MARBLED CRAYFISH (Procambarus fallax f. virginalis) RESISTANCE AND SURVIVAL RATES AT LOW (under 5oC) TEMPERATURES DURING WINTER PERIOD Katrin KALDRE, Anton MEŽENIN, Tiit PAAVER Estonian University of Life Sciences, Department of Aquaculture, Tartu, Estonia INTRODUCTION MATERIAL AND METHODS The parthenogenetic marbled crayfish (Procambarus fallax f. virginalis) was first distributed via the pet trade in Europe in the 1990s (Faulkes, 2010). Since then, marbled crayfish have spread to several European countries and have successfully established some wild populations (Patricia and Faulkes, 2011). There have been persistent concerns that the marbled crayfish will become an invasive pest species (Vogt et al., 2004; Jones et al., 2008) because parthenogenesis permits a high reproductive potential and single individuals can establish a population (Patricia and Faulkes, 2011). In recent years aquarium shops in Estonia have sold marbled crayfish to aquarists as pet species but it has not been found from nature so far. There was hope, that originating from warm climate marbled crayfish cannot adapt to harsh conditions of Nordic waters. The question, if marbled crayfish can survive winter in Estonian waters is actual. The aim of our experiment was to estimate the effect of low temperature on marbled crayfish survival and growth rate, behavior and reproduction. In 2009 two marbled crayfish from an Estonian aquarium shop were bought and stocked into the aquarium at Department of Aquaculture of the Estonian University of Life Sciences. In current experiment in 2011-2012 progeny of these crayfish of unknown age was used (Fig. 1). Figure 1. Marbled crayfish (Procambarus fallax f. virginalis). Figure 2. Tanks that were used in the experiment. RESULTS AND DISCUSSION Mean TL of animals at the beginning of the experiment was 42.2 ± 0.3 mm (n=25) in the first tank, and 31.7 ± 0.1 mm (n=25) in the second tank (Table 1, Fig. 4). Mean weight of animals at the beginning of the experiment was 2.1 ± 0.04 g (n=25) in the first tank and 0.8 ± 0.009 g (n=25) in the second tank (Table 1, Fig. 5). Figure 3. PVC pipes in tanks as shelters. Temperature The experiment with 50 marbled crayfish of various sizes (27-51 mm TL) in two outdoor 1 m3 tanks lasted 210 days from September 9th 2011 to April 18th 2012 (Fig. 2). 25 marbled crayfish were stocked into both tanks. 60 pieces of PVC pipes (6.2 to 9.4 cm long with diameter 2.0 to 2.5 cm) were placed in both tanks as shelters (Fig. 3). At the stocking time the water temperature was around 18 degrees and started to fluctuate according to air temperature changes. When th water temperature decreased below 1°C (November 21 2011), the heaters were switched on to prevent water from icing. From the beginning of the experiment until March 28th 2012 crayfish were not fed. When water temperature increased over 10°C in spring and crayfish became more active, feeding was started. At the beginning and in the end of the experiment, the animals were individually weighed and measured (TL) and examined for presence of eggs. Table 1. Marbled crayfish TL and weights at the beginning of the experiment in both tanks No. of crayfish 30 Effect of temperature on survival rate Marbled crayfish tolerated low temperatures (under 2°C) for No Tank 1 Tank 2 TL, mm Weight, g TL, mm Weight, g few days quite well. However, mortality increased rapidly 1 30 0,7 27 0,5 when period of very low temperatures lasted over 7 days. For 2 32 0,8 27 0,6 the end of the experiment the survival rate in the first tank with 3 32 0,8 27 0,5 larger crayfish was much higher (60%, n=15) than in the 4 35 1,0 28 0,6 second tank (8%, n=2) (Fig. 6, 7). Figure 6. Water temperatures and the number of live marbled crayfish in the first tank. At the 5 35 1,2 28 0,6 6 37 1,0 29 0,8 Water temperature in Estonian natural bodies of water end of the experiment three dead in unknown time crayfish were found. 7 37 1,3 29 0,7 (streams, lakes) is 0-2°C under the ice in winter. However, at 8 37 1,3 30 0,9 the depth where crayfish live in lakes, it is usually higher. The 9 39 1,5 31 0,9 difference in mortality in two tanks could be caused by 10 41 1,8 31 0,7 different size of crayfish in tanks. Smaller crayfish seem to 11 41 1,6 32 0,9 tolerate very low temperature less. However, in the tank of 12 42 1,9 32 1,0 13 43 1,9 32 0,8 smaller crayfish the temperature was lower for some period. 43 2,2 32 0,9 Also in tank of larger crayfish mainly the largest specimens Figure 7. Water temperatures and the number of live marbled crayfish in the second tank. At the 14 15 46 2,2 32 0,8 end of the experiment four dead in unknown time crayfish were found. died. 25 20 15 10 5 0 Temperature No. of crayfish 30 25 20 15 10 5 0 10 Ÿ Marbled crayfish can 12 10 at the beginning of the experiment 8 6 at the end of the experiment 4 2 0 26‐30 31‐35 36‐40 41‐45 46‐50 51‐55 TL, mm Figure 9. Marbled crayfish lengths at the beginning and at Effect of temperature on behavior the end of the experiment in the second tank. Most of the crayfish were hiding in shelters at the temperature REFERENCES 1. Faulkes, Z. 2010. The spread of the parthenogenetic marbled crayfish, Marmorkrebs (Procambarus sp.), in the North below 4°C. At the temperature under 2°C, some marbled American pet trade. Aquatic Invasions 5: 447–450. crayfish were lying motionless on the bottom of tanks as dead 2. Feria, T.P., Faulkes, Z. 2011. Forecasting the distribution of Marmorkrebs, a parthenogenetic crayfish with high invasive potential, in Madagascar, Europe, and NorthAmerica. Aquatic Invasions 6: 55–67. animals, but in closer observation movements were noticed. 3. Jones, J.P.G., Rasamy, J.R., Harvey, A., Toon, A., Oidtmann, B., Randrianarison, M.H., Raminosoa, N., Ravoahangimalala, O.R. 2008. The perfect invader: a parthenogenic crayfish poses a new threat to Madagascar's freshwater biodiversity. When the water temperature had increased over 4°C, crayfish Biological Invasions 11: 1475–1482. 4. Vogt, G., Tolley, L., Scholtz, G. 2004. Life stages and reproductive components of the Marmorkrebs (marbled crayfish), the became more active and the higher the water temperature was, first parthenogenetic decapod crustacean. Journal of Morphology 261: 286–311. the less were shelters used. View publication stats Tank 1 Tank 2 8 6 Tank 1 4 Tank 2 2 0 3.1 ‐ 3.5 No. of crayfish 14 0,9 0,8 1,1 1,0 1,1 1,1 1,0 1,1 1,1 1,4 3.6 ‐ 4.0 TL, mm 2.1 ‐ 2.5 26‐30 31‐35 36‐40 41‐45 46‐50 51‐55 33 33 34 34 34 35 35 35 35 36 2.6 ‐ 3.0 0 1.1 ‐ 1.5 at the end of the experiment 2 1.6 ‐ 2.0 4 2,9 3,1 2,7 2,6 3,1 2,7 3,3 3,1 3,8 3,5 survive for short period at temperatures 1-2°C and even moult at temperatures below 10°C. But longer period of low temperature 18 causes high mortality, 16 especially among 14 12 smaller individuals. 10 Ÿ Marbled crayfish can 8 6 live over Estonian 4 winter and reproduce 2 0 after this in summer. 26‐30 31‐35 36‐40 41‐45 46‐50 51‐55 TL, mm Ÿ It is recommended to include marbled crayfish Figure 4. Total length (TL) distribution of to the Estonian Nature marbled crayfish at the beginning of the Conversation Act as a experiment. potentially dangerous to 18 16 noble crayfish non14 12 indigenous species. 10 0.1 ‐ 0.5 at the beginning of the experiment 46 47 47 47 48 49 49 50 50 51 No. of crayfish 6 No. of crayfish 8 The mean weight was in the first tank 2.1 g (n=25) at the Figure 8. Marbled crayfish lengths at the beginning and at beginning and 2.0 g (n=15) at the end of the experiment. In the the end of the experiment in the first tank. second tank the mean weight was 0.9 g (n=25) at the 18 beginning and 1.1 g (n=2) in the end of the experiment. 16 Effect of temperature on reproduction At the start five of the 50 marbled crayfish had eggs and were stocked into the first tank to estimate the effect of temperature on reproduction. One dead crayfish with eggs was found on th January 3 2012 and all the eggs were molded. Four crayfish with eggs were later not found. When the crayfish were transferred to indoor aquarium to 20°C after the experiment, one marbled crayfish spawned the eggs immediately and some other later. 16 17 18 19 20 21 22 23 24 25 CONCLUSIONS 0.6 ‐ 1.0 12 No. of crayfish Effect of temperature on growth During experiment at least two crayfish moulted at temperatures below 10°C. Growth was insignificant during winter. If the mean TL was 42.2 mm (n=25) at the beginning of the experiment, then at the end of the experiment the mean TL was 43.2 mm (n=15) in the first tank (Fig. 8). In the second tank the mean TL was 31.7 mm (n=25) at the beginning of the experiment and in the end of the experiment the mean TL was 37.0 mm (n=2) (Fig. 9). Weight, g Figure 5. Weight distribution of marbled crayfish at the beginning of the experiment.