Lake Barlineckie is one of the largest glacial lakes in the Myślibórz Lakeland, Surrounded by morainal hills vegetated mostly by beech forests, the lake is fed by three tributaries, one of which originates in the hills in the south and supplies the lake with cold and clean spring water. Numerous springs well up on the southern slopes and in the shallow littoral of the lake; for this reason, water temperature of Lake Barlineckie is lower in summer and higher in winter than that in other lakes. Collections for this work were made in spring and summer of the years 1992-1995. Molluscs were collected down to the depth of 80 cm from 9 sites, using a scoop net and by examining aquatic plants and submerged objects. Samples from transects I, II, and III were collected with a 400 cm² Ekman-Birge grab, at 1 m depth intervals down to 8 m. The study was aimed at describing the mollusc (Mollusca) fauna of 5 selected plant species representing assemblages of helophytes, nymphaeids, and elodeids in the shallow littoral of Lake Barlineckie; vertical distribution of the molluscs was examined as well. The collection consisted, overall, of 9 308 individuals contained in 110 samples. A total of 26 gastropod (Gastropoda) and 20 bivalve (Bivalvia) species were identified. In Lake Barlineckie, gastropods were mainly associated with plants: 60% of all individuals were collected from them. Phragmites australis, Potamogeton perfoliatus, Ceratophylum demersum, Myriophyllum spicatum, and Nuphar lutea supplied 22, 16, 10, 8, and 4% of the total number of gastropods, respectively. In terms of the species richness, the highest number of species was found on N.lutea (23 species), the lowest species richness being typical of P.australis (13 species). Bivalves were found to occur within 0.5-1 m depth range where a total of 20 species were identified. Down to the depth of 2 m, the number of species decreased by 50% and was further reduced with depth. The bivalves occurring at the deepest (at depths exceeding 7 m) were Pisidium henslovanum and P.nitidum; Dreissena polymorpha was found to uniformly inhabit the bottom down to the depth of 6 m; Unio tumidus and Anodonta complanata occurred down to the depth of 2 m at the sites located close to the direct supply of spring water. Anodonta anatina inhabited the shallow littoral within the depth range of 0.5-1 m. The abundance of gastropods and bivalves along the three transects demonstrated depth-dependent variability, both in spring and summer. Both the abundance and the structure of mollusc assemblages was closely related to phenological cycles of aquatic plants. Lake Barlineckie was found to support 11 bivalve species threatened by extinction, including Pisidium lilljeborgii, an early glacial relict.

A possibility of applying the Dahl-Lea back calculation method to growth rate assessment of roach, bream, pike, and zander inhabiting open inland waters in Poland was investigated. Scales were selected for the purpose due to their availability, legibility of annual rings, and a high reliability of readings. The scales with which to investigate the body length-scale caudal radius relationship in bream and roach were collected from the fish caught in heated Konin lakes (the Licheńskie, Pątnowskie, Wąsowskie, Gosławskie) and from the coastal lakes Łebsko, Gardno, Bukowo, and Jamno. The relationship in pike was explored on scales collected from individuals caught in the coastal lakes Łebsko, Gardno, and Bukowo and from a small (about 40 ha), shallow (a kind of a natural pond) Lake Warniak in the Warmia-Masurian Lake District. Scales of zander, to be used for investigating the body length-scale oral radius relationship, were collected from individuals caught in the coastal lakes Jamno, Łebsko, Bukowo, and Kopań. The scales were collected in various years of the second half of the 20th century, during the autumn-winter season after the fish growth had slowed down. The analyses performed allowed to contend that the Dahl-Lea method of back calculations, necessitating a direct relationship between body length and scale radius, can be applied to bream and roach. In pike, the body length-scale caudal radius relationship is linear, but the free term in the equation derived (y =  22.607x +  2.6217) suggests the Rosa Lee method as more suitable. In the zander populations studied, the body length-scale oral radius relationship was linear as well. However, as the sample was not representative (a narrow range of fish sizes and low numbers of fish in various size classes), the relationship was not sufficiently reliable. For this reason, the results of growth rate calculations with the method used would carry a too heavy bias.

Variability of body weight and morphometry of the Chinese mitten crab (Eriocheir sinensis) was studied on a total of 142 individuals (68 females and 74 males) found within 15 October – 15 November 2000 in fyke nets deployed in the northern part of Lake Dąbie and in the southern part of the Szczecin Lagoon, a southern Baltic estuarine area where the non-indigenous crab had established an abundant population. The body weight, carapace length, and carapace width of the crabs were found to range within 30.1-458.9 g, 36.1-85.4 mm, and 41.1-98.4 mm, respectively, the male crabs being significantly heavier than the females. The comparative analysis of 11 metric characters of males and females revealed other indicators of sexual dimorphism in the population studied; of those, particularly pronounced differences were recorded in the relative claw length (significantly higher in males) and the relative length and width of abdomen (significantly higher in females).

The generation fecundity of roach in 1985-1990 and its population fecundity in 1987-1992 were determined in the coastal lakes Gardno and Łebsko in the Słowiński National Park. The number of specimens which attained recruitment age annually per mature female was also determined. The average fecundity of the same generations from the two reservoirs was similar at 4.1·109 eggs in Lake Gardno and 4.4·109 in Lake Łebsko. The most abundant generation of females was observed in 1985; it was also the most fecund producing 7·109 eggs in Lake Gardno and 5.3·109 in Lake Łebsko. The subsequent generations were less numerous and produced fewer eggs. The four and five year old females in Lake Gardno had the highest egg production in each of the analyzed years. The most fecund females in Lake Łebsko consisted of specimens which were five and six years old. In the 1987-1992 study period, the average fecundity of the spawning roach populations in Lake Gardno was 7.4·109 eggs and in Lake Łebsko it was 5.9·109. From eight to 14 specimens of both sexes at recruitment age (age group 2+) were reported per mature female annually.

Results of research, carried out in 2001-2002, on hydrochemistry of River Gowienica are presented. The Gowienica drainage is situated in the western part of the District of Western Pomerania. Thermal and oxygen regimes were studied, as were the organic matter load (BOD₅, COD_Cr) and nutrient (NH₄⁺, NO₃^-, NO₂^-, organic N, total N, reactive P, total P) contents. The oxygen content was found to range within 4.4-14.6 mgO2·dm^-3, while the ranges of BOD₅ and COD_Cr were 0.6-5.5 and 12.2-47.4 mgO₂·dm^-3, respectively. Mean contents (mg N·dm-3): of nitrogen compounds amounted to 0.180 for ammonia nitrogen, 0.032 for nitrite nitrogen, 0.239 for nitrate nitrogen, 0.283 for organic nitrogen, and 0.740 for total nitrogen. Mean contents of reactive and total phosphorus were 0.186 and 0.293 mg P·dm^-3, respectively. The study showed the organic matter load and nutrient contents to increase downstream, from the river’s origins to its mouth. Statistical analyses demonstrated the organic matter load and nutrient content to be directly correlated with temperature and to be inversely correlated with the oxygen content. A direct relationship between total nitrogen and phosphorus contents on the one hand and the organic matter load on the other was revealed as well.

Variability of cadmium, zinc, copper, and iron contents in water of 29 south-western Pomeranian lakes is described. The study was carried out during periods of summer stagnation as well as spring and autumn homothermy of 1999. Mean contents of copper in surface and near-bottom water were 56.7 and 63.6 mg·dm^-3, respectively; the corresponding values for lead were 58.6 and 65.6 mg·dm^-3, for cadmium 6.0 and 6.7 mg·dm^-3, for zinc 87.3 and 92.8 mg·dm^-3, and for iron 83.3 and 96.4 mg·dm^-3. The catchment properties and use determines the degree of heavy metal contamination. As evidenced by the results of statistical treatment, variability in the heavy metal contents in the lakes under study depends on their trophic status and mixing intensity. Eutrophic lakes showed higher metal contents, compared to meso- and mesoeutrophic ones. Poly- and tachymictic lakes showed higher metal contents and lower variability than in more stable eu- and bradymictic lakes.

The use of the sewage sludge in the agriculture, its possibility of use as a fertilizer was assessed. Four fertilizing treatments were applied to ponds stocked with carp fry. The hydro-chemical parameters of the ponds fertilized with sewage sludge were compared to ponds fertilized with mineral fertilizers and those non fertilized. No statistically significant difference was observed (p < 0.05) between the average total phosphorus concentration in ponds fertilized with the sewage sludge (0.29 mg P·dm^–3) and those fertilized with superphosphate (0.30 mg P·dm^–3). No negative influence of used sewage sludge on pond ecosystem was observed, measured in hydro-biological and hydro-chemical parameters. Proximity analyses did not reveal heavy metals accumulation or human pathogenic organisms presence in fish bodies. The use of sewage sludge can be recommended as the on1y source of phosphorus. Additional mineral nitrogen fertilizer is required due to sludge composition.

Establishment of protected areas requires actions aimed at preservation of natural qualities of the objects occurring in the areas to be protected. The paper describes hydrochemical conditions and trophic status of lakes Binowo (Binowskie), Glinna, and Szmaragdowe, the largest water bodies in the Szczecin Landscape Park. The study was conducted in 1997-1998. The lakes were found to differ in their water mass dynamics: while Lake Szmaragdowe was bradymictic, water dynamics of lakes Glinna and Binowo placed them among eu- and polymictic reservoirs, respectively. The oxygen regime, organic matter load, and nutrient contents found are indicative of a considerable fertility of the lakes studied. The Binowo and Glinna should be classified as strongly eutrophic. Although Lake Szmaragdowe can be regarded as mesoeutrophic, its water quality is steadily deteriorating. In terms of the lake monitoring system standards, water of the Binowo and Glinna should be considered as belonging to quality class III, the Szmaragdowe being placed in quality class II. To stop further degradation of lakes Binowo and Glinna and to retain their recreational value, it is necessary to upgrade sewage management practices within the catchment and, foremost, to stop direct discharge of municipal sewage into the two lakes.

Water samples were collected from lakes: Ostrowo, Piaski, and Przybiernowskie in summer seasons of 1980 do 1997, for 5 or 7 years; additionally, within 1995-1997 samples were collected every three months. The samples were collected from three layers (near-surface, intermediate, and near-bottom) of the water column overlying the deepest site of each lake. The results obtained allowed to classify the lakes as polymictic and eutrophic. Spatial and temporal changes of mineral forms of nitrogen were typical of eutrophic reservoirs showing a clear trend towards deposition of nitrogen in bottom sediment. The eutrophic nature of the lakes studies is confirmed also by the high concentrations of phosphorus compounds. In addition, the lakes are prone to secondary eutrophication.

In two experiments (A and B), 46 and 606 g individual weight carp, stocked in 2 m³ cages at densities of 150 and 35 individuals per cage, respectively, were fed an extruded feed of 46.3% crude protein, 24.3% lipid, and 22.94 MJ·kg^-1 gross energy contents. In the 42-day-long experiment A, the carp fed rations of 2.00; 2.75; 3.50; 4.25; and 5.00%W0.8 showed the specific growth ratio (SGR) to be: 2.84; 3.61; 4.19; 4.50, and 4.50%·d^-1, respectively, the respective food conversion ratios (FCR) amounting to 1.07; 1.07; 1.15; 1.36, and 1.58. The highest apparent lipid retention (aLR=74.13%) and the highest amount of energy retained in the body (ER=43.89%) was recorded in the carp fed the 3.5W0.8 ration, the highest net protein utilisation (aNPU=29.84%) being found in the fish receiving the lowest feed ration. In experiment B of 49 days duration, the carp fed rations of 0.8; 1.2; 1.6; 2.0, and 2.4%W0.8 showed SGR to amount to 0.89; 1.32; 1.65; 1.95, and 2.02%·d-1, respectively, the respective FCR values being 0.94; 0.92; 0.95; 1.00, and 1.17. The highest retention of lipids (aLR= 78.95 %) and energy (ER= 49.88%) in the fish body was found in the carp fed the 2.0W0.8 ration, the highest aNPU (42.77%) being recorded in the fish receiving the lowest feed ration. The results obtained allow to conclude that high-energy feeds can be successfully used to feed carp kept in intensive cultures in cooling water.