Polish-Norwegian Research Fund

1. Polish-Norwegian Research Fund Assessment of the ecological state of lakes based on ichthyofauna data Witold Białokoz and Łucjan Chybowski Department of Lake Fisheries Inland Fisheries Institute Giżycko

2. Polish-Norwegian Research Fund Tasks of the Inland Fisheries Institute Collecting and analyzing archive data relating to lake ichthyofauna Analyzing the ichthyofauna of catchment area lakes Validating metric indices developed in Poland based on the species composition and the structure of ichthyofauna Integrating the results of lake analyses based on ichthyofauna metrics Evaluating the ecological state of the studied lakes based on ichthyofauna data

3. Polish-Norwegian Research Fund Task 1. Collecting and analyzing archive data relating to lake ichthyofauna • The data from commercial lake fisheries of Dąbrowa Wielka, Dąbrowa Mała and Rumian were supplemented (from fishing logs). • Dispersed data on angling catch from Polish Angling Association (PAA) lakes were collected (archive entries in fishing logs and angling surveys). Fisheries changed during the restructuring process; most of the available data are incomplete or inconsistent with the existing assessment method.

4. Polish-Norwegian Research Fund Task 2. Analyzing the ichthyofauna of catchment lakes Ichthyofauna sampling campaigns using calibrated net sets with different mesh sizes (Nordic gillnets) were carried out in the summer and autumn of 2008 and 2009 in accordance with the optimal variant of CEN standard.

6. CEN 14757 standard A total of 288 benthic and 26 pelagic nets were set up. It should be noted that ichthyofauna sampling in line with the CEN standard is a highly laborious and time-consuming process.

8. Polish-Norwegian Research Fund The sampling campaign produced an abundance of research material supporting a detailed information of ichthyofauna structure and distribution across the studied lakes. The resulting catch was weakly represented by the pike and the tench, even in lakes where the above species are normally abundant. The numbers of older bream and roach individuals were also relatively low. Their numbers are much higher in the catch from commercial fishery. In stratified lakes, fish were rarely encountered at greater depths in oxygen-deficient water layers.

9. Polish-Norwegian Research Fund A total of 22 fish species were caught in the lakes in the catchment area of the Wel River. The greatest species abundance was observed in Lakes Rumian (13) and Dąbrowa Mała (12), and the lowest – in Lake Zwiniarz (8). In the majority of the studied lakes, the most abundant species were the perch, roach, bleak, ruffe, carp and bream.

10. Polish-Norwegian Research Fund The experimental angling campaign in Lake Kiełpińskie was carried out in joint effort with the Norwegian team. The participants exchanged their experiences and information relating to the methods for evaluating the ecological state of Polish and Norwegian lakes based on their ichthyofauna composition.

11. Lake Kiełpińskie • 24 benthic nets-- • 2 pelagic nets ---

12. Polish-Norwegian Research Fund

13. Polish-Norwegian Research Fund Lake Kiełpińskie catches with all nets Total 3166

14. Polish-Norwegian Research Fund Lake Kiełpińskie catches with benthic nets 11 specimens

15. Polish-Norwegian Research Fund Lake Kiełpińskie catches with pelagic nets 5 specimens

16. Polish-Norwegian Research Fund Lake Kiełpińskie Catch structure in all nets weight individuals

17. Polish-Norwegian Research Fund Lake Kiełpińskie Catch structure in benthic nets weight individuals

18. Polish-Norwegian Research Fund Lake Kiełpińskie Catch structure in pelagic nets weight individuals

19. Polish-Norwegian Research Fund Lake Kiełpińskie Structure of functional fish groups in all nets weight individuals

20. Polish-Norwegian Research Fund Lake Kiełpińskie Structure of functional fish groups in benthic nets weight individuals

21. Polish-Norwegian Research Fund Lake Kiełpińskie Structure of functional fish groups in pelagic nets weight individuals

22. Polish-Norwegian Research Fund Perch: length distribution in samples and mean growth of perch in Polish lakes

23. Polish-Norwegian Research Fund Bream: length distribution in samples and mean growth of bream in Polish lakes

24. Polish-Norwegian Research Fund Roach: length distribution in samples and mean growth of roach in Polish lakes

25. Polish-Norwegian Research Fund Lake Kiełpińskie catches per unit effort (CPUE)

26. In 2008, a mathematized method for evaluating the ecological status of lakes based on their ichthyofauna composition was developed in Poland*. This method may be applied only to lakes that are regularly used for commercial fishing and where multi-year data on the ichthyofauna composition of catches are available. • The lakes in catchment area of the Wel River are used mainly by individual anglers or for selective commercial fishing. For this reason, the proposed assessment method may not be directly applied in the above lakes. • The only reliable source of information on the studied lakes’ ichthyofauna are the results of our sampling campaign with the use of Nordic gillnets. The contributed information constitutes practically the first dataset in the country. The data will be used in an expert evaluation of the lakes’ ecological state. We will also attempt to outline a new method for assessing other Polish lakes. * commissioned by the Chief Inspectorate for Environmental Protection, financed by the National Fund for Environmental Protection and Water Management

27. Polish-Norwegian Research Fund Selection of characteristics (metric indices) - assumptions • Types of lakes based on catch statistics: vendace lakes, bream and pike-perch lakes, tench-pike lakes. As regards morphometric parameters, those lakes differ mainly with respect to depth. • Lakes classified to different types differ significantly as regards their natural trophy, but lakes with higher trophic levels are not always marked by a lower ecological status. • Different types of lakes vary with respect to their ichthyofauna composition and structure. • Within a given type, a change in a lake’s ecological state is accompanied by changes in ichthyofauna structure. • In lakes of lower ecological quality: • the share of cyprinids increases • the share of large-sized cyprinids decreases • the share of predatory species decreases • the share of sensitive littoral species decreases • pike-perch appear in vendace-dominated lakes

28. Polish-Norwegian Research Fund Lakes in the catchment area of river Wel

29. Polish-Norwegian Research Fund • Data available from Nordic gillnet sampling campaign: • species occurrence; • fish distribution across the studied lakes (in area and depth); • CPUE (abundance and biomass); • fish size distribution; • Metric indices available for the Wel Project: • species occurrence; • quantitative share of species and species groups; • share of species and species groups in biomass; • presence and share of typical , indicator and sensitive species (pike-perch in vendace-dominated lakes, perch, rudd, vendace); • reproductive continuity – for common species; • zone accessibility for fish (littoral, pelagic, profundal). • Fulton’s condition factor... ?

30. Polish-Norwegian Research Fund Thank you for your attention. Feel free to share your questions and comments. Lake Dąbrowa Wielka