. Overwinter mortality of older instars is 2%, of juveniles - 5-25%. Particularly high mortality rates are observed after harsh winters.

The greatest increase in mass was observed in fish in the 3rd-4th year of life - 320-515 g. In the estuary, quarries and cages, growth was better than in the Amur Bay. In the 5th-6th year the growth rate decreased. Males matured a year earlier than females.

The first breeders matured in 1974, ovulation was stimulated by the pituitary glands of carp - from 10 to 53, So-iuy mullet - from 8 to 36 mg/kg, as well as human choriogonin. The resulting eggs were fertilized in a “semi-dry” method, diluting the sperm with sea water, and incubated in water with a salinity of 20-23% c.

The larvae were fed with ciliates, then with zooplankton (rotifers, etc.), and on the 14th day - with small minced mussels and shrimp and "Equiso-1". On the 30th day, fully formed juveniles were placed in cages and fed with minced fish and artificial food in a 1:1 ratio. Juveniles in quarry ponds grew better than in cages, and by the fall they reached a length of 14 cm, an average weight of 17 g, in the 2nd year - 100 g. As a result, a replacement broodstock of 1600 individuals was formed. Thus, the possibility of obtaining offspring from producers raised in cages in the Dairy Estuary was proven.

In winter, golden grey mullet died at a water temperature of 2°C, mullet - at HS, and sawngas survived by 98% during wintering in cages, during which the water temperature dropped to 0.5°C.