Fish book son indd

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Lake sturgeon (A. fulvescens Rafi nesgue, 1817) - The Great Lakes, basin of 
St Lawrence River, the USA.
Common name: Lake Sturgeon, freshwater sturgeon, rock sturgeon, 
bony sturgeon.
Freshwater sturgeon: a near threatened species listed in the IUCN Red 
List, under category II. The fi sh reaches 206 cm in length and can weigh up to 
86 kg. It diff ers from the shortnose sturgeon A. brevirostrum, which inhabits 
the same areas, by its longer sharpened nose and shorter upper tail fi n blade. 
Its coloration depends on its age and habitat. Usually its sides and back are 
black and gray or olive-brown, and the underside is white or yellowish. 
Young specimen are lighter in coloration than adults and have dark spots on 
their sides and nose.
Freshwater sturgeon occurs across the basin of the Mississippi, in the 
Great Lakes, and in the St Lawrence to the north up to Hudson Bay, Lake 
Winnipeg, and the Saskatchewan River. It has also been introduced in a 
number of smaller lakes of North America: Mendota, Monona, Vingra, Big 
Cedar Lake etc.
The female sturgeons do not reach their maturity until the age of 20-25, 
when they are 120-140 cm long, and thereaft er they lay eggs once every 4 to 
6 years. The males reach their maturity at the age of 15-20 when they are 100-
120 cm long, and then they go to spawn once every two years, while some of 
them spawn each year. 
The females usually live longer than the males: females make up 97 
percent of sturgeons above 30 years old. The sturgeons spawn in rivers on 
gravel between late April and mid-June. In the event of a high fl ood  the 
spawning begins when the water temperature reaches 14
0
C; while in case 

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G.M.Palatnikov,  R.U.Qasimov
132
of low fl ood it begins at 14.5-15
0
C. The males usually come to the spawning 
grounds before the females. They usually occur in groups of eight or more 
specimens. The spawning begins when a sexually mature female approaches 
the group. The fertilized eggs stick to pebbles and other solid substrate. The 
fertility of females weighing 5 to 51 kg ranges from 50,000 to 667,000 eggs. 
The diameter of the eggs is between 2.7 and 3.1 mm. The eggs take 5 to 8 days 
to develop.
The sturgeons fatt en in the coastal areas of lakes and rivers at depths 
of not more than 10-15m. They eat mainly small bott om dwellers: mollusks, 
larvae, leeches, crustaceans and other invertebrates, and less frequently they 
feed on fi sh.
In the past, the commercial value of the lake sturgeon was greater than 
that of two other species of American sturgeons (the long-nose and short-
nose) taken together. In 1880, 1,536 tonnes of this sturgeon was hauled in 
Lake Michigan. In 1893 the catch on Woods Lake (Canada) was 640 tonnes. 
Only 152 tonnes of this sturgeon was caught across its entire range of habitat 
in 1951. The main reasons for the decrease in the population of lake sturgeon 
in the XX century were intensive fi shing, poaching and the pollution of water 
reservoirs. Sturgeon hauling is now limited by a quota that permits the 
catching of only sexually mature individuals. Some att empts at rearing are 
being made.
Sakhalin sturgeon (A. mikado) – Pacifi c Ocean, Sea of Japan.
Sakhalin sturgeon 
Acipenser medirostris
This is a very rare and poorly studied species that is threatened with 
extinction (category I). It is listed in the Red Book of the USSR and the 
Russian Federation. It is noted for its natural low abundance in its habitat. 
These sturgeons reach a length of over 2 m and weigh more than 60 kg. There 
are 8-10, 26-31 and 6-8 scutes on the back, side and the underside respectively. 
There are 36 to 40 rays in the dorsal fi n and 25 to 29 in the proctal. They also 

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have 18-20 gill rakers. These sturgeons are also called ‘green surgeons’ for the 
olive color of their back.
These sturgeons are widespread in the northern part of the Pacifi c Ocean 
along both the American and Asian coasts. Along the coast of America they 
occur from San Francisco to the Columbia River. Along the Asian coast they 
occur in the waters of the Sea of Japan, from Hokkaido to Wonsan (Korea). In 
Russian waters they occur from the Korean border to the estuary of the Amur 
River as well as in some rivers of Primorski Krai and Sakhalin. They are also 
recorded as having been caught in the Olyutor Bay of the Bering Sea.
This is a migratory fi sh that goes to spawn in small fast-fl owing rivers 
and does not travel far upstream. In the Far East most sturgeons go up the 
Tumnin River that fl ows into the Tatar Strait. It apparently has two forms: 
early-run and later-run. The later-run fi sh enter the Tumnin River in May 
or June when the ice drift  is over; the early-run fi sh go upstream in the fall, 
during September or October, and spend winter upstream. The spawning 
takes place in June or during the fi rst half of July. For the fi rst 4 or 5 years the 
juveniles live in fresh water and they diff er vastly in biological terms from the 
juveniles of other migratory sturgeons; they are not mobile and spend most 
of the time at the bott om. This is possibly a form of species adaptation that 
protects juveniles from being carried downstream to the open sea and high 
salinity waters too soon.
They reach their sexual maturity quite late: males at the age of around 10 
years with a weight of 8-10 kg and females - 2 or 3 years later, when they are 
greater in size. They do not spawn every year: the average interval between 
spawning seasons is 4 years for males and 5 years for females.
These sturgeons are distinguished by their rapid growth, surpassing that 
of the Amur and other sturgeons. A Sakhalin sturgeon can reach 25 kg by the 
age of 18.
In 1986-87 att empts were made to organize the farming of Sakhalin 
sturgeon. Several mature spawners (4 females and 2 males) were caught in 
the Tumnin River and their roe was obtained. The eggs were very big, close to 
those of the beluga in size, and weigh 25 to 34 mg. With a water temperature 
of 10-14
0
C, their incubation lasted for 11 days. Unfortunately, almost all 
juveniles obtained this way subsequently died. 
There is no available information on its abundance in its natural habitat. 
The main limiting factor is, apparently, the extremely limited available 
spawning ground. It is forbidden to catch this sturgeon, but it is caught by 

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