The objective of the present paper was to determine the variability of metric and meristic characters of the sample of flounder captured in the Pomeranian Bay. Moreover, the material studied allowed to describe a length distribution, age structure, growth rate of length and weight as well as the length-weight relationship. The population examined showed a high plasticity of metric characters testified by high coefficients of variability. It was stated that he relationship between the longer radius of otolith and total length of fish examined was curve-linear, therefore the growth rate of length by means of back- calculations was estimated followed the Vovk’s method. The growth rate of length and weight in the flounder studied from the Pomeranian Bay was calculated employing the v. Bertalanffy’s and modified v. Bertalanffy’s equations, respectively. In the case of 14 metric characters statistically significant differences between sexes were found used the non- parametric test of Kolmogorov- Smirnov. In meristic characters no statistically significant differences between sexes were noted.

Bioaccumulation of heavy metals (chromium, copper, nickel, cadmium, lead, and zinc) in tissues (muscles, gills, kidneys, liver) of four fish species: zander (Stizostedion lucioperca L.), perch (Perca fluviatilis L.), bream (Abramis brama L.), and roach (Rutilus rutilus L.), most important for the Wojnowskie Lakes ichthyofauna, was related to fish age, weight, and total body length. The tissue heavy metal contents were found to vary with fish age. The heavy metal bioaccumulation vs. fish age relationship was species-specific. In most cases, a negative relationship was observed. Positive correlations were recorded in zander and bream for cadmium vs. fish age and length, in bream for lead vs. age, length, and weight, and in roach for nickel vs. fish weight. In the remaining cases, statistically significant correlations between fish age and contents of the heavy metals studied were negative.

The stage of gonad development was estimated in salmon in their second year of life, in lower growth rate group that was not smoltifying in the first season. The mean fork length of females (149 individuals) was 10.25 cm, males (145 individuals) 10.45 cm. The gonadosomatic index ranged from 0.03 to 0.38 (an average of 0.17) in females, and from 0.01 to 6.22 (an average of 0.37) in males. All female gonads were at the similar stage of gonadal maturity. The most advanced in development oocytes were found in protoplasmatic growth phase, with a ring of basophilic cytoplasm situated in the peripheral cytoplasm. The diameter of the oldest generation oocytes varied between 78.8-145.0 mm (an average of 106.73). The stage of testes development was diverse. The juvenile males possessed only type A spermatogonia in the lobules whereas the maturing ones had cells at the beginning or at the late phases of spermatogenesis. The first group represented 72.4% and the second 27.6% of population, respectively.

Abstract.This paper presents detailed statistics of pikeperch (Stizostedion lucioperca L.) catches in the Polish EEZ. A comparison is made with those from European waters (10 100-17 400 tons per annum), and the pikeperch unit price reported in European markets is compared with that of other fish species. The annual pikeperch catches in the Polish EEZ in 1993-2002 ranged from 274 to 438 tons, and 60-70% of them originated in the Szczecin and the Vistula lagoons. The value of parameter (K) in the Brody-Bertalanffy growth equation was determined as part of the study and served to estimate the natural mortality coefficient (M) for pikeperch (from 0.18 to 0.22). The productivity of the exploited pikeperch population in the Szczecin Lagoon was estimated using the model by Beverton and Holt [1957] and modified by Jones [1957]. The results of the analyses indicate that, at the current exploitation rate and at a consistent level of new generation recruitment, the pikeperch minimum length in the Szczecin Lagoon and the Pomeranian Bay (45.0 cm L.t.) is appropriate for the population efficiency.

The fecundity of 169 roach females from Lake Gardno and 210 females from Lake Łebsko was estimated in 1998-2001. The dependency of body length, weight and age and the realized fecundity in roach females from both lakes was determined. The roach females spawned for the first time at the age of 3+, and the oldest specimens able to spawn were 13+. The roach from Lake Gardno had higher absolute fecundity than did Lake Łebsko specimens of the same size. The diameter of roach eggs from Lake Gardno was smaller. Roach females with a body length of 20 cm produced an average of 26 400 eggs in Lake Gardno and 25 800 eggs in Lake Łebsko. These are equal to the average European values.

The skull bones possess many characteristic features that are regarded as the main criteria of species, forms, and population differentiation. The performed measurements allowed not only to estimate the bone shapes, proportions, the extent of variability ranges but also to perceive the variability dynamics of particular bones of the individuals aged from 0+ to adults. Osteological analysis of 4 skull bones obtained from both juvenile and adult salmon and sea trout individuals revealed a lot of differences between studied forms. The dissimilarities in cranium structure between salmon and sea trout were visible in juveniles already but were more significant in adults. Mesethmoideum of both juvenile and adult salmon individuals was much more streamlined than the sea trout’s one. The praemaillare bone of juvenile individuals of salmon lacked the small process that was present in sea trout. Besides, in juveniles and adult salmon this bone was narrower. Vomer of juvenile and adult salmon differed in plate shape, the narrowing below the plate and the length of denticulated section on the corpus. The characteristic differences in os glossohyale structure concerned the length of denticulated section that was longer in sea trout, and the teeth alignment.

Research conducted in winter and summer aimed to establish the level of nitrogen elimination from fishponds fertilized with municipal sewage. Biologically treated sewage in the quantity of 30 000 m3 per day was obtained from the sewage treatment plant for Bielsko-Biała municipality and supplied to ponds of a total area of 41 ha. Research concentrated on five ponds. Two of them operated in the bead system, while the remaining ones had independent inflows and outflows. In winter one pond was stocked, and in the season the carp was stocked in three variants in polyculture with bigheaded carp and grass carp. In winter nitrogen elimination was very limited; only in the pond stocked with carp did it reach 20% for ammonia nitrogen and 13% for nitrate nitrogen. In the season, mean ammonia nitrogen reduction amounting to 23% and nitrate nitrogen reduction amounting to 61% was observed, which corresponds to 80 kg N deposited daily in the ponds provided such a level of nitrogen elimination. The use of municipal sewage for ponds fertilization is beneficial from the environmental (sewage utilization) and economic (reduced spending on artificial fertilizers) point of view.

Studies of the biometric characteristics of paddlefish selects were conducted on specimens from the 6+ year class. They confirmed that the average female body weight was 13.6% higher than that of males and that the females had greater total length and body length (Lt and Lc) as well as longer heads (C) and rostrums (R). There was also a statistically significant difference in the absolute and relative values of the height of the pectoral (hP) and the pelvic fins (hV). The studied fish exhibited correlations between head length (C) and rostrum length (R) as well as between total length (Lt) and body length (Lc).

The ingestion of rough bacteria Aer. salmonicida subsp. salmonicida (in vitro) by blood phagocytes of fishes Acipenser baeri, Siluris glanis, Cyprinus carpio was studied. Carp (16±3) and wels (14±2) neutrophiles ingested more active than sturgeon one’s (11±2), but wels thrombocytes (12±1.7) ingested higher numbers of bacteria than sturgeon (5±4) and carp (2.9±2) ones. After exposition of fishes to herbicids Roundup, Avans, Azoprim, applied in so called save doses, it was confirmed the effects (unfavourable), depended on species and the dose of the herbicide, fish species and phagocyte’s type.

Fish communities were investigated in five shallow Polesie lakes in summer and autumn 2000-2001. The percentage of the brown bullhead both in the total numbers (70.7-3.6%) and biomass (2.4-43%) of fish decreased with increase in lake trophic status (from meso- to hypertrophy). There was a clear reverse relationship between the density of brown bullhead in the lakes and its mean total length, individual weight and values of condition coefficient. Of the three methods of fishing, the most efficient, irrespective of the lake studied, was electro-shocking, the least efficient – the gill nets. The most selective tools were fykes, in which over 95% fish found were the brown bullhead. These tools can be recommended to control the brown bullhead numbers, especially in ecosystems located on areas protected by law.

Lakes Czajcze, Domysławskie, Grodno, Kołczewo, Koprowo, Liwia Łuża, Rabiąż, Resko Przymorskie, Warnowo, Wisełka, and Żółwińskie were studied in 1981-2000. All the lakes were found to be non-resistant or poorly resistant to degradation. deposited in The respective catchments of the lakes studies had an average potential to mobilise nutrient loads, a particularly high potential being shown by the Lake Resko catchment. All the lakes studied were found to undergo intensive eutrophication. Depending on a classification system used, they can be regarded as eutrophic, hypertrophic, strongly eutrophic, or eutrophic bordering on hypertrophic. The least eutrophic was Lake Grodno. The eutrophication of the lakes is confirmed by their respective summer oxygen regimes which are characterised by hyperoxygenation (180-200%) of surface water and oxygen depletion in the near $ndash; bottom layer.

The experiments were carried out in carp ponds supplied with biologically pre-treated municipal sewage. 30 000 m³ of sewage per day supplied 40.1 ha of ponds, stocked with one-year old carp fingerling wit mean body mass of 19.11-20.21 g ind^-1. The aim of the experiment was to determine of the production potential in ponds practical conditions of „Komorowice” sewage treatment plant, collecting the sewage from the town Bielsko-Biała. Under various stocking density of carp (1 750, 3 500 and 5 250 ind. ha^-1), the total yield varied from 1 280 to 2 319 kg of fish per 1 hectare, with survival rate 76-90% and final mean individual weight from 372 to 474 g ind^-1. Thanks mathematical formula based on empirical data, the theoretical optimal stocking density was calculated as 7 000 individuals of carp fingerling per one hectare.

The intensity of phosphorus elimination in the annual cycle was examined in a complex of fishponds occupying the total area of 40 ha, fertilized with biologically treated municipal sewage. During the winter season a decrease in phosphorus concentrations by approximately 30% in fishponds was observed with ten days’ sewage retention in the non-stocked ponds and at low water temperatures. During the summer season, phosphorus elimination from sewage discharged to the ponds periodically exceeded 80%. The highest rate of phosphorus elimination in the ponds was recorded in the second half of the vegetative period, concurrent with slower growth of phytoplankton and increased water turbidity.

A comparative study on production efficiency of 4 selected feed mixes differing in their nutrient levels, used in intensive culture of European wels (Silurus glanis L.) was conducted in 2001. Experiments were carried out in an active European wels culture facility equipped with a flow through system with heated water (Tisova Farm, České rybářství Mariánské Lázně, Ltd., Czech Republic). The initial individual fish weight was 450 g; water temperature during the 112 days of the experiment averaged 23ºC. The fish were kept, at 60 kg/basin stocking density, in 8 about 3 m3 basins; the water flow rate was 1-3 l·s^-1. The feed mixes used were Aqualife 14 (44% protein; 14% fat), Aqualife (42% protein, 22% fat), T 70 (44% protein, 27% fat), and Dan-EX 1344 (44% protein, 13% fat). The major parameters monitored were: fish mortality, growth, SGR, and FCR. Additionally, nutrient retention, external parameters, fish tissue chemical composition, as well as selected haematological and biochemical blood plasma were recorded. The following results were obtained: the Aqualife 14- fed fish attained 1 170 g individual weight, 0.85%·d^-1 SGR, and 1.43 FCR; the fish fed Aqualife 17 attained 1366 g individual weight, 0.95%·d^-1 SGR, and 1.26 FCR; when fed T 70, the fish grew to 1 377 g individual weight and attained SGR of 0.99%·d^-1 and FCR of 1.27; the DanEX-fed fish attained 1 110 g individual weight, 0.81%·d^-1 SGR, and 1.52 FCR. The best cost-benefit result was achieved by using Aqualife 17. Other parameters monitored showed a significant (p < 0.05 and p < 0.01) effect of the feeds applied.

Four extruded feeds for carp fry are presented. They contain grains of different cereals (barley, wheat, triticale, rye). A 50-day growth test was carried out on carp fry with a mean individual mass of 9.92 g. The studies were carried out in controlled conditions in an aquarium hall in overflow aquaria of 60 l capacity stocked with 10 fish in each one. Feeds were prepared as isonitric (38% of total protein) and isocaloric diets (3 560 kcal kg^-1 digestible energy) formed into pellets by barothermal method. The experimental feeds were evaluated on the basis of physical and chemical characteristics. On the basis of amino acidic protein in the feeds, the Chemical Score (CS) and Indispensable Amino Acid Index (IAAI) were calculated. For the evaluation of the final results of the growth test, the following indices were used: Specific Growth Rate (SGR), Survival Rate (SR), Food Conversion Rate (FCR), Protein Efficiency Ratio (PER) and Protein Retention (PR). Statistic analyses of the experimental results were carried out using Statistica 5 PL Program. The higest growth increment and growth rate were obtained in carp fry fed on feed containig triticale, while the best food conversion ratio was found in fry fed on feed containing wheat. Feed mixes containing other cereals (barley or rye) gave lower body mass increments and worse food conversion ratios.

The entirety of the whitefish stocking material (343 830 specimens) released into the Puck Bay in 1997-1999 was marked by immersion in alizarin red (S) in order to assess the share of natural reproduction of whitefish in this basin. Analyses of the presence of markers in whitefish otoliths from the 1997-1999 year-classes caught from 1999 to 2002 in the Puck Bay and Reda River indicated that from 6.2 to 12.8% of the fish were the result of natural spawning. Marker retention was still sufficiently visible even four years after marking.

Effects of mechanical and enzymatic dispersal of blastomeres and embryo’s age (1.25 and 4 h) on the number and survival of the blastodermal cells (BCs) obtained were followed, over a 24-h long period, in zebrafish (Brachydanio rerio). The study showed that, regardless of dispersion technique and embryo’s age, dispersion resulted in harvesting about 97% live BCs. In each case, the proportion of live BCs was found to decrease highly significantly (p ≤? 0.01) after 24 hours of culture. The final proportion of live BCs amounted to 89.8% in the mechanically dispersed blastomeres and 91.0% in those subjected to enzymatic dispersion, no significant differences being found between the two groups. Highly significant (p ≤ 0.01) differences in survival rates were revealed between the proportions of live BCs obtained, after a 24-h long culture, from embryos incubated for 1.5 h (85.3%) and for 4 h. The study showed that the blastoderm dispersion technique did not affect the proportion and survival of the BCs obtained; although the embryo’s developmental stage exerted no effect on the proportion of live BCs obtained, the survival rate was higher in those cells obtained from older embryos.

The aim of the present study was to evaluate, using the microscope and computer image analysis system MultiScan, the effect of 0.2 mg·dm^-3 Cu, Cd or Cu+Cd on yolk sac utilization and growth of common carp larvae Cyprinus carpio under laboratory conditions. According to many authors, yolk sac resorption and growth of larvae may be inhibited by various environmental factors, e.g. heavy metals. The results of the study indicate that heavy metals considerably inhibited utilization of the yolk sac of larvae which was bigger in metal-exposed fish, and some larvae retained it even for 12 days post hatching. Correct yolk utilization is essential for further fish development. Any disturbances reduce fish metabolic rate, which results in reduced growth. In consequence, metal-exposed fish are smaller, weaker, and show higher mortality, which may result in reduction of fish population in polluted waters.

Inducing protection against bacterial diseases in fish culture by specific vaccines is one of the most important prevention methods. But some immunization techniques actually applied to hatchery conditions are not as effective as they should be. Therefore, research is concentrating on how to improve the potency and efficacy of the antigens and how to optimally activate the immune response. In our study, we continue the study about effect of anaesthetic named Propiscin (IFI, Poland) on the effectiveness of vaccine applied by immersion in rainbow trout (Oncorhynchus mykiss). Fish were vaccinated by immersion with vaccine anti-Aeromonas salmonicida (Furogen Immersion, Aqua Health, Canada) in or without anaesthesia with Propiscin. On day 28 after vaccination, all groups of fishes were challenged with live bacteria Aeromonas salmonicida (0.1 ml of bacteria at 1×106 ml^-1). Control groups (only anaesthetized) were infected but not immunized by vaccine. The blood and pronephros were separated from 10 fish of each group before vaccination and 21, 28, 35 and 60 days after vaccination. The ELISPOT assays for the quantification of total immunoglobulin secreting cells (ISC) and specific antibody secreting cells level (ASC) were used. Also the titres of anti-Aeromonas salmonicida antibody by micro-agglutination method was examined. Mortalities were collected and tabulated and the presence of pathogen was confirmed by isolation from fish kidneys. The results of this study showed that Propiscin applied at vaccination time increased the specific immune response and protective effectiveness of vaccine after challenge with pathogenic bacteria. The higher levels of total ISC, specific ASC and titres of specific antibody in fish vaccinated in anaesthesia were observed. Cumulative mortality rates were lowest in the fish vaccinated in anaesthesia (10%), compared with fish vaccinated without anaesthesia (30%). Cumulative mortality in control non-vaccinated group of fish was 85%.

In 2000-2001, consequences of continuous predation of winter flocks of cormorants on fish communities of the secondary trout zone of the Dyje River in the Dyje River National Park (situated on the border between Czech Republic and Austria) were studied. This study was in continuation of previous ichthyological investigations realized in the area after mass invasion of large flock (250 specimens) of cormorants in years 1997-1998. At the same 4 localities, repeated ichthyological research was carried out using electrofishing. Zoobenthos samples were also taken in annual cycle to determine saprobity indexes. Fish community was evaluated applying basic ichthyological methods. In this study indexes of diversity (H΄) and equitability (E), characterizing stability of fish community ranged between 0.082-1.739 (H΄) and 0.045-0.806 (E) respectively, with the lowest values in sections 2 and 3. Abundance of brown trout fluctuated from 68 to 349 fish·ha^-1 and of grayling from 0 to 23 fish·ha^-1 (with absence in localities 2 and 4). Total biomass of the fish community varied from 15.3 to 128.5 kg·ha^-1. Bullhead (Cottus gobio) occurrence increased significantly (abundance of 30 557 fish·ha^-1 and biomass of 123.3 kg·ha^-1 in the section 3 in year 2001) as a result of considerable decrease in brown trout population density. At present (2000-2001), total fish biomass reaches only 48.6 kg·ha^-1 (54% decline), biomass of brown trout 18.9 kg·ha^-1 (60% decline) and grayling 1.1 kg·ha^-1 (90% decline). This unfavorable state of fish community corresponds with long-run reduction in angler catches, which in case of grayling is near zero (in 2001 only 0.1 kg·ha^-1). Zoobenthos analyses confirmed (index of saprobity 1.18-1.48) high water quality (oligosaprobity) typical of trout and grayling zone.

The experiment was run on carp individuals (384 ± 5g) kept in cages in heated water. The fish were randomly divided into two groups fed two different isoprotein diets, one with increased carbohydrate level (33.3% of the dietary energy; Group I) and the other with increased fat level (39.3% of the dietary energy; Group II). The experiment resulted in statistically significant differences in the contents of selected biochemical blood components as well as in the body composition of carp and culture efficiency indices in relation to the pre-experiment values and between the groups. In view of the 100% survival rate and high body weight increments, it is concluded that the diets used in the experiment, although differing in their carbohydrate and fat contents, and in spite of exerting significantly different effects on fish organism, were compatible with the fish physiological adaptive potential for their utilisation. It can be then presumed that diet-dependent modification of fish body composition to obtain certain levels and composition of lipids can play one of major roles in the intensive fish culture in the future.

Studies on the influence of pesticides on immune system functions focus on the assesment of their direct toxicity on the immunocompetent cells. Roundup (containing 41% gliphosate) is a herbicide used against weeds in agriculture and aquaculture. In the study the influence of gliphosate on metabolic and phagocytic activity of PMN and MN cells and proliferative activity of T and B cells in carp and European sheatfish was assessed. In dosis 100 mg·dm^-3 in bath (10 minutes) strongly reduces both metabolic (RBA) and phagocytic (PKA) activity of leucocytes. Also proliferative response of lymphocytes stimulated Con A and LPS was reduced. Fishes with different environmental preferences have similar sensitivity (supressive effect) to the selected xenobiotics.

The following parameters were determined in Lake Miedwie water: pH, suspended particulates, chlorophyll a, dissolved oxygen content, BOD5, CODCr, CODMn, orthophosphates, total phosphorus, ammonia nitrogen, nitrite nitrogen, nitrate nitrogen, organic nitrogen, and total nitrogen as well as parameters important for evaluation of the mineralisation level, i.e., chlorides, sulphates, carbonates, hydrocarbonates, calcium, magnesium, and electric conductivity. The results allowed to assess the Miedwie water quality. The good oxygen conditions found in the lake, an average nutrient content, and the high water transparency allow to classify the lake as a mesotrophic one. The constant supply of nutrients and organic matter from the entire catchment result in permanent nutrient and organic loads in the lake. All the mineralisation indices evidenced an average mineralisation level, typical of the Western Pomeranian surface waters, and ranged within limits typical of the water quality class 1.

The present papers demonstrates detailed biomorphometry of viviparous eel-pout Zoarces viviparus (L.) (involving 27 metric and 12 meristic characters), as well as the growth rate of length and weight (employing von Bertalanffy equations), with regard to both sexes. 150 specimens were examined in details, while in 248 the total length, body length, weight and vertebral count were recorded (with regard to both sexes). Both metric and meristic characters in the eel-pout from Little Belt are very variable, of wide ranges and high CV; especially in the length of anal fin and D depression length (in morphometrics) and count of spines, rays in D, and C fins (in meristics). Females grow a little faster in length and fairly faster in weight in the population studied. The growth rate of length and weight in fishes from Little Belt is slower when compared to data from the Pomeranian Bay. Sexual dimorphism is displayed in 5 metric characters in the sample investigated and in eel-pout from Pomeranian Bay. No confirmation is found in own results for the contention found in the literature on positive correlation between the count of vertebrae in eel-pout and salinity.

Quantitative bacteriological examinations of the water in Lake Oświn, mucus from the skin surface and gastric contents of roach and pike in this water body were conducted in spring, summer and autumn. The general number of heterotrophic bacteria (TVC 20ºC and TVC 37ºC) and the number of potentially pathogenic ones, such as P. fluorescens, P. aeruginosa and Staphylococcus sp., were determined. The number of TVC 20ºC and TVC 37ºC bacteria was 102-103 cfu·cm^-3 in water, 105-107 cfu·cm^-2 in mucus from the skin and 106-107 cfu·g^-1 in gastric contents. In the material under study, among the potentially pathogenic bacteria, Staphylococcus sp. constituted the smallest proportion, whereas P. fluorescens and P. aeruginosa were much more numerous.

The results of bacteriological examination were shown in the study, an examination that was conducted in the Experimental (Fish) Stocking Site, called ”Dgał” in Pieczarki near Giżycko (objects A and B) and in the Marine Biological Station of the University of Gdańsk on Hel (object C). Water and mucus from the skin surface of fish during intensive tank culture were examined. The results of water examination showed the most frequent occurrence of the bacteria TVC 22ºC, TVC 37ºC, TC, proteolytic, ammonifying and phase I nitrifying in the sea water of object C (site I). At the same time the highest count of FC bacteria was found in the tank water of object C (site II), and FS bacteria in the tank water of object B. The lowest count of TVC 22ºC, TVC 37ºC, TC, ammonifying and phase I nitrifying were marked in the tank water of object A, TC bacteria in the tank water of object C (site II), FC in the tank water of objects A and B, whereas FS bacteria in the tank water of object A and in the sea water of object C (site II). The examination of fish showed the highest occurrence of the average number of TVC 22ºC bacteria in the mucus from skin (1 cm²) of sterlet, which was taken from object A, TVCº37 C in the mucus of Russian sturgeon and starlet from the same object. The lowest average number of these bacteria was found in the mucus of bester SBS from object B. In the majority of the examined samples the occurrence of the following bacteria was found: of the genus Aeromonas, the genus Pseudomonas, the genus Flavobacterium, as well as of the Enterobacteiaceae family.