Basic management for spawning of the cultured sturgeon,
Acipenser sturio L., 1758, a critically endangered species
by
Patrick Williot (1, 2) & Thierry Rouault (1)
Abstract. - Some wild-born individuals of the critically endangered sturgeon, Acipenser sturio, are tentatively held in
brackish water in captive conditions in order to obtain sexual maturation, both for restocking and for preservation of the
species from extinction. Sexual maturation was recorded in males, exhibiting a large range of inter-individual variation.
Active semen was obtained in half the injected fish. In females, maturation was incomplete.
Key words. - Acipenser sturio - Broodstock management - Spawning.
Background
Most sturgeon populations are threatened worldwide.
Though protected in France since 1982, the status of A. sturio has been deteriorating. The only chance to prevent the
species from extinction depends on the capacity to build a
functional cultured broodstock. The key condition is to succeed in breeding the fish, i.e. to provide the fish with suitable
rearing conditions and appropriate management.
Methods
The present study deals with two groups of fish: group-1
(N1 = 6), composed of older fish born in the wild
(1984-1989); and to a lesser extent group-2 (N2 = 16), composed of fish born in the wild in 1994. Group-1 fish arrived
in the hatchery between 1993 and 1997, and group-2 fish
during 1995. There is only one female in group-1. Total
absence of data and experience for the species has led us to
adopt the following strategy, with regards to the methods.
The methods are based on: 1) our experience with other sturgeon species, 2) the ecology of the species, 3) a step-by-step
procedure, 4) non-invasive practices, and 5) conservative
solution. As a precaution, the fish were kept in brackish
water (around 15‰) all year round, with winter vernalization and natural daylight. The water temperature range was
from 10-12°C to 23-25°C. The fish were fed frozen shrimps.
The size and migration of the germinal vesicle (polarization
index, PI), and the in vitro maturation competence (GVBD)
of ovarian follicles were used as sexual maturity criteria.
Males were staged according to methods developed for Siberian sturgeon. Hormonal stimulation (CPE or LHRHa; 2-5
mg.kg-1 and 5-10 µg.kg-1 for males and females respectively) was required to obtain gametes. Priming with 1/10 of the
current dosage 12 h prior to completion was frequently carried out in order to speed up maturation.
Results
Throughout the year alternate feeding and growth periods are observed. Five out of six males from group-1
Table I. - Pattern of older male A. sturio maturation (N = 6) (born in
the wild from 1984 to 1988 and arrival in hatchery between 1993 to
1997).
Name
1999 2000 2001 2002 2003 2004 2005 2006
Phil (1)
x
x
x
Just (2)
x
x
x
Mario (3)
x
x
x
x
x
x
x
Ascen (4)
x
Emel (5)
x
x
x
x
Nausi (6)
x
x
Total
1
5
5
2
2
1
2
2
Table II. - Signs of maturation in females. The letters correspond to
one given specimen (year of birth).
2002
2005
2006
D (1988) D (1988)
K (1994) K (1994)
A (1994) A (1994)
L (1994)
matured in the period 1999-2006 (Tab. I). Five fish matured
in 2000 and 2001. Four of these fish matured in the two consecutive years. Only 1 or 2 fish matured in the remaining
years. Depending on the individuals, 1 to 7 maturations were
recorded within the experimental period (Tab. I). Only one
male maturation was observed in group-2. Females (the oldest and 3 youngest specimens) exhibited partial maturation
in 2002, 2005 and 2006 (Tab. II). These maturations were
characterized by an abdomen that was not swollen, difficulties in sampling ovarian follicles, some unusual patterns,
heterogeneity in germinal vesicle migration, and moderate
GVBD. Upstream migration was then simulated by transferring the mature fish into freshwater for one week prior to
further maturation control. Injected males produced good
quality semen. Hormonal stimulations increased GVBD to
90-100% on five occasions from 2002 to 2006. This high
level of GVBD also corresponded to a PI range (0.10-0.13)
that was considered to be too high. It is worth noting that PI
values exhibited a large range (e.g. 0.08-0.16) for some
(1) Cemagref, Estuarine Ecosystems and Diadromous Fish, 50 avenue de Verdun, 33612 Cestas cedex, France.
[[email protected]]
(2) Present address : 4 rue du Pas-de-Madame, 33980, Audenge, France. [[email protected]]
Cybium 2008, 32(2) suppl.: 334-335.
Williot & Rouault
spawners, illustrating an asynchronous progress in maturation. Further hormonal treatment did not induce ovulation.
Conclusions
Maturation patterns of older males showed a great interindividual variability. Simulation of upstream migration led
to collection of active semen in some cases, as some hybrid
progenies were obtained with cryopreserved semen (Bercsenyi and Horvath, pers. comm.). The few females that
matured exhibited a very limited development of their ovaries. In order to improve the results, the following changes
were made in 2006: food deprivation (one month prior to
spawning) was applied; light intensity was lowered; and
water temperature control was set to limit high summer temperatures to 18-20°C. Since the oogenesis cycle is non-annual, any effects would most likely be visible in spring 2007
or, more probably, in 20081.
1
Management to spawn cultured Acipenser sturio
References
Williot P., Rochard E., Castelnaud G., Rouault T.,
Brun R., Lepage M. & P. Elie, 1997. - Biological characteristics of European Atlantic sturgeon, Acipenser sturio, as the
basis for a restoration program in France. Environ. Biol. Fish.,
48: 359-370.
Williot P., Rouault T., Pelard M., Mercier D., Lepage M., Davail-Cuisset B., Kirschbaum F. & A.
Ludwig, 2007. - Building a broodstock of the critically
endangered sturgeon Acipenser sturio L.: Problems associated
with the adaptation of wild-caught fish to hatchery conditions.
Cybium, 31: 3-11.
Late June 2007, thousands of larvae are born from the cross of a
group-2 female with group-1 male and group-2 male gametes
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335