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Comparison of Macrophyte vegetation areas of the Kozjak lake (NP Plitvice Lakes) between the years 2002 – 2004 and 2016.

Research data of Plitvice Lakes freshwater habitats proved the changes of habitats and fish population assemblages. Kozjak is the largest of 16 National park lakes. During its research in 2002-2004, we marked 41 coastal “micro areas” distinguished by macrophyte vegetation, which covered 17, 000 square meters or 2.07% of the total lake water surface. Those areas, as the spawning ground, are significant ecological factor for the population explosion of nonnative fish species Squalius cephalus and Scardinius erythrophthalmus. One of the research goals, started 2016, was to compare possible changes of macrophyte vegetation areas during 15 years time interval. The same measurements methods were used, taking data on foot and by using electro-boats. Analyzed data show macrophyte vegetation cover 14, 000 m2 or 1.71% of the Kozjak lake water surface. Not significant difference of 0.36% may be our measurements error, management activity proposed in 2004, or something else. During the last research we estimated for the first time, not only for the lake Kozjak but also for other lakes of the National Park, habitat attributes as areas relevant to fish populations. We divided mentioned areas to: submerged woody debris, hanging banks vegetation, submerged vegetation, and macrophyte vegetation. We hope that analyzed data will be useful as reference points in further targeted research.

macrophyte vegetation, NP Plitvice Lakes, habitats, fish populations

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