Bertalanffy Function Research Articles

Comparison of non-linear mixed effect models of the growth curve of commercial turkeys

The description of the growth curve in domestic animals is of importance in management and economic decision-making. The aim here was to determine the best non-linear mixed model to adjust the growth curve in commercial turkeys. The data come from an intensive turkey farm under a subhumid tropical climate. The live weight records of 266 female and 275 male turkeys, weighed weekly, from birth to 23 weeks, were used. The models of Gompertz, yt = A × exp(-b × exp(-k × t)), and von Bertalanffy, yt = A × (1-b × exp(-k × t))3 were used to estimate parameters and predict the growth curve; where: yt = live weight at the t-th week of age; A = the expected mature weight; b = the integration constant; k = the maturation rate. Six non-linear models using the Gompertz, and von Bertalanffy functions: one with only fixed effects, four mixed models considering the fixed, 1 to 3 random effects, and a last model including the random effect of turkey were used. The analyses were performed using the NLMIXED procedure of SAS, and the selection of the best-fit model was chosen based on the Akaike (AIC) and Bayesian (BIC) information criteria. AIC and BIC values improved with the inclusion of 1 to 3 random effects, in both models for females and males. Based on AIC and BIC criteria, the best mixed NLM was the model that included random effects for A, b, and k. However, the predicted weight values of the mixed models were similar.

Statoliths of Rapana venosa (Valenciennes, 1846): Microstructure, application for age determination and growth modelling

Rapana venosa (Valenciennes, 1846) is an invasive species that has spread widely around the world, which has commercial importance. For scientifically sound fishery management, accurate age determination is necessary, while the methods currently used have disadvantages. To fulfill the need for a more accurate technique, the microstructure of R. venosa statoliths collected in the northern part of the Black Sea (near the Bolshoy Utrish cape) was studied. Statoliths have well-marked concentric increments, which allows counting with sufficient accuracy. The annual periodicity of R. venosa statolith increments was cross validated using spawning marks on the shells. The growth of veined whelks was the best described by Von Bertalanffy function, with the following coefficients: L∞ = 96.19; k = 0.125; t0 = 0.043. The model accounted for 83% of variance. Moreover, the possibility to reconstruct the age of molluscs based on statolith diameter was tested. It was revealed that the number of increments versus statolith diameter relationship is exponential, the developed model described 99% of variance. Based on these data the growth of R. venosa was modelled again, resulting model accounted for 88% of variance. Coefficients of the model were: L∞ = 106.42; k = 0.102; t0 = 0.136. Potential benefits and limitations of the applied methods are discussed.

Nonlinear modeling of growth and study of a new characterization point applied to Timahdit breed sheep under uncertain paternity

The objectives of this study are to determine which model, among those of Brody, Logistic, Gompertz, Von Bertalanffy and Richards, is the most appropriate to describe the growth of this breed and to choose a point for this model which would be closest to the slaughter weight which have to be used as a selection criterion. Also, in preparation for genetic evaluation under uncertain paternity, Henderson's Average Numerator Relationship Matrix method was used and an R code was developed for the creation of the inverse matrix A which was replaced the pedigree in the animal model. To do this, 64,282 observations corresponding to 12,944 animals, collected between 2009 and 2016, were analyzed. The Von Bertalanffy function had the smallest AIC, BIC, and deviance criteria values, indicating better data representation for both sexes. Considering the average slaughter live weight of 29.4kg in the study area, the new point of characterization named f(tbm), later than the inflection point of the growth curve, is closer to the commercial target for females intended for regular slaughter supplying butchers and for animals of both sexes intended for religious festivals. Therefore, it would be appropriate to consider this point as a selection criterion for this breed. The developed R code will be integrated into a free R package allowing the estimation of the genetic parameters of the traits of the Von Bertalanffy model.

Life-history traits variation of Lutjanus malabaricus (Bloch & Schneider, 1801) in the waters off Northern Vietnam

Abstract Lutjanus malabaricus represents a widely distributed and intensively exploited snapper species. The present article is the first attempt to describe the life-history traits of L. malabaricus in Vietnamese waters and estimate their variability. The fish were collected at the landing sites of Nghe An and Ha Tinh provinces from June 2020 to May 2021. The standard length of fish ranged from 10 to 74 cm, weight varied between 18.53 and 8972.89 g, age ranged from 1 to 17 years and all three parameters were subjected to a significant seasonal variation. A similar seasonal pattern was observed in the variation of maturity and gonadosomatic index. We assume that the observed variation of the stock structure is the result of spawning migrations when large fish migrate inshore from the foraging grounds. Growth and weight gain of fish were described via the von Bertalanffy function, constants of the equations were as follows: L∞ = 76.2, K = −0.077, t0 = −2.26 in males and L∞ = 56.9, K = −0.176, t0 = −0.48 in females; W∞ = 6498, K = −0.100, t0 = −1.96 in males and W∞ = 8317, K = −0.100, t0 = −1.31 in females. The growth constants of the North Vietnamese stock of L. malabaricus are similar to the ones of the North-eastern Australian stock. A general tendency for the reduction of the growth rate and asymptotic size from equatorial waters to higher latitudes was observed.

Different Suitability of Olive Cultivars Resistant to Xylella fastidiosa to the Super-Intensive Planting System

Until today, only Leccino and Fs-17 (=Favolosa®) olive cultivars proved resistant to Xylella fastidiosa subsp. pauca (Xfp) due to a low presence of bacteria in the xylem. Integrated disease management in olive growing areas threatened by the spread of Xfp is crucial to overcoming the environmental, economic and social crisis. Since the EU Decision allows for the plantation of resistant olive cultivars in infected areas, there is a need to define a suitable plantation system for these cultivars. The adoption of new planting systems, such as intensive and super-intensive (SHD), could compensate for the economic losses and restore the olive agroecosystem. The aim is to ascertain the suitability of the available Xfp-resistant cultivars to SHD planting systems that demonstrate the best economic and environmental sustainability. Hence, a five-year study was established in an experimental SHD olive orchard (Southern Italy) in order to analyse the main vegetative and productive traits of Leccino and Fs-17, together with four other Italian cultivars (Cipressino, Coratina, Frantoio and Urano), compared with the well-adapted cultivars to SHD orchards (Arbequina and Arbosana), by means of the von Bertalanffy function. The results indicated that cv. Fs-17 showed sufficient suitability for SHD planting systems, giving the best-accumulated yield despite some canopy growth limitations, whereas cv. Leccino did not show satisfactory results in terms of both vegetative and yield parameters, confirming its suitability for intensive planting systems. These results are useful for optimizing integrated resistance management in Xfp-infected areas by planting resistant host plants.

Comparison of nonlinear models for describing the pre-weaning growth of Timahdite lambs and genetic and non-genetic effects for curve parameters

The objectives of this study were to determine the appropriate nonlinear model for describing the pre-weaning growth curve of Timahdite lambs and to study the genetic and non-genetic effects of curve parameters with the best fit model. Nonlinear models of Brody, Gompertz, von Bertalanffy and Logistic were fitted to 46372 body weight-age records belonging to 11,620 lambs, ranging from birth to weaning age. The statistics used to compare the growth models were adjusted determination coefficient (Radj2), residual mean square (MSE), Akaike’s information criterion (AIC) and Bayesian information criterion (BIC). Among the four nonlinear models, the von Bertalanffy function had the high Radj2 and the smallest MSE, AIC and BIC values, indicating the best fit for Timahdite lambs. Parameters A, B and k of the best model were estimated to be 33.3 ± 0.70, 0.50 ± 0.01 and 0.01 ± 0.01, respectively. The flock and period of birth had significant effects on parameters A, B and k, the age of dam and birth type on parameters B and k, and the sex on parameter A only. Heritability estimates for growth curve parameters A, B and k were 0.01 ± 0.01, 0.02 ± 0.01 and 0.02 ± 0.01, respectively. Estimates of genetic correlation between A-B, A-k and B-k were 0.79 ± 0.11, −0.71 ± 0.12 and −0.23 ± 0.18, respectively. Their corresponding phenotypic correlations were 0.77, −0.81 and −0.54, respectively. It was concluded that among the nonlinear models, the von Bertalanffy model presented the best fit in describing the growth curve in Timahdite lambs and much of the improvement on growth curve parameters could be obtained by improving associated managerial and environmental conditions.

Estimation of Coregonus ussuriensis age, growth, and maturation in China's Amur River.

This study examined the age, growth, and maturation of 1,064 Coregonus ussuriensis individuals that were collected monthly from the middle section of the Amur River, China between 2016 and 2018. The fork length (FL) ranged from 14.9 to 49.1 cm for males and 21.5 to 58.8 cm for females, and the body weight (BW) ranged from 72.6 to 1,348.7 g for males and 107.9 to 2,854.9 g for females. The relationship of BW and FL was expressed as: BW♂ = 0.0324 × FL2.708; BW♀ = 0.014 × FL2.963. The sample ages ranged from 2 to 8 years for males and 2 to 9 years for females. We used the von Bertalanffy function based on otolith reading and observed FL data to simulate Coregonus ussuriensis growth, which has been suggested to be similar to that of other Salmonidae fishes. No significant difference in growth was determined between males and females. The monthly gonad somatic index (GSI) value ranged from 0.16% to 1.69% for males and from 0.73% to 16.15% for females, with a peak in November. Additionally, the reproductive staging suggested that the Coregonus ussuriensis spawning season was mainly in November and December. The size at maturity (FL50%) for males and females was 34.9 cm and 37.9 cm respectively, and the corresponding age (T50%) was 4.5 and 5.1, respectively. This study provides basic information for understanding the biological characteristics of Coregonus ussuriensis and should aid in the assessment and management of fishery resources.

토종닭 순계 12계통과 성별에 따른 성장능력 비교 연구

This study aimed to identify the growth performance of Korean indigenous chicken pure-line by sex and twelve strains conserved in Poultry Research Institute, National Institute of Animal Science, Rural Development Administration. The effect of sex and strain on body weight was significantly different in every period, with males being heavier in all periods than females. In the case of biweekly weight gain, the tendency to increase rapidly from birth to six weeks old, and to decrease in the period from twelve to fourteen weeks old was common across all sex and strains. Depending on sex and strain, there were significant differences in age and the number of peaks. Regardless of sex and strain, the determination coefficient and adjusted determination coefficient showed high goodness of fit (99.1~99.9%) to growth functions. However, for each model, the goodness-of-fit had variations by sex and strains. von Betalanffy function had the best fit to growth curves in all the female strains except strain D. On the other hand, Gompertz function had the best fit for all the male strains except strain C. Logistic function showed the lowest goodness-of-fit in all sex and strains. Mature weights were in the order of von bertalanffy, Gompertz, and Logistic models, while growth ratio and maturing rate followed the order of logistic, gompertz, and von bertalanffy functions. This information could be useful for Korean indigenous chicken management and designing crossbreeding tests and breeding programs.

Assessing thornback ray growth pattern in different areas of Western-Central Mediterranean Sea through a Multi-Model Inference analysis

The lack of information on age validation often affects ageing studies in cartilaginous fish, even in the most common species. Recently, the annual growth band deposition pattern has been directly validated for thornback ray in the Mediterranean Basin, thus providing a highly reliable protocol for age reading. In this regard, taking advantage of this new information, the present study aims to investigate this species growth for the first time over a wide area of the Western and Central Mediterranean Sea, involving four different FAO geographic sub-areas. In order to provide an accurate description of the species growth, different models were fitted to the age-length data obtained from the observation of vertebral centra thin sections. A total of 720 specimens were analysed (358 females and 362 males) with total length ranging between 11.5 and 86.4 cm. The corrected Akaike's Information criterion (AICc) indicated, among the tested models, the three-parameter von Bertalanffy function as the most robust in describing the species growth. Growth modelling outcomes revealed the thornback rays as capable of growing relatively fast during the first years; the growth rate gradually slows down allowing maximum sizes of about 90–100 cm in total length to be reached. Significant discrepancies in the growth pattern were found between sexes in all investigated areas with the only exception being in the Northern Tyrrhenian Sea. Differences in growth patterns were observed between areas, specifically in the estimated growth rate of the species for each sub-region. The present study, confirmed the importance of the availability of a validated ageing protocol and testing multiple growth models. Moreover, our results highlighted the urgent need to investigate a species growth in a wide geographic area, searching also for possible differences at sub-region level. Providing this information could indeed allow eventual management plans to be adapted to the exact growth pattern that the species exhibit in the region, in this way increasing their effectiveness.

Biology of the thornback ray (Raja clavataLinnaeus, 1758) in the North Aegean Sea

AbstractThe study deals with aspects of the population dynamics in the thornback ray (Raja clavataL., 1758), one of the most abundant cartilaginous fish caught in the North Aegean Sea. Females accounted for 73.08% and males 26.92% of all individuals. Total length of females and males ranged between 50.2 and 89.9 cm (disc width: 33.4–62.0 cm), and between 43.1 cm and 82.7 cm (disc width: 30.7–64.2 cm), respectively. Relationships between total length (TL) and total weight (TW), and between disc width (DW) and total weight (TW) were described by the equations: TW = 0.0041 TL3.10and TW = 0.0178 DW3.03, respectively. Age data derived from vertebrae readings were used to estimate growth parameters using the von Bertalanffy function: L∞= 101.71 cm, K = 0.18 y−1, t0 = −0.07 y for males and L∞= 106.54 cm, K = 0.16 y−1, t0 = −0.28 y for females. The maximum age was 8 years for males and females. Total length at first maturity of males and females was 70.9 cm and 81.2 cm, respectively. Based on the gonadosomatic index and gonadal macroscopic observations, it was determined that the spawning period lasted throughout the year. Stomach content analysis showed that crustaceans (53.03% IRI) and teleosts (14.70% IRI) were the most preferred prey.

Growth and population biology of the sand-bubbler crab Scopimera crabricauda Alcock 1900 (Brachyura: Dotillidae) from the Persian Gulf, Iran

BackgroundDotillid crabs are introduced as one common dwellers of sandy shores. We studied the ecology and growth of the sand bubbler crab Scopimera crabricauda Alcock, 1900, in the Persian Gulf, Iran. Crabs were sampled monthly by excavating nine quadrats at three intertidal levels during spring low tides from January 2016 to January 2017.ResultsPopulation data show unimodal size-frequency distributions in both sexes. The Von Bertalanffy function was calculated at CWt = 8.76 [1 − exp (− 0.56 (t + 0.39))], CWt = 7.90 [1 − exp (− 0.59 (t + 0.40))] and CWt = 9.35 [1 − exp (− 0.57 (t + 0.41))] for males, females, and both sexes, respectively. The life span appeared to be 5.35, 5.07, and 5.26 years for males, females, and both sexes, respectively. The cohorts were identified as two age continuous groups, with the mean model carapace width 5.39 and 7.11 mm for both sexes. The natural mortality (M) coefficients stood at 1.72 for males, 1.83 for females, and 1.76 years−1 for both sexes, respectively. The overall sex ratio (1:0.4) was significantly different from the expected 1:1 proportion with male-biased. Recruitment occurred with the highest number of annual pulse once a year during the summer.ConclusionsThe results, which show slow growth, emphasize the necessity of proper management for the survival of the stock of S. crabricauda on the Iranian coast of the Persian Gulf.

Mathematical modeling of Arctic sea ice freezing and melting based on nonlinear growth theory

The spatiotemporal distribution of sea ice in the cold Arctic region is of climatic and engineering significance. However, in terms of statistics, there remains a lack of quantitative mathematical descriptions of the annual periodic sea ice cycle for the entire Arctic and its regional seas. Using the semi-enclosed and seasonally ice-covered Kara Sea as a systematic case study, this quantitative study focuses on the theoretical mathematical expressions of the nonlinear freezing and melting processes of sea ice. The periodic cycle of sea ice coverage was divided into freezing, frozen, and melting stages, with the continuous ice-coverage curves clearly highlighting temporal nonlinearity during both freezing and melting periods. Thus, nonlinear growth theory was used to quantitatively simulate ice-coverage curves. Results from a comparison of the various functions showed the Logistic function to most accurately quantify the annual periodic cycle, followed by the Gompertz and von Bertalanffy functions, with the Negative exponential and Brody functions having the least suitable results. Further, our results indicate that net sea surface heat flux primarily contributes to the nonlinear temporal freezing and melting of sea ice in the periodic cycle. The nonlinear growth theory was also applied to other Arctic sea areas, including the Laptev Sea, East Siberian Sea, Chukchi Sea, Beaufort Sea, and Baffin Bay. By using the developed mathematical equations, we are able to quantify sea ice conditions at any given time for different Arctic sea areas.

Allometric models for above and below-ground biomass of wild Musa stands in tropical semi evergreen forests

Wild Musa species constitute an important component of tropical rain forests, wet evergreen forests and deciduous forests. Unlike forest trees, biomass estimation models are virtually lacking for wild Musa species. The present study aimed to determine whether growth and biomass accumulation in Musa species follow simple allometric scaling rules; and to develop allometric models for estimation of biomass storage in wild Musa balbisiana stands. A total of 156, M. balbisiana plants were harvested for above and below ground biomass for developing the biomass estimation models. The commonly used height-diameter (H-D) models: Chapman-Richard, exponential, Gompertz, hyperbolic, Michaelis-Menten (saturation growth), power-law, Weibull and Von Bertalanffy functions were used to predict missing heights from field measurement of plant diameter. The performance of the power-law model involving D alone, pseudo-stem height (Hp) alone or a combination of D and Hp was used to develop the best biomass estimation model. Nonlinear seemingly unrelated regression (NSUR) was used to model total biomass stocks. The stand density and basal area of the wild Musa stand was 14900 pseudo-stem ha−1, and 14.94 m2 ha−1, respectively. Based on the goodness of fit criteria, Hp, and D at 130 cm, the Exponential and Gompertz functions were observed to be the two best models for describing H-D relationship. A model containing D and Hp was found to be the best model for total biomass estimation in M. balbisiana. The total biomass stock predicted by our best NSUR model was 90.7 Mg ha−1, of which 55.4 Mg ha−1 was found in above-ground and 34.7 Mg ha−1 in below-ground plant parts. The present study suggests wild M. balbisiana hold significant potential to contribute to stand level biomass stock in forest ecosystems where they occur mixed with trees.

Modelación de curvas de crecimiento de novillas lecheras de reemplazo criadas en condiciones tropicales de pastoreo

Se usaron modelos mixtos no lineales para describir el patrón de crecimiento desde el nacimiento hasta la edad de concepción en novillas lecheras de reemplazo, utilizando las funciones de Gompertz, Von Bertalanffy, Verhulst y Logística. Los grupos raciales estudiados fueron Holstein-50% x Gyr-50% (HG), Holstein-50% x Jersey-50% (HJ) y Jersey-50% x Holstein-25% x Gyr-25% (JHG). En cada función matemática, se asociaron efectos aleatorios con respecto a los parámetros peso corporal asintótico (β0), constante de integración (β1) y tasa de maduración (β2). Modelos con efectos fijos y diferentes combinaciones de efectos aleatorios se compararon de acuerdo a la capacidad de ajustarse al conjunto de datos. Para evaluar los modelos se tuvo en cuenta la varianza residual, los criterios de información de Akaike y Bayesiano y los gráficos de residuos. En general, la adición de efectos aleatorios en los modelos, incrementó la precisión en las estimaciones de los parámetros, no obstante, el mejor ajuste se logró con la función Von Bertalanffy con efectos aleatorios asociados a los parámetros β0, β1 y β2. Este modelo mejoró las estadísticas de verosimilitud y redujo la varianza residual en 47% en promedio con respecto a los modelos de efectos fijos. En comparación con un proceso de crecimiento optimo bajo condiciones tropicales, las predicciones de modelo indicaron que las novillas dentro de los tres genotipos evaluados están alcanzando la concepción con pesos inadecuados como consecuencia de la baja calidad de la dieta disponible durante el periodo de cría. Los resultados sugieren que existe la oportunidad de explotar el verdadero potencial de crecimiento de las novillas al mejorar el manejo durante la crianza, la nutrición y a través de la selección de animales precoces.

Estimates on age, growth, and mortality of Gymnocypris firmispinatus (Cyprinidae: Schizothoracinae) in the Anning River, China

The age, growth, and mortality of Gymnocypris firmispinatus were studied by 582 individuals that collected between July 2015 and June 2016 from the tributaries of the Anning River, China. The total length (TL) ranged from 27 mm to 242 mm, total weight (W) ranged from 0.2 g to 148.2 g. The relationship of total length and weight was expressed as W =7.754×10-6 TL3.304 for the total samples. The age classes of males were 1–9 a, and that of females were 1–13 a. The von Bertalanffy functions based on otolith readings and observed length data were Lt♂ =198.6(1–e-0.094 ( t +3.497) ), and Lt♀ =289.3(1–e-0.089 ( t +1.109) ). The total mortality ( Z ) of male and female G. firmispinatus was estimated as 0.73/a and 0.40/a, respectively. The natural mortality ( M ) was evaluated as 0.25/a for males and 0.20/a for females, fishing mortality ( F ) was 0.35/a for males and 0.16/a for females. The exploitation ratio of the population was 0.66/a for males and 0.50/a for females. It was concluded that the growth of the fish is relatively slower than other congeneric fishes. The population of G. firmispinatus in the tributaries of the Anning River might be in over-exploitation under the current fishing intensity.

Growth and feeding habits of invasive Pseudorasbora parva in the Chabalang Wetland (Lhasa, China) and its trophic impacts on native fish

In recent years, fish invasion has become one of the main reasons for the decline of native fish stocks. Pseudorasbora parva is considered one of the major invasive species worldwide. The present study investigated the fish resources of the Chabalang Wetland (Lhasa, Tibet) during different seasons in 2009 and 2013. Four hundred and twelve individuals were subsampled to estimate age, growth, and feeding habit of P. parva. Furthermore, food relationships between P. parva and the native Schizothoracinae fish were also examined. The results revealed a significant shift in species composition and community structure characterized by the disappearance of native fish and outbreak of non-native fish. The percentage of nonnative P. parva in the fish collections significantly increased from 33.64% in 2009 to 64.08% in 2013. The standard length (SL) ranged from 22.00 to 78.71 mm, and their age was 1–5 yr. The von Bertalanffy function was used to model the observed length-at-age data as Lt =112.19(1–e-0.1495 ( t +0.8012) ) for females and as Lt =123.12 (1–e-0.1500 ( t +0.7132) ) for males. The results indicated that P. parva in Tibet has lower growth and mortality rates compared with that from the native ranges. Ninety-seven prey taxa belonging to 9 prey categories were identified in the gut of 38 P. parva. P. parva can be considered a generalized and opportunistic predator, competing with the native fish, especially Schizothorax o’connori, Schizopygopsis younghusbandi younghusbandi, and Ptychobarbus dipogon, for Bacillariophyta and Chironomid larvae. This is an important reason for the decline in native fish population.

Describing growth based on landscape characteristics and stocking strategies for rainbow trout

The achievement of target growth rates of stocked fish in a particular environment is an important component of recreational fisheries management; if stocked fish do not achieve a desired size structure, then angling effort and satisfaction may be lower than anticipated. We developed a growth model for rainbow trout (Oncorhynchus mykiss) based on a Bayesian hierarchical analysis of growth data from 142 gillnet assessments across the province of British Columbia. The growth equation was defined as a von Bertalanffy function with environmental and stocking covariates applied to the function’s asymptotic length (L∞) and metabolic rate (K) parameters. Key factors defining growth for the best performing model were the time spent in lake based on accumulated growing degree days, the life-stage at stocking, stocking density, and the stocked strain. Calculating time in-lake in terms of growing degree days experienced by fish instead of calendar days in-lake improved the prediction of growth. We explore examples of how to use this information, such as identifying stocking rates needed to achieve particular size thresholds given size-structure objectives for a stocked lake fishery. This analysis helps managers determine how to efficiently distribute hatchery-reared fish across the landscape and recognize limits to growth given particular environmental constraints while also tailoring to the diversity of angler preferences and expectations of the fishery.

Selecting Best Double Sigmoid Function to Describe Growth and Growth Rate of Rapeseed Under Water Stress

Dry matter accumulation pattern of winter cereals and rapeseed is similar to double sigmoid growth curve and can be described by sum of two different or similar singular sigmoid (S-shape) functions (e.g., Richards, Von Bertalanffy, and other functions) that they have overlap on one point. In this study, accuracy of 49 different function compositions of double sigmoid function for describing the rapeseed dry matter based on days after planting (DAP) and growing degree days (GDD) were tested. Results of this study showed that the Beta–Richards and Richards–Gompertz functions were fitted to the measured dry matter during growing season very accurately based on DAP and GDD, respectively. Sum of two Von Bertalanffy or Weibull functions can not describe the winter rapeseed growth. Results of this investigation can be used to estimate dry matter of rapeseed during growing season and analysis of plant growth rate variation under different irrigation treatments.

Population Dynamic of the Mudskipper Periophthalmus waltoni Koumans, 1941 from the Bay of Hormozgan Province, Persian Gulf

We studied the population structure and reproductive biology of the mudskipper Periophthalmus waltoni Koumans, 1941, living on the mudflats of bay of Hormozgan province, Persian Gulf. The specimens were haphazardly and monthly collected from August 2008 to July 2009. A total of 2060 fishes was sampled, sexed 690 of which 221 (32%) were males, and 469 (68%) females. The total length (TL) and weight relationship demonstrated growth in both sexes was isometric with the function W = 0.0078TL3.06. The asymptotic length (L∞) and growth coefficient (K) were estimated as 16.5 cm and 0.75 yr–1, respectively. Age of the fish at zero length (to) was calculated–0.35 and the longevity was attained 3.65 year. The estimated Von Bertalanffy function was TL(t) = 16.5[1–exp(–0.75(t + 0.35))]. Natural mortality (M) was estimated 1.74 yr–1. Four cohorts were distinguished annuallywith mean of TL = 7.35, 10.17, 12.74 and 13.92 cm. The maximum recruitment rate was in January at 17.5%. The overall sex ratio (F: M) (1: 0.49) was significantly different than 1: 1. The peak of the gonadosomatic index (GSI) occurred in February. The size at onset of sexual maturity (LM50)wasestimated at TL = 12 cm. The mean of absolute and relative fecundity were estimated as 3558 ± 2203 and 257 ± 101 eggs, respectively.

Length-weight relationships, sex ratio and growth estimates for five sympatric sillaginids (Pisces) from the northern Arabian Sea coast

Five species were collected (n = sample sizes in parentheses): Sillago arabica (8), S. attenuata (26), S. indica (971), S. sihama (77) and Sillaginopodys chondropus (18) from the northern Arabian Sea coast of Pakistan. Specimens were caught with gill nets (mesh size 2.5 cm knot-to-knot) by medium-sized commercial fishing vessels from September 2015 to April 2016. The parameter slope (b) in the length–weight relationships ranged from 2.44−3.21 for sexes grouped. Sex ratios were male-biased in all species and deviated from an ideal 1:1 sex ratio. Applying the von Bertalanffy function growth coefficient, reasonable growth (K = 0.890 year−1) was estimated for Sillago sihama, whereas this was slower in S. attenuata (0.24 year−1). Goodness of fit range was Rn = 0.32–1.0. This study provides a new reference for LWRs in three of the species (S. arabica, S. attenuata, and S. chondropus), with a new maximum total length for S. indica to add to FishBase. The data presented here on the five sillaginid species can be useful for local management and conservation of these species.