Bertalanffy Growth Research Articles

Population Growth Model and Mortality of Pakistan Lobster (Panulirus polyphagus) in Estuary Waters of Tarakan City

Lobster Panulirus polyphagus has a fairly high economic value and is found in the estuary waters of Tarakan City. This research aims to study the growth and mortality model of Lobster P. polyphagus originating in the estuary waters of Tarakan City. The research method was carried out using a quantitative descriptive method. Sampling was conducted 14 times from December 2021-May 2022 using gill nets. The results showed that the male sex ratio was more than the female. Allometric growth of males and females is negative allometric with a thin body shape. The structure of the size obtained was mostly in males ranging from 18.3-20.6 cm, and females around 20.5-22.2 cm. The maximum length growth of P. polyphagus based on von Bertalanffy's growth model was 31.519 cm in males and 31.374 cm in females. The total mortality (Z) of P. polyphagus for males and females was 1.104 and 1.119; catch mortality (F) of 0.106 and 0.253; natural mortality (M) of 0.998 and 0.866; exploitation rate (E) of 0.096 and 0.226, respectively. The high natural mortality causes the extinction of the Lobster species, so good management is needed so that it is sustainable.

GROWTH DESCRIPTION OF PURE AND CROSSBRED TURKEYS USING NON-LINEAR MODELS IN HOT AND HUMID TROPICAL ENVIRONMENT

This study was conducted to compare three non-linear growth models (Logistics, Gompertz and Von Bertalanffy) in describing the growth of 360 turkeys of three genotypes (exotic, crossbred and local). The growth curve parameters - A, B and K for each growth model were estimated for each turkey using the NLIN procedure (Marquart algorithm) for the Bayesian approach with a fixed-effect model. The best fit of the three models was also estimated. A comparison was done among the three models using Akaike Information Criteria (AIC) and the Bayesian Information Criteria (BIC). Pearson product-moment correlation coefficient (r), the correlation coefficient, was used to examine the linear relationship between two quantities, A and K growth model parameters. For comparison of growth models parameter predicted, the Von Bertalanffy's model predicted the smallest value in both criteria for all the male and local female turkeys, while Gompertz's growth model had the smallest predicted value in both criteria for the female exotic and female crossbred turkeys. Based on the goodness of fit using the Bayesian Model Choice Criteria (Deviance Information Criteria), Von Bertalanffy's growth model showed the best fit. However, the difference between Bertalanffy's and Gompertz's growth models is very minimal, thus, making both models suitable for modeling the growth curve of domestic turkey and to consider how this weight is attained.

Population dynamics and feeding habit of Oreochromis niloticus and O. mossambicus in Siombak Tropical Coastal Lake, North Sumatra, Indonesia

Abstract. Muhtadi A, Nur M, Latuconsina H, Hidayat T. 2021. Population dynamics and feeding habit of Oreochromis niloticus and O. mossambicus in Siombak Tropical Coastal Lake, North Sumatra, Indonesia. Biodiversitas 23: 151-159. Nile Tilapia (Oreochromis niloticus) and O. mossambicus (Mozambique Tilapia) are economically important fish species in Indonesia. This study aims to determine these two fish species' population dynamics, including growth, reproduction, recruitment, mortality rates, exploitation rates, and feeding habits. Samples were taken from September 2018 to August 2019 in Siombak Lake, North Sumatra Province. Data were analyzed in this study using software FISAT-II and Microsoft Excel. The results showed that Nile Tilapia had an isomeric growth pattern, and Mozambique Tilapia exhibited a negative allometric growth pattern. The estimate von Bertalanffy's growth parameters on ELEFAN-I were asymptotic length (L?) of Nile tilapia: 36.06 cm and Mozambique tilapia: 26.09 cm. The growth coefficient (K) of Nile tilapia was 0.59, and Mozambique tilapia was 0.54. The mortality rate (Z) of Nile tilapia reached 3.20 per year, and Mozambique tilapia reached 3.04 per year, whereas the natural mortality (M) of Nile Tilapia 1.24 while Mozambique Tilapia was 1.27. Based on the rate of exploitation, both fish have been overexploited. Peak spawning of Nile Tilapia was in August and December, and of Mozambique Tilapia was in March and June. Both species were omnivores, predominantly with herbivorous feeding habits.

Assessment of the biological reference point F0.1 of Greater Forkbeard, in the bay of Mostaganem west Algeria

The Biological Reference Points are values of the level of fishing mortality or of the biomass of the stock which seek a long-term sustainable exploitation of the stocks, with the best possible catch. Von Bertalanffy's growth parameters: L∞ = 39.64 (cm), K = 0.36 (year-1), t0 = -0.22 (year), W∞ = 454.85 (g), and the monthly monitoring of size frequencies, allowed to identify the size of first sexual maturity L50, total mortality (Z = 2.11), natural mortality (M = 0.57) and fishing mortality (F = 1.54), all these values were evaluated in the objective to estimate the biological reference points. The assessment was performed using length cohort analysis (LCA) and biomass and yield per recruit’s analyses as implemented in VIT4Win software, the program reconstructs the population using mortality vectors and the production per recruit analysis is based on fishing mortality (F). The values of mortality determined seem concentrated on individuals with a size between 22 and 26 cm Lt, Maximum Sustainable Yield MSY 43.25g,the total balanced biomass was estimated at 3.84 t and the yield per recruit analysis (Y/R = 27.87 g) based on current fishing effort showed that the stock is at its minimum operating limit.

Growth patterns of the pan-European freshwater mussel, Anodonta anatina (Linnaeus, 1758) (Bivalvia: Unionidae), vary with sex and mortality in populations.

Post‐maturation growth leading to indeterminate growth patterns is widespread in nature. However, its adaptive value is unclear. Life history theory suggests this allocation strategy may be favored by temporal pulses in the intensity of mortality and/or the capacity to produce new tissues.Addressing the origin of indeterminate growth and the variability of growth patterns, we studied the growth of duck mussels, Anodonta anatina, a pan‐European unionid, in 18 Polish lakes. For each population, the sex, size, and age of collected mussels were measured to estimate Bertalanffy's growth curve parameters. We integrated information on A. anatina mortality rates, lake trophy, biofouling by zebra mussels, Dreissena polymorpha, and the prevalence of parasitic trematode larvae to identify selective conditions in lakes.We found two sources of mortality in A. anatina populations, pertaining to adverse effects of zebra mussel biofouling and trophy state on mussel survival. Additionally, populations with heavier biofouling presented a smaller abundance of parasites, indicative of a relationship between filtering intensity and contraction of water‐borne trematode larvae by filtering A. anatina.Consistently for each sex, populations with a greater trophy‐related mortality were characterized in A. anatina by a smaller asymptotic size Lmax, indicative of a life history response to mortality risk involving early maturation at a smaller body size. In all populations, females featured higher mortality and larger asymptotic size versus males.Our findings support a theoretical view that adaptive responses to selection involve adjustments in the lifetime resource allocation patterns. These adjustments should be considered drivers of the origin of indeterminate growth strategy in species taking parental care by offspring brooding in body cavities.

Variability of Sea Water Temperature and Its Implication on Cakalang Fish Capture (Katsuwonus pelamis L) in Manokwari Waters, West Papua

The presence of skipjack fish resources in a fishing area is related to the suitability of the environmental conditions of the waters. This study aims to examine the relationship of sea surface temperature (SPL) to skipjack catches and the characteristics of skipjack catches in Manokwari waters. Data, both catch data and sea surface temperature data, are collected through field surveys by following fishing operations. Furthermore, the data were analyzed descriptively using graphs and mathematically like von Bertalanffy's growth model. The results of this study found that the very small variability of SPL could not explain the variation in the volume of fishermen's catches in Manokwari waters. However, a high SST during the May - August 2013 period is thought to affect the size of the skipjack caught, where the average size of the fish caught inhabited areas near sea level. In addition, the growth of skipjack fish in Manokwari waters is relatively fast with a growth coefficient of 0.42 per year1 and natural mortality between 0.79 per year and 0.81 per year.

Some Growth Parameters of Five Fish Species in the Lower Sakarya River, Turkey

In this study, a total of 1283 samples of five fish species belonging to two families, Cyprinidae and Leuciscidae, were collected from the Lower Sakarya River between June 2017 and May 2018 in order to determine some growth parameters.The samples were collected monthly with trammel net, fykenets, and electro shocker. The age of the fish was determined from the scales. The von Bertalanffy's growth model was calculated Lt = 92.18(1-e-0.054(t+0.040)) for A. brama, Lt = 69.40(1-e-0.040(t+0.030)) for B. bjoerkna, Lt = 51.09(1-e-0.114(t+0.024)) for C. gibelio, Lt = 48.11(1-e-0.088(t+0.023)) for R. rutilus and Lt = 41.74(1-e-0.104(t+0.035)) for V. vimba. The phi-prime growth performance index (Φ') value was computed as 2.628, 2.268, 2.474, 2.307 and 2.260 for A. brama, B. bjoerkna, C. gibelio, R. rutilus and V. vimba, respectively. This study provides basic information on some growth parameters of five fish species living in the Lower Sakarya River. The results of this study are useful for fishery managements and stock assessment in the Sakarya River.

A spatiotemporal Richards–Schnute growth model and its estimation when data are collected through length-stratified sampling

We propose a spatiotemporal generalized von Bertalanffy (vonB) growth model that also includes between-individual (BI) variation and male/female correlation. The generalized vonB model includes the effect of maturation on growth. The model and the methodology are applied to a long time-series of survey observations of age and length for American plaice on the Grand Bank off the northeast coast of Canada. The bias in age-length data due to size selectivity of the survey gear is accounted for. The survey design includes length-stratified age sampling which is a type of response selective sampling design for growth model estimation. We propose and implement a conditional empirical proportion likelihood approach for these data. Neglecting this sampling scheme can lead to seriously biased estimation results. We found that a 6-parameter growth model is necessary for capturing the biphasic growth patterns of the American plaice on the Grand Bank, and the survey gear selectivity and BI variation are important for a good model fit. We proposed an empirically optimal BI variation model for this data. Our estimation results indicate that there are substantial differences in size-at-age for male and female American plaice, and this changes over time and between regions.

Modeling and comparison of the maturing rates of Damara, Dorper and Swakara sheep at Neudamm Farm

Although sheep play an important role in the Namibian livestock industry, there is a paucity of information on their production performance. The objective of the study was to compare the mature weights, and maturing rates for Damara, Dorper and Swakara sheep reared at Neudamm Farm. Four hundred and eight (408) sheep (84 Swakara, 296 Damara and 28 Dorper) were weighed monthly for 6 months. The Brody, Van Bertalanffy, Gompertz and logistic growth models were fitted to the data to determine the mature size and maturing rate. Based on the R2 and the BIC, the Brody growth function gave the best fit. The estimated mature weights for Damara, Dorper and Swakara sheep were 46.8±1.1 kg, 53.9±1.0 kg and 48.8±1.1 kg, respectively, with the corresponding maturing rates of 0.0037±0.0001, 0.0025±0.0003 and 0.0021±0.0001 kg/day. Although the Damara sheep have a smaller size compared to Dorper sheep, they mature faster, making them a better breed for mutton production. The Dorper had the largest mature sizes, although their rate of maturation was lower than the Damara sheep.

Mercury accumulation from food decreases collembolans' growth

In the terrestrial environment, mercury (Hg) contamination can be originated from different inorganic and metal-organic sources, redistributed and transformed in soils. In the present study, the effects of contaminated food with environmentally relevant concentrations of Hg were evaluated in the soil-dwelling invertebrate Folsomia candida. Changes in growth rate and Hg bioaccumulation levels were observed at different concentrations of Hg in food, which can be complementary for data already available for reproduction and survival from standardized protocols. Collembolan growth was recorded every two days, and their growth rate along with a Von Bertalanffy's growth curve were derived showing that growth was dependent on Hg food concentration. Also, the final length of animals reflected the Hg concentration in food, with differences in all treatments comparing to non-exposed organisms. Toxicokinetic patterns from different Hg concentrations in food were not significantly different during the uptake phase, but differences were found in the depuration phase. Combining the two approaches, collembolans seem to invest their energy for depuration processes, neglecting other vital processes, such as growth. Also, contaminated food avoidance possibly occurred, thus decreasing their feeding and contaminant intake. Therefore, growth tests in collembolans can act as complementary tools to bioaccumulation and reproductive assays, towards a mechanistic understanding of how organisms use their energy upon contamination. Changes in growth rate, even at low and environmentally relevant concentrations, could be a warning signal when occurring in species with key roles in ecosystems. Also, this study highlights the importance of these complementary tests for a better and complete approach to risk assessment studies.

PERTUMBUHAN, UMUR, DAN DIMORFISME SEKSUAL IKAN PELANGI ARFAK, Melanotaenia arfakensis Allen, 1990 DI SISTEM SUNGAI PRAFI, MANOKWARI, PAPUA BARAT

ABSTRACTArfak rainbow fish, Melanotaenia arfakensis is an endemic fish on several river systems in the northeastern part of the Vogelkop peninsula. This study aims to describe the growth, age at first maturity, and sexual dimorphism of this endemic fish on the Nimbai Stream and the Aimasi Stream, the Prafi River system. The fish were caught using handnet, then were measured their standard length and individual weight. Data were analyzed to estimated growth patterns, von Bertalanffy's growth rate, age at first maturity and sexual dimorphism characteristics. The results showed that male growth patterns varied, with a tendency of the increase in body length faster than that of body weight (negative allometric patterns) with b values ranging from 2.886 to 3.132. On the other hand, the female individuals had positive allometric patterns (b values ranged from 3.062 to 3.378). The growth rate (K) of male body length was faster (0.165-0.174) than that of female individuals (0.159-0.163). Male individuals reached the first maturity condition earlier (at age of 1.83-2.18 years) than female individuals (at age of 2.49-2.64 years). Sexual characteristics between the sexes are related to body height starting to appear when fish are of a standard length of larger than 18.22 mm or when male fish begin to approach the time of the first sexual maturity. Understanding of growth, age, and the characteristics of the sexual dimorphism of endemic fish has an important meaning in monitoring population conditions and for conservation efforts in their natural habitat.

Calendar and thermal time-based growth models for common carp and pikeperch, and the influence of stocking strategy in Lake Balaton, Hungary

Common carp Cyprinus carpio and pikeperch Sander lucioperca are widely distributed and economically important freshwater fishes. Because these species are extensively stocked both within and outside of their native ranges, it is important to assess the effect of these actions. We aimed to analyse growth rate and its variability related to stocking strategy (season × lake area × habitat × fish size) in common carp and pikeperch in Lake Balaton (Hungary), based on cooperative tagging experiments with anglers. In both species, length increment was more closely associated with thermal time (degree-day sum) over 8 °C threshold water temperature than calendar time. Except a marked decrease with increasing fish size, stocking parameters had little effect on length increment. Growth models based on the GROTAG method and the von Bertalanffy's asymptotic length (L∞) and growth rate (K) are provided. Compared to other habitats, estimated growth rate proved to be high in common carp (128 mm year−1 at 300 mm standard length) and modest in pikeperch (61 mm year−1 at 250 mm standard length). We concluded that stocking rate even might be increased in common carp, while management of the pikeperch population should rather be based on catch restriction measures than intensified stockings.

Introducing delay dynamics to Bertalanffy's spherical tumour growth model

We introduce delay dynamics to an ordinary differential equation model of tumour growth based upon von Bertalanffy's growth model, a model which has received little attention in comparison to other models, such as Gompertz, Greenspan and logistic models. Using existing, previously published data sets we show that our delay model can perform better than delay models based on a Gompertz, Greenspan or logistic formulation. We look for replication of the oscillatory behaviour in the data, as well as a low error value (via a Least-Squares approach) when comparing. We provide the necessary analysis to show that a unique, continuous, solution exists for our model equation and consider the qualitative behaviour of a solution near a point of equilibrium.

Von Bertalanffy's dynamics under a polynomial correction: Allee effect and big bang bifurcation

In this work we consider new one-dimensional populational discrete dynamical systems in which the growth of the population is described by a family of von Bertalanffy's functions, as a dynamical approach to von Bertalanffy's growth equation. The purpose of introducing Allee effect in those models is satisfied under a correction factor of polynomial type. We study classes of von Bertalanffy's functions with different types of Allee effect: strong and weak Allee's functions. Dependent on the variation of four parameters, von Bertalanffy's functions also includes another class of important functions: functions with no Allee effect. The complex bifurcation structures of these von Bertalanffy's functions is investigated in detail. We verified that this family of functions has particular bifurcation structures: the big bang bifurcation of the so-called “box-within-a-box” type. The big bang bifurcation is associated to the asymptotic weight or carrying capacity. This work is a contribution to the study of the big bang bifurcation analysis for continuous maps and their relationship with explosion birth and extinction phenomena.

동대만 잘피밭에 서식하는 실비늘치(Aulichthys japonicus)의 성장과 생산량

실비늘치(6.70~5.32 cm TL)의 성장과 생산량에 대한 연구는 동대만 잘피밭에서 2006년도에 실시하였다. 실비늘치 시료는 소형 빔트롤에 의해서 총 888개체가 채집되었다. Bertalanffy 성장식을 이용하여 구한 전장의 성장식은 <TEX>$L_t=24.8257(1-e^{-0.5583(t+0.4816)})$</TEX>이었다. 실비늘치의 밀도, 생체량, 일일생산량, 연간생산량, 그리고 P/B ratio는 각각 <TEX>$0.01{\pm}0.009/m^2$</TEX>, <TEX>$0.17{\pm}0.16g/m^2$</TEX>, <TEX>$0.00006{\pm}0.00006g$</TEX> AFDW/<TEX>$m^2$</TEX>/day, 0.02g AFDW/<TEX>$m^2$</TEX>/yr, 그리고 0.12이었다. 실비늘치 생산량의 월변화는 컸으며, 7월(0.000182g AFDW/<TEX>$m^2$</TEX>/day), 9월(0.000127g AFDW/<TEX>$m^2$</TEX>/day) 그리고 11월(0.000123g AFDW/<TEX>$m^2$</TEX>/day)에 높았으며, 4월과 5월(0.000003g AFDW/<TEX>$m^2$</TEX>/day)에 가장 낮았다. 실비늘치의 생산량의 월변화는 개체수와 생체량, 그리고 성장률과 양의 상관관계를 보였다. The growth and production of Aulichthys japonicus (6.70~15.32 cm TL) were investigated in an eelgrass bed of Dongdae Bay, Korea throughout 2006. A total 888 A. japonicus were collected with a small beam trawl. Growth in fish total length was expressed by the von Bertalanffy's growth equation as: <TEX>$L_t=24.8257(1-e^{-0.5583(t+0.4816)})$</TEX>. The densities, biomass, daily, annual production, and P/B ratio were <TEX>$0.01{\pm}0.009/m^{-2}$</TEX>, <TEX>$0.17{\pm}0.16g/m^2$</TEX>, <TEX>$0.00006{\pm}0.00006g$</TEX> AFDW/<TEX>$m^2$</TEX>/day, 0.02g AFDW/<TEX>$m^2$</TEX>/yr, and 0.12, respectively. Monthly variation in production of A. japonicus was large; the peak occurred at July, September and November 2006 (0.000182, 0.000127 and 0.000123 g AFDW/<TEX>$m^2$</TEX>/day), where as the lowest value was 0.000003g AFDW/<TEX>$m^2$</TEX>/day at April and May 2006. Monthly change in production of A. japonicus was positive correlated with number of individuals, biomass and growth rate.

Age, body size and growth pattern of Argenteohyla siemersi pederseni (Anura: Hylidae) in northeastern Argentina

In this study we analysed the body size, age structure, age at maturity, longevity and growth pattern of Argenteohyla siemersi pederseni in north-eastern Argentina using skeletochronological methods. Body size was sexually dimorphic; females were significantly larger and heavier than males, regardless of age. As A. s. pederseni is an explosive breeder with only one reproductive episode per year, we assumed that each Line of Arrested Growth (LAG) observed was equivalent to one period of decreasing growth, LAGs reflecting a direct estimation of individual age. The minimum number of LAGs counted was two for males and three for females, but there was no sexual difference in longevity. The von Bertalanffy's growth coefficients (K) were higher in males than in females for both size and body mass. Females had a lower growth rate than males, took longer to reach the minimum maturation size, and were older and larger at reproduction.

Darkedge midshipman &lt;i&gt;Porichthys analis&lt;/i&gt; (Batrachoidiformes: Batrachoididae), a common shrimp-bycatch fish from the Gulf of California

Shrimp fishery bycatch of the Gulf of California constitutes a wide variety of highly unknown fish, crustacean, and mollusk species with very low or null economic value, in contrast to those of commercial interest. However, there are no studies yet on the role of these low economic valued species have in the community structure and function, together with their possible effect on commercial populations. With the aim of contributing to the knowledge of Darkedge Midshipman fish Porichthys analis, the most common waste species in this fishery, we estimated some population characteristics. For this purpose, we obtained shrimp-bycatch fish during the 2004-2005 fishing season and performed some research surveys. A total of 1 725 Darkedge Midshipman were captured from 350 bycatch samples. Individual size ranged from 43-352mm SL. The weight to standard length relationship was determined as W=0.000092SL(3.0509). Von Bertalanffy's growth coefficient indicated a moderate growth rate (K=0.5) with an estimated asymptotic length of L(infinity) = 352mm standard length, and a longevity of 6yr. Natural mortality was estimated as 0.97 and total mortality as 4.67. The recruitment pattern, as estimated by ELEFAN II, was extended over the year, peaking during spring and summer seasons. Sexual proportion of male:female was 1.65:1. Mature organisms appeared from August to March, and length at maturity was 157mm SL, which is larger than the mean size at capture 135mm SL. We concluded that the species is indirectly protected by its own bathymetric distribution and the off-shrimping season. This is the first study that considers population characteristics from this common but still unknown species.

Von Bertalanffy's growth dynamics with strong Allee effect

Von Bertalanffy’s model is one of the most popular differential equation used in order to study the increase in average length or weight of fish. However, this model does not include demographic Allee effect. This phenomenon is known in the fisheries literature as “depensation”, which arises when populations decline rapidly at low densities. In this paper we develop and investigate new corrected von Bertalanffy’s models with Allee effects. The generalization that we propose results from considering correction factors, one of rational type and the others of polynomial type, where two parameters are considered. The use of a parameter C > 0 leads the presented generalization, which yields some more flexible models with variable extinction rates. An Allee limit or unstable equilibrium Eu is incorporated so that the models under study have strong Allee effect. We analyze and show the transition from the strong Allee effect to the inexistence of this effect, through by a “weakening” of the Allee effect, depending on the parameters C and Eu. Finally, we discuss the flexibility of corrected von Bertalanffy’s sigmoid growth curves. So, the correspondents inflexion points are variable, i.e., the fish mass when the growth rate is maximum may be varied.

Von Bertalanffy's growth dynamics with strong Allee effect

Von Bertalanffy’s model is one of the most popular differential equation used in order to study the increase in average length or weight of fish. However, this model does not include demographic Allee effect. This phenomenon is known in the fisheries literature as “depensation”, which arises when populations decline rapidly at low densities. In this paper we develop and investigate new corrected von Bertalanffy’s models with Allee effects. The generalization that we propose results from considering correction factors, one of rational type and the others of polynomial type, where two parameters are considered. The use of a parameter C > 0 leads the presented generalization, which yields some more flexible models with variable extinction rates. An Allee limit or unstable equilibrium Eu is incorporated so that the models under study have strong Allee effect. We analyze and show the transition from the strong Allee effect to the inexistence of this effect, through by a “weakening” of the Allee effect, depending on the parameters C and Eu. Finally, we discuss the flexibility of corrected von Bertalanffy’s sigmoid growth curves. So, the correspondents inflexion points are variable, i.e., the fish mass when the growth rate is maximum may be varied.

Comparative rates of growth of the Port Jackson shark throughout its southern Australian range

Port Jackson sharks are distributed throughout southern Australia, with evidence suggesting that potential subpopulations exist. If subpopulations are evident, then phenotypic variation among groups should result in differences in life-history parameters. The present study tested for patterns of spatial variability of life-history parameters among regional Port Jackson shark populations. Rates of growth from Port Jackson sharks caught in the gulf waters of South Australia were calculated on the basis of counts of vertebral increments. Growth parameters were obtained by fitting the length-at-age data to von Bertalanffy and Gompertz growth functions. While the derived growth curves fit the length-at-age data well (r2 ranged from 0.87 to 0.91), parameters showed considerable differences between the two functions, with the von Bertalanffy function providing the more realistic estimates of growth (combined sexes: k = 0.081 year–1, L∞ = 1232 mm total length and t0 = –1.937 years). Life-history parameters for South Australian Port Jackson sharks were collated with the available data for the species, facilitating comparisons among regional populations. Growth curves among populations varied significantly; however, considerable overlap in the length ranges of size at birth and sizes at maturity among populations were evident. Overall, the data presented here do not provide definitive support for the presence of subpopulations across the distribution of the Port Jackson shark, suggesting that molecular analysis maybe required to directly test for structuring.