Von Bertalanffy Growth Parameters Research Articles

Estimation of Growth and Mortality Parameters for the Annular Seabream Diplodus annularis (Linnaeus, 1978) in the Southern Aegean Sea

The growth and mortality parameters were examined for the annular seabream Diplodus annularis collected from the Didim coast, Southern Aegean Sea. A total of 654 annular seabream individuals, 263 female (40.21%) and 391 male (59.79%), were sampled by commercial trawlers and gillnets from September 2022 to January 2024. The total length varied between 9.0 and 24.3 cm for females, 8.6 and 24.0 cm for males, and the weight varied between 8.60 and 146.57 g for females, 7.00 and 128.96 g for males. The length-weight relationships were calculated for females, males, and all individuals as W = 0.0115 x L2.9641, W = 0.0131 x L2.8995, and W = 0.0118 x L2.9440, respectively. The growth pattern was determined as negative allometric. The maximum age class was V for both females and males. The von Bertalanffy growth parameters were L∞ = 25.27 cm, k = 0.424 year-1, t0 = -0.308 years for females; L∞ = 25.63 cm, k = 0.338 year-1, t0 = -0.935 years for males; L∞ = 27.43 cm, k = 0.283 year-1, t0 = -1.121 years for all individuals. The growth performance index (Φ´) for females, males, and all individuals were 2.432, 2.347, and 2.329, respectively. This study provides the first information on the growth and mortality parameters of D. annularis along the Didim coast, southern Aegean Sea.

Freshwater Mussel (Unio pictorum) Shells Reveal Hydrological and Environmental Change From 1300 BC to the Present Day.

Preserved biological communities can provide baseline data about the historical ecosystems and environmental conditions that preceded recent anthropogenic alteration. Freshwater mussel shells show particularly good preservation, and the shell assemblages commonly found during archaeological excavations can offer insights into past ecosystems. We studied assemblages of Unio pictorum mussel shells from palaeochannel silts associated with the Late Bronze Age site of Must Farm in eastern England (c. 850 BC), on an ancient tributary of the modern-day River Nene. We compared archaeological shells from two sediment horizons (broadly 1300-700 BC) to live individuals collected from two analogous sites on the present-day Nene. Size and growth rate, interannual growth variability and stable isotope (δ18O and δ13C) composition were compared between the populations. Size and the von Bertalanffy growth parameter L∞ differed among all four populations. Mean lengths and L∞ were higher in the two modern populations (mean lengths 77.3 ± SE 0.8 and 73.8 ± SE 1.1 mm, L∞ 91.8 ± 5.4 and 79.0 ± 8.1 mm) than the ancient populations (mean lengths 58.1 ± SE 1.6 mm and 68.4 ± SE 0.9 mm; L∞ 71.5 ± 16.9 and 76.8 ± 6.2 mm). Modern individuals also showed greater variation in age-corrected year-to-year growth. δ13C was lower in modern shells (-11.8‰ for modern shells, -9.03‰ and -9.02‰ for ancient shell populations), potentially reflecting altered hydrological and nutrient regimes. δ18O and δ13C were positively correlated for all but one sampled ancient shell, but not modern shells. These results reflect changes in local environmental conditions, particularly the transition from a shallow, slow-flowing tributary to a deeper, canalised river with faster flow, as well as effects of anthropogenic nutrient enrichment. The findings demonstrate the importance of long-term data in studying anthropogenic ecosystem alteration and avoiding shifting baseline syndrome in conservation planning.

Length-weight relationship and exploitation of Macrobrachium species in the Burhi Gandak River, North Bihar, India

Three species of the Palaemonidae family, namely Macrobrachium dayanum (Henderson, 1893), Macrobrachium lamarrei (Milne Edw., 1837) and Macrobrachium malcolmsonii (H. Milne Edw., 1844) were investigated for their length-weight relationship and exploitation status in the Burhi Gandak River between July 2020 and June 2021. A total of 907 specimensof M. lamarrei, 942 M. dayanum and 962 M. malcolmsonii were collected using trap net (locally named Ghana Jal), Saalbhar Jal, Pelni, Dhonijal and Khorjal and traditional boats such as Nauka and Donga. M. lamarrei was found to be the dominant species among them in the catch composition. Peak landing was observed from June to August. The maximum length was recorded for M. malcolmsonii (16.8 cm) followed by M. dayanum (8.0 cm) and M. lamarrei (6.1 cm). The length-weight relationship of M. lamarrei, M. dayanum and M. malcolmsonii indicated negative allometric growth with slope (b) values of 2.7692, 2.6027 and 2.7513, respectively. The von Bertalanffy growth parameters viz., asymptotic length (L∞), growth coefficient (K) and age at zero length (to) were 5.67 cm, 2.3 y-1 and -0.5913 y-1 for M. lamarrei ; 10.08 cm, 0.990 y-1 and 0.6684 y-1 for M. dayanum and 16.59 cm, 0.730 y-1and -0.7289 y-1 for M. malcolmsonii , respectively. Fishing mortality was lower than natural mortality which was estimated as 1.71 for M. lamarrei, 0.15 for M. dayanum and 0.18 for M. malcolmsonii. The present study revealed that the smaller length groups had higher natural mortality, whereas larger length groups had higher fishing mortality. The current exploitation rate was 0.26 for M. lamarrei, 0.06 for M. dayanum and 0.09 for M. malcolmsonii. The research fills a critical gap providing essential insights into the population dynamics and exploitation of the three prawn species in the Burhi Gandak River, revealing their underexploited status, highlighting opportunities for sustainable harvesting and informed fishery management to support biodiversity conservation and local livelihoods. Keywords: Bihar, Burhi Gandak River, Length-weight relationship, Macrobrachium, Stock assessment

Plasticity of life-history traits in the Draa barbel <i>Luciobarbus lepineyi</i> (Pellegrin, 1939) (Actinopterygii: Cyprinidae) in the sub-Saharan Draa basin, Morocco: effect of change in flow regime and salinity

The Draa barbel Luciobarbus lepineyi (Pellegrin, 1939), an endemic and unique cyprinid of the arid Draa river basin, southern Morocco, faces a range of multiple environmental stressors, especially in intermittent rivers and ephemeral streams (IRES). We assessed the effects of flow intermittence and salinisation on the somatic condition, and life-history traits in Draa barbels. We used the scaled-mass index (SMi) to evaluate the mean individual somatic body condition in nine populations. For three contrasted localities: Iriri (IR), Mghimima (MG), and Sid El Mokhtar (SM), we aged fish from scales and calculated von Bertalanffy growth parameters using the Beverton-Holt procedure. We used these parameters to estimate growth indices and performance, size and age at maturity, longevity, and mortality rates. Mean SMi decreased markedly with increasing salinity, revealing a normal condition at 0.4 PSU in IR, a poor condition in MG at 4 PSU, and a very poor condition at 10 PSU in SM. Growth rates (k) increased with salinity. Conversely, asymptotic lengths L∞ and growth performances (phi-prime, φ′) decreased with salinity and flow intermittency. The potential longevity tmax decreased with the increase in salinity. On the other hand, the mortality rate increased with flow intermittence and salinity. The Draa barbels in the saline IRES of the arid Draa basin compensate for the high mortality by growing faster but less efficiently. They mature at an earlier age and have shorter longevity. With this high life-history plasticity, the Draa barbel would constitute a good ecological indicator and a sentinel for salinisation in variable aquatic environments in the arid Draa river basin.

Population Dynamics of Nile Tilapia (Oreochromis niloticus, Linnaeus.1758) from Khashm El-Girba Reservoir, Atbara River, Eastern Sudan

This study was conducted to assess the population parameters of Nile tilapia, Oreochromis niloticus, in the Khashm El-Girba Dam Reservoir in Eastern Sudan. Fish samples were collected from December 2019 to November 2020. Length-frequency data were collected from 1,671 specimens ranging from 5.1 to 34.2 cm in total length (TL). Analysis of the population parameters was determined using the ELEFAN I routine and the FiSAT II software computer program revealed that the estimated the Von Bertalanffy growth parameters were as follows: asymptotic length (L∞ = 36.75 cm), growth rate (K = 0.650 year -1) and age at length zero (t0 = -0.629) and the growth performance index (Φ') was calculated at 2.943. The instantaneous total mortality (Z), natural mortality (M), and fishing mortality (F) rates were determined using the length-converted catch curve and empirical models. The values obtained were Z = 2.38 year -1, M = 1.22 year -1, and F = 1.16 year -1, respectively. The exploitation rate (E) of the Nile tilapia was calculated at 0.49 year -1. The size at first capture (Lc) was estimated at 15.64 cm, which is slightly greater than the size at first maturity (Lm = 14.5 cm) and longevity (Tmax) was found to be 4.62 years. These findings indicate that the stock of the Nile tilapia population in Khashm El-Girba reservoir is overexploited, and that monitoring and management practices need to be employed to maintain the stocks at the optimum exploitation level.

Life History Parameters and Spawning Potential Ratio of Upeneus vittatus (Forsskål, 1775) in the Coastal Waters of Lebak and Sukabumi, Indonesia

Abstract It is necessary to obtain information regarding the life history and stock status of the yellow-striped goatfish (Upeneus vittatus) in the coastal waters of Lebak and Sukabumi, Indonesia. This study aims to determine the stock status of U. vittatus in the coastal waters of Lebak and Sukabumi based on their life history parameters and length-based spawning potential ratio (LB-SPR). Eight hundred seventy-four samples were collected from Binuangeun, Palabuhanratu Nusantara, and Ciwaru Fishing Ports. The monthly length frequency data were obtained from July to December 2022. The results show that the Von Bertalanffy growth parameter was Lt=254(1-e−(0.58(t+0.154)) for males, Lt=239(1-e−(0.42(t+0.221)) for females, and Lt = 258(1-e−(0.37(t+0.246)) for both. The mature gonads of U. vittatus were mostly obtained from October to December. The length of first maturity L50 and L95 were 158 mm and 236 mm for males and 149 mm and 229 mm for females, respectively. The exploitation rate (E) on male, female, and combined U. vittatus revealed that E values exceed 0.5 or are overexploitation. The estimated SPR of U. vittatus was 23%, lower than the target reference point of 40%. Therefore, U. vittatus was fully exploited in the coastal waters of Lebak and Sukabumi.

Growth patterns of the invasive crab Cronius ruber (Brachyura, Portunidae) in the Canary Islands (Central-East Atlantic)

The growth pattern, including the moult process, relative growth, and estimation of von Bertalanffy growth parameters of the invasive non-indigenus species (NIS) Cronius ruber were studied in the Canary Islands. Despite being found in both, native and invaded areas, the life cycle and ecology of this species remain unknown. The study revealed a greater abundance of females than males, with males exhibiting larger carapace sizes and weights than females. Throughout ontogeny, relative growth was observed, with males reaching carapace widths (CW) between 54.5 and 57.8 mm and females reaching 49.9 mm CW. Allometry in the growth of the males’ chelae and females’ abdomen was consistently positive. Cronius ruber was found to be a fast-growing species, reaching the postpubertal growth phase (maturity) between 0.5 and 1 year of age in males and between 0.4 and 0.8 years in females. The intermoult period increased by more than 638 % in males and 443 % in females with age. Individuals undergo 13 moults during the first phase of life (until 30 mm CW) and then reduced to 6 moults until the end of life, concluding with a final terminal moult. The lifespan until the terminal moult is approximately 2.5 years, followed by a survival time over 1.5 years. von Bertalanffy growth parameters estimated using monthly CW-frequency data for males (L∞=97.4 mm CW, k=1.89 years−1, to=0.31 years), and for females (L∞=86.72 mm CW, k=1.91 years−1, to=0.29 years). Similar results were obtained using growth increment data.

Growth, mortality, and exploitation rates of the mantis shrimp Erugosquilla massavensis (Kossman, 1880) (Malacostraca: Stomatopoda) in Iskenderun Bay, north-eastern Mediterranean of Türkiye

ABSTRACT Lessepsian Erugosquilla massavensis is one of the three Stomatopod species reported on the Levantine coast of Türkiye. Its natural habitat is the Red Sea and it is the first Red Sea stomatopod species reported from the Mediterranean. This study aims to determine the morphometric relationships, growth parameters, sex ratio, age, mortality, and exploitation rates of non-native E. massavensis in the north-eastern Mediterranean. Samples were collected monthly by commercial trawl surveys between September 2016 and March 2017 in Iskenderun Bay. Relationships between the carapace length (CL)–total length (TL) and the total length (TL)–total weight (TW) were estimated. Negative allometric growth was observed between the CL–TL and TL–TW relationship for females, males, and all. The von Bertalanffy growth parameters (vBGP) were found L ∞ = 155.4 mm, K = 0.520 year−1, t 0 = −0.199, ø′ = 4.099 for females, L ∞ = 157.5 mm, K = 0.600 year−1, t 0 = −0.127, ø′ = 4.173 for males. This research provided the first-ever data on the vBGP of E. massavensis. The study found that both sexes had a higher fisheries mortality coefficient than natural mortality (Z = 2.01, M = 0.71, F = 1.3) and were exploited (E = 0.65).

Spatial and seasonal variations in the growth of the populations of tongue sole fish (Cynoglossus quadrilineatus Bleeker, 1851) along four different stations of Makran coast by using the von Bertalanffy model

BackgroundGrowth is a most important life-history trait that defines the maximum size and age, maturation stage, and mortality of any fish species and is also involved in stock assessment models commonly used in fisheries conservation or management. ObjectivesThe present study focused on assessing the growth patterns and related parameters to the population of tongue sole (Cynoglossus quadrilineatus) along different sites of the Makran coast in temperate regions. MethodologyA total of 987 tongue sole fishes were collected seasonally from four different sites along the Makran coast (Gwadar, Pasni, Ormara, and Sur Bandar). Growth parameters i.e., length-weight relationships, length-frequency distribution, von Bertalanffy (VBGF) growth model, and stock status were analyzed. ResultsThe overall results of the length-weight relationship (LWRs) of this species showed only a significantly positive allometric growth pattern (b < 3.0; p < 0.05) observed during three seasons along the four selected sites of Makran Coast. The estimated von Bertalanffy (VBGF) growth parameters of C. quadrilineatus at four stations were described as; maximum observed length (Lmax) = 31.65 cm, asymptotic length (L∞) = 33.32 cm, size at sexual maturity (Lm) = 17.98 cm, Lopt = 20.55 cm, growth coefficient per year (k) = 0.55 year -1, t0 = 0.04 year -1, f = 2.79, Tmax = 2.80 years, tm = 0.78 year, M = 1.64 per year, topt = 1.30 years. The present study also noted seasonal variations in the length frequency distribution (LFD) data between the four selected sites. ConclusionsThus, our study concluded that the von Bertalanffy growth model (VBGF) is the best-fitted model for analyzing the growth patterns of C. quadrilineatus at different sites and during various seasons along the Makran Coast. This model demonstrated superior predictive ability and effectively described changes in growth patterns or body size across sub-populations of C. quadrilineatus at the four study sites. Thus, our research provides valuable insights into the population dynamics and life history traits of this tongue sole population in the Makran coast. Moreover, as the first study on the growth of this species, our findings offer essential information for informing sustainable exploitation, conservation, and fishery management strategies.

Life-history updates and stock assessment of Macrodon atricauda (teleostei, sciaenidae) from southern Brazil

The coastal demersal sciaenid fish Macrodon atricauda has been intensely fished since the 1950s along the southern Brazilian coast, resulting not only in decreasing abundance but also in long-term changes in its life history. Previous studies reported long-term increases in individual growth, size, and age at maturity. Using individual observed length-at-age, we did not observe the previously reported growth changes despite the increase in the mean length of older individuals from 1976 to 2023. These observed changes did not affect the estimation of the von Bertalanffy growth parameters, likely due to the species' faster growth at earlier ages and short lifespan. The length at first maturity remains smaller than the previous estimations from the 1970s but has not changed since the 2000s. The population dynamics assessed considering the updated life history parameter, including the size at maturity changes, showed that the species is not suffering from overfishing (i.e., F2019/FMSY = 0.17). However, the spawning stock biomass was estimated at low levels (i.e., SSB2019/SSBMSY = 0.59), indicating an overfished status highlighting the need for management action. The apparent stability of the life-history parameters observed for the species in the last four decades may be attributed to a combination of traits promoting resilience and recovery, including high fecundity, low age at maturity, fast individual growth, and a relatively short lifespan. In fact, despite decades of intense fishing, M. atricauda remains an important coastal demersal species in the landings of southern Brazil.

Growth parameters and stock assessment of Carangoides bajad Forsskal, 1775 (Carangiformes: Carangidae) in Jeddah fisheries

ABSTRACT The stock status of Carangoides bajad in Jeddah fisheries was assessed by estimating the growth parameters, mortality rates and size at first capture (Lc), then applying the results to estimate the yield and biomass per recruit. The length-weight relationship could be described by the power equation: W = 0.011 L3.019 (R2 = 0.99) for combined sexes. Von Bertalanffy Growth Parameters L∞, K and t0 were estimated to be 71.53 cm, 0.224 year −1, and −0.52 year, respectively. The total, natural, fishing mortality coefficients and exploitation were calculated to be 0.72 year −1, 0.337 year −1, 0.383 year −1, and 0.53 year −1, respectively. Beverton and Holt (1957) model was used to estimate the yield and biomass per recruit at Fcur and Lc and found to be Y/R = 291 g and B/R = 759 g. Compared with the two biological reference points Fmax = 0.56 year −1 and F0.1 = 0.346 year −1, the Fcur value was very close to the F0.1 value required to get the optimum Y/R. We recommend avoiding any increase in Fcur, and increasing Lc to be 38 centimetres to increase the B/R from 759 g to 793 g, which would increase the probability of sustaining sufficient recruitment to the fishery of C. bajad in Jeddah fisheries.

Length-Weight Relationships and Growth Parameters of Bogue, Boops boops, (Linnaeus, 1758) from Didim, South-eastern Aegean Sea

In this study length-weigth relationships and and growth parameters of Boops boops (Linneaus, 1756) sampled from Didim coasts, South-eastern Aegean Sea were investigated. A total of 361 specimens (226 females and 135 males) were sampled. The mean length and weights were 18.57 ± 2.46 cm and 60.74 ± 23.60 g for females and 17.63 ± 3.63 cm and 60.50 ± 36.87 g for males, respectively. The overall sex ratio (F:M) was determined as 1:1.67 (χ², P &lt; 0.05). Length-weight relationships for all individuals were described by the parameters a = 0.0113, b = 2.93 and r² = 0.974. The exponent of the b parameter represented negative allometric growth in females, isometric growth in males and negative allometric growth in both sexes. Values were statically significant (P &lt; 0.05). The von Bertalanffy growth parameters were calculated as L∞ = 35.34 cm, k = 0.156 year-1, t0 = -2.093 years for females; L∞ = 33.23 cm, k = 0.184 year-1, t0 = -1.268 years for males; L∞ = 41.23 cm, k = 0.117 year-1, t0 = -2.200 years for both sexes. The growth performance index (φ´) was estimated for females, males, and both sexes as 2.291, 2.310, and 2.302, respectively. Age determinations varied from 1 to 5 years and age class III was found dominant in both sexes.

Revealing the reproductive biology and growth dynamics of Arius maculatus (Thunberg, 1792) in the Mekong Delta estuary, Vietnam

Referring to the Mekong River, it is the largest river in Southeast Asia's Indo-Burma biodiversity hotspot, and it sustains a diverse range of fish species. In order to manage the river's fisheries in a sustainable way, it is important to have a comprehensive understanding of population dynamics. This study focuses on the spotted catfish, Arius maculatus (Thunberg, 1792), which is commercially valuable and found in the estuarine areas of the Mekong Delta, Vietnam. Monthly samplings were conducted at Tran De and Dinh An estuaries from July 2017 to May 2019, revealing distinct patterns in the gonad-somatic index (GSI) and hepato-somatic index (HSI). The spotted catfish were found to breed throughout the year, with peak breeding periods in March and August. The length at first maturity (Lm) was determined to be 12.80 cm for males and 11.79 cm for females. The fecundity, although relatively low, was measured at 16 ± 3 yolks per female and 144 ± 60 hyalines. The Von Bertalanffy growth parameters were calculated as L∞ (the asymptotic length) = 20.6 cm, K (growth coefficient) = 0.5 year−1, and t0 (theoretical age at zero length) = − 0.603 year−1. The length at first capture (Lc) was found to be 8.93 cm. Evaluation of the mortality rates revealed that the spotted catfish population is being overexploited, as indicated by an exploitation rate (E) of 0.695, which exceeds the optimum level of 0.50. It is crucial to implement effective management strategies to ensure the sustainable fisheries of Arius maculatus in the Mekong Delta estuary in Vietnam.

Kuzeydoğu Ege Denizi’nde (Türkiye) Diplodus sargus (Linnaeus, 1758)'un bazı biyolojik özellikleri

In the study, the age, growth, mortality parameters and length-weight relationship parameters of Diplodus sargus (white seabream) collected by a small-scale fisherman between August 2020 and July 2021 along the northeastern coast of Aegean Sea (Türkiye coast), were investigated. D. sargus had a range of total length and weight from 14.3 cm to 36.7 cm and from 50.5 g to 836.5 g, respectively. The length-weight relationships (LWRs) were calculated as W=0.02368*L2.881 for females, W = 0.01847*L2.959 for males and W = 0.01989*TL2.936 for both sexes. Using data from fish scales, the maximum age was determined to be 11 years. von Bertalanffy growth parameters have been calculated as follows L∞=39.01 cm TL, K=0.13 year-1, and t0= -2.58 year for both sexes combined. Total (T), natural (N) and fishing (F) mortalities were defined as Z: 0.83 year-1, M: 0.33 year-1 and F: 0.50 year-1 for both sexes combined. The exploitation rate (E) was calculated as 0.70, 0.44 and 0.60 for females, males and combined, respectively.

On the biology of blackbellied angler, Lophius budegassa Spinola, 1807, in the north-western Mediterranean

In the Mediterranean Sea, the blackbellied angler, Lophius budegassa Spinola, 1807, represents a relevant fraction of the commercial by-catch of bottom trawling and small-scale fisheries that use passive gears (e.g., set nets, bottom longlines, etc.). Despite its importance, there are no comprehensive studies on the population dynamics of this species, and there is still scarce and scattered knowledge of its biology and ecology. Biomass, morphometric, and biological data of the blackbellied angler were collected from 1994 to 2021 by means of the Mediterranean International Bottom Trawl Survey (MEDITS) programme in the Ligurian and northern Tyrrhenian Seas, and in the EU Data Collection Framework during the period of 2006-2021. Furthermore, ageing was performed on specimens collected from 2013 to 2021 during the MEDITS programme. There were high values for the density indices and the spatial distribution of biomass in the central sector of the investigated area (the Tuscan Archipelago), mostly on the continental shelf. The length-weight relationship showed negative allometric growth when considering the sexes together, and no difference between the sexes. The size at first maturity (L50) was estimated at 39.4 cm total length (TL) in females and at 29.2 cm TL in males. The obtained Von Bertalanffy growth parameters were: in females, L∞ = 74.50 cm, k = 0.10 years-1, and t0 = -0.40 years; in males, L∞ = 61.30 cm, k = 0.14 years-1, and t0 = -0.38 years. There were differences in growth between males and females for L∞ (χ2 = 10.04; p &lt; 0.05) and k (χ2 = 6.12; p &lt; 0.05).

Biological and growth parameters of Plotosus lineatus in the Mediterranean Sea.

This study examined the age distribution and growth characteristics of the striped eel catfish (Plotosus lineatus), which is an invasive alien species in the eastern Mediterranean. A total of 1,011 samples were collected from Iskenderun Bay (Turkey), with lengths ranging from 5.1 to 16.8 cm, predominantly comprising females (1:1.92). Age 3 represented the majority in the population (52.03%). The value of the scaling exponent "b" of the length-weight relationship was less than "3" for both sexes (females: 2.28; males: 2.26; combined: 2.27). The results for the von Bertalanffy growth parameters were observed for the combined sexes as, L∞ = 24.9934 cm, k = 0.1718 year-1, and t₀ = -1.7707 years. The striped eel catfish populations in Iskenderun Bay exhibited negative allometric growth patterns and were predominantly composed of adult individuals. This study presents the dataset on the length-weight correlations, age-growth characteristics, and von Bertalanffy growth parameters of Plotosus lineatus in the Mediterranean Sea, thereby significantly contributing to comprehending the stock dynamics. It is anticipated that this study will make a significant contribution to the management of P. lineatus stocks, given its invasive nature.

Age and growth estimates for the nurse shark (Ginglymostoma cirratum) over 17 years in Bimini, The Bahamas

Age and growth estimates are essential for life history modeling in elasmobranchs and are used to inform accurate conservation and management decisions. The nurse shark (Ginglymostoma cirratum) is abundant in coastal waters of the Atlantic Ocean, yet many aspects of their life history remain relatively understudied, aside from their reproductive behavior. We used mark-recapture data of 91 individual G. cirratum from Bimini, The Bahamas, from 2003 to 2020, to calculate von Bertalanffy (vB) growth parameters, empirical growth rate, and age derived from the resulting length-at-age estimates. The Fabens method for estimating growth from mark-recapture methods was applied through a Bayesian framework using Markov chain Monte Carlo (MCMC) methods. This provided growth parameters with an asymptotic total length (L∞) of 303.28 cm and a growth coefficient (k) of 0.04 yr-1. The average growth rate for G. cirratum was approximately 8.68 ± 6.00 cm yr-1. This study also suggests that the previous maximum age for G. cirratum is likely underestimated, with the oldest individual predicted to be 43 years old. Our study is the first to present vB growth parameters and a growth curve for G. cirratum. It indicates that this species is slow-growing and long-lived, which improves our understanding of their life history.

Spatio-temporal Distribution and Population Dynamics of the Red Mullet Mullus barbatus Linnaeus, 1758 from the South-east Black Sea

A total of 2930 Mullus barbatus individuals collected from the Southeastern Black Sea coast between March 2017 and April 2018 were investigated regarding growth, mortality rates and the distribution determined by depth and season. M. barbatus is abundant along of 30-45 m depth in winter. Total length-weight relationship was determined as W=0.005L3.2344. Von Bertalanffy growth parameters for all individuals were calculated as L∞=28.19 cm, K=0.16 years-1, t0=-0.144 years. The maximum age was 5 years. The total length at 50% maturity was estimated as 11.63 cm in males and 11.68 cm in females. Exponential coefficients of natural mortality, total mortality, and fishing mortality rate of red mullet are estimated as 0.33 year-1, 1.001 year-1 and 0.67 year-1, respectively. The exploitation rate of population was calculated as 0.66 year-1. The fact that exploitation rate is above 0.5 may reflect a high fishing pressure on stock.

The invasive mollusk Rapana venosa (Mollusca: Neogastropoda: Muricidae) in the mid-southern Black Sea: Distribution, growth, and stock structure

The rapa whelk, Rapana venosa (Valenciennes, 1846), known also as the veined rapa whelk or the Asian rapa whelk, settled in the Black Sea in 1940 and within the past 30 years has become an important economic contribution to local fishers along the coastline. This study examines the annual change in biomass, population structure, and interaction of the species with the ecosystem of rapa whelk in the mid-southern Black Sea. The samples were collected monthly in 2011 and 2012 by hydraulic dredge at different sites. Stock biomass was estimated at five different subregions and along four depth contours. In 2012 the biomass of rapa whelk increased significantly in in all subregions compared with the previous year sampling. Food availability is the main factor for species distribution, and in parallel, striped Venus clams, Chamelea gallina (Linnaeus, 1758), the main food source for rapa whelks, was significantly concentrated in the study area. The von Bertalanffy growth parameters (VBGP) were expressed as Lt = 121.78(1 − e−0.246(t + 0.33)). As a fisheries management point, our results highlight the overpopulation of rapa whelk in the region.

The initial assessment of an important pelagic fish, Mackerel Scad, in the South China Sea using data‐poor length‐based methods

AbstractObjectiveScadsDecapterusspp. occur widely throughout tropical, subtropical, and temperate oceans and are both economically and ecologically important species. They are among the main commercial fish species caught by the light falling‐net fishery in the South China Sea, which is dominated by Mackerel ScadDecapterus macarellusand Shortfin ScadD. macrosoma. Stock assessment is an approach used to guide effective management and maintain fishery sustainability.MethodsTwo data‐poor methods, namely length‐based Bayesian biomass estimation and length‐based spawning potential ratio, were applied to assess the status of Mackerel Scad, the most dominantDecapterusspecies in the South China Sea. Electronic length–frequency analysis was used to estimate von Bertalanffy growth parameters (asymptotic lengthLinfand growth coefficientK) to serve as priors.ResultThe results show the estimatedLinfandKof Mackerel Scad in the South China Sea as 36.0 cm and 0.37/year, respectively. Estimated natural mortality was 0.74/year, and mean fork length at 50% sexual maturity was 24.29 cm. Length‐based Bayesian biomass estimation analysis showed that the estimated relative stock size had decreased from 1.3 in 2012–2014 to 0.7 in 2019–2021, indicating an overfished status. Length‐based spawning potential ratio analysis showed that the estimated spawning potential ratio for this fishery decreased from 13% to 12%, which is significantly below the limit reference point of 20%.ConclusionOur results obtained through length‐based methods indicate the lower SPR of Mackerel Scad stock was due to catching an excess of juveniles. Therefore, we highlight the need to increase the minimum mesh size in the fishing nets and strengthen international cooperation for conserving this shared stock in the South China Sea.