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Yusuf BOZKURT

Mersin University, Faculty of Fisheries, Department of Aquaculture, Faculty Member

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Address: Mersin University
Faculty of Fisheries, Department of Aquaculture
Yenişehir 33160, Mersin, Türkiye

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Papers by Yusuf BOZKURT

Editorial: Genomic cell preservation in aquatic animals: with emphasis on cryopreservation

Frontiers in Marine Science, 2025

Editorial on the Research Topic Genomic cell preservation in aquatic animals: with emphasis on cr... more Editorial on the Research Topic Genomic cell preservation in aquatic animals: with emphasis on cryopreservation In recent years, there have been significant advancements in the conservation of fish gametes and genomic cells. Techniques such as cryopreservation and chilled storage are now commonly used to enhance hatchery management. These methods help synchronize reproduction cycles, ensure year-round availability of gametes, and conserve broodstock lines developed through selective breeding programs (Bozkurt, 2023a). Beyond aquaculture, germplasm preservation offers valuable tools for conserving natural fish populations, particularly during the early phases of domestication or genetic improvement. Preserving wild genotypes allows researchers and breeders to maintain a genetic reservoir for potential reintroduction, biodiversity enhancement, or the recovery of lost traits. Furthermore, as the number of fish species classified as threatened or endangered continues to grow, the use of cryobanks has become a vital strategy for supporting conservation, reducing genetic erosion, and facilitating species recovery. Cryopreservation of fish genomes has been explored using various cell types, including spermatozoa, oocytes, spermatogonia, primordial germ cells (PGCs), somatic cells, blastomeres, and embryos. Among these, sperm cryopreservation is the most advanced and commonly implemented method (Bozkurt, 2023b). This is mainly due to the ease of sperm collection in most species, the small size and structural simplicity of spermatozoa, their resistance to chilling and freezing stress, and their suitability for fertilization using either conventional or androgenetic techniques. However, sperm-based cryopreservation only preserves the male germ line, which limits its capacity for genetic conservation. On the other hand, the cryopreservation of other genomic cells, such as oocytes, embryos, and early germ cells, remains a complex and underexplored field in aquatic species. These cell types are more susceptible to cryoinjury because of challenges like intracellular ice formation, osmotic shock, cryoprotectant toxicity, and issues with membrane integrity. As a result, standardized and efficient protocols for the conservation of these cell types are still lacking, and significant research is needed to optimize the processes of freezing, thawing, and cell recovery.

Gene Expression Biomarkers in Aquaculture Production: Towards Sustainable Breeding Practices

Developments in Aquaculture: Trends, Challenges, and Applications - 1st Edition, 2025

Aquaculture is the fastest-growing sector of food production, crucial for meeting global protein ... more Aquaculture is the fastest-growing sector of food production, crucial for meeting global protein demand. A cornerstone of aquaculture success is effective reproductive biology – high-quality eggs and sperm from robust broodstock drive reliable fry production and stock renewal. However, reproduction in aquatic animals can be complex and easily disrupted by suboptimal conditions. Understanding the molecular underpinnings of reproduction is therefore vital for sustainable aquaculture. In particular, gene expression plays a central role in regulating reproductive processes.

Current Situation and Recent Advancements of the Aquaculture Sector in Türkiye

by Yusuf BOZKURT and Hayri Deniz

Developments in Aquaculture: Trends, Challenges, and Applications, 2025

Aquaculture in Türkiye is a relatively young sector compared to other sectors. Fish farming in Tü... more Aquaculture in Türkiye is a relatively young sector compared to other sectors. Fish farming in Türkiye is started with carp in 1960’s and rainbow trout culture fallowed it in the early 1970s. Sea bass and sea bream farming started in 1985 in the Aegean Sea. After than it has developed rapidly thanks to its huge potential, the state's support of the sector, the rapid adaptation of producers to developing and changing technologies, and their technical capacity, reaching 2,382 farms in 2022, and the total capacity reached 784,864 tons (MoAF, 2023).

Standardized Sperm Cryofreezing Technique for Caspian Sea Sturgeons (Huso huso, Acipenser persicus, Acipenser stellatus, Acipenser nudiventris)

Genetics of Aquatic Organisms (Genaqua), 2024

Sturgeons, considered "living fossils," face extinction due to various factors, according to the ... more Sturgeons, considered "living fossils," face extinction due to various factors, according to the International Union for Conservation of Nature's Red List. The present study describes a uniform sperm cryopreservation method for the endangered Caspian Sea sturgeon species, which are beluga (Huso huso), Persian (Acipenser persicus), stellate (Acipenser stellatus), and ship (Acipenser nudiventris) sturgeons for both artificial reproduction and ex-situ conservation attempts. For this aim, sperm samples were diluted 1:1 in extender composed of 118 mM Tris buffer (pH=8) and 23.4 mM sucrosebased extender containing 15% DMSO and equilibrated for one hour at 4°C. Then, sperm samples were placed into 0.50-ml straws and multi-stage cooling was applied to freeze with the help of a programmable freezer with an accuracy of ±0.1C/min, and finally stored in liquid nitrogen (-196C) tank. Thawing was performed at 40°C water baths for 25 s. The results indicated that storage for two years resulted in a 24.7% fertilization rate for the stellate sturgeon, while the Persian sturgeon had a remarkable rate of 58.2% after five years storage.

Action before the Extinction of Endangered Sturgeon Species: With Emphasis on Stock Enhancement and Conservation

Aquaculture Industry - Recent Advances and Applications, 2024

Sturgeons are one of the most valuable fish species in the world due to their pleasant meat, famo... more Sturgeons are one of the most valuable fish species in the world due to their pleasant meat, famous black caviar, and isinglass. Sturgeons are believed to be among primitive groups of vertebrates in the world and have been described as “living fossils”. It is assumed that they have been living in the natural waters of the northern hemisphere of the world for 200 million years. Their natural populations are now highly endangered because of overfishing for their black caviar and delicate flesh, destruction of spawning habitat, pollution of freshwater, and human-constructed barriers to access spawning migration. Nowadays, living populations have little chance of survival without stock enhancement and sustainable conservation programs. This review document presents general features of current restoration programs and describes how stock enhancement and conservation strategies can be used to recover Eurasian-based sturgeon resources in peril.

Broodstock Management and Nutrition in Aquaculture

by Yusuf BOZKURT and Ömer Metin

Present-Day Turkish Aquaculture and Trends in International Research, 2024

This chapter provides information about the source, selection, transportation, stocking density, ... more This chapter provides information about the source, selection, transportation, stocking density, genetic characterization, environmental requirements, and reproduction of broodstockfish. Future research avenues are also discussed, including the nutritional needs of brood-stocks, feeding strategies, the need for developing an adequate broodstock diet for successful reproduction, effect of food restriction, and specific feed ingredients. In addition, research and practices related to broodstock management and nutrition in Türkiye were evaluated.

CALL FOR "GENOMIC CELL PRESERVATION IN AQUATIC ANIMALS: WITH EMPHASIS ON CRYOPRESERVATION"

FRONTIERS IN MARINE SCIENCE, 2024

This Research Topic aims to provide a platform for researchers interested in genomic cell preserv... more This Research Topic aims to provide a platform for researchers interested in genomic cell preservation including spermatozoa, oocytes, primordial germ cells (PGCs), somatic cells, blastomers and embryos of marine species through provided topics below: • Cryopreservation • Chilled storage • Conservation • Cryobanking • Germ Cell • Reproduction • Threatened Marine Species This Research Topic welcomes original articles related to any of these objectives including reviews and articles summarising the current best practice technical protocols and the potential issues and challenges for further research development.

An evaluation of soybean lecithin as an alternative to avian egg yolk in the cryopreservation of fish sperm

Cryobiology, 2013

Plant-derived lecithin has been used as a more sanitary alternative to avian egg yolk in livestoc... more Plant-derived lecithin has been used as a more sanitary alternative to avian egg yolk in livestock sperm cryopreservation protocols but its efficacy for cryopreserving fish sperm has not previously been tested comparatively. Here various concentrations of soybean lecithin were evaluated for the cryopreservation of carp (Cyprinus carpio) sperm. Sexually mature fish were induced to spermiation and ovulation with ovopel. The extenders were prepared by using 300 mM glucose, 10% DMSO, supplemented with different ratios of lecithin (5%, 10%, 15%, and 20%) and 10% egg yolk (control I). Negative control was made without egg yolk and soybean lecithin (control II). The pooled semen was diluted separately at ratio of 1:3 (v/v) by using egg yolk and soybean-based extenders. Diluted semen placed into 0.25 ml straws were equilibrated at 4 °C for 15 min and frozen in liquid nitrogen vapor. Fertilization was conducted using a ratio of 1 × 10(5)spermatozoa/egg. Supplementation of 10% lecithin to extender showed the best cryoprotective effect for sperm motility and duration of motility against freezing damage compared to 15%, 20% and control II groups (p<0.05). Cryopreserved sperm with extender containing 10% lecithin provided a greater result in terms of fertilization success when compared to extenders containing 20% lecithin or control II (p<0.05). It is concluded that the animal protein-free extender containing 10% soybean lecithin has a similar cryoprotective actions with conventional egg yolk-based extender against freezing damages and fertilization. Therefore, soybean lecithin is a suitable alternative to avian egg yolk for the cryopreservation of fish sperm.

Comparison of different freezing techniques, extenders, and cryoprotectants on quality and fertility of cryopreserved Salmo trutta f. fario sperm

Acta Scientiarum Technology, 2024

There is still a lack of standardized methodology in the cryopreservation of Salmo trutta f. fari... more There is still a lack of standardized methodology in the cryopreservation of Salmo trutta f. fario sperm. Thus, the present study was designed to compare current freezing protocols to improve and as well as to examine the post-thaw quality and fertilizing ability of cryopreserved sperm in Salmo trutta f. fario. Sperm samples were diluted at a 1:10 ratio in one of three extenders (Alsever's solution, glucose-based, and ionic-based) containing four types of cryoprotectant (DMSO, DMA, MeOH, glycerol) at 10% concentration and frozen in 0.1 mL pellets on surface of the dry ice (solid carbon dioxide, 79°C) or in 0.25 mL straws 2 cm above of the liquid nitrogen (LN2) surface at a rate of ~30°C for 10 min. 1 before storage in a mL cryotank (-196°C). The frozen sperm cells in straws and pellets were thawed in a water bath at 25°C for 30 s and at 20°C for 6 s respectively. Fertilization was carried out using a ratio of 5x10 5 sperm/egg in both freezing methods. The glucose-based solution including glycerol produced the highest post-thaw progressive motility (62.5 ± 1.24%), motility duration (57.2 ± 0.46 s), and viability (56.4 ± 1.57%) (p < 005) in the straw method. In breeding trials, similarly, sperm frozen-thawed with the glucose-based solution including glycerol produced the highest fertilization (54.2 ± 0.36%) and hatching (30.6 ± 0.28%) in the straw method. Fresh sperm used as control produced 82.6 ± 0.45% and 78.4 ± 1.27% fertilization and hatching respectively. It was concluded that sperm frozen in straws produced higher post-thaw sperm motility and fertility of eggs than those frozen in pellets. Also, the results suggest using of glycerol-supplemented glucose solution because of producing better results in both freezing techniques.

Introductory Chapter: Biotechnological Applications in the Aquaculture Industry

Aquaculture Industry - Recent Advances and Applications, 2024

Effect of different plant extracts on microbial population in the frozen African Catfish (Clarias gariepinus) semen

Cellular and Molecular Biology, 2023

Fish sperm cryopreservation has been attempted on roughly freshwater and marine species since 195... more Fish sperm cryopreservation has been attempted on roughly freshwater and marine species since 1953. This study sought to assess the potential of various plant extracts to function as natural antimicrobial agents in the
frozen semen of African catfish (Clarias gariepinus). Diluted sperm was packaged in 0.25ml straws and left for 10min equilibration at 4°C. Following equilibration, the straws were exposed to liquid nitrogen vapor for 10 min and plunged into the liquid nitrogen (-196°C) and then thawed in a water bath at 35°C for 20s. Sperm samples were put into sterile 1.5 ml tubes immediately after thawing and the microbial count was detected with classical microbiological culture method. In the results of microbiological analyses, these tree plant extracts especially Echinacea purpurea were found highly effective for decreasing bacterial contamination levels of African catfish (C. gariepinus) semen. These plant extracts may have the potential for antibacterial effect, and they can be useful for the dilution of semen.

Conservation Strategies for the Aquatic Genetic Resources: Opportunities and Challenges

Modern Reproductive Biotechnologies in the Conservation of Aquatic Genetic Resources, 2023

Conservation strategies benefit from advances in reproductive biology and reproductive technologi... more Conservation strategies benefit from advances in reproductive biology and reproductive technologies. In this regard, choosing of type of genetic material to be preserved for different species highly depend on objective, technical feasibility, cost, and practical implications. Conservation of genetic material from aquatic species through in situ and ex situ protection methods is an important strategy to conserve genetic diversity. In situ conservation is attributed to conserve aquatic genetic resources as rearing of live individuals. On the other hand, the preservation of aquatic genetic resources as in situ carry some risks regarding problems in the rearing system, pathogen infections, and loss of genetic diversity and fitness concerning natural habitats. The other conservation method is called ex situ conservation, which is considered a secure method due to providing an opportunity to protect samples and reconstruction of the original population, folllowing the required environmental restoration.

Gamete and Embryo Cryopreservation in Aquatic Species

Modern Reproductive Biotechnologies in the Conservation of Aquatic Genetic Resources, 2023

Cryopreservation enables freezing of the biological materials at temperature of liquid nitrogen (... more Cryopreservation enables freezing of the biological materials at temperature of liquid nitrogen (LN2) (-196ºC). Thus, it is possible to conserve the biological materials as unchanged for centuries. Gamete and embryo cryopreservation is an important tool for the artificial production of economically important species, and for the conservation of threatened species with genetic biodiversity in aquatic life.

Farklı sulandırıcı ve saklama sürelerinin üreme mevsimi boyunca ot sazanı (Ctenopharyngodon idella) Spermasının motilite ve fertilizazyon başarısı üzerine etkisi

The present study was conducted to evaluate the effect of different extenders and storage periods... more The present study was conducted to evaluate the effect of different extenders and storage periods on motility and fertilizing ability of short-term stored grass carp sperm during spawning season. Sperm was collected from anesthesized males by the abdominal massage method. Having determined the main spermatological properties, the pooled ejaculates were diluted with 3 different extenders at a ratio of 1:3. The diluted sperm was packaged in small tubes and following, the tubes were stored at 4°C in a refrigerator for 8 hours. During preservation motility (%), motility duration (s) and fertilization (%) capacity of stored sperm were evaluated 2 hours intervals. Fertilization was carried out using the dry fertilization technique at 2x105 spermatozoa/egg dosage. The fertilization success was determined as the percent of eyed eggs 3-4 days after fertilization. At the end of 8 hours of storage, the highest sperm motility was found as 35±2.89% (P<0.05) with extender II in June...

Aynalı Sazan (Cyprinus carpio) Balıklarında Üreme Mevsimi Boyunca Spermatolojik Özelliklerin Belirlenmesi

Bu arastirmada aynali sazan (Cyprinus carpio) spermasinin ureme mevsimi boyunca spermatolojik oze... more Bu arastirmada aynali sazan (Cyprinus carpio) spermasinin ureme mevsimi boyunca spermatolojik ozelliklerinin belirlenmesi amaclanmistir. Arastirmada cinsel olgunluga erismis 10 adet erkek damizlik aynali sazan kullanilmistir. Erkek damizlik baliklardan sperma abdominal masaj yontemi ile alinmis ve alinan spermalarda; miktar, spermatozoa motilitesi, spermatozoa canlilik suresi, spermatozoa yogunlugu, toplam spermatozoa sayisi, sperma rengi ve spermanin pH’si belirlenmistir. Aynali sazan spermalarinda ureme mevsimi boyunca ortalama (±sd) miktar (ml), motilite (%), canlilik suresi (s), yogunluk (x109/ml), toplam spermatozoa sayisi (x109) ve pH degerleri sirasiyla Nisan ayinda 2.49 ± 1.34, 76.50 ± 12.48, 158 ± 72.75, 13.67 ± 1.65, 35.61 ± 22.26, 7.15 ± 0.33 olarak, Mayis ayinda 23.27 ± 13.99, 79.00 ± 11.73, 684.20 ± 6.96, 17.93 ± 5.16, 408.86 ± 258.03, 7.00 ± 0.23 olarak, Haziran ayinda ise 1.10 ± 0.67, 77.50 ± 17.98, 239.10 ± 221.55, 11.97 ± 1.04, 13.06 ± 8.06, 7.30 ± 0.42 olarak belir...

Evaluation of spermatological parameters of mirror carp (Cyprinus carpio) during spawning season

Ege Journal of Fisheries and Aquatic Sciences, 2006

Evaluation of spermatological parameters of mirror carp (Cyprinus carpio) during spawning season.... more Evaluation of spermatological parameters of mirror carp (Cyprinus carpio) during spawning season. Ten mature male mirror carp (Cyprinus carpio) were used as semen donors. The semen was collected by massaging the abdomens of the fish and sperm volume, spermatozoa motility, duration of movement, spermatozoa density, total spermatozoa density, colour and pH of sperm was evaluated. During spawning season mean (±sd) volume (ml), motility (%), duration of movement (s), density (x10 9 /ml), total spermatozoa density (x10 9) and pH were evaluated respectively as follows 2.49

Short-Term preservation of grass carp (Ctenopharyngodon idella) eggs: Effect of extenders and storage duration

The Israeli journal of aquaculture = Bamidgeh

The short-term effects of extenders and storage duration on fertilization, eyeing, and hatching r... more The short-term effects of extenders and storage duration on fertilization, eyeing, and hatching rates in short-term stored grass carp eggs was evaluated. Eggs were kept in one of two artificial extenders (Ringer and 300 mM glucose solutions) or in ovarian fluid in 10-cm petri dishes. About 4 ml of artificial extender or coeolomic fluid was added to each petri dish and the dishes were transferred to a dark humid refrigerator for storage at 4ºC for 120, 240, 360, or 480 min. Eggs were fertilized by adding 200 μl milt to each petri dish. The fertilization rate was determined at the gastrula stage. The eyeing rate was defined as the number of eyed eggs divided by the initial number of eggs used for fertilization. The highest fertilization rate (93%) was attained in coelomic fluid stored for 120 min. The highest eyeing rates were in eggs kept in ovarian fluid for 120 or 240 min. The glucose extender was best for longer storage (360 and 480 min). The highest hatching rate was obtained wit...

Introductory Chapter: Cryopreservation Biotechnology in Aquatic Science

Biological Research in Aquatic Science, 2019

Hatchery-Based Artificial Production of Freshwater Crayfish

New Trends in Agriculture , Forestry and Aquaculture Sciences, 2022

Vitrification: Fundamental Principles and Its Application for Cryopreservation of Human Reproductive Cells

Cryopreservation Biotechnology in Biomedical and Biological Sciences

The fundamental understanding of cryobiology through experimentation in the 1960s, 1970s, and 198... more The fundamental understanding of cryobiology through experimentation in the 1960s, 1970s, and 1980s has led to the development of today's vitrification technology. Although human embryo and oocyte vitrification was slow to evolve, it has become an invaluable technology in the field of reproductive medicine. The aim of this chapter is to discuss some of the underlying basic principles behind forming a metastable glass phase during rapid cooling in liquid nitrogen (LN 2) and the prevention of recrystallization events upon warming. We then highlight how this understanding has led to its highly effective and reliable usage in clinical IVF. Furthermore, we describe how quality control factors (e.g., ease of use, repeatability, reliability, labeling security, and cryostorage safety) can vary between vitrification device systems, potentially influencing clinical outcomes and creating possible liability issues. An open-minded approach to continued experimentation is a necessity, especially pertaining to oocyte freeze preservation, if we are to optimize the vitrification of reproductive cells and tissue in the future.