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The paper describes the first finding of the European hake Merluccius merluccius (Linnaeus, 1758) in the northern part of the Black Sea, off the coast of Crimea, in December 2022 with a sea surface temperature of 13°C. The individual was found in the catch of a bottom trap installed at a depth of 24 m. The specimen with a total body length of 30.6 cm and a weight of 213.5 g was a sexually mature 3 years old male. According to the results of back-calculations obtained during the analysis of the otolith section, the individual growth of the caught fish occurred as follows: the total length was 17.7, 25.5, and 30.6 cm by the end of the first, second, and third years of life, respectively. No food items have been found in the gastrointestinal tract of the caught specimen. The geographical variability of the hake life cycle is considered. The species reaches its maximum size and age at high latitudes and at low water temperatures. Presumably, the maximum size and age of the hake in the Black Sea may be slightly higher than in the Mediterranean Sea, but lower than in the Northeast Atlantic. The prospects for further resettlement and increase in the number of the hake in the Black Sea are analyzed. Apparently, low salinity and competition with the native ichthyofauna may prevent successful naturalization of the species. However, the continuation of the trend of increasing salinity of the Black Sea under warming conditions will increase the possibilities of the hake naturalization. [ABSTRACT FROM AUTHOR]

The painted comber Serranusscriba, a subtropical marine fish species assigned to the famiy Serranidae in the Black Sea is insufficiently studied. It is a simultaneous hermaphrodite fish. Data on age, growth, and maturity of the painted comber inhabiting the Black sea area around Crimea, including its spatial variation within the entire habitat range are reported. Overall, 537 specimens caught from July to October 2022 are analyzed. The biggest specimen ever caught in the Black Sea with 26.1 cm total length and 265.1 g weight at the age of 15 years was registered. The values for the von Bertalnffy equation parameters were estimated. Thus, asymptotic length, asymptotic weight, and growth constant made up 28.3 cm, 358.6 g, and 0.17 year−1, respectively. The exponent of 3.10 in the length-weight relationship equation (positive allometry) was estimated. Maturity was defined in 50% spesimens at 12.0 ± 0.2 cm total length in the third year of life. It was ascertained that spatial variation in the life history traits for the specimens is weakly expressed. The painted comber inhabiting the Black Sea is slightly different from the representatives of this species found in the Aegean and Adriatic Seas in age, size, and growth. In addition, the biggest and faster-growing specimens are recorded more often under the low-latitude climate conditions, in the water areas off Egypt and the Canary Islands. [ABSTRACT FROM AUTHOR]

The results of the study of the distribution and biology of the duskyfin glassy perchlet Parambassis wolffii (Bleeker, 1850) in the Mekong Delta in 2019–2020 are presented. It is established that the species reaches the highest abundance and biomass in the freshwater part of the delta. The water temperature at which individuals of the species were encountered was 27.8–34.1°C, salinity, up to 1.51‰, depths, from 2 to 35 m. The maximum total length of females and males was 20.0 and 14.7 cm, respectively, and the maximum age was 6 years. The parameters of the von Bertalanffy equation are as follows: the maximum length is 17.2 cm, the growth rate constant is 0.18, t0 = −2.35. The value of the coefficient b in the equation on the weight-length relationship is 3.002 ± 0.056 for females (isometry) and 2.774 ± 0.064 for males (negative allometry). Intersexual differences by the in Fulton' condition factor were established: in females 3.71 ± 0.04, in males 3.53 ± 0.03. The first mature individuals were found at a length of 7–8 cm at the age of 1+. [ABSTRACT FROM AUTHOR]

The shi drum Umbrina cirrosa is a rare poorly studied fish species in the Black Sea. The largest individual for this water area was recorded off the coast of the Crimea; a male, whose total length was 784 mm, standard length 706 mm, body weight 5515.2 g, age 4 years; gonads of the maturity stage III had a weight of 33.11 g. Mollusks Solen marginatus and Abra segmentum, polychaete of the family Scalibregmatidae, and the jaguar round crab Xantho poressa were found in the diet composition. The paper presents a morphological description of otoliths (sagittae). The information about the known cases of the shi drum capture in the Black and Azov seas is considered. It is revealed that the maximum size of individuals of the species in the Black Sea is higher than in the Mediterranean Sea; possible causes of geographical variability of the sizes are analyzed. It is shown that this species is one of the fastest growing fish in the Black Sea. [ABSTRACT FROM AUTHOR]

The results of the study of the sex and size-age structure, growth, maturation, sexual inversion, dynamics of the gonadosomatic index and mortality of 1948 individuals of the picarel Spicara flexuosa caught in the Crimea water area in 2020–2021 are presented. The total sex ratio in catches is biased towards females (3.5 : 1.0); sex inversion was recorded in 50% of females with a total body length of 13.5 ± 0.05 cm at the age of 3+. The maximum length of females is 15.1 cm, males, 22.0 cm; the weight is 29.0 and 132.2 g, respectively. The maximum age of females and males is 4 and 7 years, respectively. The values of the parameters of the von Bertalanffy equation are calculated: for females, the asymptotic length is 15.69 cm, the asymptotic weight is 32.0 g, the growth coefficient is 0.49 year–1; for males, 18.32 cm, 59.7 g and 0.44 year–1, respectively. A value of the exponent in the length-weight relationship is 2.68 for females (negative allometry) and 3.0 for males (isometry). The sexual maturity of 50% of females occurs at a length of 10.34 ± 0.21 cm at the age of 1+. The peak of spawning occurs in June. The rates of total, natural and fishing mortality are 1.2, 1.9 and 0.3 year–1, respectively in both sexes; the exploitation rate is 0.25, which indicates a low fishing pressure. It is established that S. flexuosa from northern populations is characterized by larger maximum sizes, a higher growth rate and a longer life expectancy. [ABSTRACT FROM AUTHOR]

The work examines the sex and size-age structure, growth, dynamics of maturation, and mortality of red mullet Mullus barbatus from the Crimean water area. Ratio of sexes in the M. barbatus catches is shifted toward females (1 : 0.72). The maximum total length and maximum age is 21.4 cm and 6 years old in females and 15.8 cm and 4 years old in males. Pronounced differences have been established between sexes with respect to growth. Values of parameters were calculated of the von Bertalanffy equation: theoretical maximum lengrh of 29.8 cm, mass (weight) of 191 g, and growth coefficient of 0.15 year–1 for females and 22.8 cm, 108 g, and 0.16 year–1 for males. Maturity is attained at total length of 10.83 cm in 50% of females and 9.73 cm in 50% of males at the age of one year old. Coefficients of the total, natural, and fishing mortality are 1.21, 0.39, and 0.82 year–1 in females and 1.60, 0.53, and 1.07 year–1 in males, respectively. Exploitation rate in both sexes is 0.65, which corresponds to overfishing pressure. Growth rate during the initial (first) years of life is the most variable characteristic of M. barbatus life cycle; its values in the studied Crimean water area are lower compared to the Mediterranean. [ABSTRACT FROM AUTHOR]

The sex and size-age structure, growth, maturation, and mortality of grass goby Zosterisessor ophiocephalus have been studied in the Karkinitsky Gulf of the Black Sea. The ratio of males and females in the catches is 1.00:0.57; the maximum total length of females is 23.1 cm, age is 5 years, of males, 24.4 cm and 6 years. There are no differences in growth rates in males and females. The values of the parameters of the von Bertalanffy equation have been calculated for both sexes; the asymptotic length is 28.7 cm, asymptotic weight, 199.9 g, growth coefficient, 0.30 year–1; 50% of females mature at a length of 12.26 cm, males, 12.99 cm, at the age of 1+. The total, natural and fishing mortality rates are 0.91, 0.61, and 0.30 year–1, respectively. Z. ophiocephalus of the Karkinitsky Gulf differs from the Mediterranean populations by its higher growth rate, larger maximum sizes, and earlier age of maturation. [ABSTRACT FROM AUTHOR]

The sex ratio, body length–age structure, growth rate, maturity dynamics, and mortality are studied in Mediterranean horse mackerel Trachurus mediterraneus from the shelf zone of Crimea. The sex ratio is close to 1 : 1, the maximum body length of the females and males is 22.5 and 20.8 cm, respectively, and the maximum age of the representatives of both sexes is 6 years. The sexual dimorphism in the growth rate is not revealed. The von Bertalanffy growth equation parameters for both sexes are as follows: asymptotic length and weight 19.0 cm and 57.4 g and growth coefficient 0.44 year–1. The females (50%) reach sexual maturity by 10.72 cm, and the males reach maturity by 10.53 cm at the age 1+. The spawning is observed from June to September. The maximum values of gonadosomatic indeces of the males (2.37%) and females (3.84%) are registered in June, and July, respectively. The coefficients of the total, natural, and fishing mortality are 1.41, 0.89, and 0.52 year–1. Within the entire range, the strong positive relationships between maximum body length, linear growth rate index and mean annual surface water temperature are registered. The difference in horse mackerel growth rate between various regions of the Black Sea is small. Nevertheless, the growth rate and maximum body length of the Black Sea individuals are smaller than these parameters in the Mediterranean Sea that is connected with the adaptation of the Black Sea population to climate seasonality. [ABSTRACT FROM AUTHOR]

The size–age structure, growth, and maturation of the spotted catfish Arius maculatus (Thunberg, 1792) from the Hau River estuary, Mekong Delta, Vietnam, were studied for the first time. A total of 460 fish specimens collected from January to March 2019 were examined. The annuli on the otoliths were visualized; their formation may be related with the alternation of the dry and rainy seasons. The male to female ratio in the catches was 1 : 1.81. The proportion of males decreased in the older age groups. The maximum total body length of the females was 21.9 cm; for the males, it was 23.7 cm. The maximum recorded age of females in catches was 7+; for males it was 8+. No inter-gender differences in growth were detected. The parameters of the von Bertalanffy equation for both sexes according to empirical data were as follows: L∞ = 28.3 cm; k = 0.15/yr; t0 = –1.03 yr; growth performance index, φ = 2.08. The coefficients of the relationship between mass and length were as follows: a = 0.0054; b = 3.22. Maturation began at a body length of 13 cm at an age of 3 yr and ended at a body length of 18 cm at an age of 6 yr; 50% of the individuals became mature at a body length of 15 cm at an age of 4 yr. No inter-gender differences in the timing of maturation were found. A. maculatus from the Mekong Delta is characterized by a low growth rate compared to other populations, which may be associated with the labile habitat conditions in the estuary zone. [ABSTRACT FROM AUTHOR]

The size and age structure and growth of Atherina boyeri from southwestern Crimea were studied. The ratio of males and females was 1.00 : 1.38, the proportion of males decreases in older age groups, and the age limit for both sexes is 4 years. The specific growth rate naturally decreases from 2.29 in the first year of life to 0.25 in the second and to 0.10 in the fourth. Maximum length and weight there are greater in females than males (12.3 cm and 9.25 g vs. 10.8 cm and 7.65 g). It has been established that the growth rate of atherina from southwestern Crimea is higher than that of estuarine and lagoon forms living in labile salinity but lower than that of marine and oceanic ones. [ABSTRACT FROM AUTHOR]

The body size and age structure, as well as the features of growth and sexual maturation, of black scorpionfish Scorpaena porcus from the coastal waters of southwestern Crimea are analyzed. The average body length and weight are larger in the females than in the males: 16.4 cm and 93.0 g vs. 14.9 cm and 62.0 g. The maximum age of the females and males in the catches is 11 and 12 years, respectively. The females (50%) reach sexual maturity by the age of 3−4 years at 13.9 cm TL, while the males (50%) reach sexual maturity by the age of 2−3 years at 13.0 cm TL. After sexual maturation, the growth rate of the fish decreases, but the growth rate of the females is higher than that of the males. The black scorpionfish from Crimea differs from the representatives of this species from the Mediterranean Sea in a slower growth rate. [ABSTRACT FROM AUTHOR]

Impact of salinity changes on the composition of the Sea of Azov ichthyofauna is considered. To date, not only the quantitative, but also the qualitative composition of ichthyofauna and commercial catches has changed. The Black Sea sprat Clupeonella cultriventris, European anchovy Engraulis encrasicolus, gobiids of the family Gobiidae, as well such alien species as so-iuy mullet Planiliza haematocheila and Prussian carp Carassius gibelio, began to dominate in commercial catches. In the eastern part of Taganrog Bay, the golden gray mullet Chelon aurata, the flathead gray mullet Mugil cephalus, and Black Sea turbot Scophthalmus maeoticus have been recorded for the first time. The number of resident semianadromous species has decreased many times due to the deterioration of environmental and spawning conditions. Recommendations are presented for the rationalization of fisheries under conditions of salinization of the Sea of Azov. [ABSTRACT FROM AUTHOR]

Age structure and growth dynamics are examined for the black scorpionfish Scorpaena porcus Linnaeus, 1758, from three sites characterized by different levels of pollution: Kazach'ya, Alexandrovskaya, and Streletskaya bays. No substantial differences were found in age structures, which largely correspond to the natural state of the population; differences between the mean age in the least polluted Kazach'ya Bay and the most polluted Streletskaya Bay are not significant (p = 0.35). According to the indicators L∞, W∞, k of females, φ of females, and φ' of females, the black scorpionfish from the least polluted Kazach'ya Bay is characterized by a higher growth rate. However, nonsignificance of differences in the values of these parameters in comparison with the more polluted Streletskaya and Aleksandrovskaya bays does not allow an unambiguous conclusion to be made about the fish growth delay in the latter two. [ABSTRACT FROM AUTHOR]

Abstract—: The striped mullet Mugil cephalus is reported to be captured for the first time in the eastern part of Taganrog Bay. Basic meristic and morphometric traits of the captured specimens are described. [ABSTRACT FROM AUTHOR]