Salmo trutta caspius, Kessler

Taxonomic description of subspecies

Snout pointed. Color: light on the sides, dark grey on the back; black cross-like or irregular spots on the sides. Teeth well developed. Scales in lateral line 177 - 133; D III 10-11, A II-III 8-9. Pyloric caeca 47-57, gill rakers on first gill arch 21-24, vertebrae 54-58.
Intraspecific forms. Caspian trout forms local stocks confined to certain rivers (Kura, Samur, Yalama, and other), which differ in morphological features, age of maturity, spawning interval (Derzhavin, 1949; Kazancheev, 1981). Dorofeeva (1967) defined Kura trout (kumzha) as a separate subspecies Salmo trutta caspius Kessler, and united the rest Caspian Sea trouts into the second subspecies Salmo trutta ciscaucasicus Dorofeeva, 1967.
Related forms: S. trutta labrax Pallas, 1814 � Black Sea trout;
S. trutta ezenami Berg, 1948 � Eizenam trout

Distribution of subspecies within the Caspian Sea

Occurs commonly at the western coast of the Caspian, from the Terek river to Sefid-Rud, seldom found in the North Caspian. Spawns in the Terek, Kura, Sefid-Rud and other minor rivers of the western and southern coasts of the Caspian Sea.
Status as per International Red Data Book: N/A
Status as per National Red Data Books: introduced into Red Data Books of Kazakhstan and Turkmenistan. 
First record for the Caspian: Pallas, Reise, 1771
Redescription of subspecies: Dorofeeva, 1967

General characteristics of subspecies

Ecologo-taxonomic group. Nekton. Anadromous form
Origin. Berg (1948) assumed the Arctic origin of theCaspian trout. Derzhavin (1929) supposed that this trout had originated from freshwater form.
Distribution. Caspian Sea endemic
Habitat. Coastal areas, depths up to 40-50m
Migrations. Caspian trout migrates for long distances, from Iranian shores to Dagestan coast. Fish tagged at the estuaries of Yalama and Keyranchai rivers, were caught 300 km southward from their release location.

Relation to abiotic environmental factors

Relation to salinity. Euryhaline brackishwater subspecies
Juveniles aged 6 months tolerate water salinity up to 6�, aged 14-16 months� up to 12�. Adult fish occurs at maximum Caspian salinity of 13�.
Relation to temperature. Stenothermic cool-water subspecies
Vertical distribution. Stenobathic subspecies restricted to 40 - 50m isobathic curve
Relation to oxygen conditions. Oxyphilic subspecies. Inhabits areas with high oxygen concentration.
Relation to fluctuations of the sea level: N/A

Feeding

Feeding type. Predatory subspecies
Feeding behavior. Preying
Food spectrum. The basic food items for juveniles are crustaceans, for adults � sprats/ kilka, silverside/ atherina, and shad juveniles.
Food supply. Unlimited
Quantitative characteristics of feeding: N/A

Reproduction

Reproduction type. Sexual
Reproduction areas. Riffles with sand and gravel river beds.
Before regulation of the Kura stream, spawners entered the river abundantly, migrated upstream to the headwaters of Aragvi, Alazani, Akera rivers up to 1,000 km. At present, single trouts from Kura population reach the dam of Varvarinskaya hydroelectric power station (600 km from the mouth). Local populations spawn in Lenkoranchai, Astarachai, Terek, and Samur.
Terms of reproduction. Spawning migration to Kura takes place from November till February. The temperature range of trout migration is rather wide, though the majority (appr.75%, immature fish with undeveloped gonads) enters the rivers at a comparatively low temperature, 8.2 � 12.8^oC in November-December. Spawning takes place only a year later, starts in October and completes in early January. Eggs are released on the bottom and buried in substrate. Incubation period continues for 30-50 days. Afterwards, spawners either die (in Kura river), or return to the sea (trouts, which spawn in the other rivers).
Fecundity. Fecundity value is moderate, similar to the other salmonids; it varies from 2.1 to 13.5*10³ eggs; in Kura population � 9.5*10³ eggs, in Yalama and Lenkoran populations � 7.1*10³ eggs.
Limiting factors

• Virtually complete lack of natural spawning
• Limited rate of artificial/hatchery reproduction
• Rampant poaching

Life history and development

Life history stages. Three early developmental periods are defined: embryonic, larval, and fry. Fry period consists of two stages, downstream migration from the river and feeding at sea.
Relation to environmental factors. This fish is highly sensitive to environmental changes, specifically, to pollution.
Age of maturity. Under conditions of natural reproduction, maturity is reached at the age of 4-9 years in Kura River, 3-5 years in Samur, seldom at 2 years (in Yalama). Males sometimes mature at the age of 1 year under riverine conditions.
Thermal conditions of development. Eggs develop at temperature 5.8-12.8^oC.
Quantitative characteristics of growth. During the first years, growth rate is high: juveniles in Keyranchai river attain 13.8-22.7 cm length and 24-102 g weight by winter. The main growth occurs in the sea. . The average weight of trout from Kura river is about 13 kg, from the Volga - 8.7 kg, Terek - 7.2 kg, Samur - 3.9 kg, Keyranchai - 2.6 kg, Yalama - 2.4 kg. The maximum recorded weight of Kura trout amounted to 51 kg.

Age-size characteristics of the Caspian trout from different habitats

Structural and functional population characteristics

Sexual structure. Females contribute to 90% of fish in commercial catches.
Age-size structure. In 1940-1950, size varied from 40 to 130 cm, 92.6 cm in average, weight - from 9.4 to 29.5 kg, 17.7 kg in average, age of fish was up to 10 years old. At present, size declined to 70-96 cm, weight � to 8-9 kg. No individuals older than 6 years are found in catches, the base stock is represented by 3 - 6-year-old fish.
Quantitative characteristics. Low-abundant subspecies.
Population trends. Currently, the abundance declined drastically as a result of illegal fishing.

Interspecific relations

Feeds primarily on pelagic fish of little economic value. Impact on the ecosystem is insignificant.

Importance of subspecies to bioresources production of the Caspian Sea

Economic significance of subspecies. Valuable commercial fish
Commercial characteristics of subspecies, catches. Annual catches in 1936-1939 peaked 410-620 tons. At present, the registered catch is several dozens specimens.
Fishing gears and fishing zones. Fishing is conducted during spawning migrations in rivers with beach seines and floating nets.

Impact of fisheries on the population status

Inessential
Human impact/Threats

• Pollution resulting from oil production
• Reduction of spawning areas as a result of economic activities
• Illegal fishing influences the population significantly

Conservation measures

• Enhance the scale of hatchery production as the basic way to species conservation under conditions of lack of natural reproduction
• Control on the sea pollution and illegal fishing

References

Abdurakhmanov, Yu.A. 1962. Freshwater fish of Azerbaijan. Azerbaijan SSR AS Publishers pp. 57-62
Berg L.S. 1923. On the origin of the northern elements in the Caspian fauna. Selected works. Vol. 5, p.143
Berg, L.S. 1948. Freshwater fish of the USSR and adjacent states. Vol. 1. pp. 242-249.
Derzhavin, A.N. 1929. Kura fisheries and Mugani amelioration. News of Baku Ichthyological Laboratory. Vol.2, 1.
Derzhavin, A.N. 1956. Kura fisheries. Azerbaijan SSR AS Publishers pp. 26-28
Dorofeeva, E.A. 1967. Comparative-morphological principles of the systematics of east European salmons. J. Voprosy Ikhtiologii (Problems of Ichthyology). Vol. 1, 1:3-18. 
Kavraiskii, F.F. 1897. Salmoniformes of the Caucasus and Transcaucasus. Caucasian Museum Publishers. Issue 1. Tiflis.
Kazancheev, E.N. 1981. Fish of the Caspian Sea. Light Food Industry pp. 56-59
Tamarin E.N., I.B. Kyazimov and Z.M. Kuliev, 1989. Caspian salmon. In: Caspian Sea. Ichthyofauna and commercial stocks. Nauka Press pp. 112-118

Compiled by:

Z.M.Kuliev (AzerNIRKh, Baku, Azerbaijan)
D.B.Ragimov (Institute of Zoology AS Azerbaijan, Baku)