Showing papers in "Archives of Polish Fisheries in 2010"

Effect of sex reversal in rainbow trout (Oncorhynchus mykiss Walbaum) using 17α-methyltestosterone and 11β-hydroxyandrostenedione

Abstract: The aim of the experiment was to compare the effectiveness of sex reversal in mature female rainbow trout using 17-methyltestosterone (6 ppm-MT) and 11-hydroxyandrostenedione (20 ppm-OHA). Hormones were administered with the first exogenous feed for up to 60 days. Among the fish treated with OHA, 95% females were reversed into mature neo-males and 1.6% to bisexual individuals. Among the fish treated with MT only, 59.7% females were reversed to neo-males and 1.8% to bisexual individuals. Functional neo-males were 1.6% and 5.3%, respectively. The rest of the neo-males had obstructed seminal vesicles in various stages. The gonadsomatic index was 3.9% at age 3+ in both groups of mature fish. The shape of the testes ranged from elongated to stunted. The bisexual fish had immature oocytes and mature testes with viable semen that was used for egg fertilization.

Effect of the synthetic pyrethroid Deltamethrin and the neem-based pesticide Achook on the reproductive ability of zebrafish, Danio rerio (Cyprinidae)

Abstract: In the present research, both male and female zebrafish, Danio rerio (Hamilton), were exposed to 96-h LC5 values of Deltamethrin (0.016 µg dm -3 ) and Achook (0.025 µg dm -3 ) for three months. The fish were then returned to normal water and allowed to breed to permit observations of fecundity and hatchability. The results show significant reductions in fecundity and hatchability in comparison to the control group. Fecundity was reduced by 54.12% in the fish treated with Deltamethrin and by 17.81% in those treated with Achook. Significant decreases in hatchability of up to 49.7% were noted in the Deltamethrin group and of 36.9% in the Achook treated fish. The number of unhatched/dead eggs increased significantly (P < 0.05 for each case). It was concluded that low concentrations (96-h LC5 values) of both pesticides can have a significant impact on the reproduction of zebrafish.

Impact of intraperitoneal and intramuscular PIT tags on survival, growth, and tag retention in juvenile pikeperch, Sander lucioperca (L.)

Abstract: The aim of the study was to compare the effects of intraperitoneal (group P) and intramuscular (group M) methods of implanting PIT tags on the growth, condition, and survival of juvenile pikeperch, Sander lucioperca (L.) (body weight about 82 g) and tag retention. After tagging, the fish were held in recirculating aquaculture systems (RAS) and reared on commercial feed for 56 days. No significant differences were noted in fish growth rate or condition between the experimental groups (groups P and M) and the control group that was not tagged (group C; P > 0.05). The feed conversion ratios were also of similar values (FCR – 1.2-1.3; P > 0.05). Tagging did not impact fish survival, which was 98.9% in group P and 100% in groups M and C on the final day of the experiment (P > 0.05). Tag retention in both groups was also 100%. The results of this study confirm that both tagging methods are suitable for juvenile pikeperch. The PIT tags were noted to migrate in the body cavity in group P (47.2% of tagged fish). Accordingly, the intramuscular method for implanting PIT tags is recommended for juvenile pikeperch (body weight > 60 g).

Impact of light intensity on the results of rearing juvenile pikeperch, Sander lucioperca (L.), in recirculating aquaculture systems

Abstract: The aim of the study was to determine the impact of different light intensities on the results of rearing juvenile pikeperch, Sander lucioperca (L.), in recirculating aquaculture systems (RAS). In experiment I, the light intensities applied were 45.1 lx (group LI) and 385.7 lx (group HI) (initial body weight - 6.1 g), while in experiment II they were 1.2 lx (group LII) and 8.0 lx (group HII) (initial body weight - 42.2 g). In both experiments, the fish reared in the tanks with lower light intensity (groups LI and LII) exhibited faster growth rates (P 0.05). The results obtained indicate that the application of low intensity light ( 6 g) rearing is justified since it has a positive impact on the behavior and growth rate of the fish, and the feed conversion ratio, which implies that it is possible to shorten the rearing period of this species.

Growth rate and reproduction of a brood stock of European whitefish (Coregonus lavaretus L.) from Lake Gaładuś under controlled rearing conditions

Abstract: Growth rate and reproduction of a brood stock of European whitefish (Coregonus lavaretus L.) from Lake Gaładuś under controlled rearing conditions The focus of the study was to analyze the effects of the artificial reproduction of whitefish, Coregonus lavaretus (L.) aged from 1+ to 4+. It was confirmed that males comprised 64.5% of the brood stock. The males were sexually mature at the age of 1+, while most females were mature at the age of 2+. The females gained weight faster in comparison to the males, and the differences were highly statistically significant (P < 0.001). Survival during the period from the first spawning at age 1+ to spawning at age 4+ was 79.6% for males and 59.6% for females. The quantity of eggs obtained, the egg size, and their survival during incubation all increased as the fish aged. The weight of the eggs obtained from fish aged 3+ and 4+ was statistically significantly higher that from younger fish (1+ and 2+) (P < 0.001). The results of the current study indicate that exploiting a whitefish brood stock under controlled conditions can begin as early as at age 2+. The highest relative fecundity and largest egg size were obtained in females aged 3+. Tempo wzrostu i rozród stada tarłowego siei Coregonus lavaretus (L.) z jeziora Gaładuś w warunkach kontrolowanego chowu Celem przeprowadzonych badań było określenie wybranych wskaźników hodowlanych oraz przeanalizowanie zmian zachodzących z wiekiem ryb w czasie chowu stada tarłowego siei w warunkach kontrolowanych. W badanej populacji tarłowej stwierdzono większy udział samców, które stanowiły 64,5% wszystkich ryb. Samce osiągnęły dojrzałość płciową w wieku 1+, a samice w większości w wieku 2+. Samice wykazywały szybszy wzrost masy ciała w porównaniu z samcami, a różnice we wszystkich rocznikach były wysoce istotne statystycznie (P < 0,001). Średnie dobowe przyrosty masy ciała zmniejszały się z wiekiem ryb, począwszy od piątego roku życia uległy praktycznie zahamowaniu i wynosiły odpowiednio 0,02% d-1 u samic i 0,01% d-1 u samców. Kondycja ryb wyrażona współczynnikiem Fultona rosła u obu płci do osiągnięcia wieku 3+ i osiągnęła wartości 1,87 ± 0,07 u samic i 1,51 ± 0,03 u samców. Poza rybami w wieku 1+ współczynniki kondycji u samic były wysoce istotnie statystycznie wyższe niż u samców (P < 0,001). Przeżywalność między kolejnymi rozrodami była wyższa u samców, przy czym obserwowano dwa okresy zwiększonej śmiertelności: bezpośrednio po tarle oraz w okresie letnim, przy wysokich temperaturach wody (powyżej 20°C). W okresie od pierwszego rozrodu w wieku 1+ do rozrodu w wieku 4+ przeżywalność całkowita wyniosła 79,6% u samców oraz 59,6% u samic. Ilość pozyskiwanej ikry wzrastała z wiekiem ryb, od samic w wieku 1+ pozyskano przeciętnie 13,7 ± 2,6 g ikry, a w wieku 4+ 173,8 ± 7,5 g ikry. Masa pozyskiwanej ikry w wieku 3+ i 4+ była wysoce istotnie statystycznie wyższa niż u ryb młodszych (P < 0.001). Masa pozyskanej ikry w przeliczeniu na 1 kg masy ciała samic stanowiła przeciętnie 3,6 ± 0,5% w wieku 1+ do 16,1 ± 0,7% w wieku 3+.Z wiekiem ryb wzrastała wielkość jaj: u samic w wieku 1+ w 1 kg ikry mieściło się 168769 ± 1185 jaj, a w wieku 4+ 148744 ± 3930 jaj (P < 0,05). Jakość produktów płciowych również zmieniała się z wiekiem ryb. Podczas pierwszego rozrodu (w wieku 1+) przeżywalność do stadium zaoczkowania wyniosła 0%. W kolejnych sezonach uzyskiwano przeżywalność do stadium zaoczkowania odpowiednio 58,5% (2+), 62,0% (3+) i 64,4% (4+). Wielkość podawanej dawki paszy wpłynęła na ilość ryb, które osiągnęły dojrzałość tarłową w wieku 1+. Stwierdzono, że w grupie ryb żywionych najwyższą dawką paszy najwięcej samców i samic osiągnęło gotowość do tarła i stanowiły one 76,9% wszystkich ryb. Wyniki przedstawionych badań wskazują, że eksploatację stada tarłowego siei w warunkach kontrolowanych można rozpocząć już w wieku 2+. W tym wieku praktycznie wszystkie samce i samice były już dojrzałe płciowo. Najwyższą względną płodność ryb i największe rozmiary ikry uzyskano u samic w wieku 3+.

Lipid peroxidation and antioxidant defense system in spawn of brown trout (Salmo trutta m. trutta L.) affected by ulcerative dermal necrosis

Abstract: The objective of the present study was to investigate the importance of the antioxidant enzymes: superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), and glutathione peroxidase (GPX) in the defense against lipid and protein oxidation in spawn from female brown trout, Salmo trutta m. trutta L. affected by ulcerative dermal necrosis (UDN). UDN induced increased lipid and protein oxidation levels. The current results show that UDN infection led to oxidative stress with the inhibition of antioxidant defense mechanisms. The inhibition of glutathione defense system activity might be responsible for this failure in cellular antioxidant defenses. UDN induces irreversible changes in proand antioxidative function which effected decreased spawn survival as well as reductions in spawning efficiency.

Dynamics of nitrogen and phosphorus in closed and semi-closed recirculating aquaculture systems during the intensive culture of goldfish, Carassius auratus auratus (L.), juveniles.

Abstract: The aim of the study was to compare the dynamics of nitrogen and phosphorus compounds in closed (cRAS) and semi-closed (scRAS) experimental recirculation systems during intensive culture of goldfish juveniles. The results obtained underscore the varied effectiveness of biological nitrification in recirculation systems, which is dependent on both the nitrogen compound loads and water exchange. Additionally, levels of nitrogen (22878.18 mg) and phosphorus (1878.55 mg) accumulation were high in the cRAS in comparison to those in the scRAS (maximum 3797.44 and 117.41 mg for nitrogen and phosphorus, respectively). This indicates that large quantities of nutrients are discharged into the natural environment as a consequence of water exchange. The data obtained from this study can be useful at the intensive aquaculture production design stage to minimize impacts on the natural environment. Based on the results obtained, the cRAS should be put into operation approximately ten days before any experimental or intensive culture is begun. With scRAS, the culture process can commence on the fourth day after disinfection. However, with scRAS the feeding rate has to be monitored closely because of the relatively low nitrification capability of this system.

Impact of supplementing natural feed with dry diets on the growth and survival of larval asp, Aspius aspius (L.), and nase, Chondrostoma nasus (L.)

Abstract: The aim of the study was to determine how natural feed supplemented with dry diets affects the growth rates and survival of larval asp, Aspius aspius (L.), and nase, Chondrostoma nasus (L.). The fish were reared for 21 days. Initially, the larvae were fed live Artemia sp. napulii, and a commercial feed SGP 493 (Aller Aqua) was added after 6 (A6), 8 (A8), 10 (A10), and 12 (A12) days. Depending on the feeding treatment, dietary supplements were then added to the natural feed at intervals of 1, 2, or 3 days. No statistically significant differences were noted in the growth of larval asp from groups A6 or A12, and groups A8 or A10. The relative growth rates (RGR) ranged from 18.16 (A8) to 18.61% d -1

Histoarchitecture and scanning electron microscopic studies of the olfactory epithelium in the exotic fish Puntius javanicus (Bleeker)

Abstract: The olfactory epithelium of Puntius javanicus (Bleeker) was examined methodically with a light microscope (LM) and a scanning electron microscope (SEM). The ovoid olfactory apparatus consists of 25 to 26 primary lamellae arranged on both sides of the narrow median raphe. The sensory epithelium occupies the upper middle and apical half of the olfactory lamellae and consists of receptor cells (both ciliated and microvillus) and mucous cells. The region from basal part of the lamellae to the junction of the median raphe is covered with non-sensory epithelium. The non-sensory epithelium is composed of non-sensory supporting cells, stratified epithelial cells with fingerprint like microridges, and mucous cells.

Distribution, migrations, and growth of tagged sea trout released into the Vistula River

Abstract: The aim of the study was to determine the distribution, migrations, and growth of summer Vistula sea trout, Salmo trutta L., released as smolts into the lower Vistula River. During the 1972-1977 period, 16985 2+ smolts with external tags were released, and 1696 tag returns were obtained (10.0%), including 1412 returns from sea trout whitling (8.3%) and 284 (1.7%) from smolts and post-smolts. Almost immediately after being released into the Vistula River, the sea trout smolts descended to the sea and then migrated throughout the Baltic mainly toward the east reaching the Bothnian Bay and the Gulf of Finland. These fish were mainly caught in the southern Baltic, especially in the region of the Gdansk Bay and the Vistula River mouth in the second year after stocking (65.7%). They were noted in the southern part of the Gdansk Bay and the Vistula River mouth more frequently in the first year after stocking during the period from November to March, while in the second year after stocking more were noted during the period from July to March. Most of the tag returns were received from Polish fishers (80.7%). One year after stocking the sea trout had attained a mean body length of 57 cm and a mean weight of 1523.3 g. The mean lengths and weights two and three years after stocking were 69.6 cm and 4355.7 g and 78.7 cm and 6035.7 g, respectively.

Ichthyofauna of a mountain stream dammed by beaver

Abstract: The aim of the study was to examine the impact of the European beaver, Castor fiber L., on the ichthyofauna of Negrylow Stream. Three study sites were designated in segments of the stream with running waters and two in beaver ponds. The waters at all the sites were characteristic of naturally polluted mountain streams. The occurrence of brown trout, Salmo trutta trutta m. fario L.; Siberian sculpin, Cottus poecilopus Heckel; common minnow, Phoxinus phoxinus (L.); and stone loach, Barbatula barbatula (L.), was confirmed. The highest density and abundance of brown trout was noted in the ponds, where the mean lengths and weights of brown trout were also the highest noted in the current study. Large trout occurred only in the ponds. In the shallow, running segments of the stream mostly brown trout fry were caught. Differences among fish assemblages in the segments of the stream and the ponds were statistically significant. After the introduction of the beavers, the state of the ichthyofauna in Negrylow Stream, which had suffered substantial degradation from forestry works, improved markedly. In comparison to analagous segments of other streams in the Bieszczady Mountains, fish density and biomass here were very high.

Impact of dibutyl phthalate and benzyl butyl phthalate on motility parameters of sperm from the European pikeperch Sander lucioperca (L.)

Abstract: The present study was the first attempt to evaluate the impact of dibutyl phthalate (DBP) and benzyl butyl phthalate (BBP) at concentrations of 100, 1000, and 10000 µg DBP dm -3 and 20, 200, and 2000 µg BBP dm -3 on the motility parameters of the sperm of European pikeperch, Sander lucioperca (L.), using computer assisted sperm analysis (CASA). The in vitro studies were conducted in the seminal plasma, which is the natural environment of the sperm, using two methods. The first was with the immediate activation of sperm movement in the presence of phthalates (0 h), while the second utilized phthalate incubation for 4, 24, and 48 h. It was confirmed that none of the compounds analyzed had a significant impact on the percentage of motile sperm (MOT), average path velocity (VAP), curvilinear velocity (VCL), straight line velocity (VSL), or amplitude of lateral sperm head displacement (ALH) (P > 0.05). It is plausible that in natural aquatic ecosystems, neither dibutyl phthalate nor benzyl butyl phthalate will affect motility of fish sperm at external fertilization event. It is necessary to track in vivo the impact these compounds have in concentrations similar to existing in the natural environment on the fish sperm quality.

Genetic characterization of Polish cultured brook trout, Salvelinus fontinalis (Mitchill), based on microsatellite DNA analysis

Abstract: The genetic variability of two farmed strains of brook trout, Salvelinus fontinalis (Mitchill), was examined using six microsatellite DNA loci. The objective of the present study was to evaluate locus-specific genetic markers in brook trout strains cultured in Poland and to assess their levels of genetic diversity. The average number of alleles at all loci in the studied stocks differed between the two groups: 2.20 in the Rutki strain and 7.20 in the Canada strain. For the microsatellites examined, the number of alleles per locus ranged from 1 (locus Ssa-171 in the Canada strain) to 24 (locus Sfo-292 in the Canada strain). The results suggested that the Canada strain had higher gene diversity than the Rutki strain. The molecular analysis described in the present study will be useful for monitoring long-term genetic variation and for the identification of suitable parents for the development of stocks with suitable gene diversity in cultured Polish brook trout.

Morphometry of the gill respiratory area in ruffe, Gymnocephalus cernuus (L.)

Abstract: The structure of the gill respiratory surface area (GRSA) was analyzed in nine specimens of Gymnocephalus cernuus (L.) of different body weights. The observed GRSA values increased from 4638.46 mm 2 in the smallest specimen to 19522.8 mm 2 in the largest one. The allometric relationship of different gill components to body weight were estimated using the equation Y = aW b . The calculated allometric relationship between GRSA and body weight is expressed with the equation: Y=1348.16W 0.687 . The relationships between GRSA and body weight are statistically significant, the correlation coefficients are positive and significant (P < 0.01), and their values range from 0.95 to 0.99. The results obtained show that previously published GRSA values for ruffe were overestimated.

Impact of diets supplemented with rapeseed, soy, and sunflower oils on growth rates and the histological picture of the livers of juvenile pikeperch, Sander lucioperca (L.)

Abstract: Juvenile pikeperch (120 g initial body weight) were fed a commercial diet (group CD) or experimental diets supplemented with rapeseed (group RO), soy (group SO), or sunflower (group SFO) oils for 55 days. The experimental diets were made by adding the given vegetable oil (VO) in quantities of 160 g kg feed (84% of the total raw lipid in the diet) to a base of an extruded, commercial diet (containing 30 g kg raw lipid). The dietary treatments had no significant influence on fish growth rates, apparent net protein retention (ANPR), or apparent net energy retention (ANER) (P > 0.05). The apparent lipid retention (ALR) in group SO was significantly higher than in the other groups (P 0.05)).

Influence of temperature on the effectiveness of the hormonal stimulation of male ide, Leuciscus idus (L.)

Abstract: Increasing the temperature of water (by 1-2C) in which spawners of rheophilous fish are held following hormonal stimulation until gametes are obtained is a common procedure in hatching practice. The aim of the study presented here is to determine the influence of water temperature following stimulation with Ovopel on the investigated quantitative and qualitative characteristics of ide, Leuciscus idus (L.), milt. The experiment comprised subjecting the fish to hormonal stimulation using a single intraperitoneal injection of Ovopel at a dose of 1 pellet kg -1 of body weight. After injection, the water temperature of group I was maintained at a constant level of 10C, while for the other two groups it was increased to 12C (group II) and 14C (group III) within 4 hours. Changes of temperature after hormonal injection had no statistically significant effect either on milt quantity or its quality parameters. The values of motility were low in all groups (29, 30, 35% for groups I, II, and III, respectively). The mean values of seminal plasma osmotic pressure were 129, 139, and 154 mOsm kg -1 for groups I, II, and III, respectively. The mean

First record of brown bullhead, Ameiurus nebulosus (Lesueur), in the Łyna River drainage basin (northeast Poland)

Abstract: This paper presents the first records of the occurrence of brown bullhead, Ameiurus nebulosus (Lesueur), in the £yna River drainage basin. In February 2010, 77 brown bullhead were collected in Lake Czarne, and one in July 2010 was caught by angling method in Lake D³ugie in Olsztyn (northeast Poland). The specimens collected in Lake Czarne range from 72 to 154 mm total length (TL) and weighed from 3.9 to 36.8 g. Among measurable characters, the greatest variability was noted in head width, preanal distance, and snout length. The least variability in measurable characters was noted with regard to dorsal fin length, eye diameter, and preventral distance. Because of the adverse impact brown bullhead would have on the indigenous ichthyofauna of the £yna drainage basin, its spreading occurrence in this region is an ecological and economic threat. The brown bullhead, Ameiurus nebulosus (Lesueur), is native to eastern and central North America from Nova Scotia and New Brunswick to the Great Lakes region and south to Alabama. It has also been intro- duced throughout the United States (Scott and Crossman 1973). A. nebulosus is found in lakes, ponds, oxbow lakes, reservoirs, canals, and

When did the black bullhead, Ameiurus melas (Teleostei: Ictaluridae), arrive in Poland?

Abstract: One specimen of the non-native ictalurid catfish the black bullhead, Ameiurus melas, was found in the collection of the Museum and Institute of Zoology of the Polish Academy of Sciences in Warsaw, Poland. This finding strongly supports the hypothesis that the black bullhead was co-introduced into Polish waters with the brown bullhead, Ameiurus nebulosus, at the end of the nineteenth century. The species might be distributed widely throughout Poland, thus careful investigation on the identity of the ictalurid catfish population throughout the country should be carried out.

Patterns of river lamprey size and sex ratio in the Baltic Sea basin

Abstract: A comparative study of the size distribution of river lamprey, Lampetra fluviatilis (L.), was conducted in several rivers in the Baltic Sea basin. Total length and weight data were collected from 7503 lamprey individuals. Sex ratio distributions were also examined in some of the river lamprey populations. The length of lamprey varied from 20.0 to 51.0 cm. The smallest lamprey were in Finland, where mean length in different rivers ranged from 27.9 to 30.8 cm. Larger individuals were noted in Latvia, with mean lengths from 34.0 to 39.5 cm, and in Lithuania from 33.5 to 36.4 cm. The largest lamprey were in Poland, where mean length was from 38.3 to 42.9 cm. The heaviest lamprey were noted in Poland with mean body weights from 45 to 230 g, while slighter individuals were noted in Finland with mean body weights from 12 to 90 g. The body length and weight ranges indicate regional variation. The smallest lamprey individuals were noted in the populations in the rivers of the northern region of the Baltic Sea basin. The analysis of the sex ratio distribution indicated that in most rivers populations of river lamprey males slightly outnumbered females.

Age and growth of vendace, Coregonus albula (L.), from Lake Wigry (northeast Poland)

Abstract: The aim of the study was to determine the age and length growth rates of vendace, Coregonus albula (L.), from Lake Wigry (northeastern Poland). Fish were captured from 2001 to 2005 in the months of August and September. The most frequent age group in the catches was 2+, which comprised 53% of all fish caught. Growth was determined using Dahl-Lee and Rosa Lee back-calculation methods. These were the basis for calculating mathematical growth rate models. The growth that best corresponded with the empirical data was that calculated with a second-degree polynomial model based on Rosa Lee back-calculations. Fish aged 3+ were characterized by average length growth and attained a mean body length (SL) of 17.2 cm.

Growth rate and condition of a population of migratory common whitefish, Coregonus lavaretus (L.), from Oder estuary waters

Abstract: The aim of the study was to describe the biological and population characteristics of common whitefish, Coregonus lavaretus (L.), from Oder River estuary waters and to evaluate theoretical growth models for this species. Of the 100 fish analyzed, there was a greater share of males (56%), and individuals aged 2+ dominated (63%). The mean individual weight and total length was 957.6 g (range 401.0-2738.0 g) and 446.9 mm (range 358.0-605.0 mm), respectively, and the values of these parameters for the females were statistically significantly higher (P < 0.05). The analyzed fish exhibited substantially faster growth in the first years of life and slower annual growth in subsequent years. In comparison with data from the literature, whitefish length growth was significantly higher than in the 1950s, but similar to the results of studies from the 1980s.

Possibilities of using the length differentiation of hatchery sea trout, Salmo trutta m. trutta L., parr to predict numbers of one-year smolts

Abstract: Growth and smoltification were followed during the first year of life in 14 full sibling families of sea trout, Salmo trutta m. trutta L., originating from the Vistula stock. Until January, the families were reared separately, and then together after they had been PIT tagged. The degree of smoltification was evaluated in the second spring. Smolts were noted in each family. The percentage of these, which ranged from 14 to 66%, depended on mean fish length in October (r 2 = 0.338) and January (r 2 = 0.346). In either October or January the fish that smolted next spring were, on average, longer than those that did not, but this difference was not manifested by the bimodality of length distribution, and it did not allow predicting the number of smolts based on division of distributions of fish length in autumn or winter into Gaussian components.

Management of fish populations in lobelia lakes in the vicinity of Bytów (northern Poland)

Abstract: The aim of the studies was to describe the fisheries management of five lobelia lakes and one non-lobelia reference lake. Data from commercial catches was used to estimate the size of the catches, and to determine the species and ecologial structure of the catches, and to describe stocking. During the period from 1968 to 2006, eleven fish species belonging to five families were noted in the catches. The species structure of the commercial catches of the analyzed lobelia lakes corresponded to that of either vendace or eutrophic lakes. Catches made in lobelia lakes were from 2.5 to 5-fold smaller in comparison to the reference lake. The dominant species in commercial catches made in basins with lobelia vegetation were roach, Rutilus rutilus (L.), and pike, Esox lucius L., but bream, Abramis brama (L.), vendace, Coregonus albula (L.), and carp, Cyprinus carpio L., also occurred in some lakes. Pike was caught most frequently, followed by bream, roach, and perch. The largest catches were made in either March or November. During the period from 1968 to 2006, the lakes were stocked with ten fish species, nine of which were noted in the official statistics. Only six species occurred naturally in these lakes. Peled, Coregonus peled (Gmelin), is an alien species, and its occurrence was certainly connected with stocking. Pikeperch, Sander lucioperca (L.), was translocated outside of its area of natural occurrence, while carp and Prussian carp, Carassius gibelio (Bloch), were alien species.

Genetic variability in European populations of Coregonus lavaretus (L.): an assessment based on mitochondrial ND-1 gene haplotypes

Abstract: The genetic variability of whitefish, Coregonus lavaretus (L.), was studied based on 114 individuals from nine populations inhabiting Polish lakes, including the Szczecin Lagoon, and from one population each from lakes in Austria and Switzerland. Differences within and among populations were assessed with mitochondrial ND-1 gene sequences that were PCR amplified and digested with ten restriction enzymes. The ten composite haplotypes obtained were sequenced and analyzed with MEGA4 software. The highest intrapopulation variability was noted in the whitefish populations inhabiting lakes Insko, Miedwie, Marianowo, Wisola, Œremskie, Morzycko, the Szczecin Lagoon, and Lake Lucerne, which possessed from two to five composite haplotypes. In contrast, populations inhabiting lakes Woœwin, Czarne, and Traunsee were fixed for the most common haplotype H2.

Feeding strategies and resource utilization of 0+ perch, Perca fluviatilis L., in littoral zones of shallow lakes

Abstract: The aim of the study was to analyze the diet and feeding strategies of 0+ perch, Perca fluviatilis L., in two lakes (Gos3awskie and Do3gie Wielkie) with different trophic and thermal regimes. Water temperature was higher in Lake Gos3awskie (Mann-Whitney test, P 0.05). The mean abundance, biomass, and species richness of zooplankton during the study period were statistically significantly lower in Lake Gos3awskie (test U Mann-Whitney, P < 0.0001. The share of perch with empty digestive tracts was very low. The fish from Lake Do3gie Wielkie had higher condition factors (mean 1.87) than did those from Lake Gos3awskie (1.73). The analysis of the size structure of the prey consumed by perch from the two lakes indicated that the fish employed different foraging strategies. In Lake Do3gie Wielkie the perch consumed a large quantity of small plankton organisms (copepodites and Daphnidae) that occurred in large quantities, while in Lake Gos3awskie, where zooplankton abundance was low, the basic diet comprised larger organisms (Sida crystallina, larval Chironomidae). Perch feeding intensity in Lake Do3gie Wielkie was positively correlated with body length, while in Lake Gos3awskie it remained at the same level.

Classifying Vistula and Pomeranian sea trout populations using discriminant functions based on selected scale characters

Abstract: This paper presents the results of studies of the effectiveness of a discriminant function system based on selected scale characters of sea trout populations from the Vistula River and Pomerania. Selected parameters of sea trout scales from comparable groups from the period prior to the mixing of the two populations were compiled and function effectiveness was tested. The reference discriminant functions obtained were used to classify the individuals from the mixed stock into corresponding groups. The best results (89.7% conformity) were obtained by applying the discriminant function to classify Vistula sea trout from the winter spawning run from Pomeranian sea trout. The lowest conformity at 64.6% was noted for the function segregating the sea trout from the two Vistula spawning runs. Discriminant analysis of the scale parameters and body length can be used in selection procedures which are used in the program to restore migratory fish species to Poland.

Length and weight distribution of the river lamprey, Lampetra fluviatilis (L.), sampled in the Nemunas River Estuary

Abstract: Data on the population state, catch sizes, migration time, and intensity of the river lamprey, Lampetra fluviatilis (L.), are presented. Biological indexes of lamprey sampled in 2007-2009 in the lower reaches of the Nemunas River were analyzed. The study revealed that lamprey body length and weight characteristics have remained almost unchanged in recent years. However, it was found that reproducers had become smaller in size compared to investigation findings from the twentieth century.

An assessment of parasite variation in wild populations of roach, Rutilus rutilus (L.), in Lithuanian rivers.

Abstract: This study determined the composition of roach, Rutilus rutilus (L.), parasites in Lithuanian rivers. A total of 3558 individuals were examined for parasites from 12 rivers in 2005-2009. A total of 27 parasite species belonging to Ciliophora (6), Monogenea (3), Digenea (7), Cestoidea (4), Crustacea (3), Nematoda (1), Acanthocephala (1), Hirudinea (1), and Bivalvia (1) were recorded. Parasitological examinations of the roach showed significant variation in the prevalence of nine parasite species in the rivers studied. These results suggest that parasitological studies of specific parasite species in this freshwater fish can be used as bioindicators to provide information about environmental conditions in rivers.

Histopathological changes in naturally-infected Chirruh snowtrout, Schizothorax esocinus (Heckel), with Adenoscolex oreini (Caryophyllidea: Capingentidae).

Abstract: The aim of this study was to carry out histopathological studies on the intestines of Chirruh snowtrout, Schizothorax esocinus (Heckel), naturally infected with the caryophyllidean cestode, Adenoscolex oreini. The specimens of S. esocinus (25-40 cm) were collected from the Jhelum River, Kashmir, India. Heavily infected fish (> 50 worms per individual host) with only A. oreini were chosen for the histopathological investigation. The intestinal tissues with parasites in situ were fixed and processed for routine histological investigations. About 12.7% of the snowtrout were found to harbor A. oreini infection. With heavy worm burden, the aggregation of worms and increased mucus secretion were noted in infected intestines. The worm scolex lacked a specialized attachment organ and penetrated deeply into the intestinal wall. The pathology induced by this worm in the gut included mucosal damage at the site of attachment and the compression of villi adjacent to the strobila. Intense cellular response induced by the worm at the site of attachment was also observed.

Impact of feeding juvenile pikeperch (Sander lucioperca (L.)) diets supplemented with vegetable oils on proximate body composition and fatty acid profile

Abstract: Juvenile pikeperch, Sander lucioperca (L.) were reared in recirculating aquaculture systems for 55 days and fed a commercial trout diet (group CD) or diets supplemented with the following vegetable oils (VO): rapeseed (group RO), soy (group SO), sunflower (group SFO). The level of feed supplementation with VO was 84% of the total crude fat (CF), which was achieved by adding 160 g VO kg -1 feed to the commercial feed base that contained 30 g CF kg -1 feed. The diets tested did not have a significant impact on the proximate composition of the whole fish, fillets, or viscera (P > 0.05). Significant differences were noted in the protein and fat contents of the pikeperch livers; these were significantly higher in the groups fed diets supplemented with VO (P 0.05). They were, however, significantly lower than the values noted in group CD (P < 0.05) (1.03-2.07 vs. 3.50).