Caspian Lamprey Caspiomyzon wagneri (Petromyzontidae): A Review of Historical and Modern Data

Abstract

Historical and modern data on the taxonomic status, external morphology, distribution features, biology, economic importance, history of fishing, conservation status, and protection measures for the Cas-pian lamprey Caspiomyzon wagneri are presented. The Caspian lamprey is an endemic species and the only anadromous lamprey in the Caspian Sea basin. The abundance of this species has declined everywhere; as a result, the species nowadays is on the verge of extinction. Being an important target of fishing in the past, the Caspian lamprey has completely lost its economic importance. It is subject to serious threats of an anthropo-genic nature. Constructing of locks and dams without fish passages that prevent spawning migrations, water pollution, dredging and mining of sand and gravel leading to the destruction of habitats and spawning grounds, poaching and lack of legal protection mechanisms are the main threats for this lamprey species.

Full text

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ISSN 0032-9452, Journal of Ichthyology, 2022. © Pleiades Publishing, Ltd., 2022.
Caspian Lamprey Caspiomyzon wagneri (Petromyzontidae):
A Review of Historical and Modern Data
A. M. Orlova, b, c, d, *, R. M. Barkhalovb, c,f, N. I. Rabazanovb,
S. Yu. Orlovaa, e, g, and A. F. Sokol’skiih
a Shirshov Institute of Oceanology, Russian Academy of Sciences, Moscow, Russia
b Caspian Institute of Biological Resources, Dagestan Federal Research Center,
Russian Academy of Sciences, Makhachkala, Russia
c Dagestan State University, Makhachkala, Russia
d Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences, Moscow, Russia
e Russian Federal Research Institute of Fisheries and Oceanography, Moscow, Russia
f Dagestan State Nature Reserve, Makhachkala, Russia
g Vavilov Institute of General Genetics, Russian Academy of Sciences, Moscow, Russia
h Astrakhan State University of Architecture and Civil Engineering, Astrakhan, Russia
*e-mail: orlov@vniro.ru
Received December 20, 2021; revised February 5, 2022; accepted February 7, 2022
Abstract—Historical and modern data on the taxonomic status, external morphology, distribution features,
biology, economic importance, history of fishing, conservation status, and protection measures for the Cas-
pian lamprey Caspiomyzon wagneri are presented. The Caspian lamprey is an endemic species and the only
anadromous lamprey in the Caspian Sea basin. The abundance of this species has declined everywhere; as a
result, the species nowadays is on the verge of extinction. Being an important target of fishing in the past, the
Caspian lamprey has completely lost its economic importance. It is subject to serious threats of an anthropo-
genic nature. Constructing of locks and dams without fish passages that prevent spawning migrations, water
pollution, dredging and mining of sand and gravel leading to the destruction of habitats and spawning
grounds, poaching and lack of legal protection mechanisms are the main threats for this lamprey species.
Keywords: jawless fishes, taxonomic status, morphology, distribution, biology, protection, threats
DOI: 10.1134/S00329452220 40166
INTRODUCTION
Lampreys occupy a special position in aquatic eco-
systems. They serve as intermediate and reservoir
hosts of nematodes, being the main sources of infec-
tion for freshwater and anadromous fish, which they
parasitize (Butorina, 1988). Parasitic lamprey species,
attacking fish, cause great damage to fish stocks,—first
of all, to important commercial objects such as
salmon, herring, and cod (Birman, 1950; Myagkov,
1983; Orlov et al., 2009; Orlov, 2016). This may cause
major environmental catastrophes, for example, regis-
tered in the Great Lakes basin (USA) in the 1930s
(Birznek, 1967). Lampreys themselves serve as a food
for various animal species, such as fish, birds, marine
and terrestrial mammals (Orlov et al., 2009; Orlov,
2016; Clemens et al., 2019).
Some lamprey species are of commercial interest
(Almeida et al., 2021). Namely, in the first half of the
XX century, lamprey fishing was well developed in the
USSR, they were caught in the basins of the Baltic,
White, Barents, and Caspian seas, as well as in the
Amur River (Ivanova-Berg, 1932; Manteifel, 1945;
Bogaevskii, 1949). In addition to their use as food
products, lampreys were used to obtain vitamin, fat,
protein food for cattle and poultry, and fishmeal
(Close et al., 1995). Ammocoetes (lamprey larvae) are
good bait for catching various fish species, they may
also serve as an ideal food for rearing juvenile salmon
(Scott and Crossman, 1973; Close et al., 1995). Lam-
preys are also of particular interest for aquaculture,
both in terms of obtaining raw materials for the pro-
duction of delicacy food products, and for implement-
ing projects to restore stocks of endangered species
(Robinson et al., 2002).
Lampreys are also of pharmaceutical interest as
potential sources of raw materials for the production of
anticoagulant medicines; the specimens that died after
spawning serve as a source of biogenic elements in oli-
gotrophic water bodies (Close et al., 1995). Due to the
accumulation of heavy metals (including mercury) in

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ORLOV et al.
lamprey organs and tissues, some species may serve as
bioindicators (Shooshtari et al., 2011).
In recent decades, the abundance of many lamprey
species has significantly decreased under the inf lu-
ence of climate change and increased anthropogenic
pressure. More than half of the lamprey species are
currently classified as vulnerable, endangered, or
extinct, at least in some part of their range (Renaud,
1997). The Caspian lamprey Caspiomyzon wagneri
Kessler, 1870 is one of these species; it is endemic to
the Caspian Sea and the rivers of its basin (Freyhof,
Kottelat, 2008). Despite the fact that its regular study
has begun more than a hundred years ago, at early XX
century (Pravdin, 1913a, 1913b), many issues of the
life cycle of the Caspian lamprey still remain poorly
understood (Lucas et al., 2020).
Meanwhile, since 2005, the Caspian lamprey has
been intensively and comprehensively studied in Ira-
nian waters (South Caspian Basin), so numerous sci-
entific publications appeared, including two major
review papers (Coad, 2016; Nazari et al., 2017). At the
same time, information on the distribution and biol-
ogy of the Caspian lamprey in the rest of the species
range is still fragmentary and scattered, often pub-
lished in local sources that are difficult to access for a
wide range of specialists.
The purpose of this review is to summarize infor-
mation about the distribution, biology, commercial
use, and protection of the Caspian lamprey in the
northern and central Caspian Sea basin.
TAXONOMIC POSITION
In accordance with recent ideas, modern lampreys
belong to the ancient group of lower vertebrates of the
superclass Agnatha, class Petromyzontidae, repre-
sented by single order (Petromyzontiformes). Previ-
ously, it was believed that this order included a single
family, Petromyzontidae (Hardisty, 1963; Holčík,
1986; Kottelat et al., 2005). Currently, it includes three
families: Petromyzontidae (8 genera and 43 species,
Northern Hemisphere), Geotriidae (2 genera, 3 spe-
cies, Southern Hemisphere) and Mordaciidae (1 genus,
3 species, Southern Hemisphere) (Van der Laan,
Fricke, 2022). At the same time, the species diversity
of lampreys remains insufficiently studied both in the
world ichthyofauna (Hardisty, 1986; Renaud, 2011;
Maitland et al., 2015; Potter et al., 2015; Tutman et al.,
2017; Clemens et al., 2020; Riva-Rossi et al., 2020;
Pereira et al., 2021) and in the waters of the Russian
Federation (Levin et al., 2016). Four new lamprey spe-
cies have been described in the last decade (Van der
Laan and Fricke, 2022).
Representatives of the Lampetrinae subfamily,
which includes six genera, inhabit the basins of the
Mediterranean, Black, and Caspian seas. Representa-
tives of four genera are found in the central part of
Eastern Europe (the European part of Russia). Spe-
cies of the genera Lampetra (the northeastern part of
the Atlantic Ocean, the southern coast of the Black
Sea, and the rivers of Europe) and Lethenteron (the
basins of the White and Barents seas, the Arctic Ocean
and the north Pacific Ocean) are represented by both
migratory (anadromous, potamodromous) and fresh-
water (resident) ecological forms. The genus Caspio-
myzon (basin of the Caspian Sea and the rivers of
Greece) includes one species of anadromous lamprey
C. wagneri and two species of residential lampreys,
C. graceus (Renaud and Economidis, 2010) and
C. hellenicus (Vladykov, Renaud, Kott et Economidis,
1982) living in the rivers of Greece. On the contrary,
the genus Eudontomyzon (rivers of the basins of the
Black, Azov, and Caspian seas) is currently repre-
sented only by freshwater forms (Holčík, 1986; Levin,
Holčík, 2006; Renaud, 2011; Potter et al., 2015; Tsim-
balov et al., 2015; Artamonova et al., 2016; Nazari et
al., 2017; Zvezdin et al., 2021). Based on the results of
a comparative morphological analysis, it was earlier
established that the genus Caspiomyzon is a sister g rou p
to five other genera (Tetrapleurodon, Entosphenus,
Eudontomyzon, Lampetra, and Lethenteron), which
include both Eurasian and American species (Gill
et al., 2003). This study revealed a basal polytomy and
failed to determine the relationship between the fami-
lies Geotriidae, Mordaciidae, and Petromyzontidae.
Recent molecular genetic studies using multiloci phy-
logeny (Pereira et al., 2021) report that the family
Petromyzontidae is monophyletic, it comprises two
related groups, one of which combines the genera Cas-
piomyzon, Ichthyomyzon, and Petromyzon, and the
other one, the rest of the lamprey species of the North-
ern Hemisphere. At the same time, the first genus in
its clade occupies the most basal position, which may
indicate its more ancient origin. This confirms the
results of previous studies regarding the old origin of
the Caspiomyzon genus, which has existed at least since
the Miocene (Meek, 1916; Holčík, 1986; Kucher yavyi
et al., 2016). According to recent genetic studies
(Pereira et al., 2021), a divergence of C. graceus and
C. hellenicus from C. wagneri occurred ~7 million
years ago.
EXTERNAL MORPHOLOGY
AND COLORATION
Like it is observed in all lampreys, the body of the
Caspian lamprey is eel-like, scales and paired fins are
absent (Fig. 1a). There are two dorsal fins, which are
separated by a gap, the second dorsal fin smoothly
transforms into the caudal fin. There are seven gill
openings on each side of the body (Fig. 1b). The skin
is covered with poisonous mucus. The mouth is a fun-
nel-shaped sucking disc with blunt horny teeth. One
small, blunt, rounded tooth locates at the place of the
maxillary plate (Fig. 1c). The mandibular plate usually
bears five blunt teeth. Anterior lingual plate without
depression in the middle. The labial teeth are usually

JOURNAL OF ICHTHYOLOGY 2022
CASPIAN LAMPREY CASPIOMYZON WAGNERI (PETROMYZONTIDAE) 3
arranged in radial rows. The sides of the mouth open-
ing are bordered by 11 internal labial teeth, which are
never bifid. There are three stamens directed into the
pharyngeal cavity at the anterior end of the gill tube
(Kazancheev, 1981; Renaud, 2011; Coad, 2016).
Females are larger than males and have a smaller
urogenital papilla. During spawning migration, the
lamprey undergoes certain morphological changes,
which are partly related to sex; in particular, the size of
the fins increases, the dorsal fins almost join at the
base in males, and the body coloration changes.
Ammocoetes are pale gray to yellowish with a white
belly (Ginzburg, 1936; Agamaliev, 1971b; Holčík,
1986; Renaud, 2011; Coad, 2016). Pre-spawning
adults are dark gray on the back and silvery white on
the sides (Agamaliev, 1971b; Holčík, 1986; Nazari,
Fig. 1. The Caspian lamprey Caspiomyzon wagneri from the Volga River basin: (a) appearance, (b) anterior part of the body,
(c) sucking disc (photo by E.V. Nikitin), (d) specimen from the Shirud River in spawning coloration (photo by H. Nazari).
(a)
(b)
(c) (d)

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JOURNAL OF ICHTHYOLOGY 2022
ORLOV et al.
2012). Spawning adults become black on the back and
sides with a gray abdomen covered with dark oval
spots, or turn golden (Pravdin, 1913a; Holčík, 1986)
(Fig. 1d). Sometimes, sexually mature males with a
greenish color are found at the mouth of the Shirud
River (Nazari, 2012; Nazari et al., 2017).
DISTRIBUTION AND LIFESTYLE
The Caspian lamprey is endemic to the Caspian
Sea and the rivers of its basin (Fig. 2), flowing into the
northern, western, and southern parts of the coast in
Russia, Azerbaijan, Iran, Turkmenistan, and Kazakh-
stan (Holčík, 1986; Freyhof, Kottelat, 2008; Zvezdin
et al., 2021). There are no data indicating the existence
in the past of any phylogenetically closely related
forms in the basins of the Black and Azov seas, so the
range of the Caspian lamprey is limited to the Caspian
Sea, which is generally not typical for endemic Cas-
pian fish (Kottelat et al., 2005; Naseka and Diripasko,
2008; Bogutskaya et al., 2013).
Previously, the Caspian lamprey entered the Volga
River and its tributaries, Ural, Terek, Samur, and Kura
rivers, the rivers of the Lankaran region (Azerbaijan)
and further along the Iranian coast, including the
Sefidrud and Babol rivers, in large numbers for breed-
ing. Before the construction of a cascade of hydroelec-
tric power plants (HPPs) on the Volga River (late
1930s–early 1940s), its river system was almost com-
pletely populated by the Caspian lamprey (Zvezdin
et al., 2021), the spawning migrations of this species
exceeded 2600 km. In the Volga River, the upstream
migrations ended nearby the city of Kalinin (nowa-
days, Tver) and in the mouth of the Tvertsa River (left
tributary of the Volga River); along the Kama River, it
reached the rivers Chusovaya and Vishera, along the
Oka River, the mouth of the Moskva River; along the
Kura River, it reached its upper reaches (Mtskheta)
and entered its tributaries (Alazan, Aragvi, Araks, and
others); along the Terek River, it reached the Baksan
River, and along the Ural River, the city of Orenburg
(Berg, 19 48; Agamaliev, 1971b; Kazancheev, 1981;
Atlas…, 2002; Ivanov, Komarova, 2012). Varpak-
hovskii (1886, 1891) indicated the Caspian lamprey as
part of the ichthyofauna of the Kazan and Nizhny
Novgorod provinces in the Pyana (tributary of the
Sura River), Kama, and Oka rivers. Artaev et al. (2013)
noted that this species spawned up to the Kama River
and in the mouth of the Vyatka River before the con-
struction of dams on the Volga River. Magnitskii
(1928) first observed the mass entry of the Caspian
lamprey into the Sura River in 1926, when the spring
flood reached its secular maximum. That year the
lamprey has reached the areas located upstream the
city of Penza in the Sura River up to the dam near the
city of Kuznetsk. At the same time, it was registered in
the tributaries of the Sura River (Penza, Inza, Aiva,
V’yas, and Insar rivers). Migration routes in the Volga
River were first blocked by dams in its upper reaches
(the section between the source of the Volga River and
the confluence with the Oka River, and then com-
pletely blocked after the construction of the Volga
hydroelectric power station (Ginzburg, 1969, 1970;
Holčík, 1986; Yakovlev et al., 2001; Atlas…, 2002).
Nowadays, only single specimens of the Caspian lam-
prey are recorded upstream of the dam of the Volgo-
grad Reservoir (Shashulovskii, Ermolin, 2005; Shashu-
lovskii et al., 2016), it is absent when moving further
upstream, in the Saratov Reservoir (Ermolin, 2010).
Along the Kura River, lamprey migration is limited to
the Mingachevir hydroelectric power station (below
the Varvara dam), along the Terek River, it reaches the
Baksan River (Kazancheev, 1981; Holčík, 1986; Shi-
khshabekov et al., 2008; Ivanov and Komarova, 2012;
Orlov et al., 2021). In the tributaries of the Terek River
(Sunzha, Argun, and Dzhalka rivers), the Caspian
lamprey has recently been found quite often according
to surveys of amateur fishermen.
The Caspian lamprey leads a migratory lifestyle,
living both in the sea and in rivers, without forming
freshwater populations or a freshwater resident form
(Berg, 1948). However, it is assumed that there is also
a purely marine form in the Caspian Sea, which
spawns in the coastal zone of the western coast of the
Caspian Sea and has a spotted coloration characteris-
tic of sea lampreys (Nikitin, 2016). There is no infor-
mation on the depth-dependent distribution during
the marine life period, since the Caspian lamprey liv-
ing near the bottom in the sea is practically inaccessi-
ble for observations.
HABITAT AND MIGRATION
The Caspian lamprey lives in rivers at the larval
stage, while adults feed in the sea. The duration of the
larval stage is estimated as 3 years in the Volga River
and 2–4 years in the Kura River basin (Agamaliev,
1971a). Young individuals transformed in the river
migrate to the sea to feed (Holčík, 1986; Kottelat and
Freyhof, 2007; Renaud, 2011; Nazari et al., 2017).
Lamprey larvae live in bottom sediments. Their habi-
tats change as they grow. As the linear sizes increase,
the ammocoetes, preferring earlier a substrate with
fine-grained sand with a small amount of clay and
detritus, seek for a substrate containing silty sand with
a large amount of plant debris and macrophytes
(Nazari et al., 2017; Clemens et al., 2020). In the
Aldzhiganchay River (a tributary of the Kura River),
the densest communities of ammocoetes on the bot-
tom are found at the 30–85 cm depths, while in the
Volga River, these are usually the depths of 6–8 m
(Agamaliev, 1971a; Coad, 2016). In addition, in the
Volga River, the maximum depth of ammocoetes'
habitat has been recorded, 22 m from the water surface
(Ginzburg, 1970). Ammocoetes prefer areas of river
bends with moderate flow, where they burrow into the
river substrate for 1–2 cm. They may also be found in
the central part of the riverbed, in creeks, canals, and

JOURNAL OF ICHTHYOLOGY 2022
CASPIAN LAMPREY CASPIOMYZON WAGNERI (PETROMYZONTIDAE) 5
bays. Lampreys at the stage of metamorphosis prefer
the sites that locate deeper, characterized by a higher
flow rate, lower water turbidity, and without macro-
phytes (Ginzburg, 1970; Agamaliev, 1971a; Holčík,
1986).
Most information on adults relates to the spawning
migration stage; very limited data are available for
other stages of the life cycle, especially the marine
phase. The habitats of adults in the Caspian Sea are
unknown, although some individuals were caught at
depths of 600–700 m off the Iranian coast (Jolodar
and Abdoli, 2004).
The spawning migration of the Caspian lamprey is
predetermined by the hydrological regime of the rivers
and by environmental conditions. Spawning migra-
tions upstream the Volga River exceeded 2600 km
(Berg, 1948); however, the dams prevent migrations
nowadays (Moser et al., 2015). The lamprey migrates
Fig. 2. Distribution map of the Caspian lamprey Caspiomyzon wagneri: ( )—lost parts of the range, ( )—modern range (accord-
ing to: Berg, 1948; Kazancheev, 1981; Freyhof and Kottelat, 2008; Ivanov and Komarova, 2012).
BLACK SEA
CASPIAN SEA
Volga R.
Ural R.

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JOURNAL OF ICHTHYOLOGY 2022
ORLOV et al.
in flocks (Fig. 3). Larger lampreys are able to migrate
at greater speeds and to make longer migrations. How-
ever, smaller individuals are the first to reach the river
mouths, probably, they start migrating to spawning
grounds earlier. The speed of lampreys varies from 1.9
to 15.9 km/day (Kazancheev, 1981; Ivanov and Koma-
rova, 2012), although Pravdin (1965) has indicated
that it can travel up to 50 km per day in the Volga
River. Adults at the age of 4–6 years rise upstream for
spawning to the Volga, Kura, Ural, Terek, Samur,
Sefidrud, and Gorganrud rivers, as well as into small
rivers of the western coast of the Caspian Sea (mainly
in the spring rivers of the Karasu River system) and its
southern coast. Migration takes place during two peri-
ods: in spring, from mid-March to mid-May (the most
intensive run is observed in April at a water tempera-
ture of 11–15°C), and in autumn, from the end of Sep-
tember to mid-January (the most intensive run takes
place in November–December at the water tempera-
ture of 11–16°C) (Kazancheev, 1981; Bogutskaya and
Naseka, 2004; Orlov et al., 2021). At the same time,
the period of spring migration is somewhat shorter
comparing to autumn one. The dates of the beginning
and end of the spawning migrations of the Caspian
lamprey vary in accordance to different authors and
for different rivers. In the Volga River, migration
begins in mid-September with the peak in mid-Octo-
ber–mid-December and ends at the end of December.
Peaks of migration are observed in late December–
February near the city of Saratov and in March near
the city of Kazan; in the Kura River, lamprey appears
from November to February, with a peak in Decem-
ber–January (Pravdin, 1913b; Berg, 1948; Abdura-
khmanov, 1962; Kazancheev, 1981; Holčík, 1986;
Nazari, 2012; Nazari et al., 2017). In the Kura River,
the Caspian lamprey often migrates attached to the
Caspian trout Salmo caspius Kessler, 1877 in the area
of gill covers (Berg, 1948; Agamaliev, 1971b; Coad,
2016), similar to other lamprey species (Tretyakov,
1949; Scott and Crossman, 1973; Orlov et al., 2007;
Guidelines…, 2018). During the period of upstream
migration, lampreys are inactive during the day, the
intensity of migration increases at night (Pravdin,
1965; Holčík, 1986; Nazari and Abdoli, 2010).
According to Nazari and Abdoli (2010), lampreys
migrate most actively in the dark, with a peak observed
approximately 2–3 hours after sunset. When moving
along a river channel, migrating lampreys never travel
along its entire width, but stay closer to the banks and
the bottom, preferring coastal or midway paths and the
areas with a flow velocity of 0.4–0.6 m/s
(Kazancheev, 1981; Coad, 2016). Sexually mature indi-
viduals migrating in autumn–winter in rivers, overwin-
ter in various substrates (among stones or in thickets).
During winter and spring, lampreys are found curled
into a ball under stones, they are almost unresponsive
to external stimuli (Askerov et al., 2001).
LAMPREY SIZES
The maximum length of the Caspian lamprey
ammocoete is 130 mm (Holčík, 1986; Renaud, 2011).
The total length and body weight of adults within the
species range vary from 190 to 553 mm and from 30 to
206 g, respectively (Holčík, 1986; Nazari et al., 2009,
2010; Nazari and Abdoli, 2010; Renaud, 2011; Nazari,
2012; Vatandoust et al., 2015; Abdoli et al., 2017;
Almeida et al., 2021). The average body length and
weight are 387 mm and 107 g (Lampreys…, 2015). At
the Dagestan coast of the Caspian Sea, the length of a
mature Caspian lamprey varies from 185 to 405 mm,
weight, from 30 to 130 g (Barkhalov et al., 2012). In the
southern part of the Caspian Sea, the minimum and
maximum length and weight of spawning individuals
are 271 and 492 mm, and 34.5 and 164.0 g, respec-
tively, in the Shirud River; 295 and 428 mm, 54 and
133 g in the Talar River (Nazari et al., 2010). The aver-
age total length of adult lampreys is 296 mm in the Sar-
dabrud River (Abdoli and Naderi, 2009).
Generally, females are slightly larger than males
(Ghasempouri, 1993). It is noted that the average
length of males and females in the Volga River is 360
and 369 mm, respectively; in the Kura River, it varies
from 426 to 432 mm for males and from 436 to 440 mm
for females (Smirnov, 1952; Agamaliev, 1971a, 1971b;
Kazancheev, 1981). In 2000–2001, spawners in the
Volga River population of the Caspian lamprey were
presented by females with average length of 372 mm
and a weight of 65.4 g and males with average length of
360 mm and a weight of 60.0 g (Nikitin, 2016).
AGE AND GROWTH
There are still no data on the age composition of
the Caspian lamprey, since the methodology for
determining its age has not been yet developed. The
larval stage of anadromous lampreys is the longest
stage of the entire life cycle (Dawson et al., 2015;
Moser et al., 2021; Quintella et al., 2021). Since meta-
morphosis with transformation into an adult and
migration from the river to the sea in the Caspian lam-
prey occurs in the fourth year of life, and the duration
of the marine period is at least 1 year and 5 months, it
is assumed that its age limit is 6 years (Holčík, 1986;
Kottelat and Freyhof, 2007; Renaud, 2011; Ivanov and
Komarova, 2012; Coad, 2016).
Information on the growth rate of the Caspian lam-
prey is also fragmentary and limited. Three age groups
of larvae with an average length of 31, 62, and 101 mm
have been recorded in the Volga River (Ginzburg,
1970); in Kura River, 2–4 age groups (Holčík, 1986;
Coad 2016). The marine life span of the Caspian lam-
prey is 17 months or slightly exceeds it (Holčík, 1986;
Kottelat and Freyhof, 2007; Renaud, 2011). Ammoco-
etes and adults are characterized by allometric growth
(Holčík, 1986). Negative allometric growth of lam-
preys migrating upstream of the Shirud and Talar riv-

JOURNAL OF ICHTHYOLOGY 2022
CASPIAN LAMPREY CASPIOMYZON WAGNERI (PETROMYZONTIDAE) 7
Fig. 3. Spawning run of the Caspian lamprey Caspiomyzon wagneri in the Shirud River (a–c) and sampling of the specimens (d)
(photo by H. Nazari).
(a) (b)
(c) (d)
ers was noted (Nazari et al., 2010). After metamorpho-
sis, there is a gradual reduction in the total length of
lampreys by an average of 22.3% within 5–6 months
(Renaud, 1982; Holčík, 1986). The total length and
weight of adult Caspian lampreys in the Shirud River
decrease in males and females by 6.8 and 18.8%, and
by 13.6 and 26.2%, respectively (Nazari et al., 2017),
which is noticeably less compared to other lamprey
species, such as the Pacific lamprey Entosphenus tri-
dentatus (Richardson, 1837), which loses up to 30% of
the body length (Clemens et al., 2010). During the
pre-spawning and spawning periods, the length and
weight of the Caspian lamprey gradually decrease,
while the condition factor increases (Fig. 4), indicat-
ing that the rates of growth of body length and weight
during this period differ, especially in females (Holčík,
1986; Nazari et al., 2010). Factors determining condi-
tion factor include the size of the individuals, the
maturity state, and the geographic location of the river
(Holčík, 1986). For example, the condition factor of

8
JOURNAL OF ICHTHYOLOGY 2022
ORLOV et al.
the Caspian lamprey from the Volga River varies from
0.13 to 0.14, remaining stable from December to April,
but in May and June it increases up to 0.16 (Ginzburg,
1969; Holčík, 1986). In the Kura River, it ranges as
0.133–0.293 in females (Smirnov, 1953), in the Shirud
River, 0.095–0.347 (Nazari et al., 2010; Nazari, 2012).
At the same time, the condition factor is higher in
individuals migrating in autumn comparing to those
migrating in spring. Since the condition factor
depends on the gonad maturity state, autumn migrants
entering the river look more mature than the individ-
uals of the spring group (Nazari, 2012). It should be
noted that the condition factor of the Caspian lamprey
falls within similar limits of other lamprey species, for
example, the Arctic lamprey Lethenteron camchaticus
(Tilesius, 1811) and the Pacific lamprey; the latter spe-
cies is also characterized by maximum values of this
parameter in the spring-summer period (Orlov et al.,
2008, 2014).
REPRODUCTIVE BIOLOGY
Lampreys are characterized by a complex life cycle.
The Caspian lamprey can live up to 4 years in fresh
water before migrating to the Caspian Sea where it
spends the next 1.5 years. Throughout its life, the Cas-
pian lamprey performs regular migrations, which may
be divided into four types (Holčík, 1986): (1) spawning
migration of adults from the sea to rivers; (2) feeding
migration of ammocoetes; (3) migration of ammoco-
etes preparing for metamorphosis; (4) feeding migra-
tion of ammocoetes, which undergone metamorpho-
sis, to the sea.
Pre-spawning individuals begin their migration to
rivers in autumn and winter, depending on hydrologi-
cal and meteorological conditions, such as tempera-
ture, f low velocity, water level in the river, water qual-
ity and turbidity, illumination and the phase of the
lunar cycle (Holčík, 1986; Nazari and Abdoli, 2010).
At the beginning of spawning migration, the Caspian
lamprey is characterized by a very high fat content
(30–34%), which reduces greatly down to 2.0–3.5%
as the individuals reach the spawning grounds. During
spawning migration, when the gonads mature, lam-
preys do not feed, and the development of the gonads,
especially the ovaries, depends on the accumulated
energy reserves during this period. During the period
of natural starvation, the Caspian lamprey undergoes
a sharp body transformation, which uses the reserves
of fat and protein, accumulated mainly in the muscles
and skin, for the gonad development. During the
spawning period, the appearance of the lamprey
changes; in particular, its body shortens, the teeth
become blunt, the size of the fins increases, the dorsal
fins become higher and closer, the coloration changes,
the urogenital papilla is formed near the anus, reach-
ing an average length of 1.2–4.8 mm in males and 0.6–
1.5 mm in females (Renaud, 1982; Nazari and Abdoli,
2010; Coad, 2016). Spawning takes place from March
through June in shallow waters with a moderate water
flow and a sandy-pebbly bottom.
In the rivers of the central and northern Caspian Sea,
migration is most intense at the water temperature of 6–
11°C (Pravdin, 1913b; Abdurakhmanov, 1962; Ginzburg,
1969, 1970; Agamaliev, 1971b; Kazancheev, 1981; Iva-
nov and Komarova, 2012). In the Shirud River, mass
migration of the Caspian lamprey begins at a water
temperature of 16°C and ends when it reaches 21°C;
individuals need 208–470 degree-days to reach sexual
maturity after they have started upstream migration
(Pravdin, 1965; Nazari and Abdoli, 2010; Farrokhne-
jad et al., 2014; Nazari et al., 2017).
On the spawning grounds, the males or the individ-
uals of both sexes build oval-shaped nests, moving
gravel and small stones with sucking discs using wave-
like movements of the body (Abdurakhmanov, 1962;
Maitland et al., 1994); as a result, a shallow depression
~0.5–1.0 m in diameter is formed at the bottom.
According to Nikitin (2016), lampreys can also use
artificial pebble spawning grounds of other anadro-
mous fish, such as sheefish Stenodus leucichthys
Fig. 4. The Caspian lamprey Caspiomyzon wagneri from the Volga River basin in a state of maximum fatness (photo by E.V. Nikitin).

JOURNAL OF ICHTHYOLOGY 2022
CASPIAN LAMPREY CASPIOMYZON WAGNERI (PETROMYZONTIDAE) 9
(Güldenstädt, 1772) and the representatives of the
family Acipenseridae, in the areas with depths of down
to 2 m, flow velocity of 0.8 m/s, and dissolved oxygen
content of 8–12 mg/L.
Most authors note the predominance of females
over males in the lamprey populations, the males to
females ratio varies from 0.62: 1.00 to 1.00: 2.92 (Pra-
vdin, 1913a, 1913b; Dyuzhikov, 1956; Ginzburg, 1969;
Holčík, 1986; Nazari and Abdoli, 2010; Ahmadi et al.,
2011; Nazari, 2012; Nazari et al., 2017). Although,
some authors report about the dominance of males at
the spawning grounds in a ratio of 2.2 : 1.0 (Ghasem-
pouri, 1993). Probably, these contradictions are due to
different observation periods, since males usually pre-
dominate at the beginning of spawning as they mature
earlier than females (Farrokhnejad et al., 2014), but
during the entire spawning period, the ratio of males
and females is more or less close to 1 : 1 (Smirnov,
1953; Nazari and Abdoli, 2010). Lampreys often spawn
in groups, when there are several males per female.
During mating, males attach their sucking discs to the
female’s head and wrap their bodies around the female
body (Coad, 2016). The Caspian lamprey is character-
ized by one-time spawning (Kazancheev, 1981; Ivanov
and Komarova, 2012; Nazari et al., 2017; Orlov et al.,
2021). During the release of reproductive products,
the tails of individuals of both sexes tremble, eggs and
sperm are released simultaneously (Coad, 2016). The
spawning process takes several days, since the female
lays only a few sticky eggs, colored from white to yel-
low, at a time (Coad, 2016; Nazari et al., 2017). The
egg diameter is 0.60–1.15 mm in the Caspian lamprey
of the Volga River population (Pravdin, 1913a, 1913b;
Berg, 1948; Smirnov, 1953; Ginzburg, 1969, 1970;
Holcik, 1986). For Iranian waters, similar values are
reported: 0.78–1.15 (average 0.92 ± 0.08) mm (Nazari
and Abdoli, 2010; Lampreys…, 2015).
Since lampreys do not feed during the upstream
migration, females die of starvation immediately after
spawning, but males remain alive for several more days
or weeks until spermatogenesis stops (Smirnov, 1952,
1953; Larsen, 1980; Kazancheev, 1981; Holčík, 1986;
Ghasempouri, 1993; Coad, 2016; Nazari et al., 2017).
Nevertheless, some authors suggest that nowadays
some individuals may remain alive after the first
spawning and participate in spawning in the new
spawning season after feeding in the sea due to the
reduction in migration routes (Ivanov and Komarova,
2012; Coad, 2016; Orlov et al., 2021). Cases of
repeated spawning are also known in other lamprey
species (Michael, 1980).
The absolute fecundity of the Caspian lamprey of
the Volga River population is 16–43 (average 21–36)
thousand eggs (Table 1), of the Kura population, 14–
38 (average 24) thousand eggs (Pravdin, 1913a, 1913b;
Kazancheev, 1981; Holčík, 1986; Nikitin, 2016). In
Iranian waters, the absolute individual fecundity of
the Caspian lamprey is noticeably higher, reaching
32–51 (41.9 ± 5.4, on average) thousand eggs in the
individuals migrating in spring (Nazari and Abdoli,
2010; Lampreys …, 2015).
In the Caspian lamprey, absolute fecundity
depends significantly on the body size and weight
(Holčík, 1986; Ahmadi et al., 2011; Nikitin, 2016).
According to Nikitin (2016), in the Volga River, the
minimum absolute fecundity (20.7–22.6 thousand
eggs) is observed in lampreys weighing 46–55 g, the
Table 1. Fecundity of the Caspian lamprey of the Volga population depending on body weight (according to: Nikitin, 2016)
Min–max—limits of indicator, M—mean. Here and in Table. 2: “–”—no data.
Body weight, g
Absolute fecundity,
thousand eggs
Relative fecundity,
thousand eggs/g of body weight
min–max Mmin–max M
46–50 19.0–26.0 22.6 0.400–0.540 0.460
51–55 16.0–24.0 20.7 0.290–0.460 0.380
56–60 20.0–38.0 26.4 0.350–0.630 0.450
61-65 20.0–31.0 25.0 0.300–0.500 0.360
66–70 – 25.0 – 0.360
71–75 28.0–30.0 29.0 0.390–0.400 0.390
76–80 – 36.0 – 0.460

10
JOURNAL OF ICHTHYOLOGY 2022
ORLOV et al.
maximum (29.0–36.0 thousand eggs), in the individ-
uals weighing 71–80 g (Table 1).
The relative fecundity of the Caspian lamprey of
the Volga River population varies within 290–630 eggs
per 1 g of body weight (Table 1), the maximum values
are typical for specimens weighing 46–50 g and 76–80 g
(Nikitin, 2016). In the waters of Iran, the relative
fecundity of the Caspian lamprey is characterized by
similar values, amounting 260.8–677.4 (average 397.6 ±
93) eggs per 1 g of body weight or 80.3–148.1 (107.2 ±
15.1) eggs per 1 mm of body length (Nazari and
Abdoli, 2010; Lampreys…, 2015).
The gonadosomatic index (GSI) in females varies
from 2.67 in the Volga River to 35.12 in the Shirud
River (Table 2). At the same time, the average GSI
value of the lamprey population in spring is somewhat
higher than in autumn, when maximum values are
noted in April–May (Ghasempouri, 1993). During
the spawning period, the GSI reaches its maximum
values, while both in spring and autumn migrating
lampreys, the gonads are at maturity stage IV. The
hepato-somatic index averages 0.85 and 1.02 in matur-
ing females and males, respectively, while that of
mature ones is 1.310 and 0.975, which indicates starva-
tion during this period and the expenditure of energy
reserves accumulated in the liver for the development
of gonads (Ahmadi et al., 2011; Coad, 2016).
After 9–11 days at a water temperature of 15–22°C,
the fertilized eggs hatch into worm-shaped larvae
(ammocoetes) with a body length of 3.3–4.2 mm.
They have no teeth, a mouth hood, eyes covered with
skin, and a light-sensitive area near the tail. Ammoco-
etes burrow into bottom sediments consisting of fine-
grained sand with a small amount of silt and detritus,
and a large amount of plant debris, macrophytes, and
submerged wood (Coad, 2016; Nazari et al., 2017).
These transparent, blind, and poorly swimming larvae
are carried downstream from the spawning grounds
(nests) to the areas with the deposits of sand, silt, and
detritus, where they later spend most of their lives (2–
4 years), feeding on microorganisms by filtration. In
the northern part of their range, ammocoetes live in
the river until they reach a length of 10–12 cm, after
which they undergo metamorphosis. The latter usually
takes place from July to December (Holčík, 1986), in
the rivers of the Iranian coast, in October, when a total
body length of ammocoetes reaches 8–11 cm
(Renaud, 1982, 2011). During metamorphosis, they
do not feed. After metamorphosis, lampreys migrate
to the Caspian Sea, where they fatten before returning
to fresh water to spawn (Holčík, 1986).
FEEDING AND TROPHIC RELATIONSHIPS
Almost nothing is known about the feeding of the
Caspian lamprey in the sea, which contributed to dif-
ferent ideas (Quintella et al., 2021). Sabaneev (1892)
reported that individuals of this species fed on organic
matter and silt, but most of all, on the flesh of living
and dead fish. Based on observations by Kessler (1870)
and Kavraiskii (1897), the Caspian lamprey attacked
the Caspian trout; Hubbs and Potter (1971) and Lelek
(1987) came to the conclusion that individuals of this
species parasitized on fish; Abakumov (1965) believed
that they attacked the Caspian trout. However,
Kavraiskii (1897) pointed out that the Caspian lam-
prey used the Caspian trout only for transportation to
the spawning grounds. The Caspian salmon Salmo cis-
caucasicus Dorofeeva, 1967 is another fish species, on
which the traces of the sucking disc of the Caspian
lamprey have been found. However, similar to the
Caspian trout, the Caspian lamprey attaches to the
opercular area and uses salmon as a transport species
during spawning migrations (Quintella et al., 2021).
The idea of a non-parasitic way of life of this species is
supported by Holčík (1986) and Agamaliev (1971b),
reporting that the teeth of the Caspian lamprey are
already blunt during the transformation period, and
this completely excludes the possibility of parasitism
on other fish. Vladykov and Kott (1979) suggested that
the Caspian lamprey could feed on the eggs of benthic
fish or on some invertebrates. Renaud (1982) found
juvenile acanthocephalans (Corynosoma sp.) in the
Caspian lamprey intestines and suggested that it fed on
amphipods, since the latter served as an intermediate
host of these parasites. However, Holčík (1986) spec-
ulated that these acanthocephalans could have been
consumed by lampreys with the infected decaying fish.
Renaud et al. (2009) considered the Caspian lamprey
to be a scavenger, but he noted the presence of well-
developed buccal glands that could compensate for its
blunt teeth and allowed it to feed on fish. In general,
most authors tend to believe that the Caspian lamprey
cannot parasitize on fish and is classified as a scaven-
ger by the type of food based on the findings of algae
and detritus in its intestines and the presence of blunt
teeth (Abdurakhmanov, 1962; Kazancheev, 1981;
Shooshtari et al., 2011; Ivanov and Komarova, 2012;
Bogutskaya et al., 2013; Quintella et al., 2021; Orlov
et al., 2021). However, even now the considered spe-
cies is classified by some authors as a parasitic lam-
prey, which is supported by direct observations (Lam-
preys…, 2015). Nikitina and Salnikov (2000) found
traces of lamprey sucking disc in the tail part of the
sterlet Acipenser ruthenus Linnaeus, 1758 (45-cm
long), caught in the Volga River near the village of
Nikolsky. A cavity measuring 100 × 40 × 20 mm with
uneven edges was eaten out inside the sterlet’s body,

JOURNAL OF ICHTHYOLOGY 2022
CASPIAN LAMPREY CASPIOMYZON WAGNERI (PETROMYZONTIDAE) 11
Table 2 . Some characteristics of the Caspian lamprey females during the reproductive period and the sex ratio (males : females) in the spawning part of populations
River (period, year) Body length, mm Body weight, g Gonad weight, g Gonadosomatic
index Fecundity, eggs Sex ratio Source
Volga 305–530 47.0–180.0 4.60–7.90 2.67–11.10 25.000–43.000 1.13–1.94 : 1.00 Pravdin, 1913a, 1913b;
Holčík, 1986
Volga (2000–2001) 320–410 46.0–80.5 7.30–9.40 7.20–11.30 24.770–39.020 1.00 : 1.00 Nikitin, 2016
Kura 388–447 88.0–124.0 3.89–10.30 – – – Smirnov, 1953;
Holčík, 1986
Kura 330–530 46.0–192.0 3.89–10.30 3.38–11.70 14.000–38.000 – Agamaliev, 1971b;
Kazancheev, 1981
Shirud (autumn
2011)
293–443 55.4–168.6 9.12–23.68 6.38–25.38 17.514–64.425 0.62–0. 94 : 1.00 Nazari et al., 201 7
Shirud (spring of
2006 and 2012)
330–369 74.1–91.4 19.8 0 –32.1 0 9.51–35.12 45.793–51.198 0.87–1.07 : 1.00 Nazari, Abdoli, 2010;
Farrokhnejad et al., 2014

12
JOURNAL OF ICHTHYOLOGY 2022
ORLOV et al.
while the wound was filled with blood and mucus.
Contradictory data on the type of feeding of adults
indicate a rather high trophic plasticity of the Caspian
lamprey.
During the period of spawning migration, both in
the lower reaches of the Volga River and in the rivers
of the Iranian coast, blue-green algae are found in the
intestines of the Caspian lamprey, which are acciden-
tally sucked together with water (Nikitina and Sal-
nikov, 2000), or enter the digestive tract from a solid
substrate, to which lampreys attach themselves
(Nazari et al., 2010). Large numbers of crustaceans
parasitizing on the amphipods Monoporeia affinis
(Lindström, 1855) are also found, which may indicate
that lampreys feed on the latter during the marine
period of life (Nikitina and Salnikov, 2000).
Ammocoetes are filter feeders, consuming diatoms
and detritus. Migrating, metamorphosing and spawn-
ing lampreys do not feed. The intestinal diameter
decreases from 2.7 mm in pre-spawning lampreys
down to 1.4 mm in spawning specimens (Renaud,
1982). Benam et al. (2016), examining the gastrointes-
tinal tract of maturing and mature lampreys in the
Shirud River, have found that their intestines are
empty, confirming the fact that lampreys stop feeding
when migrating to the river. In addition, these authors
report that the lamprey’s digestive tract and associated
organs (liver and pancreas) have undergone degenera-
tion (especially in females).
Lampreys play a vital role in freshwater and marine
ecosystems, serving as food for fish and other verte-
brates (Orlov et al., 2007; Maitland et al., 2015;
Guidelines…, 2018). Predatory fish such as the north-
ern pike Esox lucius Linnaeus, 1758 feed on the Cas-
pian lamprey (Fig. 5)1, as well as wels catfish Silurus
glanis Linnaeus, 1758, burbot Lota lota (Linnaeus,
175 8), z and er Sander lucioperca (Linnaeus, 1758) and
beluga Huso huso (Linnaeus, 1758) (Coad, 2016). The
Eurasian otter Lutra lutra (Linnaeus, 1758) and near-
water birds (Nazari et al., 2010; Coad, 2016) hunt of
the lamprey as well.
PARASITES AND DISEASES
Little is known about the parasites and diseases of
the Caspian lamprey. Pravdin (1913a) and Zekhnov
(1958) reported on finding the acanthocephalan Echi-
norhynchus sp. in the body cavity of pre-spawning
individuals in the Volga River and in the Caspian Sea.
Juveniles of the acanthocephalan Corynosoma sp. were
1https://kaspyinfo.ru/news/gorod/54314; assessed December
2021.
Fig. 5. Individuals of the Caspian lamprey Caspiomyzon wagneri, found in stomach of the northern pike Esox lucius, caught in the
Volga River (photo from the site https://kaspyinfo.ru/news/gorod/54314).

JOURNAL OF ICHTHYOLOGY 2022
CASPIAN LAMPREY CASPIOMYZON WAGNERI (PETROMYZONTIDAE) 13
found in migrating lamprey in the upper reaches of the
Kama River and in the Iranian rivers Shirud and Talar
(Zakhvatkin, 1936; Zekhnov, 1958; Renaud, 1982;
Nazari and Abdoli, 2010; Nazari et al., 2010). Parasitic
larvae of bivalve mollusks (glochidia) were also found
on the gills of pre-spawning lampreys (Zakhvatkin,
1936). Abnormalities in the development of the caudal
and anal fins and various infections have been noted in
some lampreys migrating upstream the Shirud River
(Abdoli et al., 2017; Nazari et al., 2017).
INTRASPECIFIC STRUCTURE
Berg (Berg, 1931, 1948) reported that the Caspian
lamprey had two adult forms: a typical form with a
body length of 370–553 mm and a dwarf form (prae-
cox) with a body length of 190–310 mm.
When comparing the lampreys caught in the Volga
and Kura rivers, no significant differences in their
morphology were found (Smirnov, 1952, 1953).
Nazari and co-authors (2009) found significant dif-
ferences in morphometric characters of lampreys from
the Shirud and Talar rivers and the absence of statisti-
cally significant differences between them in meristic
characters. Comparison of lampreys sampled from
two other Iranian rivers of the southern Caspian
(Babolrod and Kheyrod) revealed significant differ-
ences between a number of morphometric features
(Vatandoust et al., 2015). This allowed the authors to
conclude that the Caspian lamprey in the southern
Caspian was represented by at least two morphological
forms, and there was an independent population in
each of the studied rivers. A different point of view was
proposed by Kucheryavyi and co-authors (2016), who
suggested that the Caspian lamprey was a homoge-
neous metapopulation consisting of mixing individu-
als during their sea period of life in the Caspian Sea.
NUTRITIONAL VALUE, ECONOMIC AND
SOCIO-ECONOMIC IMPORTANCE
The Caspian lamprey was of great economic
importance in the Caspian Sea basin in the past (Berg,
1948; Kazancheev, 1981; Kottelat and Freyhof, 2007;
Renaud, 2011), which is currently true to a certain
extent only for the waters of Iran (Imanpoor and
Abdollahi, 2011). In terms of nutritional value, it is
almost unique, being a valuable delicacy product
(Kazancheev, 1981). Lamprey flesh contains up to
29.0–30.3 fat, 11.8–13.2 proteins, 1.9 mineral salts,
1.4 ash, and 55.1–57.5% moisture, the energy value is
324 kcal per 100 g of wet weight (Chemical composi-
tion…, 1987). Lamprey fat contains a lot of iodine, a
full set of essential amino acids, vitamins A, B, B12, C,
D1, E and others; it is very useful and palatable (Hajib-
ababekov, 1939; Holčík, 1986; Askerov et al., 2001).
However, Coad (1979, 2016) states that Caspian lam-
prey meat is toxic, and intoxication occurs within a
few hours after eating it. Contact with lamprey mucus
may cause skin irritation. Therefore, to prevent the
described phenomena, lamprey must be soaked in
brine before use.
In the past, the Caspian lamprey was dried and
used as candles or for fat, and also caught by man for
consumption (Berg, 1948; Kazancheev, 1981; Kottelat
and Freyhof, 2007; Renaud, 2011). In Russia, the Cas-
pian lamprey was used for food and for lighting by the
non-Muslim population of the Caucasus, while the
Muslims used it exclusively for making candles
(Almeida et al., 2021). In the XX century, the Caspian
lamprey in Russia began to be cooked fried and pick-
led (Orlov et al., 2021). In Turkmenistan, the Caspian
lamprey is believed to be useful as a remedy for hem-
orrhoids and asthma. In Iran, this species has no com-
mercial value and is practically not eaten for religious
reasons due to the lack of scales. Nevertheless, it is still
fished, for example, in the Gorganrud River, and is
used to treat health problems, and is also eaten smoked
or aged in brine (Coad, 2016; Nazari et al., 2017; Shi-
rood Mirzaie et al., 2017).
POPULATION DYNAMICS
AND LIMITING FACTORS
The abundance of the Caspian lamprey may only
be judged by the changes in its catches. In the past, its
numbers were quite high, being of great commercial
importance. At the lower reaches of the Volga River,
the annual catch amounted to 552 tons in 1875–1884,
incr easing u p to 2478 tons in 19 00–1915, and the max -
imum annual catch was recorded in 1903, when
4440.7 tons of lamprey were fished in the Volga River
delta (Mitropol’skii, 1916; Strubalin, 1989; Nikitina,
1998). Subsequently, its catches decreased sharply. In
1932–1937, they averaged 30–80 tons (Kazancheev,
1981). According to other sources, they decreased
from 640 to 150 tons from 1925 to 1942 (Nikitin,
2016).
In the Kura River, in 1891–1935, the minimum
five-year catch was recorded in 1891–1895, when only
11 thousand lampreys were caught, while the five-year
catch peaked at 612000 individuals in 1911–1915. After
1935, 213000 lampreys were caught in 1936, and a
catch of 304000 lampreys was reported in 1937. The
annual catch in the Chur River varied from 10 to 269
tons in 1930–1963 (Berg, 1948; Holčík, 1986;
Renaud, 2011).
Since the middle of the XX century, due to the con-
struction of the dams at the Mingachevir and Volga
hydroelectric power stations, the numbers of the Cas-

14
JOURNAL OF ICHTHYOLOGY 2022
ORLOV et al.
pian lamprey began to decline; its annual catches in
the Volga and Kura rivers have decreased from 150 to
10 tons in 1951–1960 (Kazancheev, 1981; Nikitin,
2016). In the middle and in the end of the XX century,
lamprey was fished mainly in the Astrakhan region
nearby the Nikol’skoe village (230–300 km upstream
the city of Astrakhan), where the main spawning
grounds of the species were located. Here, the average
annual catches of lamprey were about 0.8 tons in
1966–1987, 5.6 tons were caught in 1992 (Nikitina,
1995, 1998; Nikitin, 2016).
On the Iranian coast of the Caspian Sea, the num-
ber of lampreys remains relatively high; during the
spawning migration in some rivers, up to several hun-
dred kilograms of Caspian lamprey may be caught
within an hour (Fig. 6) (Coad, 2016). However, the
abundance of this species in Iran has noticeably
decreased in recent years (Nazari et al., 2017).
The main reasons for the sharp decline in the num-
ber of populations of the Caspian lamprey are associ-
ated with the regulation of river flow by dams and
locks, the construction of hydraulic structures, a
decrease in spawning areas, water pollution due to
human activities, climate change towards aridity,
water intake for irrigation, dredging and sand mining,
which destroys spawning grounds and habitats of
ammocoetes (Nazari et al., 2017; Orlov et al., 2021).
Lack of public awareness of the characteristics of the
biology of the Caspian lamprey (people still believe
that it harms fish stocks) stimulates a barbaric opinion
and fishing, when caught individuals are killed or not
returned to their natural habitat (Nazari et al., 2017;
Orlov et al., 2021). In the Terek River, dredging oper-
ations to remove sand from the bottom nearby the vil-
lages of Chervlenaya and Azamat-Yurt led to the death
of many ammocoetes, thereby reducing the number of
recruits (Orlov et al., 2021). In addition, intense winter
water releases from the Volga HPP, observed in recent
years, affect the flow velocity, the state of the spawn-
ing grounds of the Caspian lamprey, and its spawning
process. In some areas, illegal lamprey fishing (poach-
ing) is possible, but it probably has a lesser impact on
the state of stocks (Nikitin, 2016).
FISHING
The history of the Russian fishery of the Caspian
lamprey has ~300 years (Almeida et al., 2021). Until
1997, it was classified as a valuable commercial object
in the Russian Federation (the lower reaches of the
Volga River) and Azerbaijan (the Kura River) (Niki-
tin, 2016). At present, it has completely lost its com-
mercial value (Almeida et al., 2021; Orlov et al., 2021).
In the XIX century, lamprey was probably not in a
great demand for the population of the lower reaches
of the Volga River. In the request of the Chernoyarsk
Fig. 6. Catch of the Caspian lamprey Caspiomyzon wa gneri in the Shirud River during the autumn migration (photo by H. Nazari).

JOURNAL OF ICHTHYOLOGY 2022
CASPIAN LAMPREY CASPIOMYZON WAGNERI (PETROMYZONTIDAE) 15
fish merchants for the “Permission of lamprey fat
burning”, sent to Tsar Alexander II in May 1877, it was
reported that ordinary people do not eat lamprey, dis-
gusted by it because of the serpentine body shape.
Lampreys were used at that time mainly for rendering
fat and for lighting (dried lampreys were burned
instead of candles). They caught lampreys with special
traps of the “fish top” type (local name “neredy”),
which were woven from thin brushwood or wood twigs
(most often willow) and were usually installed near the
shore. In winter, local residents caught lampreys in
holes with their hands and with the help of nets (Pal-
las, 1788). Here is how Pravdin (1965, p. 60) describes
ice fishing for the Caspian lamprey: “In those days, on
the Volga [River], lampreys were caught with a "lan-
tern”, believing that it was striving for light. On the ice,
above the fast [water], usually not very deep, where the
densest run of the lamprey was assumed, a brightly
burning lantern was placed near the hole, and at some
distance from it, several more holes were punched, in
which they scooped lamprey by “saks” [fishing nets],
believing that it [lamprey] “swirls” around illuminated
strip of water. Indeed, the lamprey gathers near the
illuminated strip, but this is not due to the fact that the
fish strives for the light, but because, on the contrary,
it avoids it. The lamprey, moving all the time in the
dark towards the fast-flowing stream, runs into the
light and, hiding from it, rises up into a darker space,
where it falls into the “sak” hold by fisherman” (Fig. 7).
Lampreys were fished in the summer to obtain fat,
caught in the winter, they were salted and delivered to
the markets of the cities of Moscow, Riga, Nizhny
Novgorod, Smolensk, and Kiev (Minkh, 1902).
CONSERVATION STATUS
AND CONSERVATION MEASURES
The population of the Caspian lamprey has
declined sharply in recent decades, mainly due to
destruction and degradation of habitats and spawning
grounds (Renaud, 1997; Clemens et al., 2013). The
Caspian lamprey was first proposed to be listed in the
Red Data Book of the USSR in 1985 (Pavlov et al.,
1985). It is listed as “vulnerable” in Europe (Lelek,
1987; Maitland, 1991). Due to the scarcity of the Cas-
pian lamprey, it is included in the IUCN Red List
(Freyhof and Kottelat, 2008), category “Near threat-
ened” (NT), and in the Appendix 3 of the Bern Con-
vention (The Bern Convention…, 1979). It is listed in
the Red List of the Russian Federation (category and
status 2, species declining in numbers and/or distribu-
tion) (Kucheryavyi, 2021) and the Red Lists of a num-
ber of its regions: the Republic of Dagestan (category
and status 2) (Abdusamadov and Barkhalov, 2020),
the Republic of Kalmykia (2) (Poznyak, 2013), the
Republic of Chechnya (2) (Batkhiev and Kaimov,
Fig. 7. Scheme of ice fishing for the Caspian lamprey Caspiomyzon wagner i in the Volga River with the use of light (according to:
Pravdin, 1965, with modifications): 1—light source (lantern); 2—water column illuminated by a beam of light rays; 3—ice hole
with a lantern, 4—ice surface, 5—ice hole where fishing takes place; (→)—flow direction.
Riverine current
2
1
435

16
JOURNAL OF ICHTHYOLOGY 2022
ORLOV et al.
2020), the Republic of North Ossetia-Alania (category
and status 1, endangered species) (Sokhno, 1999), the
Republic of Mordovia (category and status 0, probably
an extinct species) (Vechkanov, 2005), the Republic of
Chuvashia (0) (Alyushin et al., 2010), Astrakhan
Oblast (1) (Red List…, 2014), Saratov Oblast (1) (Shlyakh-
tin et al., 2021), Volgograd Oblast (2) (Boldyrev, and
Yakovlev, 2017), Ivanovo Oblast (0) (Barinov, 2007),
Nizhny Novgorod Oblast (0) (Anufriev et al., 2014),
Orenburg Oblast (category and status 4, species with
insufficiently clarified distribution and abundance)
(Chibilev, 2019), and Stavropol Territory (0) (Mish-
velov, 2013).
In Iran, the Caspian lamprey was previously con-
sidered endangered due to the loss of major spawning
grounds and a sharp decline in numbers (Kiabi et al.,
1999). Currently, its status is set to NT (Clemens et al.,
2020). It is also included in the list of vulnerable spe-
cies of the Republic of Kazakhstan (category 2, species
rapidly reducing its numbers within the range) as a
result of disturbance of habitats and spawning grounds
caused by the construction of hydroelectric power
plants (Red List…, 2006); it is currently considered in
the category “Vulnerable” (VU) (Clemens et al., 2020).
In Turkey (Fricke et al., 2007) and Azerbaijan (Clem-
ens et al., 2020), this species has been assigned the sta-
tus of “Extinct” (EX), however, in the waters of Azer-
baijan, an increase in its abundance has been noted in
recent years (Yusifov and Ahmadov, 2021). In Turk-
menistan, the Caspian lamprey is considered in the
status of “Data Deficient” (DD) (Nazari et al., 2017;
Clemens et al., 2020).
Most of the conservation efforts in the Caspian Sea
basin are focused on high-value commercial fish such
as sturgeon and Caspian trout. Unfortunately, the
Caspian lamprey is not added to this list, so it does not
receive legal protection. Despite the different conser-
vation status of the species in different countries and
even within the same country, three common features
may be distinguished for its conservation (Clemens
et al., 2020): (1) international or local protection mea-
sures have not been developed; (2) there is a high level
of anthropogenic threats within the range; 3) the
degree of knowledge remains insufficient regardless of
the country. The lack of complete information about
the ecology and distribution of the Caspian lamprey in
many parts of its vast range makes it difficult to
develop appropriate conservation measures.
The most serious threats to the Caspian lamprey
are the following: (1) dams and locks that prevent lam-
preys from accessing spawning grounds (Holčík, 1986;
Coad, 2016; Nazari et al., 2017; Orlov et al., 2021);
(2) climate aridization, causing disturbance of habi-
tats as a result of shallowing and drying of spawning
grounds and areas inhabited by ammocoetes (Abdoli
et al., 2017; Coad, 2016; Nazari et al., 2017; Clemens
et al., 2020); (3) water withdrawal for irrigation, which
leads to a deterioration of spawning grounds and dis-
turbance of lamprey habitats (Rabazanov et al., 2017;
Rabazanov et al., 2019); (4) pollution of rivers by
industrial and household effluents, which have a neg-
ative impact on the survival of lampreys at different
stages of ontogenesis and their reproductive ability
(Nasrollah Pourmoghadam et al., 2015; Eagderi et al.,
2017); (5) dredging and sand mining destroying
spawning grounds and habitats of ammocoetes
(Nazari et al., 2017; Clemens et al., 2020; Orlov et al.,
2021); (6) illegal (poaching) fishing, reducing the
population already low in numbers (Nikitin, 2016;
Nazari et al., 2017; Clemens et al., 2020); and
(7) insufficient awareness of the local population
about the state of the environment and the conserva-
tion status of rare and endangered species (Nazari
et al., 2017).
Pollution is one of the key factors that have a nega-
tive impact on the state of the stocks of the Caspian
lamprey. Recent studies on the Iranian coast of the
southern Caspian evidence that lamprey sperm motil-
ity and morphology, and ultimately reproductive suc-
cess, may be adversely affected by the increased con-
centrations of heavy metals (Shooshtari et al., 2011;
Eagderi et al., 2017). Concentrations of heavy metals
in the aquatic environment have been increasing in
recent years, especially in areas where industrial, agri-
cultural, and mining activities are widely carried out.
At the Iranian coast of the Caspian Sea, the concen-
tration of mercury in the muscles of the adult Caspian
lamprey is 10 times lower than in ammocoetes
(Shooshtari et al., 2011). It is assumed that the
increased content of mercury in the ovaries may
adversely affect the reproductive ability of females
(Shooshtari et al. 2011).
It is believed that the illegal fishing of the Caspian
lamprey does not have such a negative impact on its
stocks as other factors (Nikitin, 2016). However, in
Iranian waters it is recognized as a rather serious type
of anthropogenic impact (Nazari et al., 2017; Clemens
et al., 2020). Iranian fishermen kill lampreys or leave
them to dry on the shore, believing that the lampreys
parasitize important commercial fish species. This is
partly due to the poor awareness of the local popula-
tion about the ecological characteristics of the Cas-
pian lamprey, as well as the lack of effective measures
for its conservation.
Currently, there are no special measures for the
protection of the Caspian lamprey (Almeida et al.,
2021; Clemens et al., 2020; Orlov et al., 2021). In order
to preserve and restore the population of the Caspian
lamprey in modern conditions, it is necessary to carry
out regular monitoring studies and conservation and

JOURNAL OF ICHTHYOLOGY 2022
CASPIAN LAMPREY CASPIOMYZON WAGNERI (PETROMYZONTIDAE) 17
regulatory measures aimed at improving the condi-
tions for natural reproduction. In this regard, the
experience of restoring the abundance of some species
of anadromous lamprey species from the North
Pacific (Clemens et al., 2020), including the removal
of barriers to spawning migration routes, equipping
dams and locks with fish passes to allow breeders to
spawn, restoration of river habitats and their regular
monitoring, and control of pollutant content in rivers.
It is necessary to conduct research in order to deter-
mine the damage to the stocks of the Caspian lamprey
from the operation of water intake facilities with the
direction of the funds received for its artificial repro-
duction and the release of reared juveniles (ammoco-
etes) into natural reservoirs (Nikitin, 2016). There is
an experience in the artificial reproduction of the Cas-
pian lamprey experimenting on catching and long-
term keeping of producers, obtaining mature sexual
products, fertilizing eggs and incubating them in Weiss
apparatus (Nikitina and Salnikov, 1996; Nikitina,
1998). In particular, in the experiments performed in
1989–1991, they managed to bring the incubation to
the stage of isolation of the anterior part of the
embryo, but the attempts to obtain viable offspring
under artificial conditions did not produce results.
Along with these measures, raising the public
awareness of the state of the environment, ecology,
and conservation status of rare and endangered species
is an important element of the management of aquatic
biological resources (Clemens et al., 2020). Efforts in
this direction will help improve the environmental
awareness of the population, will eradicate the bar-
baric opinion and activities on accidentally caught
specimens of the Caspian lamprey, and will contribute
to their return to their natural habitat (Fig. 8).
GAPS IN KNOWLEDGE AND MAIN
DIRECTIONS FOR FUTURE RESEARCH
There are huge gaps in many areas of knowledge
regarding the Caspian lamprey (Lucas et al., 2020)
compared to other species, especially sea lamprey
Petromyzon marinus Linnaeus, 1758 and the Pacific
lamprey. These include, for example, threats and fac-
tors limiting its distribution and abundance; habitats
of adults and ammocoetes, population structure, loca-
tion of spawning grounds, length of migration routes,
sea period of life of adults, and peculiarities of their
feeding in the sea (Renaud, 2011; Nazari et al., 2017;
Renaud and Cochran, 2019; Quintella et al., 2021).
This species is poorly studied, especially in the north-
ern and western parts of the Caspian Sea basin. After a
rapid decline of its abundance in the basins of the
Volga and Kura rivers, the studies of the current distri-
bution and state of stocks have not been carried out.
On the contrary, in the southern part of the Caspian
Sea basin (in the waters of Iran), a significant number
Fig. 8. The Caspian lamprey Caspiomyzon wagneri accidentally caught in the Volga River and returning to habitat (photo by
E.V. Nikitin).

18
JOURNAL OF ICHTHYOLOGY 2022
ORLOV et al.
of studies have been carried out to assess the distribu-
tion and structure of populations of the Caspian lam-
prey, basic biological information has been obtained,
the locations of spawning grounds and ammocoete
habitats have been determined in recent years (Jolodar
and Abdoli, 2004; Nazari, Abdoli, 2010; Nazari et al.,
2010; Ahmadi et al., 2011; Coad, 2016; Nazari et al.,
2017). All these measures are the first and most
important steps towards the conservation of biologi-
cally, socio-economically, commercially, culturally,
and historically important species, which is endemic
to the Caspian Sea basin.
In the coming years, the research efforts should be
focused on studying the feeding ecology, identifying
the localization of modern spawning grounds
(Ahmadi et al., 2011) and habitats of the Caspian lam-
prey during the sea period of life cycle (Holčík, 1986;
Renaud, 2011; Nazari et al., 2017; Quintella et al.,
2021), which may be facilitated by analyzing the envi-
ronmental DNA (aquaDNA) in the water samples
(Nikiforov et al., 2018). Physiology (Imanpoor,
Abdollahi, 2011) and population structure (Quintella
et al., 2021) of the considered species are still poorly
studied. It seems relevant to compare samples from
different parts of the range by molecular genetic meth-
ods using different markers; this is especially import-
ant for the Caspian lamprey from the northern and
southern parts of the Caspian basin, since different
results have been obtained regarding the intraspecific
structure of the Caspian lamprey (Smirnov, 1952,
1953; Nazari et al., 2009; Vatandoust et al., 2015;
Kucheryavyi et al., 2016). The issue of age determina-
tion remains very relevant; it is intractable for all lam-
prey species, since traditional methods of age determi-
nation using calcified structures (statoliths) are poorly
applicable to lampreys due to the complex life cycle
with metamorphosis. Isotope method of age determi-
nation currently being developed on eye lens of the
Pacific lamprey seems to be very promising (Pelekai,
2021).
ACKNOWLEDGMENTS
The authors are sincerely grateful to Hassan Nazari
(University of South Bohemia, České Budějovice, Czech
Republic) and Eduard Nikitin (Volga-Caspian Branch of
VNIRO, Astrakhan, Russia) for the courtesy in providing
the photographs of the Caspian lamprey. The authors
express their gratitude to two anonymous reviewers for their
careful reading of the manuscript and valuable advices and
comments, which made it possible to significantly improve
the paper.
COMPLIANCE WITH ETHICAL STANDARDS
Conf lict of interests. The authors declare that they have
no conflict of interest.
Statement on the welfare of animals. All applicable inter-
national, national, and/or institutional guidelines for the
care and use of animals were followed.
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