196
J. Kubiak and S. Machula
in water trophies, there are also changes in the size of fishing production, which
initially increases quickly, then undergoes inhibition, and in highly eutrophicated
tanks decreases [15, 50–52].
The tendency to change the ichthyofauna syndrome along with the progressive
eutrophication has a univocal nature, regardless of climatic conditions. Although
species composition of fish is different, changes in subtropical lakes are similar to
those observed in temperate lakes [51, 52].
Analyzes of quantitative and qualitative changes of ichthyofauna caused by the
eutrophication of lakes progressing in Poland, among others Iwaszkiewicz [54] and
Leopold et al. [55]. The vast majority of domestic lakes were dominated by families of
cyprinidae and perchidae (Percidae) whose requirements correspond to the environmental conditions existing in these reservoirs (mesotrophy, and above all eutrophy).
These families, although poorer in economically valuable species, develop well even
in shallow, strongly political tanks, in which there are often mass algae blooms as
well as summer and zoning oxygen deficits. This means that eutrophication of lakes,
which does not lead to saprophy, does not threaten the existence of most species
included in these families. On the contrary, in some mesotrophic reservoirs, the
increase in fertility, even by the subsequent intensified development of macrophytes,
may create better conditions for reproduction and living of a significant number of
fish from these families. Most of our mesotrophic lakes are approaching or have
already reached the level of eutrophication, after which there will no longer be an
increase in the total biomass of fish [50].
The increase in the level of trophic waters and its effects cause the need to look
for ways to slow down, inhibit, or even reverse this unfavorable process or remove
its negative consequences [7, 8, 34]. Water protection is based on a comprehensive knowledge of ecosystems, which are open structures exchanging substances
and energy with their surroundings. There is a need to analyze these interrelations
and interactions, taking into account both biotic and abiotic factors. It is appropriate to assess the quality of the ecosystem based on physical-chemical, biological,
and ecomorphological criteria [11]. At present, in the protection of lakes, internal
reclamation methods, used within the lake basin, and external—protective ones,
concerning their catchments are distinguished. The basic, most effective way to
protect lakes is to reduce or eliminate feed sources in biogas [5, 7, 8]. Therefore it is
necessary to eliminate point sources of pollution and maximum reduction of sewage
disposal, without removing biogenic compounds.
Necessary for the protection of lake ecosystems and their rational use is the recognition of the natural resistance of lakes to degradation and the role of the basin in
accelerating or inhibiting this process [2, 32, 57–59]. Depending on the natural physical and geographical features, the catchment can accelerate or inhibit the supply of
matter (including nutrients) to the lake. The effects of the supply of matter can be
different in the tank, depending on the natural resistance, resulting from morphometric and hydrological features [4, 59]. This requires individual consideration of the
use and protection of the reservoir, taking into account not only the current water
J. Kubiak and S. Machula
in water trophies, there are also changes in the size of fishing production, which
initially increases quickly, then undergoes inhibition, and in highly eutrophicated
tanks decreases [15, 50–52].
The tendency to change the ichthyofauna syndrome along with the progressive
eutrophication has a univocal nature, regardless of climatic conditions. Although
species composition of fish is different, changes in subtropical lakes are similar to
those observed in temperate lakes [51, 52].
Analyzes of quantitative and qualitative changes of ichthyofauna caused by the
eutrophication of lakes progressing in Poland, among others Iwaszkiewicz [54] and
Leopold et al. [55]. The vast majority of domestic lakes were dominated by families of
cyprinidae and perchidae (Percidae) whose requirements correspond to the environmental conditions existing in these reservoirs (mesotrophy, and above all eutrophy).
These families, although poorer in economically valuable species, develop well even
in shallow, strongly political tanks, in which there are often mass algae blooms as
well as summer and zoning oxygen deficits. This means that eutrophication of lakes,
which does not lead to saprophy, does not threaten the existence of most species
included in these families. On the contrary, in some mesotrophic reservoirs, the
increase in fertility, even by the subsequent intensified development of macrophytes,
may create better conditions for reproduction and living of a significant number of
fish from these families. Most of our mesotrophic lakes are approaching or have
already reached the level of eutrophication, after which there will no longer be an
increase in the total biomass of fish [50].
The increase in the level of trophic waters and its effects cause the need to look
for ways to slow down, inhibit, or even reverse this unfavorable process or remove
its negative consequences [7, 8, 34]. Water protection is based on a comprehensive knowledge of ecosystems, which are open structures exchanging substances
and energy with their surroundings. There is a need to analyze these interrelations
and interactions, taking into account both biotic and abiotic factors. It is appropriate to assess the quality of the ecosystem based on physical-chemical, biological,
and ecomorphological criteria [11]. At present, in the protection of lakes, internal
reclamation methods, used within the lake basin, and external—protective ones,
concerning their catchments are distinguished. The basic, most effective way to
protect lakes is to reduce or eliminate feed sources in biogas [5, 7, 8]. Therefore it is
necessary to eliminate point sources of pollution and maximum reduction of sewage
disposal, without removing biogenic compounds.
Necessary for the protection of lake ecosystems and their rational use is the recognition of the natural resistance of lakes to degradation and the role of the basin in
accelerating or inhibiting this process [2, 32, 57–59]. Depending on the natural physical and geographical features, the catchment can accelerate or inhibit the supply of
matter (including nutrients) to the lake. The effects of the supply of matter can be
different in the tank, depending on the natural resistance, resulting from morphometric and hydrological features [4, 59]. This requires individual consideration of the
use and protection of the reservoir, taking into account not only the current water