Diversity of Ecosystems
Water quality in 80% of Latvian rivers is estimated as good or satisfactory. Since the use of fertilisers in agriculture has drastically decreased, the situation is stable.Many mesotrophic lakes (in the 50s and 60s) have turned into eutrophic. This occurred both due to natural eutrophication and nutrient leakage from agricultural lands. About 40% of lakes suffer from heavy antropogenic influence. Occasionally drainage along shores has caused signficant decrease in number of waterfowl both breeding and migrating. In Engure Lake the number of the breeding waterfowls has decreased disastrous in the last five years. The main disfavourable reason for all of the bird groups is increaseng of the number of the introduced American Mink and nest destructions.
A particular critical situation has occurred inland, where due to wide hydrotechnical works and melioration, biotopes were partly damaged. Widely distributed and expansive species are ousting the ones whose ecological amplitude is narrower and with limited ability of competition. Presently these species have disappeared completely or only small populations have remained in some lakes. Commercial fishing is comparatively small in inland waters and most of it is related to fish catch in ponds (mostly carps). In the first 4 months of 1995 the inland catch was 234.4 tons which is 0.64% of the total fish catch. If compared to the same period of 1994, the increase is 58.2 tons.
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