The high plasticity, or the ability to differentiate into various cell types, and capacity to become both gametes of early-stage germ cells (eGCs) allows them to be used for the long-term storage and recovery of genetic information. In this study, species-specific protocols (isolation period, enzymatic separation solution, incubation period, appropriate cryoprotectant, and cryopreservation protocol) were established for the isolation and longterm preservation of Black Sea trout eGCs. In addition, the difference between the application of cryopreservation to the whole gonad tissue and to the enzymatically separated cells has been shown in terms of viability and the number of cells obtained. According to the cell count made from the histological sections of the testicular tissue throughout the year, the period with the highest concentration of eGCs in the tissue is between May and June. To identify the optimal enzymatic dissociation solution, we subjected testicular tissues to digestion using various combinations of trypsin (T) and collagenase (C) (0.3-0.5% T and 0.1-0.3% C). Our findings revealed that the 0.3% C provided the highest yield of viable cells (90.9%). We cryopreserved the enzymatically dissociated cells (EDCs) using six different cryoprotectants (Dimethyl sulfoxide, Glycerol, and CryoSOfree™, in both L-15 and phosphate-buffered saline -PBS mediums). Additionally, whole tissue exclusively with CryoSOfree™. After storing the samples at -152 °C for two years, the group of EDCs cryopreserved in L15+Glycerol exhibited the highest viability at 93.3%. Meanwhile, the whole tissue group yielded the greatest number of cells per ml after thawing, with a count of 33 210 000 cells. When considering both the viability (91.11%) and the number of cells obtained (33 210 000 cells/ml), the whole tissue cryopreservation group outperformed all the other methods.

This study compared the growth performance of triploid and diploid Black Sea trout (Salmo trutta labrax) during their fry (initial weight 0.21 – 0.21 g), fingerling (1.97 – 2.08 g) and juvenile (52.15 – 57.81 g) stages. The carcass ratio, gonadosomatic index (GSI), hepatosomatic index (HIS), proximate and fatty acid composition for the juvenile fish were also investigated. The results evinced no metabolic advantage resulting from triploidy before sexual maturation of Black Sea trout as the triploid growth was equal to diploid siblings. The juvenile triploid Black Sea trout grew faster than diploid having significantly higher weight gain, length increment, thermal growth coefficient, specific growth rate, and lower feed conversion ratio. The GSI values tended to increase over time in diploid and their significantly lower values were observed in triploid in the last three months of the trial. The HSI of triploids were significantly higher than diploid siblings. Triploid had significantly higher fat contents, and possessed higher levels of saturated and monounsaturated fatty acids than diploid. Diploid had higher polyunsaturated fatty acids than triploid siblings. These findings indicate the potential for superior triploid growth with better carcass ratio suggesting a great benefit of induced triploidy in Black Sea trout culture.

A comparative analysis of juvenile anadromous and freshwater (stream) forms of the Black Sea brown trout Salmo trutta labrax Pallas, 1814 was conducted using 10 meristic and 62 morphometric characters of cranial bones. This analysis included the counts of teeth and pores in the bones, as well as measuring of their shape characters. As a basis for comparison, data on juvenile anadromous and freshwater Atlantic salmon Salmo salar Linnaeus, 1758 were used. The osteological differences between ecological forms were more pronounced in the brown trout than in the Atlantic salmon. In the brown trout, a greater number of meristic characters differentiated the forms compared to the salmon. However, for morphometric characters, the reverse pattern was observed. The freshwater forms exhibited characteristics intermediate to the anadromous forms of the two species, being more similar to the anadromous form of their species than to each other. Juvenile anadromous Black Sea trout typically had the fewest teeth, while juvenile Atlantic salmon had the most, with freshwater forms showing intermediate values. The most significant differences in the shape of cranial bones were also observed between the juvenile anadromous forms of two species. The characteristics pertaining to the number of pores in cranial bones did not reveal clear patterns when comparing the samples. Among the studied bones and characteristics, those showing the most significant differences between Black Sea trout and Atlantic salmon were identified, and species-specific features were noted. The results obtained show that juveniles of different ecological forms within the same species of the genus Salmo exhibit statistically significant osteological differences, suggesting a high genetic determination of these traits and the influence of selection within river systems on the divergence between freshwater and anadromous forms. Despite this, the variability in all studied characteristics indicates plasticity, resulting in the differences between the species and ecological forms within the genus Salmo typically not reaching the threshold for subspecies differentiation. These results align with previous studies on adult individuals and indicate that the freshwater form of the Atlantic salmon displays osteological characteristic of a more ancestral species, namely the brown trout.

Sperm motility is an important character for the assessment of milt quality and indicator to the expected rate of fertilization. Many factors can affect the sperm motility, including nature of water used as sperm activator medium after stripping the milt from the male fish. The aim of this study was to gain motility to spermatozoa and improve sperm kinematic parameters by applying a non-chemical method. The effects of magnetic field on samples of hatchery water exposed to magnetic field of 2.71, 4.51 and 8.11 mT for the duration of 12, 24 and 36 hours on Salmo trutta labrax sperm motility were investigated with computer-assisted sperm analysis (CASA) system; 4.51 mT exposure for 36 hours (A2H3) was greater in motility kinematic parameters (p < 0.05) and progressive kinematic parameters (VAP, VSL and VCL) with values of (93.1244 ± 37.222, 88.6111 ± 36.137, 96.8378 ± 35.396 μm/s) and (102.9167 ± 32.546, 100.9767 ± 31.894, 105.8778 ± 30.401 μm/s) respectively. But there was no (p ≥ 0.05) in the slow phase just in the VCL parameter had (p ≤ 0.05) (35.8789 ± 39.127 μm/s) among other parameters. There was (p ≤ 0.05) in starting motility time until vibration point (s) for 4.51 mT in 12 hour (A2H1) (27.3333 ± 1.527 s), but total time of motility was greater for 4.51 mT in 36 hour (A2H3) with (p ≤ 0.05) (49.6667 ± 2.081 s) compared with other treatments.

In this study, Black Sea trout (<em>Salmo trutta labrax, </em>Pallas, 1811) and Rainbow trout (<em>Oncorhynchus mykiss, </em>Walbaum 1792) were reared in mono and duo-culture groups. Duo-culture groups were designed to include changing numbers of individuals for each species to assess the effect of dominance. The effect of the culture strategy on growth and survival rates during the feeding transition period was compared. The growth performance of mono and duo-culture groups were found similar whereas the survival rates of the groups differed significantly. The survival rate of the duo-culture group with the 75/25 stock density for two species was found lower when compared with monoculture groups and groups of 50/50 stock density. The feed conversion ratio (FCR) for all groups was similar.

In this study, sperm characteristics of Black Sea trout (Salmo trutta labrax) and effects of ions, their concentrations and osmolality of the solution on sperm activation were evaluated. Two different activation solutions with ionic and non-ionic osmolality levels were investigated. After the definition of conditions where osmolality played a role, activation solutions containing calcium ion (Ca2+) in different molarity levels were tested under single and combined solutions to determine their relations (Sperm motility percentage was determined by using computer-aided sperm analysis system (CASA) for each activation solution). It was found that Black Sea trout sperm motility is initiated with iso-osmolality and activation solution with non-ionic osmolality had no effect on motility whereas ionic osmolality was effective on motility. The best solution determined in this study for the Black Sea trout is proved to have the same osmolality as the seminal plasma of the handled fish prepared with NaCl containing 2–32 mM CaCl2.

Changes in the motivational component of rheoreaction (the ratio of rheoreaction types) during starvation in some fish species has been analyzed. The presence of fish motivation to migrate (before starvation) is the major pattern of the future changes in the motivational component of rheoreaction resulting from starvation. All fish of the families Cyprinidae and Salmonidae studied with initially behavior as resident individuals show the same type of response to starvation. Their preference for currentwise movement increases on the 2nd–5th days of starvation, then the preference for movement against the current increases on the 7th–12th days, and the ratio of rheoreaction types approaches the initial one. Juveniles of the Black Sea salmon (Salmo trutta labrax) with a motivation to downstream migration, represent a different response to starvation: the downstream movement of individuals monotonically increased from two days after starvation.

In this study, the quality and reproductive success of wild Black Sea Trout (Salmo trutta labrax) were investigated. In total 32 wild trout (27.3±13.6 g and 13.9±2.3 cm) from the Bıçkı Stream in Kocaeli Province in the Marmara Region were kept in circular fiberglass outdoor flow-through tanks (1.5m ø) at the mean water temperature of 11.8±4.5 °C. In November 2016, when the water temperature was 8.4 °C, the first spawning of wild trout occurred. Sperm volume (ml), Motility (%) and VCL (µm/ sec) values were determined to be 7.5±2.5, 70.42±0.83 and 70.35±3.98, respectively. The weight (g), total fecundity and egg diameter (mm) values of female fish were listed to be 513.75±78, 1.171±171, and 3.84±0.02, respectively. In the experiment, 5.859 wild Black sea trout eggs were fertilized. The eyed-egg stage occurred 24 days (288 day-degree) post fertilization and the survival rate from fertilization to the eyed-stage was 28%. Wild Black Sea trout larvae from P1 (Paternal Generation) hatched 48 days after fertilization with the hatching rate of 7%.

In this study, the effect of combined feeding Black Sea trout (Salmo trutta labrax) broodstock with commercial feed and mealworm larvae (Tenebrio molitor) for 50 days before the breeding period in order to evaluate the gamete quality. While the control group was fed with commercial feed, mealworm larvae were given as an additional protein source 2 days a week and 3 days a week to the experimental groups formed from female and male individuals. In addition to the growth parameters, the number of eggs (number/individual) and the egg diameter (mm), sperm volume (ml), density of spermatozoa (×109 cell/ml), total motility (%), progressive motility (%) and average curvilinear velocity (VCL, µm/sec) values were determined. At the end of the study, the highest live weight gain was found as 46.2 g in the control group of male. The egg diameters were 4.3 ± 1.8 mm and 4.5 ± 1.4 mm in the worm treatment groups fed twice and three times with mealworm respectively. As a result, it was determined that feeding fish with mealworm larvae as an addition to the commercial diet in female individuals did not affect the amount of eggs (p > .05), but the egg diameters were significantly smaller in the control group than the mealworm groups (p < .05). In spermatological characteristics, only the amount of sperm was different between the groups (p < .05); all other parameters were found to be similar to each other with no statistical differences (p > .05).

Turkey has a rich variety of fish species in the rivers with a total length of 177,714 km in Turkey. Freshwater fish live in rivers, streams, creeks, dam lakes, natural lakes, wetland areas, etc. The life of migratory fish is threatened by the anthropogenic impact on aquatic habitats. Human activities that disrupt river integrity can be listed as; dam and hydro power plant constructions, high levees, sluices, weirs and bridges, sand-gravel quarries, recreational works, wetland depletion, water pollutions, overfishing, habitat losses, climate changes, water pumping from a river to other river basins, drinking water, dried river beds etc. The most important diadromous fish species in Turkey are sturgeon species (Acipenseridae), European eel (Anguilla anguilla) and Black Sea trout (Salmo trutta labrax). In this study, the past and present status of these species are reviewed.

Bu çalışma, Marmara Bölgesi’ ndeki bir işletmede kültürü yapılan Karadeniz alabalıklarında (Salmo trutta labrax) görülen ölümlerin nedenini belirlemek, etkenin dokularda meydana getirdiği patolojik değişikliklerin tespiti yanı sıra etkene karşı uygun olan tedaviyi belirlemek amacı ile yürütülmüştür. Bu amaçla altı adet hasta Karadeniz alabalığı (400-500 g) bakteriyolojik, parazitolojik ve histopatolojik metotlar kullanılarak incelenmiştir. Hasta alabalıklarda iç bakıda sırt bölgesinde renkte koyulaşma, adipoz yüzgeç ve kuyruk yüzgeçlerinde erime yanı sıra kaudal yüzgeç etrafında kaslara kadar inen derin deri lezyonları; dış bakıda ise splenomegali, karaciğerde solgunluk, sindirim kanalı etrafındaki damarlarda hiperemi gibi klinik bulgular tespit edilmiştir. İncelenen hasta balıklarda herhangi bir parazitin varlığına rastlanılmamıştır. Hasta balıkların karaciğer, böbrek ve dalak gibi iç organlarından Tryptic Soy Agar (TSA) besiyerine yapılan ekimlerin inkübasyonu sonucunda besiyerinde üreyen bakterilerin morfolojik, fizyolojik ve biyokimyasal özellikleri incelendiğinde izole edilen bakteriler Pseudomonas fluorescens ve Staphylococcus sp. olarak identifiye edilmiş ayrıca izole edilen bu bakterilerin en çok flumekuine karşı duyarlı olduğu tespit edilmiştir. Histopatolojik olarak, pilorik sekalar arasında hemoraji, bağırsak lümenini örten epitel hücrelerinde nekroz ve lümene dökülme, böbrek tübülerinin parankim epitelyum hücrelerinde dejenerasyon, periglomerular ödem, hemapoietik dokuda boşalma, karaciğerin parankim hücrelerinde dejenerasyon ve nekroz, dalak dokusunda kırmızı pulpada boşalma ve melanomakrofaj odakları yanı sıra solungaç filamentlerinde nekroz gözlenmiştir. Bu çalışma ile kültür çalışmaları yapılan hasta Karadeniz alabalıklarında ilk kez hastalık etkeni olarak Pseudomonas fluorescens ve Staphylococcus sp. izole ve identifiye edilmiş ayrıca bu patojen bakterilerin dokularda meydana getirdiği patolojik değişiklikler detaylı bir şekilde verilmiştir.

The article highlights the future development of salmon cultivation at the example of breeding bull-trout ( Salmo trutta labrax Pallas, 1814) inhabiting the Black Sea and Azov Sea. There has been made the analysis of key biotechnical processes of forming brood stock and reproduction of bull-trout in order to replenish the endangered fish population. The deficiency of producers, low abundance of the brood stock and, actually, a low number of bull-trout population (bull-trout is listed into the Red Book of the Krasnodar region and the Red Book of the Russian Federation) are the main limiting factors of the species reproduction. There has been given the review of the current state of species reproduction, as well as the analysis of the trout-breeding plant “Adler” efforts on reproduction and preservation of bull-trout population. In order to produce viable breed for further releasing into the natural habitat and replenishing population of this valuable species, as well as due to low ability to survive (13%) there have been given recommendations on using live feed such as gill-footed crustaceans Artemia salina along with artificial feed. The work on reproducing and forming the brood stock should become the main objective of the trout hatchery “Adler” over the medium term.

This study was conducted to determine changes in the growth performance and distal intestine villi morphology of juvenile Black Sea trout ( Salmo trutta labrax ) fed diets with three different protein levels (40%, 45% and 50%). It was carried out in two separate sections; freshwater (RAS) and seawater. Juvenile Black Sea trout, having average initial weights of 3.44g (freshwater) and 17.70g (seawater), were fed for 90 days. WG, SGR, FCR and survival weren’t affected by dietary treatment. However distal intestine villi length (VL), width (VW) and length to width ratio (VL/VW) were affected by dietary treatments. Villi length, width and length to width ratio in the fish fed with diet containing 50% protein in freshwater were found to be higher than those fed with other diets. Villi length in the fish fed with diet containing 50% protein in seawater was higher than those fed with other diets. Results showed that feeding with diets contained different protein levels did not effect on growth performance of Juvenile Black Sea trout, but affected on distal intestine villi morphology.

This study was conducted to determine the effect of age, sex and weight on the middle intestine villi morphology of fifth-generation Black Sea trout (Salmo trutta labrax Pallas, 1811). The fish were kept in the freshwater ponds (June-October) and marine cages (November-May) to provide the life cycle of species. Intestine tissue samples were taken during period when fish were kept in marine cages. According to the results obtained, middle intestine villi morphology changed depending on age (1, 2, 3, 4 and 5 years old) and different live weight of similar ages (16 months old). The lowest intestine villi development was obtained in 1 years old fish. This was followed by 2 years old fish. The highest intestine villi development was obtained in 3 years old fish. Besides, intestine villi development of high weighted fish was higher than those of low weighted fish. However, it was found that middle intestine villi morphology didn’t changed depending on sex.

In this research, the culture characteristics of the fifth generation of Black Sea trout ( Salmo trutta labrax PALLAS, 1814) were evaluated. First of all, trout were cultured in recirculating aquaculture system (RAS) and they kept in RAS until smoltification. After that, they were transported to marine cages till market size. Thus, the ratios of specific growth rate (SGR), feed conversion (FCR), mortality and condition factor (CF) were specified from hatching to 16 th month and the results were evaluated as pre-smoltification and after-smoltification individually. Moreover, the meat yield and proximate composition of Black Sea trout’s fifth generation was specified in market size. Samplings were carried out monthly between February 2014 and May 2015. Fish were started to feed in 0.105±0.007g until they reached to 335.50±44.39g in May 2015. According to results; SGR, CF, FCR and mortality were determined as between 0.98-2.70, 0.82-1.15, 1.02-1.30 and 7.67-7.78% until smoltification stage, respectively. However, they were detected between 0.68-2.36, 1.04-1.20, 0.98-1.35 and 0.01-5.82% after smoltification. Also, the meat yield, viserosomatic index (VSI) and hepatosomatic index (HSI) were found to be 60.30%, 9.28% and 1.65% in market-size respectively. According to chemical analyses, trout meat contains crude protein as 15.47%, fat as 7.21%, ash as 1.57% and water (moisture) as 74.83%. In the view of the results, culture characteristics, proximate composition and meat yield were found similar to other cultured trout species. With these features, the fifth generation can be recommended to aquaculture sector considering the economic value of the Black Sea trout in Turkey.

Populations of brown trout in the Mzymta River and its tributaries include anadromous (mainly female) and resident (mainly males) fish. Some resident males in the basin of the Mzymty River attain sexual maturity at the age 1+, and resident females mature at the age 2+ or 3+. The maximum age of resident fish is 4+ in the samples studied. Migrations of anadromous brown trout to the sea occur at the ages 1+, 2+, or 3+. Future spawners spend from 1 to 4 years at feeding grounds in the sea. Smolts of the population are characterized by performing not only spring but also autumn migrations to the sea. One smolt specimen has been detected upstream from the dam in the river where spawners of anadromous brown trout do not migrate; this means that the capability for sea migrations persists long in the population represented only by resident specimens of brown trout. The diversity of life cycles and ecological forms in populations of brown trout is not lower than in populations of brown trout in Northern and Western Europe. The comparison of the data obtained with published data makes it possible to come to the conclusion about the high plasticity of ontogenesis of Black Sea brown trout.

Conditions of reproduction and distribution of the Black Sea trout Salmo trutta labrax in the basin of the Mzymta River after Olympic objects′ construction are considered. In the main river channel of the Mzymta, the structure of spawning and nursery grounds are destroyed along 57 km from the river mouth. The total area of these grounds in the Mzymta basin is 572800 m2, and 49% of this area is situated above the dam of the Krasnopolyanskaya Power Plant and is inaccessible for spawners of the migratory form of the Black Sea trout listed in the Red Data Book of the Russian Federation. Consequently, natural reproduction of the migratory form discontinued. The resident form of trout still exists in the upper parts of the Mzymta and in 19 of its tributaries not affected by construction. On the 2.4-km-long stretch of the riverbed situated below the inflow of the Pslukh tributary, the substrate is in the process of natural restoration due to the descent of mudslides followed by washing of the substrate by the flow. The river is partially inhabited by trout individuals from habitats not affected by construction.

The content of Na+, K+, Cl–, and Ca2+ in blood of farm-raised juveniles of Black Sea trout at the age 10 and 12 months, at the stage of selection of life strategy, was measured. Change in ion exchange related to smoltification in the fish kept in freshwater begins in females earlier than in males. After differentiation of parr in the smolt, the concentrations of Na+ and Ca2+ decrease and the concentration of K+ increases in comparison with that of the resident form. An increase in water salinity does not activate osmoregulatory restructuring of the organism. The decrease in the concentrations of Na+ and Cl– in blood of the Black Sea trout may indicate the beginning of the smoltification process.

We compared the digestion rate of commercial, and farm-prepared feeds, in three species (Onchorynchus mykiss, Dicentrarchus labrax, and Salmo trutta labrax) reared at two temperatures (12˚C and 17˚C). Rearing conditions, except for hydrodynamic conditions of the offshore farms, were simulated in the experiment. There were significant differences in overall digestibility between the diets; overall protein digestibility of the farm-prepared feed was much higher than that of the commercial feed (P&lt;0.01). Lipid digestibility of farm-prepared diets was competitive but not significant compared to commercial feeds. The results may be attributed to poorly digestible ingredients of commercial feeds while farm-prepared feeds include mainly fresh anchovy and other ingredients such as hardtack meal, corn meal, wheat flour, and soybean meal. Consequently, farm-prepared diets seem to be much more competitive in respect to both digestibility, and cost, compared to commercial diets. In addition, the nutrient digestion rate of farm-prepared feeds was more balanced and stable.

We compared the digestion rate of commercial, and farm-prepared feeds, in three species (Onchorynchus mykiss, Dicentrarchus labrax, and Salmo trutta labrax) reared at two temperatures (12˚C and 17˚C). Rearing conditions, except for hydrodynamic conditions of the offshore farms, were simulated in the experiment. There were significant differences in overall digestibility between the diets; overall protein digestibility of the farm-prepared feed was much higher than that of the commercial feed (P&lt;0.01). Lipid digestibility of farm-prepared diets was competitive but not significant compared to commercial feeds. The results may be attributed to poorly digestible ingredients of commercial feeds while farm-prepared feeds include mainly fresh anchovy and other ingredients such as hardtack meal, corn meal, wheat flour, and soybean meal. Consequently, farm-prepared diets seem to be much more competitive in respect to both digestibility, and cost, compared to commercial diets. In addition, the nutrient digestion rate of farm-prepared feeds was more balanced and stable.