Von Bertalanffy Growth Model Research Articles

Phenotypic homogenization and potential fitness constraints following non-native introgression in an endemic sportfish.

Introgressive hybridization may lead to contrasting evolutionary outcomes that are difficult to predict, since they depend on the fitness effects of endogenous genomic interactions and environmental factors. Conservation of endemic biodiversity may be more effective with require direct measurement of introgressed ancestry and fitness in wild populations, especially for keystone taxa at risk of hybridization following species introductions. We assessed the relationship of non-native ancestry with growth and body condition in the basin-restricted Neosho Bass (Micropterus velox; NB), focusing on two streams in the NB native range that are admixed extensively with non-native Smallmouth Bass (M. dolomieu; SMB). We quantified genetic composition of 116 fish from Big Sugar Creek (N=46) and Elk River (N=70) at 14 microsatellite loci. Using back-calculated total length-at-age estimated from sagittal otoliths, we assessed whether genetic ancestry explained variation in von Bertalanffy growth model parameters, accounting for sex and stream effects. We then assessed the relationship of ancestry and body condition. We found no differences in growth parameters by sex, stream, or ancestry, suggesting phenotypic homogenization which could be mediated by selection on body size. We found a negative correlation between SMB ancestry and condition, including lower condition in Big Sugar Creek, possibly reflecting a trade-off between maximum length and condition with respect to overall fitness. We show that ongoing non-native introgression, which may be augmented by anthropogenic SMB introductions, may attenuate evolutionary differentiation between species and directly influence fitness, possibly having critical implications for long-term persistence and management of adaptive potential in a popular and ecologically important endemic sportfish.

Age, Growth, Sex Composition, and Diet of the Burbot, Lota lota, the Only Freshwater Species of the Family Lotidae in the Amur (Heilongjiang) River, Northeast China

Information about the population structure, including the age and sex composition, growth characteristics, and diet of fish, is essential for the conservation and sustainable exploitation of fish stock. The burbot, Lota lota, is the only freshwater species of the family Lotidae in the Amur (Heilongjiang) River catchment located in northeastern China. Information on the biological characteristics and data on the population structure of this fish from the Amur River are scarce. To study these factors in burbot, Lota lota, in the Amur River of China, 749 specimens from four sampling areas were taken and analyzed in October 2022, January 2023, and May 2023. The ages of the sampled fish ranged from 1+ to 7+ years. The female/male ratio was 1.04:1, and body length and mass varied from 175 to 595 mm and 73.5 to 1958.7 g, respectively. The length–weight regression parameter b value was estimated as 2.80. The parameters of the von Bertalanffy growth model were L∞ = 596, K = 0.221, and t0 = −0.771 for all sampled fish; L∞ = 625, K = 0.208, and t0 = −0.756 for females; and L∞ = 584, K = 0.219, and t0 = −0.980 for males. The analysis of the stomach contents showed fish to be the major source of nutrition across all areas and sampling periods. In January, the secondary prey of burbots in the Huma reach of the upper Amur River was aquatic insect larvae, while, in the Tongjiang and Fuyuan reaches of the middle Amur River, the secondary prey was shrimp. The mean stomach fullness index and rate of empty stomachs differed with the sampling area, with the greatest proportion of empty stomachs observed in the Luobei reach of the middle Amur River, and the lowest in the Tongjiang and Fuyuan reaches. The mean stomach fullness index showed the opposite trend. In the Huma reach, the contributions of fish to the diet and the mean stomach fullness index were significantly higher in May than in October and January. The study provides the first detailed information on the population age and sex structure, growth patterns, and feeding ecology of burbots from the Amur River, China. The results will aid in formulating management strategies and regulations for local populations of burbots in the Amur River, China.

Appendage damage effects on Southern Rock Lobster growth and mortality

Handling of crustaceans can result in injuries such as limb damage, reducing post-release survival and subsequent growth. Quantifying the impact of handling damage can provide insight into the effects of increased handling, which can occur when undersized animals are released by fishers or during translocations of animals between areas. We investigated the impact of handling on the Southern Rock Lobster (Jasus edwardsii) using three decades of scientific tag-recapture data from a no-fishing reserve. We used a Bayesian modeling approach with a modified Von Bertalanffy growth model which is robust to measurement error and Cormack-Jolly-Seber capture-recapture model to estimate growth and survival probability parameters. We found that even low levels of damage (1–4 appendages) can decrease growth by ∼ 10 % in the subsequent moult. Male lobsters suffered greater effects of handling-induced damage than did females, potentially due to the additional energy reserves available to brooding females.

DINAMIKA POPULASI IKAN CAKALANG (KATSUWONUS PELAMIS) DI LAUT SERAM

This study examines the skipjack tuna fishing industry in North Seram District, Central Maluku Regency, which has been operated by local fishermen for many years. This fishery is categorized as a small-scale and concentrated effort in the Seram Sea, one of the small seas in the Indonesian archipelago, which is part of the Pacific Ocean, covering an area of approximately 12,000 square kilometers. The study employs the length-weight relationship analysis method and the von Bertalanffy growth model. The results indicate that the growth of skipjack tuna can be represented by the equation W = 0.0133L^3.0999 with a determination coefficient of 94%. The b coefficient value for the sampled skipjack tuna was 3.0999, indicating isometric growth (length and weight grow proportionally). The growth coefficient (K) of skipjack tuna was 0.17 per year, with an asymptotic length of 49.586 cm and a t0 value of -0.0748 years. The resulting von Bertalanffy equation is Lt = 49.58{1- e^-0.175(t+0.0748)}, which describes the growth pattern of skipjack tuna in the Seram Sea.

Growth and Mortality Models of Mozambique Tilapia (Oreochromis mossambicus; Peters, 1852) Wildly Enter Inside the Fish Farming Ponds in Tarakan City, North Kalimantan

Graphical Abstract Highlight Research The results of this research showed that allometric growth in males and females had negative allometric growth characteristics. The growth condition index in male and female fish is dominated by thin and fat body shapes.The maximum length growth (L∞) and growth speed of males is higher than that of females. Total mortality and fishing mortality for males is higher than for females, but natural mortality for females is higher than for males. The exploitation rate of males and females is in the Under-exploitation category because the E value is <0.5. Abstract Exploring the length-weight relationship of fish and characterising growth parameters is essential in fisheries as they offer fundamental biology and population dynamics data to establish good management strategies for fisheries resources. This study examines the growth and mortality patterns of Oreochromis mossambicus. Data was collected between September and December 2022 using quantitative descriptive survey sampling. The study involved 20 repeats and deliberate random sampling of 30-50 fish per sample, emphasising total length, weight, and sex parameters. Based on 726 samples of O. mossambicus (352 fish identified as male and 374 fish identified as female). The growth model study revealed the typical negative allometric growth for both sexes (male and female). Male individuals attained a length of 33.449 cm after 37 days has a growth trend ± 0.3265 year-1, and females reached 21.150 cm in 34 days with a growth rate around 0.3135 year-1, as per the von Bertalanffy growth model. There were complex mortality patterns, with males contributing to most total deaths. This study emphasises the complex biology of tilapia and its untapped potential in the aquaculture pond system ecology in Tarakan.

Raising double-muscled breed cattle and their crossbreds in the tropics: insight from growth models.

In tropical conditions, modeling the predictive parameters of live weight, including those at birth, pre-weaning, post-weaning, finishing, and maturing, and the average daily gain, is challenging. The heat load significantly influences the growth rate and final mature weights in the tropics. The study compared the growth rates of Kedah-Kelantan (KK), Brahman (BRAH), and Belgian Blue (BB) crossbred calves. The study conducted growth analysis using the non-linear regression growth models as it approximates the sex, breed, and growth physiology changes in beef cattle. It is supported by the utility of the most common growth functions (Brody, Logistic, von Bertalanffy, and Richard's model) in normal-muscled tropical breeds and double-muscled crossbred beef cattle in the tropics. The BB crossbreds outperformed the KK and BRAH breeds by 50%-100% in live weight gains under tropical conditions. The crossbreds display the double-muscled effect and highlight the advantages of heterosis, making them suitable for upgrading local herds. The study's findings on the growth characteristics of BB crossbred cattle were best described by the von Bertalanffy growth model, which had a high coefficient of determination (R2 > 0.8) and yielded estimated mature weights of 527.5 kg for males and 518.5 kg for females. According to results, raising BB crossbreds in the tropics as a solution to ensure a sustainable beef supply could yield significant growth and economic benefits.

Exploring Growth Patterns of Maurolicus muelleri across Three Northeast Atlantic Regions

Maurolicus muelleri is an important component of mesopelagic ecosystems; nevertheless, we possess only limited knowledge about its biological features. We collected samples of M. muelleri from six scientific surveys between 2019 and 2021 in three geographical areas in the Northeast Atlantic waters (from South to North): the Bay of Biscay, the Celtic Sea, and the Norwegian Sea. Geographical variations in otolith growth, fish age, length, weight, and condition, as well as length–weight relationships and von Bertalanffy growth models (VBGMs), were investigated. Length-weight relationships revealed differences associated with the fish’s origin, paralleling the annual and daily otolith growth. VBGM parameters increased progressively northwards, in accordance with Bergmann’s rules. Fish length was positively related to the otolith radio, and Lee’s phenomenon was undetected. The impact of environmental variables, such as temperature and food availability, is debated, with these considered potential drivers of this variability. Populations may belong to separated units, either genetically or morphologically, representing differences in biological parameters as a signal of geographical divergence.

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.

Age, growth, and mortality of Blackfin Tuna in the Gulf of Mexico

AbstractObjectiveAn otolith‐based aging approach was used to evaluate age and growth relationships, sexual dimorphism in growth, and derive mortality estimates for Blackfin Tuna Thunnus atlanticus in the Gulf of Mexico (GOM).MethodsBlackfin Tuna (n = 395) were sampled from recreational fisheries and aged from 0 to 13 years, representing an increase over previous estimates of longevity for the species.ResultRapid growth was exhibited during the first two years of life, and the Richards growth function provided a better fit (L∞ = 907 mm, k = 0.112 /year, a = 1.05, b = 0.25) to the data compared with the von Bertalanffy growth model (L∞ = 824 mm, k = 0.365/year, t0 = −0.96). Sexual dimorphism in growth was observed, with males (907 mm) reaching a larger L∞ than females (857 mm), and otolith mass was a strong predictor of age in both sexes. Estimated instantaneous total (Z = 0.532/year) and natural (M = 0.467 year) mortality rates for Blackfin Tuna in the GOM were low relative to previous estimates in the southwestern Atlantic, where fishing mortality (F) is likely much higher.ConclusionResults represent critical baseline estimates of size‐at‐age, longevity, and natural mortality for Blackfin Tuna at relatively low levels of exploitation that can be used to inform future assessments.

Application of growth models to South African Boer goat castrates and does under feedlot conditions

Mathematical models may aid researchers in describing biological processes, like growth, in animals. This study aimed to collect the body weight data of 18 Boer goat castrates and 20 Boer goat does, from birth until maturity, to model growth and determine growth trends. This is a novel investigation as sufficient information on an age-weight database for these two Boer goat sexes from birth to maturity, is lacking. Using age-weight data, four nonlinear models, namely the Brody, Gompertz, Logistic and Von Bertalanffy growth models, were plotted and evaluated. The model parameters of each growth model were compared for differences between the two sexes. The statistical effectiveness of fit was determined for each model using AIC and RMSE, with R2 also being considered. All models except the Brody model, predicted significantly heavier mature weights for castrates. The Brody model was deemed unfit to describe Boer goat growth as the function severely over-predict weights from birth until maturity for both sexes. The Von Bertalanffy (R2 = 91.3) and Gompertz functions (R2 = 91.3) showed the best fit for Boer goat castrates, while the Gompertz model (R2 = 95.1) showed the best fit for Boer goat does. The Gompertz function is the preferred model to depict Boer goat growth overall, as it accurately characterized growth of both sexes. According to the Gompertz model the age at which the inflection point of the growth curve was reached, did not differ significantly between castrates and does (141.80 days versus 136.31 days). There was also no significant difference in maturation rate between the two sexes.

Bioeconomics of juvenile seahorse (Hippocampus erectus) culture: Optimal harvest time

AbstractThe culture of seahorses Hippocampus erectus in captivity represents a window of opportunity for the diversification of the aquaculture activity in the ornamental industry. In this study, we have constructed a bioeconomic model to evaluate the optimal harvest time (OHT) over a culture period of 562 days. The bioeconomic model was integrated with three submodels: biological, technological, and economic. Three different mortality rates were used for different periods in culture, registering a higher survival in the period from 0 to 60 days with a rate of 53.4%. The sensitivity analysis showed that the mortality rate in this period was the parameter with the greatest influence on the benefits. The Von Bertalanffy growth model was indicated to describe the growth of H. erectus given its statistical significance using Theil's inequality coefficient, registering parameters of (L∞ = 141.62 mm) and (k = 0.0049 month‐1). The bioeconomic model determined the OHT in the 4th month of culture, the time when the maximum profit is recorded. It is concluded that the culture presents challenges to be addressed although the bioeconomic model allows for demonstrating the OHT.

Urbanization effects on growth and otolith asymmetry in Chrysichthys nigrodigitatus and Oreochromis niloticus within tropical coastal lagoon watersheds

In this study, we investigated the growth dynamics and otolith shape asymmetry of two fish species, Chrysichthys nigrodigitatus (CN) and Oreochromis niloticus (ON), within urbanized watersheds of the southern lagoon system, Nigeria. Using the von Bertalanffy growth model (VBGM), in addition to sediment metal concentration indices such as the average shale content, index of geoaccumulation (Igeo), contamination factor (CF), pollution load index (PLI), and potential ecological risk (PER) index, contamination levels were classified, and ecological risks were assessed. Notably, a lower growth potential (t0) was observed in CN at Ikorodu than at Epe, with similar trends for ON in the Epe during the dry season. Otolith asymmetry patterns, particularly in the CN at Ikorodu and ON in the Epe during the dry season, exhibited distinct ecological variations, indicating heightened stress levels at Ikorodu. Sediment analyses revealed moderate to strong contamination (Cd, Pb, Ni, and Cr) in both Lagos Lagoon (Ikorodu) and Epe Lagoon, with Ikorodu exhibiting notably high to moderate contamination levels according to the CF index. Elevated PLI values for Cd and Pb in Ikorodu, in addition to greater PER, indicated increased risk, with Cd posing a high risk (61.42%) and Pb posing a moderate risk (49.50%). Additionally, the reduced asymptotic length in the Epe during the dry season suggests that Chrysichthys nigrodigitatus is adaptable to seasonal variations, while divergent growth patterns in both areas indicate the existence of trade-off mechanisms in response to changing conditions. Habitat-specific otolith asymmetry and metal contamination underscore species adaptability, with wider stressor variability in Lagos than in Epe. Furthermore, multidimensional scaling analysis highlights the intricate relationship between otolith shape variables and environmental factors, emphasizing the need for tailored conservation efforts in urbanized watersheds.

Growth and yield of Retrophyllum rospigliosii pure plantations in the Colombian Andes

Most reforestation in Colombia, especially in the Andean region, are monocultures of pines and eucalyptus with defined nursery and silvicultural packages. Planting native species would avoid the widespread controversy over reforestation with exotic species. Nevertheless, there are few studies that evaluate the growth and yield of native species and provide supported data to establish new projects. Here, we modeled the growth and yield of the native coniferous Retrophyllum rospigliosii in different areas of the Colombian Andes in terms of mean diameter (D), height (H), and volume (V) as a function of age, based on longitudinal data from 115 research sample plots from three sites that were remeasured between 4 and 9 times for 20 years. We fitted the von Bertalanffy growth model for D, H, and V through Bayesian generalized nonlinear mixed models to model tree growth. The adjustment of the models for the absolute growth of R. rospigliosii was 0.99, 0.99, and 0.97 for D, H, and V, respectively. All models fulfilled all regression assumptions. Although the growth rates of R. rospigliosii differed between planted sites, R. rospigliosii plantations generally exhibited low growth and barely reached the sizes required for commercialization. These results suggest that the extensive use of R. rospigliosii in pure plantations is unlikely and discourages the massive propagation of R. rospigliosii.

A COMPARATIVE ANALYSIS OF GROWTH MODELS ON NIGERIA POPULATION

Growth models have been applied over time to track and forecast changes in variables such as population, body height, biomass, fungal growth, and other aspects of numerous fields of study. This research focuses on modelling the growth of Nigeria’s population from the year 1981 to 2021 and determining the best fit model to represent Nigeria’s population growth (male, female and total). Seven growth models were considered in this research which includes: the linear, the exponential (Malthusian), Logistic (Verhulst), Gompertz, Hyperbolic, Brody and the Von Bertalanffy growth models. The criteria used for comparison of best fitted model were the coefficient of determination (R2), Akaike Information Criterion (AIC), Mean Square Error (MSE), and Bayesian Information Criterion (BIC). The R2 showed that the exponential, the logistic and the Gompertz growth models were all better fits for Nigeria’s population (male, female and total) having the highest R2 (0.999). Further comparison with the MSE, AIC and BIC revealed that the exponential growth model best represented Nigeria’s population growth (male, female and total) having the least MSE, AIC and BIC. Hence the exponential growth model should be considered by researchers in Nigeria population projection.

Optimization of Feed Ration Size in Aquatic System According to the Optimal Control Approach: Implications of Using the von Bertalanffy Growth Model

Rationing aquaculture farming feed is challenging for producers due to high feed costs, representing 30%–60% of the total operating costs. Therefore, optimal timing of feeding could lead to improved economic returns from an aquatic system. An optimal dynamic feeding model has been determined considering the von Bertalanffy growth model. A bioeconomic model of tilapia production in Mexico for specific markets was used for numerical illustration. The von Bertalanffy growth model was parameterized with experimental data from tilapia (Oreochromis niloticus) fed four ration sizes (50%, 80%, 100%, and satiety), in order to determine different optimal rationing for different fish sizes (200, 300, and 400 g), market prices (Monterrey, Cancún, Mexico City, and On site), and optimal harvesting times (OHT), considering the time value of money. The results of the modeled optimal feeding trajectories show a continuous decrease from stocking to reach a minimum value and then slightly approaching the harvest size. This result contrasts with the recommendations of the feed suppliers and with those found when a potential growth model was used. The results in the case study showed that the Monterrey market presented the highest present value of the benefits in the OHT and the different market sizes. The implications of the Bertalanffy model for optimal rationing trajectories are presented in the discussion.

Ulam type stability for von Bertalanffy growth model with Allee effect.

In many studies dealing with mathematical models, the subject is examining the fitting between actual data and the solution of the mathematical model by applying statistical processing. However, if there is a solution that fluctuates greatly due to a small perturbation, it is expected that there will be a large difference between the actual phenomenon and the solution of the mathematical model, even in a short time span. In this study, we address this concern by considering Ulam stability, which is a concept that guarantees that a solution to an unperturbed equation exists near the solution to an equation with bounded perturbations. Although it is known that Ulam stability is guaranteed for the standard von Bertalanffy growth model, it remains unsolved for a model containing the Allee effect. This paper investigates the Ulam stability of a von Bertalanffy growth model with the Allee effect. In a sense, we obtain results that correspond to conditions of the Allee effect being very small or very large. In particular, a more preferable Ulam constant than the existing result for the standard von Bertalanffy growth model, is obtained as the Allee effect approaches zero. In other words, this paper even improves the proof of the result in the absence of the Allee effect. By guaranteeing the Ulam stability of the von Bertalanffy growth model with Allee effect, the stability of the model itself is guaranteed, and, even if a small perturbation is added, it becomes clear that even a small perturbation does not have a large effect on the solutions. Several examples and numerical simulations are presented to illustrate the obtained results.

Age, growth, and energy storage of the subterranean fish Triplophysa rosa (Cypriniformes: Nemacheilidae) from Chongqing, China

BackgroundThis study explores the age, growth, and energy storage of Triplophysa rosa, a troglobitic cavefish. A total of 102 wild T. rosa specimens were collected in Wulong County, Chongqing, China, between 2018 and 2022, with otoliths used for age determination.ResultsThe earliest mature individuals were determined to be 4.8 years old, while the maximum ages for females and males were estimated at 15.8 years and 12.2 years, respectively. The length (L, cm)-weight (W, g) relationship was found to be the same for both sexes, following the eq. W = 0.0046 L3.03. Von Bertalanffy growth models were applied to the total length-at-age data, resulting in an asymptotic length of 23.4 cm and a K-parameter of 0.060 year−1. The body content of protein, ash, and glycogen did not show a significant correlation with the total length of T. rosa. However, both lipid and energy content exhibited a significant increase with total length. The lipid content ranged from 40.5 to 167.1 mg g−1, while the energy content ranged from 4.50 to 11.39 kJ g−1, indicating high storage features of T. rosa.ConclusionsThe results affirm that T. rosa exhibits life traits conducive to its population dynamics in cave conditions, characterized by slow growth, small size, and high lipid energy storage.

Unveiling growth and reproduction of a giant Patagonian galaxiid: an experimental rearing study

ABSTRACT Understanding the life history of understudied native and threatened fishes is crucial to develop conservation strategies for freshwater ecosystems. Puye grande (Galaxias platei) is an endemic freshwater fish of Patagonia with little known about its life history traits. To bridge this information gap, comprehensive studies under controlled conditions could expand our basal understanding of puye grande’s life history. We conducted a long-term experimental study using one cohort of puye grande throughout its lifespan. We collected 423 postlarvae individuals from the Riñihue Lake (southern Chile) and reared them for 11 years under captivity. We documented the maximum longevity of this species as 11 years, with a survival rate of 0.47% for the entire study period. Hatchery-reared individuals showed isometric growth (b = 2.75). Parameters of the von Bertalanffy growth model were asymptotic total length L ∞ = 20.80 cm, growth coefficient K = 0.75 yr−1, and theoretical age at-length zero t 0 = 0.45 yr, including both sexes. Puye grande showed an iteroparous life history, with the first spawning event occurring at age 2+ and consecutive spawning events occurring mainly in fall and winter. Females had a mean (standard deviation) total fecundity of up to 58 500 (23 331) eggs individual−1 and a mean relative fecundity in fall of 621 (109) eggs g−1 wet mass; males had a mean spermatic density of 28.41 (4.18) × 109 spermatozoa mL−1. The embryonic development until eclosion occurred 432 h post fertilization (hpf) at 12 °C. Our valuable baseline findings about the life history of puye grande can contribute to future strategies for managing and conserving galaxiids under global environmental change in Patagonia.

Population Dynamics and Exploitation Level of Stolothrissa tanganicae Regan, 1917 and Limnothrissa miodon (Boulenger, 1906), Two Clupeid Fish Species of Commercial Interest of Burundian Waters Northeast of Lake Tanganyika

Aims: Show exploitation level and propose rational management measures of the two clupeid-fish species of commercial interest, Stolothrissa tanganicae and Limnothrissa miodon&#x0D; Study Design: Modeling the demography of clupeid fishes of Lake Tanganyika.&#x0D; Place and Duration of Study: Two stations (Kajaga and Nyamugari) situated in the northern part of Lake Tanganyika on the Burundian coast from December 2019 to April 2020.&#x0D; Methodology: Monthly fish sampling was done with local fishermen Demographic parameters were determined according to the Von Bertalanffy growth model using size frequency distributions based on total length. Excel 2013 and FAO-ICLARM. Stock Assessment Tools (FiSAT II version 1.2.2 software).&#x0D; Results: The values of the growth parameters obtained for each of the two species are close at the level of the two stations. For S. tanganicae, we have L∞= 135 mm and 118 m and K=0.94 yr-1 and 0.99 yr-1 respectively at Kajaga and Nyamugari. For L. miodon, we have L∞= 148 mm and 132 m and K=1.04 yr-1 and 0.92 yr-1 respectively at Kajaga and Nyamugari. The Ø' values obtained are high and vary from 4.14 to 4.58 depending on the species and the stations: For S. tanganicae, higher Ø' was recorded at Kajaga (Ø'= 4.23). In L. miodon, it was observed at Nyamugari (Ø’=4.58). M oscillate around 1 (M varies from 1.08 to 1.17 year-1) for the two species at two stations. F is high everywhere and varies from 3.03 to 6.49 yr-1 depending on the species and the stations. Both species are overexploited : 0.73&lt;E&lt;0.86, so E is close to 1. Small-sized individuals dominate catches: minimum sizes are between 24 and 30 and 42 and 54 mm respectively in L. miodon and in S. tanganicae.&#x0D; Both the fish species adapt well to their environments (the values of Ø' are very high).&#x0D; Conclusion: Both species of fish adapt well to their environments (the values of Ø' are very high). Given their overexploitation, the existing rational management measures must be strengthened and rigorously applied.

Corroborating otolith age using oxygen isotopes and comparing outcomes to scale age: Consequences for estimation of growth and reference points in northern pike (Esox lucius)

AbstractAccurate age estimates are crucial for assessing the life‐histories of fish and providing management advice, but validation studies are rare for many species. We corroborated age estimates with annual cycles of oxygen isotopes (δ18O) in otoliths of 86 northern pike (Esox lucius) from the southern Baltic Sea, compared results with visual age estimates from scales and otoliths, and assessed bias introduced by different age‐estimation structures on von Bertalanffy growth models and age‐structured population models. Age estimates from otoliths were accurate, while age estimates from scales significantly underestimated the age of pike older than 6 years compared to the corroborated reference age. Asymptotic length () was larger, and the growth coefficient was lower for scale ages than for corroborated age and otolith age estimates. Consequentially, scale‐informed population models overestimated maximum sustainable yield (), biomass at (), relative frequency of trophy fish (), and optimal minimum length limit but underestimated fishing mortality at (). Using scale‐based ages to inform management regulations for pike may therefore result in conservative management and lost yield. The overestimated asymptotic length may instill unrealistic expectations of trophy potential in recreational anglers targeting large pike, while the overestimation in MSY would cause unrealistic expectations of yield potential in commercial fishers.