Peak Spawning Research Articles

Assessment of Sexual Maturity and Spawning Biology of Channa punctata (Bloch, 1793): Conservation and Reproduction

The study was conducted in the freshwater station of the Bangladesh Fisheries Research Institute in Mymensingh between September 2021 and August 2022. Finding the sex ratio, sexual maturity, LWR, reproductive biology, fecundity, and histological examination of gonads of C. punctata were the main objectives of the present study. The correlation between length and weight was determined by analyzing the power function. Both sexes showed positive allometric growth and the correlation between length and weight was TW= 0.011TL3.09 for males and TW= 0.009TL3.11 for females. The mean condition factor for males was 1.09 (0.89 to 1.24), whereas the mean condition factor for females was 1.12 (0.95 to 1.25). In both cases, the condition factor was more than 1, indicating that the physical condition of both sexes was excellent. Among the 329 samples, 142 (43.16%) were male and 187 (56.84%) were female (male: female = 1: 1.32). The chi-square test showed a significant departure from the 1:1 ratio between the number of males and females within the sample months (df = 1, χ2= 0.01, p=0.05). When they reached first sexual maturity (L50), both sexes were of similar size, as evidenced by their lengths of 14.95 cm. The peak spawning season for both sexes was observed in June and July; however spawning season lasted from April to July. According to the study results, July was recorded the highest absolute fecundity (23609), while December recorded the lowest (1998).

Reproductive biology of endemic sailfin silversides fish Telmatherina antoniae Kottelat, 1991 in Matano Lake, South Sulawesi

Sailfin silversides (Telmatherina antoniae) is an endemic species from Matano Lake, South Sulawesi. This study aims to learn about sailfin silversides’ reproductive aspects including sex ratio, length at first maturity, gonad maturity stage, gonad maturity index, fecundity, and egg diameter. Fish samples were taken using multifilament nets from March 2018 until February 2019. A total of 1,792 individuals fish comprises 922 males and 870 females were captured during the study period. The sex ratio was found in a balanced condition with 1.06:1. Length at first maturity for males and females were 48.08-57.73 mm and 56.78-68.55 mm, respectively. Based on sailfin silversides’ gonad maturity stage and maturity index are thought to be year-round spawning with a peak spawning season around March. The reproductive potential of sailfin silversides fish is estimated to be 179–1,690 eggs. Based on the egg diameter distribution, the sailfin silversides fish is classified as a partial spawner.

Reproductive Biology of Striped Snakehead (Channa striata, Bloch, 1793) in Floodplain of Lubuk Lampam, South Sumatra

Striped Snakehead (Channa striata) is one of the fish species inhabiting the flooded floodplain. Currently, the striped snakehead fish population in the Lubuk Lampam floodplain is undergoing a significant decline due to continuous and unregulated fishing activities. To prevent this population decline, there is a need for comprehensive efforts in managing their reproduction. The objective of this study was to investigate the reproductive behavior of striped snakehead fish in the floodplain of Lubuk Lampam, South Sumatra. The research spanned five months, from December 2022 to April 2023, and involved the collection of fish samples from four different floodplain types: river, lebung, lebak kumpei, and rawang. A total of 284 striped snakehead fish were examined, and measurements of length- weight and their reproductive biology were observed. The findings revealed that the sex ratio of striped snakehead fish was skewed toward females, with a ratio of 1:1.7 (females to males). The size at which female striped snakehead fish reach maturity was determined to be 28.5 cm, while male striped snakehead fish matured at 29.30 cm. The peak spawning season for striped snakehead fish occurred in December, coinciding with the rainy season. The spawning grounds for striped snakehead fish were predominantly located in the lebung station in the upper reaches of the Lubuk Lampam Floodplain. Striped Snakehead fish exhibited a partial spawning behavior. Furthermore, these fish demonstrated a relatively high reproductive potential, with fecundity ranging from 5,859 to 30,321 eggs.

Species identification, reproductive biology, and nutritional value of marine shellfish (Meretrix lyrata) in the Bay of Bengal

Meretrix lyrata which is under the family of Veneridae and under the order of Venerida, is a nutritionally and economically important edible mussel in Bangladesh. However, studies on species identification and nutritional value in M. lyrata are scarce. Therefore, a detailed investigation was conducted on (i) species identification of the common edible mussel through DNA-barcoding and morphometrics, (ii) reproductive features, such as size at sexual maturity, spawning, and peak-spawning seasons under different environmental factors, and (iii) nutritional status through proximate analysis of M. lyrata mussel collected from the Bay of Bengal, Bangladesh. The results indicated that the size at sexual maturity for M. lyrata was 4.2 cm and the spawning seasons were significantly affected by the dissolve oxygen and salinity. The study also demonstrated that the spawning of M. lyrata occurred from January to June and December while peak spawning season was May in the Bay of Bengal. The higher protein and moisture contents with lower fat in M. lyrata indicated that are value-added seafood with higher nutritional values for consumers.

Trophic interactions and the diet composition of sympatric finfish predators in the tropical demersal ecosystem in the Bay of Bengal.

The dietary composition, foraging strategies, and interspecific trophic interactions were identified for four major demersal carnivorous finfishes, namely, croaker Otolithes ruber, hairtail Trichiurus lepturus, threadfin bream Nemipterus japonicus, and lizardfish Saurida undosquamis, along the north-western part of Bay of Bengal from 2014 to 2016. Two species, Trichiurus lepturus and Saurida undosquamis, were identified as finfish feeders due to the high number of teleost (clupeids and engraulids) prey. One species, Nemipterus japonicus, had a significantly different diet of metapenaeids and charybdids, and was identified as a shellfish feeder. The final species, Otolithes ruber, preyed equally on crustaceans and teleosts, and was identified as a shellfish-finfish feeder. The feeding activity of all four species was lower during peak spawning periods and tended to increase with maturity. Feeding preferences varied with seasons. The trophic level ranged from 3.49 to 4.01, classifying the four species as medium-carnivores or meso-predators. Niche breadth ranged from 0.170 to 0.421, with seasonal and ontogenetic variations. Individual or subgroup specialization was observed on dominant prey, but intraspecific diet variations indicated all four species to be opportunistic predators. There was substantial prey overlap for Saurida undosquamis with Otolithes ruber and Trichiurus lepturus, which increased ontogenetically and coincided with their peak spawning. Sharing of abundant prey resources together with temporal and ontogenetic resource partitioning at intra- and interspecific levels possibly lowered dietary competition, thereby facilitating the coexistence of these demersal predators. This study provides new information on feeding interactions from a tropical demersal ecosystem that can be applied for the ecosystem-based management of trawl fisheries.

Reproductive biology and length-weight relationship of the Pool Barb Puntius sophore (Hamilton, 1832) in Mymensingh, Bangladesh

The study was conducted within the Freshwater station of the Bangladesh Fisheries Research Institute in Mymensingh from November 2019 to October 2020. The main objectives were to acquire additional knowledge regarding length-weight connection, condition factor, sex ratio, gonadosomatic index, and fecundity of P. sophore. It was possible to determine the spawning season each month by comparing the levels of the gonadosomatic index for the two sexes. Both sexes of the P. sophore species showed negative allometric growth, as indicated by the length-weight relationships of TW=0.0165TL2.852 for females and TW=0.035TL2.956 for males. For females, the average condition factor was 1.17±0.096, while for males, it was 3.24±0.19. Both times, the condition factor's value was high (>1), demonstrating that both sexes are in good health. From collected fish, 147 (55.12%) of the 264 fish samples that were taken were females, whereas 117 (44.88%) were males (Females: Males=1:0.82). The chi-square test showed that the male-to-female ratio during the sample months was not significantly different from 1:1 (χ2= 0.15, p>0.05). The spawning season extended from May through July, with June representing both sexes' peak spawning time. According to the study, the month of June had the highest absolute fecundity, which was 7829 and the absolute fecundity value was found to be lowest in the month of October 803 with an average value of about 3560 throughout the study period. For the management and protection of this species, this data will be valuable to researchers and those who decide on fisheries policy.

Growth patterns and reproductive aspect of Naleh (Barbonymus sp.) in Krueng Lanca, Nagan Raya Regency, Aceh Province

Naleh (Barbonymus sp.) is one species of native fish found in Aceh Waters. This study examines the growth patterns and reproductive aspects of the fish in Krueng Lanca of Nagan Raya, Aceh Province. The study lasted five months (January - May 2022). Sampling was carried out purposively, once a month, on five different stations using gill nets (mesh size: 0.5 inches, 1.0 inches, and 1.5 inches and cast nets (D: 6 meters, mesh size: 0.5 inches). A total of 171 Naleh was caught in these waters. The calculation results obtained a length-weight relationship W = 0,0003*L2.2234 (r2 = 0.8823) for males, which shows the nature of allometric and W = 6E-06*L3.0684 (r2 = 0.8566) for females which shows the isometric. The sex ratio of Naleh in these waters was 1.1: 1. The size of the first mature gonads was 60-69 mm (males) and 90-99 mm (females) with a Gonadosomatic Index of 1.92-3.04 % (Males) and 8.73-11.61 % (females). The peak of the Naleh spawning season in Krueng Lanca waters was thought to occur from March to April, with the number of eggs ranging from 1,853-3,813 and a diameter of 1.18-1.43 mm. Based on the oocyte distribution, the peak of spawning of the fish was categorized as multiple spawners.

Acoustic telemetry reveals the drivers behind estuary–sea connectivity of an important estuarine-dependent fishery species, Pomadasys commersonnii, in the Breede Estuary, South Africa

The spotted grunter Pomadasys commersonnii is an important estuarine-dependent fishery species known to spawn along the east coast (KwaZulu-Natal Province) of South Africa. However, recent evidence suggests that this species also spawns along the southwest coast in the Western Cape Province (WC), which has necessitated the investigation of estuary–sea movements of adult P. commersonnii in the WC, and their link with spawning season and changing environmental conditions. Seasonal gonad maturation of adult P. commersonnii (n = 112) was investigated using histology and the gonadosomatic index. Seven adult P. commersonnii were acoustically tagged and monitored in the Breede Estuary (WC) between November 2016 and March 2020. Tagged individuals spent more time in the estuary (83.5%) than in the adjacent marine environment. Sea trips (n = 90) lasted on average 3.23 (SD 4.55) days (range 1–37 days), with most sea trips (82.6%) having a duration of less than 5 days. The majority of sea trips (>50%) occurred in austral summer, which coincided with the peak spawning season. Increases in estuary water temperatures in summer and river inflow in winter also influenced the presence of tagged fish in the sea. The high degree of residency of P. commersonnii in the Breede Estuary and short sea trips, along with increased frequency of reproductively ripe fish during summer months, supports the conclusion that regional spawning is occurring along the southwest coast. We suggest that management strategies should be put in place to protect the P. commersonnii population along the South African southwest coast, especially during summer, for the recovery of this population.

Evidence of isotopic maternal transmission influence on bluefin tuna (Thunnus thynnus) larval growth

Pre-flexion stages of Atlantic bluefin tuna (Thunnus thynnus) larvae were collected in 2014 during the peak of spawning in the two main spawning areas: Gulf of Mexico (GOM) and Mediterranean Sea (MED). We examined daily growth, otolith biometry, and stable isotopes and found that the GOM grew at a faster rate, had larger otoliths, wider daily increments, and significantly lower values of δ15N when compared to the MED. In addition, an intra-population comparative analysis between slow- and fast-growing individuals (deficient vs. optimal growth groups, respectively) showed that optimal growth groups had significantly lower δ15N within each spawning area, implying a direct relationship between growth potential, development, and maternal transmission of isotopic signatures. A third pre-flexion larval group that was aquaculture-reared also exhibited the same pattern to the wild larval groups. In addition, for the first time, we estimated the maternal trophic niches using models developed with field-captured pre-flexion larvae. The estimated maternal trophic niches for the GOM were narrower than the MED, implying differences in the maternal trophodynamics from each nursery area. Overall, the inter-population (GOM vs. MED) and intra-population growth groups (deficient vs. optimal) grew faster and had narrower maternal niches. This study shows the advantages that larval SIA research can aid in the understanding of the trophodynamics of their breeders by examining the trophic relationship of a spawning stock jointly with the development of growth potential in offspring within the same breeding season.

Age and growth analyses of the purple sea urchin Heliocidaris crassispina inhabiting different feeding environments in the Shimane Peninsula, Japan

The purple sea urchin Heliocidaris crassispina is an echinoid responsible for the denudation of rocky shore seaweed in recent years. We used the gonad index to estimate the spawning period and rotula bones of the mouth to determine the age of H. crassispina individuals living in different feeding environments in the Shimane Peninsula. Seasonal changes in the gonad index suggested that the spawning season for H. crassispina was from May to July, with peak spawning in June. Ring forms in H. crassispina once a year based on the timing of the appearance of the dark zone on the rotula bone; this generally begins around June during the peak spawning period. The age (years) and test diameter (TD, mm) data were fitted to various growth equations. The von Bertalanffy equation that separately used data from the “seaweed bed area” and the “isoyake area” (rocky shore seaweed denudation) resulted in the best fit, with TDt=70.5 (1−e−0.174(t+1.018)) and TDt=60.8 (1−e−0.191(t+1.463)), respectively. This suggested that differences in the feeding environment have a significant effect on the growth of H. crassispina, even in the same bay area. Furthermore, the oldest specimen was estimated to be 25 years old, suggesting that H. crassispina has a higher longevity than that previously reported. Therefore, it is important to manage the H. crassispina population by systematic extermination and not by relying on natural mortality to prevent the decline of seaweed beds.

Population structure and reproductive dynamics of the ridged swimming crab Charybdis natator in the southern Taiwan Strait of China: significant changes within 25 years

The ridged swimming crab Charybdis natator (Portunidae) is a commercially important crustacean species in China. The purpose of this study is to compare its population structure and reproductive pattern within the same fishing area (the southern Taiwan Strait) from two datasets over 25 years; one from 1994−1996 (the early years of the C. natator fishery) and the other from 2019. The overall sex ratio (male:female) changed from a male bias (1:0.76, p < 0.01) in 1994−1996 to a female bias (1:1.38, p < 0.01) in 2019. Male body sizes (carapace width, CW) were significantly larger than those of females in both datasets (p < 0.05). The average CW and body weight (BW) of males and females in 2019 were significantly smaller (p < 0.01) and lighter (p < 0.01) than those in 1994−1996. The maximum body size and the proportion of large-sized individuals (CW > 10 cm) decreased dramatically over 25 years. One spawning peak season was identified from each dataset, i.e., March−August 1994−1996 and February−April 2019, revealing a 1-month shift. The minimum body sizes for female maturation (carrying eggs) were 6.9 cm CW in 1994−1996 and 6.1 cm CW in 2019, an 11.6% reduction over 25 years. For the first time, the CW at 50% female maturation, the relationship between female absolute fecundity and CW, and egg diameters were obtained from the 2019 dataset, which can be applied in the future comparisons. Recent studies have revealed a consistent spawning peak in February–April for several commercially important crabs in the southern Taiwan Strait. These findings should be considered in crab fishery management. Furthermore, both fishery- and environment-associated factors influencing crustacean population structure and reproductive dynamics merit further investigation.

Gonad Maturity and Fecundity of Indian Mackerel (Rastellinger kanagurta) in North Gorontalo Waters, Indonesia

Indian mackerel (Rastellinger kanagurta) is one of the fish that can be caught by fishermen in North Gorontalo waters. Excessive fishing without regard to the condition of the fish will cause a decrease in the quality and quantity of fish resources. Estimation of size at first maturity is one way to determine population development in water. This study aims to determine the relationship between the level of gonad maturity and the fecundity of Indian mackerel in North Gorontalo waters. This research was conducted in October-December 2021 at the Kwandang Archipelago Fishing Port. The level of maturity of the gonads was observed morphologically and the determination of fecundity was observed using volumetric and gravimetric methods. The maturity level of Indian Mackerel fish in North Gorontalo waters is dominated at level 1. The highest fecundity is 14,800 eggs and the lowest is 5,000 eggs. The relationship between the level of gonad maturity and fecundity is directly proportional, if the gonadal maturity value is high, the fecundity value will also be higher. The spawning season for Indian mackerel in North Gorontalo waters does not take place in October-December, this is characterized by low fecundity. Based on the gonadal maturity values every month, the peak spawning of Indian mackerel (Rastellinger kanagurta) allegedly occurred shortly after the highest GSI values.

Reproductive Condition in the Caspian Anadromous Shad Alosa kessleri kessleri (Alosidae) during Spawning Migration in the Volga River

This paper describes the state of the gonads of Caspian anadromous shad, Alosa kessleri kessleri (Grimm, 1887), migrating for spawning in the Akhtuba River. In May of 2021, the peak of spawning was recorded at a water temperature of 17–18°C. Females and males had gonads at the developing and spawning-capable phases. The fork length (FL) of females averaged 254.1 mm, and their body weight was 178.9 g; for males, this was 209.9 mm and 87.5 g, respectively. Most females were over three years old, while males were between one and three years old. The gonadosomatic index (GSI) in females and males averaged 8.71 and 3.67%, respectively. Among the asynchronously developing secondary growth oocytes in the spawning capable gonads, three different-sized groups were distinguished for intending to spawn the same number of oocyte batches. The number of primary growth oocytes (26.7–59.4% of germ cells on sections) allows for considering these fish as iteroparous. The diameter of the tertiary vitellogenic oocyte was about 800 µm.

Environmental Conditions Affect Striped Red Mullet (Mullus surmuletus) Artisanal Fisheries

The influence of environmental variables (oceanographic and climatic) on the catch rates of striped red mullet (Mullus surmuletus) by artisanal fishery was investigated using different time series models (Dynamic Factorial Analyses; Min-Max Factorial Analyses and Generalized Least Square models). Climatic and oceanographic survey data were collected at different areas of the Portuguese coast (Northwestern, Southwestern and South-Algarve) with distinct oceanographic regimes. Time series analyses reveal an effect of fishing effort in catch rates in Southwestern areas. Variability in M. surmuletus catch rates was associated to regional environmental multi-controls. Upwelling and westerly winds were the main drivers of catch rates variability across the three areas but the type of relationship varied among them. A consistent relationship between catch rates and environment factors was identified during the peak period of seasonal recruitment (spring to summer) in Southwest and South-Algarve coast, with Upwelling-summer and Sea surface temperature-spring affecting short term (lag 2 years) catch rates. In South-Algarve the increase in SST in summer, during peak of spawning, was correlated with the catch rate increase with a lag of two years. Environmental effect on catch rates reveals that fisheries management needs to accommodate the regional effect of environment variables on species biology to better define future assessment plans (catch limits).

Ageing of juvenile coral grouper (Plectropomus maculatus) reveals year-round spawning and recruitment: implications for seasonal closures.

Temporal patterns in spawning and juvenile recruitment can have major effects on population size and the demographic structure of coral reef fishes. For harvested species, these patterns are crucial in determining stock size and optimizing management strategies such as seasonal closures. For the commercially important coral grouper (Plectropomus spp.) on the Great Barrier Reef, histological studies indicate peak spawning around the summer new moons. Here we examine the timing of spawning activity for P. maculatus in the southern Great Barrier Reef by deriving age in days for 761 juvenile fish collected between 2007 and 2022, and back-calculating settlement and spawning dates. Age-length relationships were used to estimate spawning and settlement times for a further 1002 juveniles collected over this period. Unexpectedly, our findings indicate year-round spawning activity generates distinct recruitment cohorts that span several weeks to months. Peak spawning varied between years with no clear association with environmental cues, and little to no alignment with existing seasonal fisheries closures around the new moon. Given the variability and uncertainty in peak spawning times, this fishery may benefit from additional and longer seasonal closures, or alternative fisheries management strategies, to maximize the recruitment contribution from periods of greatest reproductive success.

Reproductive ecology of the soft-shell clam (Mya arenaria) in Eastern New Brunswick, Canada: Assessing size-at-maturity and spawning time to inform fisheries management

Soft-shell clams, Mya arenaria, are fished commercially and recreationally across much of their distribution. Several management measures have been implemented in Atlantic Canada to regulate the clam fishery, including a minimum legal size limit of 50 mm. This legal size limit, however, is not based on contemporary data. A regional understanding of soft-shell clam reproductive biology in eastern New Brunswick is lacking, yet the management of this fishery would greatly benefit from this localized knowledge. As such, we collected soft-shell clams in Kouchibouguac National Park, New Brunswick, Canada, during the Spring, Summer and Fall of 2021, to assess size-at-maturity and time of spawning. Histology was used to determine the sex and maturity stage of individual soft-shell clams and maturity ogives were generated for female and male clams. Temporal changes in the gonadosomatic index (GSI) were also used to identify likely spawning times for female and male clams. Sex ratios were significantly unbalanced for most of the sites sampled, favouring females, with an overall sex ratio of 2.3:1 (F: M). Size-at-maturity was estimated at 39.7 mm and 40.7 mm for female and male soft-shell clams, respectively. Overall, GSI was higher in males, peaking in late May, declining sharply in June, and showing a more gradual decline from July until September. Female GSI also peaked in late May, but exhibited a continuous, gradual decline from mid-June through to September, suggesting that peak spawning likely occurred from late May to mid-June in 2021 but that some degree of spawning likely continued thereafter. Overall, these results provide insights into the reproductive biology of sub-legal sized soft-shell clams in eastern New Brunswick, providing managers with contemporary scientific information.

Effects of Estuarine Environmental Heterogeneity on the Habitat of Gobiidea Species Larvae

AbstractIn aquatic ecosystems around the world, gobies comprise one of the most diverse groups of fishes in estuaries. The Yangtze River estuary, the biggest estuary in the western Pacific, is a major habitat for larval gobies, with the peak spawning and breeding season occurring during late spring and summer. To investigate the adaptation mechanism of larval gobies to environmental factors, three models (a global generalized linear model, a generalized additive model, and a geographically weighted Poisson regression) were used to simulate and forecast the major habitat distributions of larval gobies based on the survey data from 2018 to 2020. Six species of gobies were studied:Rhinogobius giurinu,Odontamblyopus rubicundus,Tridentiger barbatus,Parachaeturichthys polynema,Tridentiger trigonocephalus,andTrypauchen vagina. The habitats for brackish speciesT. barbatuswere mainly in freshwater (where, using the practical salinity scale, salinity is 0–1) of the south branch, whereas the marine speciesP. polynemawas mainly caught in oligohaline waters (where salinity is 1–5) of the north branch. The other euryhaline species were near the exit of the north branch or dispersed throughout the surveyed region. Year, season, salinity, and sample location had significant effects (P < 0.001) on determining the habitat distributions of larval gobies. The geographically weighted Poisson regression identified that the temperature, depth, distance from the coast, and chlorophyllahad a significant effect (P < 0.001) on the local distribution of habitats. This work supplements information about the distribution of major habitats and their interactions with the environment for the ecologically important species of goby in the Yangtze estuary during the larval stage, and the conclusions provide a basis for the management of aquatic ecosystems and biological habitats.

First approximation of the growth and the spawning period of Symphodus ocellatus (Linnaeus, 1758) (Pisces: Labridae) in the southeastern Black Sea

The aim of this study was to provide a first approximation of the growth, reproduction, and length–weight relationships of Symphodus ocellatus in the southeastern Black Sea, Turkey. A total of 320 specimens (273 males, 47 females) were collected between June 2015 and May 2016, and their biological parameters were estimated for each sex and both sexes combined. Total length ranged from 6.90 to 13.70 cm and the parameters (a, b) in the power length–weight relationships were a = 0.065 and b = 2.38 for males and a = 0.102 and b = 2.20 for females. Age was successfully estimated by commonly accepted procedures for otolith analysis. The von Bertalanffy growth parameters from the otolith age estimation were L∞ = 12.66 cm, k = 0.764, and t0 = –1.151 (0–3 years) for males, and L∞ = 14.15 cm, k = 0.764, and t0 = –0.188 (1–3 years) for females. The monthly gonadosomatic index values reflected a spawning period between April and July, with a spawning peak in May–June. The present study provides the first estimate of the growth and reproduction of S. ocellatus in the southeastern Black Sea of Turkey and compares the results with those from other areas.

Age, Growth, Maturation and Mortality of Picarel Spicara flexuosa (Sparidae) from the Crimea Water Area (Black Sea)

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

Population Structure, Exploitation Status, and Prospects of Brown Meagre Sciaena umbra Linnaeus, 1758 From the Turkish Coast of the Black Sea

The brown meagre (Sciaena umbra Linnaeus, 1758) population has experienced dramatic population declines, and it was regionally assessed as “Near Threatened” in the Mediterranean. In this study, the current status of brown meagre populations in the Black Sea was evaluated by estimating growth and mortality rates based on age readings from the otolith. All specimens were collected by commercial trammel nets between March 2019 and February 2020 in the Turkish coast of the Black Sea. A total of 324 brown meagre were sampled during the study period, ranging in age from 0 to 26. The peak spawning season of the species was from June to July. The Von Bertalanffy growth parameters of (L∞ = 54.15, k = 0.14 yr-1, t0 = -3.11) supports previous studies and suggests that brown meagre is a long-lived and slow-growing species. The exploitation ratio of 0.53 for females and 0.47 for males. Life-history features and mortalities indicate that the brown meagre has relatively high fertility but may be undefended to intense fishing pressure. However, the impact of overfishing, pollution and climate change can have increasingly detrimental effects on the overall population size of this population.