Status of species, population structure and survival capabilities of Freshwater pearl mussel Margaritifera margaritifera (Linnaeus 1758) in Latvia Mud īte Rudz īte Museum of Zoology, University of Latvia Māris Rudz ītis Museum of Geology, University of Latvia Ark ādijs Poppels Department of Hydrobiology, Faculty of Biology, University of Latvia Aiva Onkele Latvian Malacological society Jānis Birzaks Institute of Food Safety, Animal Health and Environment - "BIOR", Didzis Tjarve Department of Botany and Ecology, Faculty of Biology, University of Latvia The oldest historical data about pearl fishing in territory of Latvia are from J.B.Fischer “Versuch einer Naturgeschichte von Livland”, 1791. Now Pearl mussel is found in 8 seperated tributaries of 2 rivers. Total number ~25 000, overall lenght of range ~65 km. Down: The river Palsa (Palz) is the tributary of Gauja (Livlandishe Aa), with the catchment area about 236,3 km². There are 3 nature reserves (NATURA 2000) since 2004 in the Palsa basin. Up: Adjacent basin of tributary Abul, more relief, but disturbed with dams, water mills, agricultural lands and town. Now Margaritana lives not in this river, but Unio still is present. The aim of these nature reserves is to protect populations of 2 mussel species - Margaritifera margaritifera and Unio crassus and habitats - Water courses of plain to montane levels. Margaritifera margaritifera Unio crassus freshwater pearlmussel thick shelled river mussel The most of Latvian Margaritifera margaritifera population lives in the basin of Palsa river. Unio crassus is present on all the territory of Latvia, but many of populations are aged and dissapearing. On the basin of Palsa river this species have numerous, but fragmented population. We have studied condition of populations of both species in the river Palsa basin. Population density In the 2009, 2011 and 2013 in the nature reserves the pearl and river mussels was accounted in 1 m x 50 m transects. (Using the method of monithoring of pearl mussels in NATURA 2000 sites.) Population density (mussels/m2) on 21 transects. 2009, 2011. 18 16 ) -2 14 12 10 8 6 Population density (mussels m 4 2 0 L.1 L.2 L.3 L.4 L.5 R.1. R.2. R.3. R.4. R.5. R.6. R.7. R.8. R.9. R.10. R.11. R.12. R.13. R.14. R.15. R.16. R.17. R.18. R.19. R.20. R.21. S.24.* S.25. S.26. S.27. S.28. S.29. M.m. 0 0,42 1,14 0 0,02 0 0 0 0,22 0,9 0,12 0,16 0,18 0,44 0,38 1,88 8,14 0,7 0,82 1,9 4,34 0,22 0,58 1,3 0,02 0,1 9,36 5,02 8,48 4,6 10,1 3,82 U.cr. 15,98 2,62 6,18 0,08 0,02 9,4 10,54 0,4 4,96 9 0,02 0,04 0,1 0 0 2,02 4,06 0,24 0,22 0,84 6,32 1,16 2,42 0,6 1,86 0,7 4,3 0 0,06 0 0 0 Serial numbers of transekts M.m. – M. margaritifera, (black,) U.cr. – Unio crassus ( dotted) Age structure of Margaritifera margaritifera in different years. 20 18 16 14 1999 12 2004 % 10 2005/2007 8 2011 6 4 2 0 40- 45- 50- 55- 60- 65- 70- 75- 80- 85- 90- 95- 100- 105- 110- 115- 120- 125- 130- 135- 44 49 54 59 64 69 74 79 84 89 94 99 104 109 114 119 125 129 134 139 mm The shell length/age classes with steps of 5 mm. (Hruška 1992; Erikson et al. 1998; Heinisch et al. 2001; Rudz īte 2001; Bespalaya et al. 2007). Abu sugu popul 30 25 20 2011.gadā 15 ciju vecumstrukt 10 Relative distributio (%) 5 0 30-34 ā The shell length/age35-39 classes 40-44 45-49 50-54 55-59 60-64 65-69 ū 70-74 ra Length 7classes5-79 (mm) 80-84 85-89 90-94 95-99 100-104 105-109 U.cr. – 110-114 115-119 Unio crassus 120-124 125-129 130-134 135-139 U.cr. M.m. M.m. – M.margaritifera chemical analyzes • from 21 points, year 2006. Content of Oxigen in the water, 2006 yr., may and aug./september Sk ābek ļa daudzums ūden ī 15 10 maijs mg/l 2 aug./sept. O 5 0 20. 1. 21. 6. 15. 3. 4. 9. 16. 17. 2. 5. 7. 8. 10. 11. 12. 13. 14. 18. 19. maijs 7,52 10,7 10,6 8,89 11 10,9 9,87 9,72 9,69 11,1 11,1 9,85 9,91 9,76 9,84 10,1 9,23 9,14 10,2 10,3 aug./sept. 8,92 4,86 4,08 5,25 8,72 4,91 4,21 5,21 5,25 5,12 7,45 5,81 5,19 6,05 5,69 8,61 6,59 6,34 7,32 6,88 6,67 Paraugu ņemš. vietu nr. Points 20.1., 21., 6., 15. - human activities affected sites, ie site just downstream of anthropogenic pollution intakes or a straightened section of the river where the rapids habitat mechanically destroyed; Points 3., 4., 9., 16., 17. - Beaver affected section of the river - the flush and directly downstream of the beaver dam; 2., 5., 7., 8., 10., 11., 12., 13., 14., 18., 19. - typical of rapids habitat, as far as possible from sources of pollution and the impact of beavers. Water conductivity in the Palsa 2006 yr., may and aug./september. Ūdens elektrovad ītsp ēja 600 500 400 maijs 300 aug./sept. 200 EVS qS/cm EVS 100 0 20. 1. 21. 6. 15. 3. 4. 9. 16. 17. 2. 5. 7. 8. 10. 11. 12. 13. 14. 18. 19. Paraugu ņemš. vietu nr. Water pH in the Palsa 2006 yr., may and aug./september. Ūdens pH 8,3 8,2 8,1 8 7,9 maijs 7,8 aug./sept. 7,7 7,6 7,5 7,4 20. 1. 21. 6. 15. 3. 4. 9. 16. 17. 2. 5. 7. 8. 10. 11. 12. 13. 14. 18. 19. Paraugu ņemš. vietu nr. Summary Nitrogen in the Palsa 2006 yr., may and aug./september. Kop ējais sl āpek ļa daudzums ūden ī 3 2,5 2 maijs 1,5 aug./sept. 1 N kop. mg/l N kop. 0,5 0 20. 1. 21. 6. 15. 3. 4. 9. 16. 17. 2. 5. 7. 8. 10. 11. 12. 13. 14. 18. 19. Paraugu ņemš. vietu nr. Bacteria Sphaerotilus nitens in extremally polluted stretch downstream a pig farm Ammonium in the Palsa 2006 yr., may and aug./september Amonija sl āpek ļa daudzums ūden ī 2 1,5 maijs mg/l 1 4 aug./sept. NH 0,5 0 20. 1. 21. 6. 15. 3. 4. 9. 16. 17. 2. 5. 7. 8. 10. 11. 12. 13. 14. 18. 19. Paraugu ņemš. vietu nr. Phosphorus (summary) in the Palsa 2006 yr., may and aug./september Kop ējais fosfora daudzums ūden ī 0,25 0,2 0,15 maijs 0,1 aug./sept. P kop. mg/l kop. P 0,05 0 20. 1. 21. 6. 15. 3. 4. 9. 16. 17. 2. 5. 7. 8. 10. 11. 12. 13. 14. 18. 19. Paraugu ņemš. vietu nr. zoobenthos samples • were taken in all the 20 sites, used for chemical analyzes of water. • Special sampling at extremal pollutant pig farm. • in the may and aug./september of 2006. Zoobentos dominant invertebrate groups: • Chironomidae - chironomids • Ephemeroptera - Mayflies or shadflies (Heptagenia sulphurea, Baetis rhodoni, Habrophlebia lauta); • Trichoptera - Caddisflies (Hydropsyche angustipenis, Goera pilosa, Silo spp .); • Mollusca (Unio crassus, Ancylus fluviatilis, Pisidium amnicum). macrozoobenthos structure Spongia Turbellaria Nematomorpha Oligochaeta Hirudinea Gastropoda Bivalvia Crustacea Plecoptera Ephemeroptera Heteroptera Megaloptera Trichoptera Odonata Diptera 160 140 120 100 g/m2 80 60 40 20 0 Nr.1. Nr.2. Biomass Nr.3. In the summer ammountNr.4. of zoobenthos is sufficient for salm and other fish feed. Nr.5. g/m2 (may) g/m2 (august) Nr.6. (g/m Nr.7. 2 ), Nr.8. may/ Nr.9. Nr.10. august Nr.11. Nr.12. Nr.13. Nr.14. Nr.15. Nr.16. Nr.17. Nr.18. Nr.19. Nr.20. onide Host fish populaton • studied in 1996, 2001, 2006. • Salmo salar - Atlantic salmon – only young fishes are found on estuary of river Palsa where pearl mussel do not occur. • brown trout - Salmo trutta trutta and Salmo trutta fario – found small number up to 2001, • In 2005.- 2008. The artificially breeded smolts 1+ of Salmo trutta fario (local population) are released in Palsa basin. on inventory In 2006. these young fishes are found. Host fish of Unio crassus: • 5 species known as hosts found on Palsa river, populations are stable. Leuciscus leuciscus, Phoxinus phoxinus, Pungitius pungitius, Perca fluviatilis, Cottus gobio (rare) Main pollutants in Palsa: • Old sewage plants in willage. Renovated in 2010. • The pig farm. Probably, will be closed in 2013. • Beavers, living in all territory of Palsa river and tributaries. • In 2005. - 2007. hunters in 28 km of rivers has destroyed 181 beaver dams and hunted 215 beavers, some stretches became beaver free. beaver dams • now cooperation with hunters are interrupted, in 2010. un 2011. beavers retuned back. Resume • Margaritifera margaritifera surviving possibilities in the Palsa basin are not good, population is aged, host fish population is not stable. • Unio crassus surviving possibilities are good. The young mussels are present, host fish populations are sufficient.