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Biology

Biology

Russian, English and Latin names: Sakhalin taimen, Sakhalin huchen, Parahucho perryi.

 Taxonomical status:

Type Chordata;

Class Actinopterigii Klein, 1885;

Order Teleostei;

Group  Salmoniformes;

Family Salmonidae Cuvier, 1816;

Genus Parahucho Vladykov, 1963;

Species Parahucho perryi Brevoort, 1856.

   Diagnosis

The Sakhalin taimen is the largest of salmon, and in general one of the biggest freshwater fishes of the planet. The maximum length of 210 cm is historically noted (1937, the Tokatsugava, Hokkaido River). The mass of such large fishes could reach 100 kilograms, and age – more than 30 years.

 The body is covered with large scales. In the sea coloring silvery. From the beginning of the spawning course the body gets a reddish shade, on sides 5-8 light-crimson cross strips appear.

Meristical signs: D III 9-14; A III 8-12; sp. br. 12-14 (10-22); LL 97-122; p. c. 157-254; vert 55-62

(D – number of beams in a back fin; 

A – number of beams in an anal fin;  

P – number of beams in chest fins; 

V – number of beams in belly fins; 

sp.br. – number of gill races;

LL – number scales in a sideline;

p.c. – number piloric appendages; 

vert. – number of vertebras).

 Within an area the Sakhalin taimen appears morphological as a uniform species. Interpopulation distinctions the meristic signs at him are insignificant.

Modern nature protection status

Category according to the Red book of Russian Federation

Population of Sakhalin Island. Category 2 – the populations of species, endemic for the Far East (The Red List of the Russian Federation, 2001) which are reduced in number.

Category according to the IUCN Red list

Critically Endangered A4abcd - "being in critical condition" on all area (Rand, 2006).

Other Red books (category):

The Red book of the Sakhalin region - on the 3rd category with the status "the local endemic species of the Far East with the reduced number needing protection" (The Red book of the Sakhalin region, 2000, 2016).

The Red book of Primorsky Krai – on the 2nd category with the status "reduced in number" - taxons and populations with steadily reduced number which at further influence of the factors reducing number can get to short terms in category being under the threat of disappearance (The Red book of Primorsky Krai, 2002).

It isn't included in the Red book of Khabarovsky Krai.

In the Red list of the Ministry of environmental protection of Japan (the edition of 1999) and on the Red List Hokkaido (2001)  taimen is carried to the species which are under the threat of disappearance.

Intraspecific structure

On features of ecological strategy of populations all a taimen concern K-strategists with repeated spawning and with considerable age and the amount of the first maturing of individuals. For this reason all of them are vulnerable, first of all, in relation to irrational catch.

 On all area Sakhalin taimen has 3 ecological forms:

  1. The semi-anadromous which is leaving for feeding in sea to near coast, but not departing far from mouths of the rivers.
  2. Lake and lagoon, migrating within fresh and saltish waters.
  3. River, carrying out all life cycle in the large rivers.

There are also purely freshwater populations living in the reservoirs which are cut off by dams. Perhaps, the only such blocked population in the Russian part of an area exists in the lake Taynoe near Kholmsk in the southwest of Sakhalin.

 Genetic structure of populations

Actually each isolated population of any kind possesses a unique gene pool which demands protection. The aspiration to it is justified though implementation is problematic.

For long-term survival of populations important not only preservation of the minimum number, but also rather high genetic variety. It decides as number of genes on more than one alleles (polymorphic genes), and number of alleles of each polymorphic gene. Then in population there are heterozygotic individuals receiving various alleles of a gene about parents. The genetic variability allows a species to adapt to changes of the environment better. In general rare species have a smaller genetic variety, than widespread, and are more subject to extinction threat (Primak, 2002).

On Sakhalin within 3 years the "Studying of Population Structure of the Sakhalin Taimen for Development of Measures of Preservation of His Gene Pool" project by group of Institute of the general genetics of N.I. Vavilov (Moscow) under the leadership of Doctor L. A. Zhivotovsky was carried out. A main objective of work was definition of extent of genetic differentiation of populations of the Sakhalin taimen on DNA markers for assessment of their reproductive isolation from each other and development of measures of preservation of their gene pool.

Researches on the project have confirmed that the complex of the limiting factors leads to decrease in number and fragmentation of an area of dwelling of the Sakhalin taimen that in turn leads to reproductive isolation of individuals of this species. Reproductive isolation at species with low number can be the main reason for genetic differentiation of populations that has been revealed when studying polymorphism of DNA markers. By means of these markers it is possible to estimate extent of genetic differentiation of species, level of inbreeding, migrations and other population and statistical data which are important for development of measures for protection and monitoring of rare species.

In general for the sake of appearances interpopulation a component of a gene variety it was maximum among all salmons – from 21,8% (Edo et al., 2012) up to 22,6%.

Species

Interpopulation component gene variety, %

Oncorhynchus gorbusha

1.91

O. keta

2.90

O. nerka

7.00

O. tshawytcha

6.52

O. kisutch

11.30

Parahucho perryi

22.6

It is considered that at Gst values (a measure of an interpopulation variety) of higher than 20% exchange of migrants between populations practically doesn't happen. Nevertheless, also exceptions are sometimes noted (Komiyama, 1981; own data).

For the characteristic of a genetic variety of a taimen not displaced assessment of heterozygosity which has averaged 0,503 was used. Peripheral populations (Iturup island) show the reduced level of a genetic variety (0,308-0,371), and populations of the large rivers of the South of Khabarovsk Krai, on the contrary, have the increased value of heterozygosity (0,606 - 0,627) (Yurchenko et al., 2012).

For a research of genetic uniqueness of populations and assessment of their proximity coefficients of genetic similarity between all possible couples of selections on L.A. Zhivotovsky's formula have been to each other calculated (1979). On the received matrix of paired similarity calculated the main components with use of the SPSS program.

 (Zhivotovsky L. A. An indicator of similarity of populations on polymorphic signs // Zhurn. general biology. 1979. T. 40, No. 4. Page 587-602)

Arrangement of selections of the Sakhalin taimen in space main a component on DNA markers for populations of the northern rivers of Sakhalin (Report …, 2012).

 Three genetic clusters of the selections representing geographically subdivided population groups of a taimen of Sakhalin Island are unambiguously allocated. It is group of a taimen of reservoirs of the western Sakhalin: lake Ainu, Agnevo and Viakhtu Rivers. The second group - reservoirs of northeast Sakhalin: Val, Dagi, Nabil’, Tym’. The third – selections of the basin of the river Poronay: Onor, Elnaya and main bed of the river Poronay.

Within each group of population of the Sakhalin taimen also differ from each other, though it is less, than from populations of other groups. Nevertheless, the indicator of interpopulation differentiation for them is rather big: 9,4% for the western Sakhalin (without differentiation between repeated selections of the lake Ainu), 8,6% between populations of northeast Sakhalin, 11,7% within the river system of the river Poronay. These are very big sizes for anadromous fishes which speaks about very limited stream of genes between populations (Report …, 2012; Yurchenko et al., 2012).

An intra population variety of the studied populations is low, but nevertheless above, than specified for populations of the Hokkaido island: number of alleles – 1,9-2,6; heterozygosity – 0,27-0,45 (Edo et al., 2012).

Characteristic and analysis of habitats

 The Sakhalin taimen at different stages of life cycle uses a wide variety of habitats of upper courses and lower reaches of the rivers, estuaries, lagoons, lakes, gulfs and sea coast. The taimen prefers waterways of the wetlands having a small gradient (a flat bias), deep holes, high canopy. The most plentiful populations inhabit the rivers having large brackish lagoons in the basins (Poronay, Dagi, Evay, Nabil, Ainu).

Sakhalin taimen spawns in the top tributaries with meandered courses and well remained coastal vegetation in the rather deep places on transition border from depth to shallow water (also known as the beginning of shallow water). A typical spawning station – small a channel of the main course 3-4 m wide, about 1 m in depth, with a speed of current of 0,3-0,5 m/s. Sand-and-pebble bottom. Spawning areas are located on sites of infiltration of the descending river waters in a subchannel stream (Parpura, 1991; Fukushima, 1994). According to the main characteristics of spawning area of taimen, chinooks or pink salmon are similar to that (Leman, 2003).

Density of spawning taimen, as well as other salmon, is higher on sites with the increased tortuosity (length of 50 m) (Fukushima, 2001). The number of redds is indifferent to the hanging vegetation, but it is more in zones with the wood remains and the cut coast (Mori et al., 1997).

The larvae of a taimen 27-29 mm long which have left redds and weighing 140-290 mg run away with current. At the end of summer juveniles live in the region of spawning areas and in several km below. They form flocks which keep in the warmed-up shallow water at sandy and pebbly spits when from there was already gone away of juveniles of other salmon. Keep in puddles between large pebble where depth often doesn't exceed 3-5 cm, and the water temperature 1-3 C higher, than on a midstream (Krykhtin et al., 1964; Gritsenko, Churikov, 1977; Gritsenko, 2002). Important for juveniles existence of stagnant zones in channels and creeks where they can take cover during unexpected summer floods (Fukushima, pers. comm.).

In the fall  fingerlingswere most numerous in3 orders tributaries. The size of fishes has been positively connected with depth of water and size of shelters. The juveniles occupy the same dwellings, as masu's juveniles, but use different types of a forage (Sagawa et al., 2003).

The juveniles since one-year-old age occupy big whirlpools and rather deep reaches. A typical station of juveniles – a whirlpool from 20-40 to 100-150 m long with rather slow current, the silted pebble or sand at the bottom, with the bushes hanging or fallen off to the river at the washed-away coast. Avoids sites with frequent alternation of reaches, whirlpools and rifts (Gritsenko, Churikov, 1977; Gritsenko, 2002).Takes positions in a deep-water zone of  slow current at the bottom, in shelters (Zhivoglyadov, 2004).Prefers  complexes similar lakes in the meandered courses with dense riparian vegetation.(Honda et al., 2010b; Honda et al., 2012). In many rivers the areas only in the lower current are suitable for feeding of juveniles. In general in the small rivers the area used by juveniles of a taimen for feeding is less than feeding area of juveniles of a loach, kundzha, masu or coho salmon (Gritsenko, 2002).

Distribution of adults in the Hokkatdo rivers was studied by methods of tagging and acoustic telemetry. In the summer they choose big holes with a slow current and with a shadow or shelters. The quantity of individuals positively correlates with percent of shadow or shelters, the maximum size of body – with area of hole bottom. These results show importance of preservation of large deep holes with shadiness or shelters and possibility of fishes to migrate up (inflows 1,2,3 orders) and down (4 order) through river system (Sagawa et al., 2002).

Total number marked has shown to taymen extensive use of river system, and upper courses and lower reaches. 20% of fishes inhabited consistently habitats in headwaters from spring to fall, and 40% have shown wide use of the whole river system above and below. 39% of marked fishes used 2 or more main inflows of the river, 6% used only the main course. Adults show high plasticity of behavior, fishes can choose habitats, based on their own requirements (Honda et al., 2012).

The Sakhalin taimen doesn't go far to the sea, like the Pacific salmon. His movements between fresh and salty water remind those as semi-anadromous – bulltrouts and kundzha. As a rule, in the sea he keeps directly at coast, sometimes forming leaky congestions in the places convenient for feeding. Large individuals are detained in the brackish lakes by that more than are more closely connected with the sea (Zavgorodnyaya et al., 1964).

In October the taimen begins to come into the rivers on wintering, on distance to several tens kilometers. During winterings the bulk of a taimen accumulates in holes separately from other species of fish (Gritsenko, Churikov, 1977; Gritsenko, 2002).

Characteristic and analysis of sexual, age, social and spatial structure of populations

The ratio of sex in populations of a taimen is close to 1:1.

The maximum noted age – 24 years. In the majority of modern populations the age structure is deformed as the individuals who aren't reaching reproduction period are withdrawn.

During the early period of life cycle of a larva lead a gregarious life in shallow water, then pass to territorial distribution in the deep places with shelters. During spawning males hold tournaments. After spawning individuals form in estuaries of congestion. Congestions are characteristic also of winterings in large holes of the lower current of the rivers and in lakes.

In all other cases of an individual lead the single or poorly aggregated life.

Characteristic and analysis of reproduction and mortality

 In the rivers of the Hokkaido island  the Sakhalin taimen ripens in 4-6 years with a length of 40-70 cm, in the rivers of Primorye - with a length not less than 75 cm, at the age of 8 - 10 full years. In the lake Ainu according to 70-80 cm, 3-6 kg of weight, at the age of 6-7 years. In the north of Sakhalin average age of achievement by puberty taimen – 10-11 years. Males begin to ripen for a year before females (Krykhtin et al., 1964; Yamashiro, 1965; Kimura, 1966; Kawamura et al., 1983; Parpura, 1990; Fukushima, 1994; Gritsenko, 2002).

In the rivers of Northern Primorye adult females spawn every two years; only 25-30% of mature producers participate in reproduction (Parpura, Semenchenko, 1989). On Sakhalin the absolute fertility of a taimen in the Nabil' River averaged 8300 eggs (3380-17680), and in the river Bogataya – 10880 eggs (4670-16970) (Gritsenko, Churikov, 1977; Gritsenko, 2002). To the Peya River (Primorye) this indicator was 11405 eggs (5200-16620). Between length of a body of females and fertility there is a positive linear dependence (Gritsenko, 2002). The relative fertility of seaside fishes in comparison with Sakhalin was much higher (Parpura, 1990).

Representatives of all forms of a taimen spawn in the rivers during the early-spring period. Spawning takes place right after recession of a snow flood since the beginning of April (Hokkaido) until the beginning of June (North of Sakhalin). Females have an adaptation to the choice of the suitable place for construction of a nest depending on water level in the river. Average daily water temperature during spawning reaches 4-7 C (Krykhtin et al., 1964; Parpura, 1991; Fukushima, 1994).

As well as all salmon, digs in eggs in soil, arranging spawning redds (Kimura, 1966). At the same time females right after spawning dig in a nest with eggs that pulls together them with the Pacific salmon (Esteve et al., 2009; Esteve, 2012). Tops of nests with the laid eggs have the V-shaped form. Quantity of nests on average 3 on one redd, it is possible to estimate in a redd form. False redds of other form meet. The quantity of nests and eggs in them and also depth of laying of eggs in soil correlate with a length of a female. The carried-out opening of redds has given the following figures – on 11-920 eggs in a nest (an average 546,7). It is possible to recognize quantity of females – 1/3 from quantity of spawning nests (Edo et al., 2000). However, according to other research (Fukushima, 1994) nests in a redd 1-2, on average 1,8. The measured size of spawning redds 145 x 84 cm (Fukushima, 1994) and 227 x 122 cm (Edo et al., 2000).

The unusual fact has noticed O. F. Gritsenko (2002). At for the first time the ripening females scales before spawning don't plunge rather deeply into skin that does doubtful a possibility of the device by them nests in soil. At repeatedly spawn of individuals prespawning changes of integuments are expressed strongly and quite protect fish from injuries when digging soil.

Diameter of mature egg is from 4 to 6,4 mm, the average mass of egg – from 120 to 164 mg (Krykhtin et al., 1964; Gritsenko, 2002). The stage of a peephole and relative tolerance to physical impacts comes at achievement of 200 degree days. Egg develops quickly, mass exit comes approximately in month (320 degree days) and an exit from redds at achievement about 500 degree days (Parpura, 1991).

Possibly, in natural populations mortality of fingerlings is extremely high. Only those individuals who safely overwinering survive, and to age 1+ have switched to the second summer of life on predatory type (Zolotukhin, Semenchenko, 2008).

 The coefficient of natural mortality calculated by Baranov-Tyurin's method (Tyurin, 1963), was equal to 16-19%. Dynamics of an mass is calculated – she reaches a maximum in 11-12 years when his mass maturing comes to an end. From here trade measure - 80 cm is proposed. Coefficients of the general mortality for river Bogataya – 16,5%, for the Nyysky bay – 58,5% are exceeded three times by coefficient of natural mortality that already then testified to unreasonably big trade load and need of introduction of restrictive measures of his trade (Gritsenko, Churikov, 1977).

(Tyurin P. V. Biological justification of regulation of fishery on internal reservoirs. M.: Pishchepromizdat, 1963. 120 pages)

 Mobility, seasonal migrations

Migrations of fishes usually are explained by difference in amount of food between sea and river habitats (Arai et al., 2004). In the river a taimen generally moved down in the spring, up in the summer and down in the fall. Influence of water temperature is noted – fishes aspire towards cold water (Honda et al., 2009; Honda et al., 2012).

The history of migrations was studied by method of definition of a ratio of Sr/Ca (strontium/calcium) in the otolits of adult fishes (Arai et al., 2004; Suzuki et al., 2008; Arai, 2010; Honda et al., 2010a; Suzuki et al., 2011; Zimmerman et al., 2011). All studied 8 taymen of the lake Ainu represented a typical anadromous form (Arai et al., 2004). To keep individuals in live, the distinctive sign of anadromous fishes from river – guanin pigmentation of scales at the basis of a tail fin is offered (Edo et al., 2005).

Spawning and in the south of Sakhalin takes place in the rivers of Hokkaido at the end of April - the beginning of May, in the north – from May 20 to June 5. In the early spring mature individuals roll down in the sea on feeding and in May come into the rivers for spawning again (Gritsenko et al., 1974; Gritsenko, Churikov, 1977). However, the short-term slope before spawning isn't confirmed by other observations.

The repeated slope of fishes after spawning usually happens in July, and from August to November they come into fresh water again. After a slope both juveniles, and individuals after spawning keep near mouths of the rivers or in lakes and estuaries. The taimen doesn't make extended sea migrations what numerous calling fresh water during a summer feeding.

In the large rivers juveniles of taimen are acquired up to 5-7 years, reaching length of 40-50 cm. The limitation of places for feeding in the small rivers promotes a juveniles slope at earlier age (2-4 years) and at the smaller sizes (10-25 cm) (Krykhtin et al., 1964; Zavgorodnyaya et al., 1964; Gritsenko et al., 1974; Gritsenko, Churikov, 1977; Gritsenko, 2002).

At the end of September - the beginning of November the taimen comes back to a wintering to lower reaches of the rivers or the lake. In lower reaches of the small rivers only small individuals winter.

Unlike the Pacific salmon, communication of a taimen through passage with sea waters not so strong, many fishes leave to lower sections of the rivers, to estuaries and sea gulfs, and the high sea don't reach. Moreover, an essential part of individuals from populations of the large rivers puts out not every year to sea and remains for all summer in fresh water. On duration and extent of migrations the Sakhalin taimen reminds not salmon, but semi-anadromous fishes more – bulltrout or kundzha.

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