Fish Sex Research Articles

Multiple sex chromosomes in teleost fishes from a cytogenetic perspective: state of the art and future challenges.

Despite decades of cytogenetic and genomic research of dynamic sex chromosome evolution in teleost fishes, multiple sex chromosomes have been largely neglected. In this review, we compiled available data on teleost multiple sex chromosomes, identified major trends in their evolution and suggest further trajectories in their investigation. In a compiled dataset of 440 verified records of fish sex chromosomes, we counted 75 multiple sex chromosome systems with 60 estimated independent origins. We showed that male-heterogametic systems created by Y-autosome fusion predominate and that multiple sex chromosomes are over-represented in the order Perciformes. We documented a striking difference in patterns of differentiation of sex chromosomes between male and female heterogamety and hypothesize that faster W sex chromosome differentiation may constrain sex chromosome turnover in female-heterogametic systems. We also found no significant association between the mechanism of multiple sex chromosome formation and percentage of uni-armed chromosomes in teleost karyotypes. Last but not least, we hypothesized that interaction between fish populations, which differ in their sex chromosomes, can drive the evolution of multiple sex chromosomes in fishes. This underlines the importance of broader inter-population sampling in studies of fish sex chromosomes.This article is part of the theme issue ‘Challenging the paradigm in sex chromosome evolution: empirical and theoretical insights with a focus on vertebrates (Part II)’.

Gonadal development and molecular analysis revealed the critical window for sex differentiation, and E2 reversibility of XY-male spotted scat, Scatophagus argus

In vertebrate the development of gonad into testis or ovary requires the combined effect of genes and hormones to trigger differentiation from a bipotential gonadal primordium. Knowledge of the gonad development process is vital in studies on fish sex determination and differentiation. The spotted scat (Scatophagus argus) is an economically important marine fish with an XX/XY sex-determining system and exhibits sexual growth dimorphism in favor of females. Meanwhile, information on gonad development and gene expression patterns in the early gonads is unknown. This study explores the pattern of spotted scat early gonad development by morphological and molecular means. In the undifferentiated gonads, the number of germ cells in females is not significantly different from males. At age 3 mph (months post-hatch), the number of germ cells in females was significantly higher than in males. The sex differentiation began in females before males with the proliferation of primary oocyte and spermatocytes at 3.5 and 4 mph, respectively. In the early gonads, dmrt1 and amh were significantly higher in XY-fish, while cyp19a1a and foxl2 were higher in the XX-fish. Within the critical period of sex differentiation, estradiol treatment was able to sex-reverse XY-male to XY-female. In the sex-reversed group, male (dmrt1 and amh) and female (cyp19a1a and foxl2) related genes were suppressed and increased, respectively. 17α-Methyltestosterone or aromatase inhibitor (letrozole) could not induce sex reversal in XX-fish due to the absence of the male-specific dmrt1 required for testes development. Conclusively, this study identifies the critical window for sex differentiation and significantly higher germ cell numbers in future females than males. We provide evidence that the phenotypic XY-male is reversible, while the phenotypic XX-female is irreversible. Dmrt1 is necessary for testis differentiation, amh in males, and cyp19a1a and foxl2 in females could also be used as molecular markers in early gonads. This study explicitly presents valuable information for research development on sex determination and differentiation and sex control in spotted scat.

Length-Weight Relationship and Condition Factor of Layang Fish (Decapterus russelli) Landed at Tenda Fish Landing Base, Gorontalo

The study aims to figure out growth pattern and condition factor of the flying fish (Decapterus russelli) landed at the Fish Landing Base Tenda, Hulonthalangi District, Gorontalo City. Sampling of 360 layang fish was carried out randomly based on a simple random sampling method for three months. Determination of fish sex was conducted visually by dissecting samples and observing the gonads. The study showed that the layang fish (D. russelli) landed in PPI Tenda had a positive allometric growth pattern with condition factor values ranging from 1.005 to 1.014 and 1.002 to 1.620 for male and female, respectively

A simple and rapid method for fish sex identification based on recombinase-aided amplification and its use in Cynoglossus semilaevis

Fish sex identification is a basic technique of great importance for both fish genetic studies and fisheries. Due to the sexual reversal phenomenon in many fish species, a simple and rapid molecular identification method for fish genetic sex is urgently needed to suit versatile detection scenarios, such as point-of-need applications. In this study, we took Cynoglossus semilaevis as an example, established a recombinase-aided amplification (RAA)-based method for sex identification, and combined the RAA-detection with two result visualization approaches with distinct features, capillary electrophoresis (CE) and lateral flow dipstick (LFD). Specific primers and probe were designed to specifically detect the sex chromosome W of C. semilaevis in order to distinguish the genetic sex between males, pseudo-males and females. To evaluate the performance of our methods, the genetic sex for twenty-eight males, sixty-eight pseudo-males and fifty-four females were examined with the RAA-based method and classical PCR-based genotyping method, demonstrating the consistent results of sex identification between both methods. The RAA-LFD method is operationally simple, rapid (~ 30 min) and holds great potential for point-of-need applications of fish sex identification, including fishery fields. The method presented here could be effective for identifying fish gender with the ZW karyotype.

Acoustic telemetry reveals strong spatial preferences and mixing during successive spawning periods in a partially migratory common bream population

Partial migration, whereby a population comprises multiple behavioural phenotypes that each have varying tendencies to migrate, is common among many animals. Determining the mechanisms by which these phenotypes are maintained is important for understanding their roles in population structure and stability. The aim here was to test for the temporal and spatial consistency of migratory phenotypes in a common bream Abramis brama (‘bream’) population, and then determine their social preferences and extent of mixing across three successive annual spawning periods. The study applied passive acoustic telemetry to track the movements of bream in the River Bure system of the Norfolk Broads, a lowland wetland comprising highly connected riverine and lacustrine habitats. Analyses revealed that individual migratory phenotype was highly consistent across the 3 years, but this was not predicted by fish sex or length at tagging. During the annual spawning periods, network analyses identified off-channel areas visited by both resident and migrant fish that, in non-spawning periods, were relatively independent in their space use. Within these sites, the co-occurrence of bream was non-random, with individuals forming more preferred associations than expected by chance. These associations were not strongly predicted by similarity in fish length, sex or behavioural phenotype, indicating that the resident and migrant phenotypes mixed during their annual spawning periods. The results suggested these different phenotypes, with spatially distinct resource use in non-spawning periods, comprised a single population, with this having important implications for the management of this wetland resource.

Masculinization in common carp (Cyprinus carpio) by androgen immersion: The interaction effect of hormone concentration and immersion time.

Synthetic androgens (male hormones) administered to fish nursery are being used in aquaculture to avoid sexual differentiation and unwanted spawning at the eggs or the first feeding fry stage of fish. Present trial was conducted with the aim to produce male common carp (Cyprinus carpio) by egg immersion technique. Through this little insight, the effect of different hormone concentrations (17α-methyltestosterone @ HC:150, 300, 450 and 600 µgl-1) with immersion times (IT: 24, 48 and 72 hrs) and their interaction effect (HC x IT) on the hatching percentage of Cyprinus carpio eggs, percent survival and percent of male's production was evaluated specifically. Results showed that egg hatching percentage decreased with increased IT likewise, survival of treated fry was affected by increasing the IT (P<0.001). The main interaction effect of HC x IT showed that the highest percent of male individuals (95%) was obtained at 450-600 µgl-1 HC for 72 hrs IT, followed by 88-92.50% at 150-300 µgl-1 HC for 72-hrsof IT, 87.50% at 48-hrs of IT for rest of the hormone treatments, and lowest 47.50% was recorded in control (P<0.05). Increased percent male of Cyprinus carpio was obtained with increasing HC across all ITs. It was observed that the immersion treatment at 600µgl-1 for 72 hours was more effective to change the sex ratio of pre hatch Cyprinus carpio. A comparative outlook made from this experimental trial that sex induction of Cyprinus carpio by eggs immersion using synthetic male steroid hormone is an alternative safe technique of fish sex reversal in contrast to oral administration of hormone in fish feed.

Life-history studies on infrapopulations of Mazocraes alosae (Monogenea) parasitising Alosa immaculata (Actinopterygii) in the northern Black and Azov Seas.

The life-history of Mazocraes alosae Hermann, 1782 on one of its hosts, the Pontic shad Alosa immaculata Bennett, is described for the first time. This anadromous fish, which occurs off the coast of the Crimea and migrates from the Black Sea to the Sea of Azov and into the River Don for spawning, was studied throughout its migration and during all seasons. It is demonstrated that the period of reproduction of this monogenean is significantly longer than that reported for the population in the Caspian Sea, lasting from April to November with a peak in April-May, and continues both in the sea and the river. Experiments showed that water salinity does not limit the development of the eggs or the hatching of the oncomiracidia. Our data reveal that the abundance of M. alosae is not determined by the size or sex of mature fish and that shad of less than two years old can also be infected with this monogenean, although less frequently than older fish. The direction of the migration of A. immaculata, either from the Black Sea to the Sea of Azov and into the rivers or in the opposite direction, does not influence the number of monogeneans present on the host. The main factor affecting the dynamics of the abundance of this monogenean is season, and, as has been indicated previously in the Caspian Sea basin, there is a synchronisation between the parasite's life-history and both the host's spawning behaviour and the duration of its migration.

The Effect of Immersion Doses of Hybrid Coconut Water on Guppy (Poecillia reticulata) to Increase the Male Larvae Percentage

Abstract Guppy fish is one type of ornamental fish that has its charm where it has beautiful colours and a slender body shape. Male guppy fish are more attractive, have more beautiful colour patterns, longer tail fins, and a slimmer body than female guppies. Hence, their selling price is much higher and is in demand in the market in the ornamental fish industry. One way that can be done to produce male guppy fish is by using the sex reversal or masculinization method. The sex reversal method that can be used is to use a solution of young hybrid coconut water (Cocos nucifera) with different doses. The immersion process will affect the percentage of male sex in guppy fish because in the young coconut water solution there is a content of potassium which plays a role in the sex reversal process which functions to regulate testosterone regulation in the body and direct the work of androgens. The purpose of this study was to determine the effect of young coconut water on the sex ratio of male guppies resulting from the immersion of female broodfish and to determine the best dose for the success rate of masculinization of guppy fish. The research was conducted from April to June 2020 in guppy fish farmers in Sidomulyo Village, East Ungaran District, Semarang Regency. The test animal used was the Black Moscow fish. This study used an experimental method with a completely randomized design of 4 treatments and 3 replications. Treatment of different immersion doses of young coconut water solution used were A (without immersion), B (40%), C (45%), D (50%). The data observed included the percentage of the male sex, survival rate and water quality. The results obtained from the research showed that the percentage value of male guppy fish was treated A (50.57 ± 3.48%), B (84.90 ± 2.55%), C (90.42 ± 1.67%), D (96.90 ± 1.34%). The results of the survival rate are treatment A (98.91 ± 0.95%), B (95.58 ± 2.48%), C (91.25 ± 3.46%), D 84.36 ± 3.62 %. The results of water quality observations were in the form of temperatures ranging from 26.9-28.9 ℃, pH (7.2-7.9), and DO ranging from 3.5-5.5 mg/ L. The conclusion was that immersion of young coconut water solution in pregnant guppy broods with different doses had a significant effect (P &lt;0.05) on the percentage of the male sex. The best treatment was treatment D (50%) which resulted in the percentage value of male sex 96.90 ± 1.34%. Keywords: Black Moscow, potassium, masculinization, androgen hormone

Population dynamics of an emergent invasive fish, striped piggy, Pomadasys stridens (Actinopterygii, Perciformes, Haemulidae) in the Gulf of İskenderun, north-eastern Mediterranean

The striped piggy, Pomadasys stridens (Forsskål, 1775), is a recent invasive fish species in the eastern Mediterranean. Although its population dynamics was investigated in detail in its natural distribution area, the western Indian Ocean, an important data gap still exists in the Mediterranean. This study was carried out to determine the growth, mortality, and the length–weight and length–length relations of invasive striped piggy right after its establishment in the area. Samples were collected seasonally between April 2014 and December 2015 by using bottom trawl from 10 and 20 m depth contours off the north-western coast of the Gulf of Iskenderun. After the length, weight, and sex of fish were recorded, sagittal otoliths were extracted and examined for age determination. Then length–length, length–weight, and length at age relations, growth performance, and mortality rates were calculated for both sexes and pooled data. In the study, a total of 1131 individuals were investigated, the total length of which ranged between 7.3 and 18.9 cm. The mean length was 12.32 ± 0.11 cm. There was no significant difference between the length–weight relation (LWR) parameters of sexes and pooled data. The overall LWR was found to be TW = 0.0113 * TL^3.096 in all specimens. The von Bertalanffy growth parameters were not significantly different between males and females. The model parameters for both sexes were L∞ = 22.01 cm, K = 0.22 years–1, t0 = –1.30 years. The growth performance index (Ø′) was calculated as Ø′ = 2.03. For combined sexes, the total, natural and fishery mortality rates were Z = 1.14 years–1, M = 0.66 years–1, and F = 0.48 years–1, respectively. The exploitation rate of the stock was found to be E = 0.42. The growth performance of the invasive striped piggy population was determined to be similar to the ones reported from the Gulf of Suez where was the closest natural distribution area of the species. Although striped piggy is proper for human consumption and commercially caught in its native range, its fishery has not yet been established in the Eastern Mediterranean and we found that there was insufficient fishery pressure on the invasive population.

АНАЛИЗ СОСТОЯНИЯ ЗАПАСОВ ОСНОВНЫХ ПРОМЫСЛОВЫХ РЫБ КУЙБЫШЕВСКОГО ВОДОХРАНИЛИЩА ЗА ПЕРИОД 2000–2018 ГГ. И ЭФФЕКТИВНОСТЬ ИХ ИСПОЛЬЗОВАНИЯ ПРОМЫСЛОМ

The article presents a review of the main commercial fish stocks of the Kuibyshev Reservoir based on the long-term research data (2000–2019). The Kuibyshev Reservoir is the leading fishery reservoir in the Republic of Tatarstan, Mari El, Chuvashia, Ulyanovsk and Samara Re-gions. There have been given the data of regular observing species, sex, size-weight and age composition of fish, their reproduction efficiency, distribution, abundance and reproduction of aquatic biological resources, their habitat, as well as control over their fishing and conservation. The analysis of the influence of environmental factors (level and temperature regimes) and fishing on the fish stocks formation is presented. Based on the presented materials, there have been shown the data about the stocks of the main commercial fish species of the Kuibyshev Reservoir (bream, zander, pike, carp, catfish, sterlet) and of the small-sized ordinary fish stocks, the optimal development of which will bring the catches up to 10 thousand tons and more. It has been inferred that for rational fishing in the reservoir, it is necessary to develop a strategy for the integrated effective development of biological resources of the reservoir on an ecosystem basis for better use of the bioproduction capabilities of its biological resources.

COMUNIDADES DE PARÁSITOS DE PATAGONOTOTHEN TESSELLATA (RICHARDSON, 1845) (PISCES: NOTOTHENIIDAE) DE CHILE AUSTRAL: ¿QUÉ TAN DETERMINANTE ES EL SEXO DEL HOSPEDERO?

El conocimiento de comunidades de parásitos es muy abundante en peces marinos; sin embargo, hay varias especies que tienen escasa información parasitológica, como es el caso de Patagonotothen tessellata (Richardson, 1845), que posee una amplia distribución y abundancia en la Patagonia. Este estudio tuvo como objetivos determinar la composición comunitaria de parásitos en P. tessellata, y determinar el efecto del sexo de los hospederos en la composición parasítica a través de los descriptores poblacionales y comunitarios de parásitos. En enero de 2018 se recolectaron 118 ejemplares de P. tessellata en dos localidades cercanas entre sí, Muelle Prat y Muelle Remota, Puerto Natales, Chile Austral. En los peces capturados se encontró un total de 13 especies de parásitos, principalmente del Phylum Nematoda y Acanthocephala, de los cuales el nemátodo Pseudodelphis sp. seguido por el acantocéfalo Hypoechinorhynchus magellanicus (Szidat, 1950) fueron los de mayor prevalencia (78,8% y 53,4%, respectivamente) y abundancia (7,18 ± 17,95 y 7,30 ± 15,21, respectivamente). Se determinó que hospederos machos y hembras tenían iguales tamaños corporales y la misma correlación positiva entre peso-longitud, además, no se observaron diferencias significativas en composición y carga parasitaria. Mientras que el género de los peces tampoco afectó la composición parasítica para P. tessellata, pues, no hubo diferencias significativas en la prevalencia ni en la abundancia promedio de las especies de parásitos entre hospederos machos y hembras. Estos resultados indican la semejanza en las comunidades de parásitos entre sexos de P. tessellata y dan a presumir de que las condiciones del hábitat o la dieta de este pez son similares entre machos y hembras. De este modo, ambos grupos estarían expuestos a la infección de las mismas especies parásitas y en similares condiciones ambientales.

The intersection of stress, sex and immunity in fishes.

While sexual dimorphism in immune responses has been documented in other vertebrates, evidence for a similar phenomenon in fish is lacking. Here, we review the relationship between immunity, stress, spawning, and sex hormones in fish to gain a better understanding of sex-based differences in fish immune responses and its consequences for aquaculture. It is well known that there is a strong link between the stress response and immune function in fish. In addition, research to date has demonstrated that sexual dimorphism in the stress response exists in many species; yet, the relationship between the sexual dimorphic stress responses and immune function has rarely been explored together. Aside from stress, spawning is also known to trigger changes in fish immune responses. Estrogens and androgens have been shown to modulate the immune system which could account for differences between the two sexes of fish when spawning; however, evidence regarding the sexual dimorphism of these changes varies between fishes and is likely related to the spawning strategy employed by a given species. Sex hormones are also used in aquaculture practices to produce monosex populations, and exposure to these hormones early in development has been shown to impact the development of immune organs in several fishes. While female fish are generally thought to be more robust than males, aquaculture practices should also consider the role that maternal stress has on the immune function of the offspring and what role this plays in compromising the immune response of farmed fish.

An Investigation of ZZ/ZW and XX/XY Sex Determination Systems in North African Catfish (Clarias gariepinus, ).

An investigation of sex-specific loci may provide important insights into fish sex determination strategies. This may be useful for biotechnological purposes, for example, to produce all-male or all-female fish for commercial breeding. The North African catfish species, Clarias gariepinus, has been widely adopted for aquaculture because its superior growth and disease resistance render the species suitable for hybridization with other catfish to improve the productivity and quality of fish meat. This species has either a ZZ/ZW or XX/XY sex determination system. Here, we investigate and characterize these systems using high-throughput genome complexity reduction sequencing as Diversity Arrays Technology. This approach was effective in identifying moderately sex-linked loci with both single-nucleotide polymorphisms (SNPs) and restriction fragment presence/absence (PA) markers in 30 perfectly sexed individuals of C. gariepinus. However, SNPs based markers were not found in this study. In total, 41 loci met the criteria for being moderately male-linked (with male vs. female ratios 80:20 and 70:30), while 25 loci were found to be moderately linked to female sex. No strictly male- or female-linked loci were detected. Seven moderately male-linked loci were partially homologous to some classes of transposable elements and three moderately male-linked loci were partially homologous to functional genes. Our data showed that the male heterogametic XX/XY sex determination system should co-exist with the ZZ/ZW system in C. gariepinus. Our finding of the co-existence of XX/XY and ZZ/ZW systems can be applied to benefit commercial breeding of this species in Thailand. This approach using moderately sex-linked loci provides a solid baseline for revealing sex determination mechanisms and identify potential sex determination regions in catfish, allowing further investigation of genetic improvements in breeding programs.

Myxobolus (Myxosporea: Myxobolidae) polyinfection patterns in Oreochromis niloticus in Adamawa-Cameroon

Fish are prone to several parasitic diseases among which are the myxosporean infections. The goal of this study was to assess the prevalence and patterns of Myxobolus infection in O. niloticus in the Adamawa region of Cameroon. Specimens of Oreochromis niloticus were collected monthly in Mape dam from May 2016 to May 2017, and examined for Myxosporean infections. The overall prevalence was 45.43%. Myxobolus tilapiae significantly exhibited the highest prevalence (15.14%) followed by Myxobolus brachiosaurus (12.29%). Myxobolus pharyngeus (0.86%) was the less prevalent parasite. Out of 350 examined fish, 23.14% were poly infected. Five categories of poly infections were observed i.e. bi (15.71%), tri (4.00%), tetra (2.29%), penta (1.14%) and hexa specific (0.57%) corresponding to two to six parasite species combinations respectively. Their prevalence dropped significantly with the number of coexisting species whatever the fish sex, class size, infection site and season. Kidneys harbored up to four categories of poly infections, and Myxobolus tilapiae was the most associated contrary to Myxobolus agolus which appeared only in one combination of the tetra specific infection. Fish were significantly more poly infected during the dry season (28.76%) than the rainy season (18.78%). The poly infection of O. niloticus with Myxobolus species is an alert calling for urgent control strategies.

Một số đặc điểm sinh sản và tăng trưởng của Cá dọn bể (Pterygoplichthys spp.) giai đoạn tiền trưởng thành ở tỉnh Khánh Hòa, Việt Nam

Pterygoplichthys spp. is an invasive alien species distributed in most water bodies of southern Vietnam. Pre-matured fish (70 - 188 mm in length) were sampled from Am Chua canal (12o17.436' N, 109o6.063' E) in Khanh Hoa province, Vietnam and analyzed for reproductive and growth characteristics. Morphology analysis of gonad of these fish indicated that sex of small fish (≈ 8 cm in length, 4 g in weight) could be distinguished using naked eyes. Male to female ratio for the population was 1:1. Weight of gonad at stage I was significantly smaller those at stage II (both collected at the same and different sampling period). Fish at pre-matured stage tended to grow in length more than in weight (b&lt;3). Research results indicated that this species had diverse reproductive characteristics and well adapted to water bodies in south Vietnam.

Study of cestode infection in relation to the sex of the host fish, Mastacembelus armatus

The present communication deals with the study of cestode infection in a popular freshwater fish, Mastacembelus armatus in relation to the male and female sex of the host. In this study the author calculated the maximum prevalence, mean intensity and relative density in the males of host fish.

Igf3 is essential for ovary differentiation in zebrafish†.

Zebrafish gonadal sexual differentiation is an important but poorly understood subject. Previously, we have identified a novel insulin-like growth factor (Igf) named insulin-like growth factor 3 (Igf3) in teleosts. The importance of Igf3 in oocyte maturation and ovulation has been recently demonstrated by us in zebrafish. In this study, we have further found the essential role of Igf3 in gonadal sexual differentiation of zebrafish. A differential expression pattern of igf3 between ovary and testis during sex differentiation (higher level in ovary than in testis) was found in zebrafish. An igf3 knockout zebrafish line was established using TALENs-mediated gene knockout technique. Intriguingly, all igf3 homozygous mutants were males due to the female-to-male sex reversal occurred during sex differentiation. Further analysis showed that Igf3 did not seem to affect the formation of so-called juvenile ovary and oocyte-like germ cells. Oocyte development was arrested at primary growth stage, and the ovary was gradually sex-reversed to testis before 60 day post fertilization (dpf). Such sex reversal was likely due to decreased germ cell proliferation by suppressing PI3K/Akt pathway in early ovaries of igf3 mutants. Estrogen is considered as a master regulator in fish sex differentiation. Here, we found that igf3 expression could be upregulated by estrogen in early stages of ovarian follicles as evidenced in in vitro treatment assays and cyp19a1a mutant zebrafish, and E2 failed to rescue the defects of igf3 mutants in ovarian development, suggesting that Igf3 may serve as a downstream factor of estrogen signaling in sex differentiation. Taken together, we demonstrated that Igf3 is essential for ovary differentiation in zebrafish.

Effect 17&lt;i&gt;α-Metiltestosterone&lt;/i&gt; Hormone with Different Dosage to Percentage Male Sex, Absolute Weigh Growth, and Survival to Congo Tetra Fish (&lt;i&gt;Micraleptus interruptus&lt;/i&gt;)

Congo Tetra fish is one of the freshwater ornamental fish species which is in great demand because of its high economic value. Male congo tetra fish have a higher selling value than female fish, because the morphology of their bodies looks more attractive, especially their brighter colors and long fins. Sex reversal technology is one technique that can be used to obtain male monosexual offspring.The hormone 17α-methyltestosterone in male fish can increase spermatogenesis and determine secondary sex markers in male fish through the formation of sexual characteristics in fish morphology and body color. The administration of the hormone 17α-methyltestosterone with the right dose can increase the percentage of male sex of Congo Tetra fish. The purpose of this study was to determine the effect of the hormone 17α-methyltestosterone with different doses on the percentage of male sex, absolute weight growth, and survival of congo tetra fish, to determine which 17α-methyltestosterone hormone dose had the best effect on the percentage of male sex, growth in absolute weight, and survival in congo tetra fish. This research was conducted at the Regional Technical Service Unit of the Fish Seed Center for Ternate City. The time for conducting the research starts from March to May, 2020. In this study, 4 treatment doses of hormones were used, each treatment was repeated 3 times. The treatments tried were as follows: Treatment A: Dose 2 mg/l, Treatment B: Dose 3 mg/l, Treatment C: Dose 4 mg/l, Treatment D: Dose 0 mg/l (control).The results showed that the hormone 17α-methyl testosterone with different doses had a very significant effect on the male sex percentage of congo tetra fish, but it was not significantly different on the growth in absolute weight and survival of congo tetra fish. The highest average percentage of male sex in congo tetra fish was found in treatment C (dose 4 mg/l) which was 86.6%, the highest average value of growth in absolute weight was found in treatment A (hormone dose 2 mg/l) of 1.083 g, and the highest survival was found in treatment D (control) of 90.473%.

Biological parameters of Luciobarbus callensis populates Beni-Haroun dam, north-eastern Algeria

The fish age and growth data mainly assist many ichthyologists to understand the life history features of species and population. The growth is a major process of fish biology, and considered as one of the key processes of length-structured models of fishes. Thus, the present study was devoted to studying the growth of an autochthonous species (Luciobarbus callensis), populating the dam of Beni-Haroun (Mila city, northeast Algeria), and is known by its socio-economic value and aquaculture interest. The study was conducted on a sampling of 257 fish individuals during the year 2015 – 2016. The age of Luciobarbus callensis was determined by using the described method or the scalimetry method, providing an easier sampling and reading procedures, and also a high precision. Fish sexes were identified via the observation of gonads, by naked eye based on gonad shape and color, where the number of females was higher (165) than males (92). The obtained results revealed a maximum longevity as seven years of Luciobarbus callensis, and the determined growth parameters of the separated and combined fish sexes were found to be as follow: L∞= 47,37 cm ; K= 0,29 ; t0= -0,51 ; Ø’= 2,813 (females); L∞= 42,11 cm ; K =0,26 ; t0= -0,58 ; Ø’= 2,663 (males); and L∞= 47 37 cm ; K= 0,20 ; t0= -0,75 ; Ø’ =2,652 (combined sex). Moreover, the evolution of the total weight of fishes with respect to their size presents a minor allometry (b&lt;3), (with or without sex distinction).

A PCR-based genetic sex identification method in spotted mandarin fish (Siniperca scherzeri) and big eye mandarin fish (Siniperca kneri)

Sex-specific markers are extremely important for unisexual breeding and understanding of sex determination mechanisms. Spotted mandarin fish (Siniperca scherzeri) and big eye mandarin fish (Siniperca kneri) are economically important freshwater fish in China. Here, for the first time, we successfully identified three male-specific markers in the two species. Through genome sequencing and bioinformatic analysis of three males, three females, one male mixed pool and one female mixed pool of spotted mandarin fish, we screened 27 potential male-specific sequences. After PCR validation, three male-specific markers were further identified. Moreover, these markers could also be used to identify genetic sex of spotted mandarin fish from different populations with 100 % accuracy. In addition, these markers were also successfully used in the identification of genetic sex of big eye mandarin fish. Notably, the sequences of male-specific markers were highly similar in the two species and the corresponding sequence of one marker was highly similar to partial genome sequence of amhy gene in mandarin fish (Siniperca chuatsi). In all, the verified male-specific markers suggested XY sex determination system existed in spotted mandarin fish and big eye mandarin fish and would play an important role in future work of sex control breeding.