Northern navaga

Northern navaga, an important commercial fish in the White and Barents Seas.

Content

• What kind of fish is navaga?
• Navaga lifestyle
• How navaga spawns
• Development of navaga
• What does navaga eat?
• Navaga's enemies
• How navaga grows
• Commercial significance of navaga

 

 

What kind of fish is navaga?

Where is the navaga fish found? In the Arctic Ocean and its marginal seas, in the North Atlantic and the North Pacific Ocean, there are two types of navaga - northern navaga and Far Eastern navaga.
Northern navaga (Eleginus navaga) is distributed in the southeastern part of the Barents Sea, in the White Sea and in the Kara Sea to the Ob River.

Navaga lifestyle

The navaga fish leads a bottom-dwelling lifestyle. Navaga does not make long-distance migrations; migrations are seasonal: from the coast to deeper areas and back.
Northern navaga is a cold-loving fish. Navaga lives near the coast, at shallow depths. In September-October, as the water cools, northern saffron cod en masse begins to approach the shallow coastal waters. During the pre-spawning period, northern navaga approaches the shore in masses and enters rivers 10–20 km with tidal currents.

How navaga spawns

Navaga begins to mature at the age of less than 2 years.
Spawning approaches of navaga are observed annually in the same areas. During the autumn pre-spawning period, navaga is intensively fattened.
The sex ratio in navaga populations during the spawning period is approximately 1: 1. In pre-spawning aggregations, females, as a rule, predominate, then the sex ratio levels off, and after spawning, males slightly predominate for some time.
However, spawning of northern navaga occurs only in sea water from December to January under ice at a depth of 8-10 m in the straits between the islands, in places with strong currents and a rocky or sandy bottom; The eggs of navaga are bottom-dwelling, but the eggs do not stick to the ground. The duration of development of navaga eggs is up to 4 months.
After hatching, pre-larvae and larvae of navaga live in the surface layers of water for some time. In the areas of spawning grounds, navaga apparently do not stay long, as they are carried by the ebb and flow of currents.

Development of northern navaga

Embryonic development of navaga takes place under ice at relatively stable temperature and salinity of water. To the greatest extent, the conditions of reproduction of navaga affect the number of future generations of navaga during the period of hatching of larvae and their transition to active feeding. The main abiotic factor determining the survival of larvae is the thermal regime. The development of eggs at a water temperature of 1.4 - 1.5 °C lasts about 3 months. Hatching usually begins at the end of April when the ice breaks up. During the period of hatching and subsequent development of larvae, the surface water temperature ranges from negative values to 10-15 °C. The upper temperature threshold for the development of navaga larvae is no higher than 5-6 °C. Higher temperatures cause the death of navaga larvae.

What does navaga eat?

What does navaga eat? The basis of the navaga's diet consists of benthic organisms. Only underyearlings of navaga feed on plankton until they reach a size of 5.5–6 cm. In this case, the main food of navaga is copepods (Acarliabililosa, Pseudocalanus elongatus, Ternora longicorn is, Eury/termora hiru ndoides, Harpacticoida). As the navaga grows, it switches to feeding on nektobenthic organisms. The basis of the food spectrum of adult navaga is fish, polychaete worms and crustaceans, and the ratio of these components varies depending on the season and feeding area. The composition of navaga's food also varies from year to year. Among the fish, navaga consumes herring, smelt, sand lance, stickleback, cod, as well as its young. Already in the food of underyearlings of navaga there are fry of herring and smelt. The food of adult navaga is dominated by herring and smelt in slightly smaller quantities.
The highest feeding intensity of navaga is observed in March, when its post-spawning fattening begins, in June and the first half of July. During the period of intensive fattening, navaga feeds mainly on fish (50-100% of the total filling index). In summer, when the waters warm up to the maximum (June and August), the feeding intensity of navaga decreases. During periods of low feeding intensity, navaga consumes mainly crustaceans and polychaete worms. Of the crustaceans, decapods (Crangon Crangon), mysids (Mysis oculata, Mysis mixta), and amphipods (Gammarus sp.) predominate in the food of navaga. From September to March, the proportion of crustaceans in the navaga feed decreases, which is associated with a seasonal reduction in their numbers. After a summer decrease in feeding intensity during the pre-spawning period (October-December), the feeding activity of navaga increases again. In January, during spawning, navaga stops feeding.
Some differences in the diet of saffron cod by habitat are associated with the ecological characteristics of the areas and differences in their fauna.
Changes in the feeding intensity of navaga from year to year depend on fluctuations in the number of main food organisms, the state of stocks of this fish, as well as on hydrometeorological conditions.
Northern navaga has similarities in diet with cod, flounder, lumpfish, goby, etc.

Navaga's enemies

The enemies of the White Sea navaga include smelt. Cod also feeds on navaga. Navaga's enemies are also marine mammals - seals and beluga whales.

How navaga grows

How fast does navaga grow? The most rapid linear growth of navaga is observed during the first 2 years of life, before the onset of puberty. In contrast to linear growth, a high increase in body weight is maintained in navaga throughout his life. Saffron cod reaches a length of up to 30-35 cm. The usual length of commercial saffron cod is less - 15-23 cm: commercial saffron cod is a fish suitable for spawning at the age of 2-4 years.

Commercial significance of navaga

Northern navaga in the White Sea is one of the main fishing grounds. Navaga periodically accounts for more than half of the total catch at sea. Northern saffron cod is a very tasty commercial fish; cod saffron cod is caught with ripples under the ice during a mass approach to the shore for spawning, mainly from November to January.

The productivity of navaga generations is determined by the spring water temperature. Since navaga is a fish with a short life cycle, the entry into the fishery of even one lean generation immediately negatively affects the state of the stock and the catch. If unfavorable conditions during the hatching period of navaga larvae persist for several years in a row, then after 2-3 years, when generations of these years enter the fishery, a significant decrease in the stock and catch of navaga is usually observed.