<abstract><title style='display:none'>Abstract</title> This study was designed to evaluate morphological differences between cultured and wild African catfish, Clarias gariepinus (Burchell). Fish samples were collected from the lower Benue River (axis in Makurdi), while cultured fish were obtained from the University of Agriculture Makurdi research farm. The results revealed significant sex-related variation in the fish from different environments. Significant differences were observed in all morphometric parameters measured and in three of the five meristic counts recorded. Discriminant analysis and cluster analysis of morphometric parameters showed a high divergence among the populations, hence the tested fish samples were grouped into respective environments by sex. The meristic count, however, overlapped broadly showing no divergence among the populations. The morphometric differences between the cultured and wild African catfish could have been linked to genetic differences or environmental factors or a combination of both factors.</abstract>

Intraspecific morphological variation between cultured and wild Clarias gariepinus (Burchell) (Clariidae, Siluriformes)

<abstract xml:lang="en"><title style='display:none'>Patterns of river lamprey size and sex ratio in the Baltic Sea basin</title>A comparative study of the size distribution of river lamprey, <italic>Lampetra fluviatilis</italic> (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.</abstract>

Department of Migratory Fish, The Stanisław Sakowicz Inland Fisheries Institute in Olsztyn, Synów Pułku 37, 80-298 Gdańsk, Poland

Department of Environmental Protection, Republic of Lithuania, Vilnius, Lithuania

Finnish Game and Fisheries Research Institute, Helsinki, Finland

Department of Fisheries Research, Institute of Food Safety Animal Health and Environment (BIOR), Riga, Latvia

Sea Fisheries Institute, Świnoujście, Poland

Museum of Natural History, Wrocław University, Poland

Department of Ecology, Institute of Meteorology and Water Management, Wrocław, Poland

Department of Ichthyology, The Stanisław Sakowicz Inland Fisheries Institute in Olsztyn, Poland

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

<abstract><title style='display:none'>Abstract</title>The anatomical structure of the olfactory organ and the organization of various cells lining the olfactory mucosa of <italic>Clupisoma garua</italic> (Siluriformes; Schilbeidae) were investigated with light and scanning electron microscopy. The olfactory organ was composed of numerous lamellae of various sizes, radiating outward from both sides of the narrow midline raphe, forming an elongated rosette. Each lamella consisted of the olfactory epithelium and a central lamellar space, the central core. The epithelium covering the surface of the rosette folds was differentiated into zones of sensory and indifferent epithelia. The sensory part of epithelium was characterized by three types of morphologically distinct receptor neurons: ciliated receptor cells, microvillous receptor cells, and rod receptor cells for receiving olfactory sensation from the aquatic environment. The indifferent epithelium comprising a large surface area of the lamella, was covered with compact non-sensory cilia. The non-sensory epithelium contained stratified epithelial cells with microridges, mucin secreting mucous cells, labyrinth cells, and basal cells, which were arranged in a layer at the base of the epithelium. Various cells on the olfactory epithelium were correlated with the functional significance of the fish concerned.</abstract>

Histology and surface morphology of the olfactory epithelium in the freshwater teleost <italic>Clupisoma garua</italic> (Hamilton, 1822)

<abstract xml:lang="en"><title style='display:none'>Effect of the synthetic pyrethroid Deltamethrin and the neem-based pesticide Achook on the reproductive ability of zebrafish, <italic>Danio rerio</italic> (Cyprinidae)</title>In the present research, both male and female zebrafish, <italic>Danio rerio</italic> (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 &lt; 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.</abstract>

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

<abstract xml:lang="en"><title style='display:none'>Controlled reproduction of pikeperch <italic>Sander lucioperca</italic> (L.): a review</title>Mastering techniques for conducting the controlled reproduction of a given fish species, the procedures for performing hormonal stimulation, and the choice of the appropriate hormonal preparation and dosage all have a significant impact on the effectiveness of spawning, and, in turn, on the quantity of stocking material produced. This paper presents reproduction techniques for pikeperch, one of the most economically valuable species of freshwater European fish. The methods discussed include cage spawning, the artificial reproduction of wild fish (obtained from the natural environment), and out-of-season spawning. The principles of stimulating spawning with either photothermal or hormonal methods are also described. It is demonstrated that using <italic>in vivo</italic> methods for determining the maturation stage of oocytes and hormonal stimulation (especially in less mature females) permits increasing cage and artificial spawning of wild fish. Among the hormones and hormonal preparations tested to date in the artificial spawning of pikeperch (gonadotropins (GtH), gonadoliberins (GnRH), and synthetic analogues (GnRHa)), the most effective have been carp pituitary extract (CPE) and human chorionic gonadotropin (hCG). This paper also presents the most recent techniques used in the production of pikeperch stocking material.</abstract>

Department of Aquaculture, The Stanisław Sakowicz Inland Fisheries Institute, Olsztyn, Oczapowskiego 10, 10-719 Olsztyn, Poland

Department of Ichthyology, University of Warmia and Mazury, Olsztyn, Poland

Controlled reproduction of pikeperch <italic>Sander lucioperca</italic> (L.): a review

<abstract><title style='display:none'>Abstract</title>
The study investigated the potential for increasing carp (<italic>Cyprinus carpio </italic>L.) production in temperate climates without expanding farming area and simultaneously reducing wastewater discharge in intensive fish production using an in-pond cage system. An earthen pond with a stocking density of 209.3 kg per ha−1 and four cages stocked with 8.12 kg m−2 (A1 and A2) and 2.61 kg m−2 (B1 and B2) were monitored. The gross yield from the cages was 27.09 kg m−2 (A1), 24.3 kg m−2 (A2), 10.09 kg m−2 (B1), and 9.73 kg m−2 (B2). The fish in the pond had the highest specific growth rate (SGR) at 0.98%, and the feed conversion ratio (FCR) was above 3 for all the cages. The cages provided a high enough nutrient load to enable a net fish production of about 450 kg ha−1 in the pond. Ineffective feed utilization affected the production performance in the cages. Thanks to the high yield obtained in the pond, the overall return on the investment was 16%, which rendered production profitable.
</abstract>

Integrated cage-pond carp farming for increased aquaculture production

<abstract>
<title style='display:none'>Abstract</title>
Feed additives are gaining popularity as dietary supplements with the potential to support growth, immune competence, and the general health of aquaculture species. This study aimed to evaluate growth performance and feed utilization in juvenile Asian seabass, <italic>Lates calcarifer</italic>, fed experimental diets containing enzymes derived from the solid-state fermentation (SSF) of <italic>Aspergillus niger</italic> and mannan oligosaccharides (MOS), both individually and in combination. Fish were fed six experimental diets: control (no additives), SSF (0.025% &amp; 0.05%), MOS (0.1% &amp; 0.2%), and combined SSF (0.025%) + MOS (0.05%). The feeding trial was conducted for ten weeks in triplicate for each experimental diet consisting of 51 fish in 120 L tanks. Following the collection of growth performance metrics, proximate analysis of muscle and feces samples was performed, and all datasets were statistically analyzed with One-way ANOVA. The results showed that the highest specific growth rate (SGR = 1.29%) and lowest feed conversion rate (FCR = 1.0) were obtained by fish fed the diet supplemented with SSF (0.025%) + MOS (0.05%). The synergistic effects of SSF as an exogenous enzyme source and MOS in supporting gut health likely facilitated enhanced nutrient digestibility and absorption, which supported the growth of juvenile Asian seabass.
</abstract>

Alltech European Bioscience Centre, Sarney

Beijing Alltech Biological Products Co Ltd

Effects of dietary supplementation with mannan-rich oligosaccharides and solid-state fermented <italic>Aspergillus niger</italic> on the growth performance of juvenile Asian seabass, <italic>Lates calcarifer</italic>

<abstract>
<title style='display:none'>Abstract</title>
Fish distribution in the lagoon complex of Lake Nokoué and Porto-Novo Lagoon is poorly documented. The lagoon complex is of particular interest because of its contribution to the local supply of animal protein. The fish communities in the complex were studied monthly between January and December 2015 at six sampling sites using two sets of gillnets with varying mesh sizes. The study applied a non-linear self-organizing map (SOM) method to classify the sampling sites based on the composition of fish assemblages, and an index of indicator value (IndVal) was calculated for each species identified. In total, 58 species from 49 genera and 34 families were cataloged with 45 species observed in Lake Nokoué and 48 in the Porto-Novo Lagoon. Notably, 35 species were common to both water bodies. The analysis revealed a dominance of occasional continental (20.7%) and strict estuarine species (20.7%). The SOM analysis suggested a tripartite structure of the fish communities, largely influenced by the geographical positioning of the sampling sites. The IndVal method identified 28 indicator species in the typical assemblages delineated by the SOM approach. The study highlights the importance of these indicator species for the conservation efforts aimed at sustaining the ichthyofauna of the lagoon complex.
</abstract>

Spatial and temporal patterns of fish assemblages in Lake Nokoué and the Porto-Novo Lagoon (Benin, West Africa)

<abstract>
<title style='display:none'>Abstract</title>
This study analyzed the rearing indicators of Siberian sturgeon (<italic>Acipenser baerii</italic>) juveniles reared in tanks of different shapes and at various stocking densities. Rearing was conducted in autonomous hatching and rearing modules. Fish of an average body weight of 47.3±1.0 g were divided into four experimental groups: CL, RL, CH, and RH, which differed in stocking density (20 specimens and 50 specimens) and tank shape (C – circular, R – rectangular). The experiment ran for 28 days. Two-factor analysis indicated that lower stocking density significantly affected the final body weight of juvenile Siberian sturgeon, while tank shape had no effect on growth. The results of the current study on rearing Siberian sturgeon juveniles indicated that tanks of different shapes can be applied, but faster growth was obtained at a lower stocking density.
</abstract>

Preliminary rearing outcomes of Siberian sturgeon, <italic>Acipenser baerii</italic> Brandt, juveniles in autonomous hatching and rearing modules

<abstract>
<title style='display:none'>Abstract</title>
The present study was performed to investigate the effects of dietary yeast β-1,3/1,6-D-glucans after 15-, 30-, and 45-day feeding periods on the development of oxidative stress, antioxidant defenses, and lysosomal functioning in gills and hepatic tissue of rainbow trout, <italic>Oncorhynchus mykiss</italic> (Walbaum). The fish were fed a control diet or an experimental diet containing the supplement Yestimun® at a dose of 1% in the basal feed (with 85% content of β-1,3/1,6-glucans). On days 15, 30, and 45 of the experiment, the following were analyzed in gills and hepatic tissue: oxidative stress biomarkers (2-thiobarbituric-acid-reacting substances [TBARS]); aldehydic and ketonic derivatives of oxidatively modified proteins; activities of superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), and glutathione peroxidase (GPx); total antioxidant capacity (TAC); activities of lysosomal enzymes (alanyl aminopeptidase [AAP], leucyl aminopeptidase [LAP], acid phosphatase [AcP], β-N-acetylglucosaminidase [NAG]). The dietary β-glucans stimulated CAT, GPx, LAP, and AcP activities in gills and hepatic tissue compared to the control group; however, the opposite trend was observed in TAC levels in gills on days 30 and 45. The present study suggests that β-glucans can enhance immune response, antioxidant capacity, and lysosomal functioning effectively in rainbow trout.
</abstract>

Modulation of oxidative stress biomarkers and lysosomal functioning in gills and liver of rainbow trout (<italic>Oncorhynchus mykiss</italic> Walbaum) fed a diet supplemented with yeast β-glucans

<abstract>
<title style='display:none'>Abstract</title>
Efficient, cost-effective DNA extraction methods are crucial for molecular research on sturgeon embryos given that substantial sample sizes must frequently be analyzed in short periods of time. The high lipid and carbohydrate contents of sturgeon embryo yolk sacs mean that obtaining genetic material of sufficient quality is challenging. The predominant methods used include tissue/cell lysis, organic extraction, purification on spin columns, and ethanol precipitation. However, these methods are expensive and time-consuming, which significantly limits the throughput of PCR-based molecular analyses. In the present study, we evaluated the usefulness of an in-house Chelex-100 DNA extraction method on sterlet (<italic>Acipenser ruthenus</italic>) embryos at the neurula developmental stage (48 hours post fertilization) and compared it with two other commercial silica membrane-based kits for isolating genetic material–NucleoSpin Tissue® (Macherey Nagel, Duren, Germany) and Sherlock AX (A&amp;A Biotechnology, Gdynia, Poland). The yield and quality of nucleic acid, its suitability for PCR amplification, and the total cost and complexity of the extraction methods were evaluated and compared. Our results indicated that the in-house Chelex-100 is inexpensive and can be used as an effective high-throughput method of DNA isolation for sterlet embryos.
</abstract>

Applicability of an in-house Chelex-100 DNA isolation method for extracting genetic material from sterlet (<italic>Acipenser ruthenus</italic>) embryos

<abstract>
<title style='display:none'>Abstract</title>
Mass fish kills caused by wastewater treatment plant (WWTP) failure are uncommon. In this study, we analyzed the recovery of the fish community in the Czarna Hańcza River after a fish kill caused by a WWTP incident in Suwałki in 2018. The research focused on brown trout, the dominant fish species in this river. The incident lasted about six hours and accounted for 7% of the mean river’s flow during the accident. The fish population recovered quickly, and ten months after the fish kill, the number of fish species and their abundance were similar to the pre-incident state, but the species structure was different. In subsequent years, fish species richness decreased conspicuously, while their numbers remained at a high, relatively constant level. Species that are more resistant to difficult environmental conditions, such as white bream and European perch, returned to the river first. Concurrently with the improvement of environmental conditions, more demanding species, including brown trout, began to dominate in the river. Fulton’s condition factors decreased significantly as the river self-purified and the density of the brown trout population increased (P &lt; 0.05). Our results indicated that the brown trout population was able to recover relatively quick, presumably because of stocking. Other species that were not stocked required more time to recover.
</abstract>

Changes in the fish community of the Czarna Hańcza River (NE Poland) after a fish kill caused by a wastewater treatment plant failure

<abstract><title style='display:none'>Abstract</title>The objective of the present study was to determine the optimum dosage of vitamin E (alpha-tocopherol) in the diet of keureling, <italic>Tor tambra</italic> (Val.) fingerlings for optimal growth performance and feed utilization. Five doses of vitamin E were tested: 0 mg kg−1 feed (control); 150 mg kg−1 feed; 300 mg kg−1 feed; 450 mg kg−1 feed; 600 mg kg−1. The feed ratio was 5% body weight, which was delivered twice daily at 08:00 and 17:00 for 60 days. The results showed that higher growth performance, feeding conversion ratios, feed efficiency, protein retention, and protein digestibility were obtained at 600 mg kg−1 feed, but the value was not significantly different from the other doses. The optimal dose in terms of the hepatosomatic index and survival rate was 300 mg kg−1. Hence, it was concluded that the optimum, most economical dose of vitamin E supplement for keureling (<italic>T. tambra</italic>) was 150 mg kg−1 feed, because this value was not significantly different from the doses of 300 and 600 mg kg−1 feed.</abstract>

Department of Aquaculture, Faculty of Marine and Fisheries, Syiah Kuala University, Banda Aceh 23111, Indonesia

Department of Aquaculture, Faculty of Marine and Fisheries Syiah Kuala University, Banda Aceh 23111, Indonesia

School of Biological Sciences, Universiti Sains Malaysia Penang, Malaysia

Centre for Marine and Coastal Studies, Universiti Sains Malaysia Penang, Malaysia

Growth performance and feed utilization of keureling (<italic>Tor tambra</italic>) fingerlings fed a formulated diet with different doses of vitamin E (alpha-tocopherol)

<abstract xml:lang="en"><title style='display:none'>The Influence of Temperature during the Embryonic Period on Larval Growth and Development in Carp, <italic>Cyprinus Carpio</italic> L., and Grass Carp, <italic>Ctenopharyngodon Idella</italic> (Val.): Theoretical and Practical Aspects</title>This work proposes modifications to the existing system for identifying the steps of embryonic and larval development in fish. The term "compensatory phase of development" is proposed for the phase from hatching to the first intake of food. Both the new designations of these steps and the new name of this phase do not require a declaration of whether the hatched individual is considered to be an embryo or a larva, something that has been, to date, a matter of dispute. Unification will allow for the wider use of the new nomenclature, and make easier the comparison of results. This work examines the influence of the thermal history during the embryonic period (temperatures of 20, 24, 28, and 32°C) on later development, growth, and survival of common carp, <italic>Cyprinus carpio</italic> L., and grass carp, <italic>Ctenopharyngodon idella</italic> (Val.) larvae, at a constant temperature of 23°C. It was confirmed that the optimal temperature ranges for the embryonic development of common carp and grass carp are higher than those currently applied widely in practice of 18-22°C and 21-26°C, respectively. Based on the evaluation of the development, growth, and survival of the larvae, it was determined that the optimal temperature for embryonic development is 26-28°C for the common carp and 32°C for the grass carp. It was confirmed that even a short-term increase in temperature from 20°C to 24°C during the compensatory phase has a positive influence on subsequent common carp larvae growth.</abstract>

The Influence of Temperature during the Embryonic Period on Larval Growth and Development in Carp, <italic>Cyprinus Carpio</italic> L., and Grass Carp, <italic>Ctenopharyngodon Idella</italic> (Val.): Theoretical and Practical Aspects

<abstract xml:lang="en"><title style='display:none'>Effect of sex reversal in rainbow trout (<italic>Oncorhynchus mykiss</italic> Walbaum) using 17α-methyltestosterone and 11β-hydroxyandrostenedione</title>The aim of the experiment was to compare the effectiveness of sex reversal in mature female rainbow trout using 17α-methyltestosterone (6 ppm-MT) and 11β-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.</abstract>

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

<abstract xml:lang="en"><title style='display:none'>Artificial off-season spawning of Eurasian perch <italic>Perca fluviatilis</italic> L.</title>The aim of the study was to conduct off-season spawning of perch, Perca <italic>fluviatilis</italic> L. Spawners were obtained in late September from Lake Kortowskie. The fish were transported to the hatchery and divided into two size groups: G1 - small fish (30-70 g), and G2 - large fish (200-400 g). All males from G1 group spermiated after a two-month period of photo-thermal stimulation, but only 25% of the males from G2 group produced milt. Better results were obtained with fish that were stimulated after three months of chilling. All the stimulated males spermiated and produced higher volumes of milt. The best results, defined as ovulation success and embryo survival to the eyed-egg-stage, as well as spawner survival rate, were obtained with large females (G2-B) stimulated with a double dose of hormone (2 Ovopel pellets kg-1). The egg strands obtained from females from group A (small and large fish stimulated with GnRHa and metoclopramide at 0.1 and 1 pellet kg-1after 24 hr) were usually fragmented. All females responded to the hormonal injections after 4 to 5 days.</abstract>

Department of Aquaculture, The Stanisław Sakowicz Inland Fisheries Institute, Oczapowskiego 10, 10-719 Olsztyn, Poland

Department of Lake and River Fisheries, University of Warmia and Mazury, Olsztyn, Poland

Artificial off-season spawning of Eurasian perch <italic>Perca fluviatilis</italic> L.

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