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Hypoxia tolerance in Acipenser sturio juveniles
Philippe Jatteau, Rémy Fraty, Nicolas Delage
To cite this version:
Philippe Jatteau, Rémy Fraty, Nicolas Delage. Hypoxia tolerance in Acipenser sturio juveniles. 7th International Symposium on Sturgeon, Jul 2013, Nanaimo BC, Canada. pp.1, 2013. �hal-02601432�
Hypoxia tolerance in Acipenser sturio juveniles
Jatteau Philippe, Fraty Remy and Delage Nicolas.
Irstea - Estuarine Ecosystems and Migratory fish Research Unit, 33612 Cestas Cedex, France
ISS7 – 7th International Symposium on Sturgeon, 21-25 July 2013, Nanaimo, Canada Formerly present in European coastal waters from Black Sea to North Sea, European sturgeon (Acipenser sturio) populations have drastically declined
due to anthropogenic pressure (Lepage et al. 2000; Williot et al. 2002).
The last population, which colonized the Gironde-Garonne-Dordogne basin for reproduction, is greatly threatened of extinction. An ambitious restoration program was defined in the framework of the Berne Convention (Rosenthal et al. 2010) with concrete action plan developed in France and Germany
(Anonyme 2011; Gessner et al. 2010). As part of the restoration program, stocking operations were managed (Acolas 2012) and from 2007, more than 1 million larvae or juveniles were stocked in the Gironde-Garonne-Dordogne basin.
During their migration to reach the estuary, stocked fish have to cross a mud plug located in the upper part of the estuary, which presents severe hypoxic events during summer (Abril et al. 1999).
The goal of this study was to assess the hypoxic tolerance of European sturgeon juveniles.
Temperature did not seem to have a great influence on the appearance of behavioural indicators (loss of equilibrium – death). Conversely, OBF clearly increased with temperature.
The rise of OBF with decreasing O2 level is probably a compensatory mechanism to maintain oxygen consumption and so metabolism. The decrease of OBF
could correspond to the critic O2 pressure (PO2 crit) after which metabolism is depleted. This result led to hypothesized that the European sturgeon is probably an oxyregulator as other sturgeon species (Nonnotte et al. 1993; Randall et al. 1992; Ruer et al. 1987).
Loss of equilibrium is an expression of functional and metabolic disturbances, preventing fish to escape from danger (Beitinger et al. 2000), would determine the lower limit of O2 level to preserve the likelihood of fish survival.
These oxygen levels were already, but rarely, recorded during severe summer hypoxic events, in the upper part of the Gironde estuary, near Bordeaux. The
crossing of the mud plug by 3 month old European sturgeon juveniles during their downstream migration is probably without negative consequence considering the oxygen parameter.
Experimental approach
based on Critical Thermal Limit (la ref biblio) and U-Crit (les ref biblio) determining
Fish
Age : 3 months
Length: 12±0.1 cm mean±SE Weight: 7.3±0.3 g mean±SE Number of fish per tank: 3
Behaviour (Figure 3)
At 20°C, altered swimming was observed at 3.13
± 0.10 mg.l-1 mean±SE compared to 3.59 ± 0.07 mg.l-1 mean±SE at 25°C (Mann Whitney, p=0).
On the other hand, no significant difference was recorded between the 2 temperatures for the other behavioural indicators.
0 1 2 3 4 5 6 7
-60 -45 -30 -15 0 15 30 45 60 75 90 105 120 135 150 165 180 195 20°C
70% 25°C
O2mg.l-1
Time min 55%
40%
30%
20%
10%
20 °C : Speed = 2.72 mg.l-1.hour-1 14 Kpa
11 Kpa
8 Kpa
6 Kpa
4 Kpa 2 Kpa
25 °C : Speed = 2.48 mg.l-1.hour-1
Figure 1
100 120 140 160 180 200 220
6,35 5,1 3,8 2,9 2,04
Hypoxia Control
O2mg.l-1 Nb beat.min-1
Figure 4
100 120 140 160 180 200 220
5,8 4,5 3,3 2,5 1,7
Hypoxia Control
O2mg.l-1 Nb beat.min-1
Figure 5
0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0
Altered swimming Loss of equilibrium death
25°C 20°C
O2mg.l-1
Figure 3
Material and Methods
Discussion
Results
Experimental method
Programmed deoxygenating procedure (Fig 1) 3 behavioral indicators (altered swimming, loss of equilibrium, death)
Opercula beats (video recording)
Four 14 liters experimental tanks (3 replicates + 1control) (Fig 2)
3 experiments per temperature
Loss of equilibrium appeared at 1.71± 0.05 mg.l-1 mean±SE and 1.83 ± 0.06 mg.l-1 mean±SE at 20 and 25°C respectively, and was significantly different from altered swimming and death (Mann
Whitney, p=0). Whatever the temperature, fish in the control tank did not exhibit any modification of their behavior.
Opercular Beat Frequency (OBF) (Figures 4 and 5)
Whatever the temperature, OBF exhibited a similar pattern, with an increase with decreasing O2 level until 3.8 and 3.3 mg.l-1 for 20 and 25°C respectively, and a decrease afterwards. At both temperature, OBF in fish exposed to hypoxia were significantly different from
control fish (Kruskall-Wallis, p=0).
At 25°C OBF were increased in both experimental and control groups compared to 20°C (Mann-Whitney, p=0)
Figure 2
Poster created by Philippe Camoin - Irstea -2013
