Life history characteristics of the silky shark Carcharhinus falciformis from the central west Pacific

2018 ◽  
Vol 69 (4) ◽  
pp. 562 ◽  
Author(s):  
Michael I. Grant ◽  
Jonathan J. Smart ◽  
William T. White ◽  
Andrew Chin ◽  
Leontine Baje ◽  
...  
Keyword(s):  
Life History ◽  
Growth Parameters ◽  
Growth Models ◽  
Significant Risk ◽  
Growth Parameter ◽  
Parameter Estimates ◽  
West Pacific ◽  
Average Litter Size ◽  
Silky Shark ◽  
Carcharhinus Falciformis

In the central west Pacific region, silky sharks (Carcharhinus falciformis) are commonly taken in fisheries, forming up to 95% of incidental elasmobranch bycatch. The present study examined the life history of silky sharks (n=553) from Papua New Guinean waters. Age was analysed using sectioned vertebrae, and a multimodel approach was applied to the length-at-age data to fit growth models. Females ranged in length from 65.0- to 253.0-cm total length (TL), with the oldest estimated at 28 years. Males ranged in length from 68.4 to 271.3cm TL and were aged to a maximum of 23 years. The logistic model provided the best fitting growth parameter estimates of length at birth L0=82.7cm TL, growth coefficient g=0.14year–1 and asymptotic length L∞=261.3cm TL for the sexes combined. Females reached sexual maturity at 204cm TL and 14.0 years, whereas males reached maturity at 183cm TL and 11.6 years. The average litter size from 28 pregnant females was 8 (range of 3–13). The growth parameters and late ages of sexual maturation for silky sharks in the central west Pacific suggest a significant risk from fisheries exploitation without careful population management.

scholarly journals Growth Parameters and Spawning Season Estimation of Four Important Flyingfishes in the Kuroshio Current Off Taiwan and Implications From Comparisons With Global Studies

2022 ◽  
Vol 8 ◽  
Author(s):  
Shui-Kai Chang ◽  
Tzu-Lun Yuan ◽  
Simon D. Hoyle ◽  
Jessica H. Farley ◽  
Jen-Chieh Shiao
Keyword(s):  
Growth Parameters ◽  
Growth Models ◽  
Growth Parameter ◽  
Optimal Growth ◽  
Kuroshio Current ◽  
Parameter Estimates ◽  
Special Importance ◽  
Von Bertalanffy ◽  
Multiple Model ◽  
The Kuroshio

Growth shapes the life history of fishes. Establishing appropriate aging procedures and selecting representative growth models are important steps in developing stock assessments. Flyingfishes (Exocoetidae) have ecological, economic, and cultural importance to many coastal countries including Taiwan. There are 29 species of flyingfishes found in the Kuroshio Current off Taiwan and adjacent waters, comprising 56% of the flyingfishes taxa recorded worldwide. Among the six dominant species in Taiwan, four are of special importance. This study reviews aging data of these four species, documents major points of the aging methods to address three aging issues identified in the literature, and applies multi-model inference to estimate sex-combined and sex-specific growth parameters for each species. The candidate growth models examined included von Bertalanffy, Gompertz, Logistic, and Richards models, and the resulting optimal model tended to be the von Bertalanffy model for sex-combined data and Gompertz and von Bertalanffy models for sex-specific cases. The study also estimates hatch dates from size data collected from 2008 to 2017; the results suggest that the four flyingfishes have two spawning seasons per year. Length-weight relationships are also estimated for each species. Finally, the study combines the optimal growth estimates from this study with estimates for all flyingfishes published globally, and statistically classifies the estimates into clusters by hierarchical clustering analysis of logged growth parameters. The results demonstrate that aging materials substantially affect growth parameter estimates. This is the first study to estimate growth parameters of flyingfishes with multiple model consideration. This study provides advice for aging flyingfishes based on the three aging issues and the classification analysis, including a recommendation of using the asterisci for aging flyingfishes to avoid complex otolith processing procedures, which could help researchers from coastal countries to obtain accurate growth parameters for many flyingfishes.

scholarly journals Intraspecific demography of the silky shark (Carcharhinus falciformis): implications for fisheries management

2019 ◽  
Author(s):  
Michael I Grant ◽  
Jonathan J Smart ◽  
Cassandra L Rigby ◽  
William T White ◽  
Andrew Chin ◽  
...  
Keyword(s):  
Life History ◽  
Fisheries Management ◽  
Life Stage ◽  
Leslie Matrix ◽  
Parameter Estimates ◽  
Shark Species ◽  
Life History Parameter ◽  
Silky Shark ◽  
Carcharhinus Falciformis ◽  
Management Approaches

Abstract The silky shark (Carcharhinus falciformis) is one of the most heavily fished tropical shark species globally, and currently there is increasing concern for its conservation status. However, large differences and ambiguity in life history parameter estimates among regions complicates its conservation and fisheries management. Using a Leslie matrix model that incorporated stochastic effects, we analysed the intraspecific demography of C. falciformis using available life history data from seven regions. Among regions, large differences were observed in generation time and age-specific reproductive contributions. Carcharhinus falciformis generally had low resilience to fishing mortality (F) throughout its distribution. Age-at-first-capture and age-at-last-capture management approaches resulted in substantial differences among regions. This was largely influenced by age-at-maturity. However, in scrutinizing some regional life history studies, it is likely that sampling design and methodological differences among regions have resulted in inaccuracies in life history parameter estimates and subsequent demographic attributes. This implies that age and life-stage-dependent management approaches using these possibly inaccurate life history parameters may be inappropriate. We suggest that a greater emphasis needs to be placed on eliminating human sources of error in elasmobranch life history studies to ensure management for wide-ranging species, such as C. falciformis, is most effective.

scholarly journals Modeling the Lag Time of Listeria monocytogenes from Viable Count Enumeration and Optical Density Data

2002 ◽  
Vol 68 (12) ◽  
pp. 5816-5825 ◽  
Author(s):  
F. Baty ◽  
J. P. Flandrois ◽  
M. L. Delignette-Muller
Keyword(s):  
Listeria Monocytogenes ◽  
Optical Density ◽  
Growth Parameters ◽  
Growth Models ◽  
Growth Parameter ◽  
Viable Count ◽  
Linear Increase ◽  
Lag Phase ◽  
Parameter Estimates ◽  
Phase Duration

ABSTRACT The following two factors significantly influence estimates of the maximum specific growth rate (μmax) and the lag-phase duration (λ): (i) the technique used to monitor bacterial growth and (ii) the model fitted to estimate parameters. In this study, nine strains of Listeria monocytogenes were monitored simultaneously by optical density (OD) analysis and by viable count enumeration (VCE) analysis. Four usual growth models were fitted to our data, and estimates of growth parameters were compared from one model to another and from one monitoring technique to another. Our results show that growth parameter estimates depended on the model used to fit data, whereas there were no systematic variations in the estimates of μmax and λ when the estimates were based on OD data instead of VCE data. By studying the evolution of OD and VCE simultaneously, we found that while log OD/VCE remained constant for some of our experiments, a visible linear increase occurred during the lag phase for other experiments. We developed a global model that fits both OD and VCE data. This model enabled us to detect for some of our strains an increase in OD during the lag phase. If not taken into account, this phenomenon may lead to an underestimate of λ.

Validated age, growth and reproductive biology of Carcharhinus melanopterus, a widely distributed and exploited reef shark

2013 ◽  
Vol 64 (10) ◽  
pp. 965 ◽  
Author(s):  
Andrew Chin ◽  
Colin Simpfendorfer ◽  
Andrew Tobin ◽  
Michelle Heupel
Keyword(s):  
Life History ◽  
Logistic Model ◽  
Growth Models ◽  
Growth Parameter ◽  
Information Criterion ◽  
Age And Growth ◽  
Parameter Estimates ◽  
Eastern Australia ◽  
Reef Sharks ◽  
Carcharhinus Melanopterus

Inadequate life-history information can compromise management of shark populations. The present study examined the life history of blacktip reef sharks (Carcharhinus melanopterus) from north-eastern Australia with predictions that they would show life-history patterns similar to those of other reef sharks species. Age and growth estimates were derived from vertebrae and five growth models. Males were 543–1390 mm total length (LST) and females were 514–1600 mm LST. Longevity was 10 years (males) and 15 years (females). Chemical marking confirmed annual band pair deposition but indicated probable age underestimation of large individuals. The logistic model was preferred (second-order Akaike information criterion (AICc) weight 0.7536), with growth parameter estimates of length at birth (L0) = 617 mm LST; asymptotic length (L∞) = 1585 mm LST; k (from logistic model) = 0.251 year–1. Males matured at 4.2 years (1050 mm LST) and females at 8.5 years (1335 mm LST), although further verification is needed. Mating and parturition occurred in summer and autumn, females having three or four pups per litter. Data were inconclusive in determining reproductive periodicity. These data contribute to the species management and conservation and suggest that the species may be sensitive to fishing pressure and habitat loss. The study also demonstrated potential complications in using vertebrae to estimate age and growth of chondrichthyan fishes.

scholarly journals 690Growth in childhood and age at menarche: Insights from individual trajectory modelling

2021 ◽  
Vol 50 (Supplement_1) ◽  
Author(s):  
Lynne Giles ◽  
Melissa Whitrow ◽  
Alice Rumbold ◽  
Michael Davies ◽  
Vivienne Moore
Keyword(s):  
Random Effects ◽  
Growth Parameters ◽  
Growth Parameter ◽  
Hazard Ratio ◽  
Age At Menarche ◽  
Parameter Estimates ◽  
Early Puberty ◽  
Random Effects Models ◽  
Childhood Growth ◽  
Menstrual History

Abstract Background The relationship between patterns of weight gain across childhood and the onset of puberty remains unclear. We aimed to derive growth parameters (size, tempo, and velocity) from models of weight across childhood and to estimate their effects on age at menarche. Methods Serial height and weight measurements from birth to age 9.5 years for 557 children who took part in the Generation 1 cohort study were used, along with girls’ menstrual history at age 12-13 years. Shape invariant random effects models were fit to log(weight+1) for all available participants’ data (282 girls, 260 boys), and AIC used to identify the best-fitting model. In time-to-event models subsequently fit to the girls’ data to estimate effects of the growth parameters on menarcheal age, a censoring age of 12 years was used to define early puberty. Results A model with 4df and fixed and random effects for size and tempo and a fixed effect for velocity was preferred. Some 19% of girls began menstruating before age 12 years. Size and tempo were each associated with an increased hazard of earlier menarche; a 0.1 unit gain in size was associated with a hazard ratio of 1.75 (95%CI 1.32–2.33), and a 0.1 unit gain in tempo with a hazard ratio of 7.84 (95%CI 3.41–18.05). Conclusions Using all participants’ data gave more precise growth parameter estimates. Key messages Understanding mechanisms that drive increased size and tempo of childhood growth may help to elucidate the links between obesity and girls’ risk of early puberty.

Effects of intrapopulation variability on von Bertalanffy growth parameter estimates from equal mark–recapture intervals

1997 ◽  
Vol 54 (9) ◽  
pp. 2025-2032
Author(s):  
E B Smith ◽  
F M Williams ◽  
C R Fisher
Keyword(s):  
Growth Parameters ◽  
Growth Parameter ◽  
Parameter Estimates ◽  
Growth Equation ◽  
Size Distributions ◽  
Von Bertalanffy ◽  
Initial Size ◽  
Estimation Errors ◽  
Mark Recapture ◽  
Intrapopulation Variability

The effects of intrapopulation variability on the parameter estimates of the von Bertalanffy growth equation have received discussion in the literature. Here we evaluated the effects of intrapopulation variability, using computer simulations, on four commonly used methods for estimating the von Bertalanffy growth parameters: the Ford-Walford plot, Ricker's method, Bayley's method, and Fabens' method. Intrapopulation variability in growth rates (k) and maximum sizes ( L infinity ) plus initial size distributions and measurement error, were tested for their effects on the accuracy of the parameter estimates using simulated mark-recapture data with equal recapture intervals. Fabens' method and a modified Ford-Walford plot provided the most accurate estimates in all cases, but when intrapopulation variability was large, they performed poorly. With moderate intrapopulation variability, the bias in estimates was small although between-sample variance was quite large. Biased initial size distributions without either small or large size classes cause a magnification of the estimation errors. Without knowledge of the degree of intrapopulation variability in a natural population, large errors of unknown magnitude in parameter estimation can result, and care should be taken when interpreting these estimates. However, if this variability can be quantified, then approximate parameter estimate errors can be obtained.

scholarly journals Estimating growth parameters and growth variability from length frequency data using hierarchical mixture models

2019 ◽  
Vol 76 (7) ◽  
pp. 2150-2163
Author(s):  
Luke Batts ◽  
Cóilín Minto ◽  
Hans Gerritsen ◽  
Deirdre Brophy
Keyword(s):  
Mixture Models ◽  
Growth Parameters ◽  
Growth Parameter ◽  
Melanogrammus Aeglefinus ◽  
Parameter Estimates ◽  
Frequency Data ◽  
Length Frequency ◽  
Frequency Distributions ◽  
Growth Variability ◽  
Length Frequency Data

Abstract Analysis of length frequency distributions from surveys is one well-known method for obtaining growth parameter estimates where direct age estimates are not available. We present a likelihood-based procedure that uses mixture models and the expectation–maximization algorithm to estimate growth parameters from length frequency data (LFEM). A basic LFEM model estimates a single set of growth parameters that produce one set of component means and standard deviations that best fits length frequency distributions over all years and surveys. The hierarchical extension incorporates bivariate random effects into the model. A hierarchical framework enables inter-annual or inter-cohort variation in some of the growth parameters to be modelled, thereby accommodating some of the natural variation that occurs in fish growth. Testing on two fish species, haddock (Melanogrammus aeglefinus) and white-bellied anglerfish (Lophius piscatorius), we were able to obtain reasonable estimates of growth parameters, as well as successfully model growth variability. Estimated growth parameters showed some sensitivity to the starting values and occasionally failed to converge on biologically realistic values. This was dealt with through model selection and was partly addressed by the addition of the hierarchical extension.

Quantifying the Growth of Female Pacific Hake (Merluccius productus): An Example of Measuring Uncertainty and Bias in Non-linear Parameter Estimation

1990 ◽  
Vol 47 (4) ◽  
pp. 672-681 ◽  
Author(s):  
David W. Welch ◽  
Gordon A. McFarlane
Keyword(s):  
Growth Parameters ◽  
Growth Models ◽  
Nonlinear Models ◽  
Somatic Growth ◽  
Maximum Size ◽  
Diagnostic Methods ◽  
Parameter Estimates ◽  
Intrinsic Variability ◽  
Merluccius Productus ◽  
Size At Age

Estimates of size-at-age are commonly reported in fisheries studies, but statistical uncertainty and intrinsic variability in the growth parameters are less frequently examined. We examine these questions using recently-developed statistical methods for quantifying uncertainty and bias in parameter estimates for nonlinear models with independent and additive Gaussian errors. We also describe diagnostic methods to determine when the usual method for examining parameter uncertainty, linearization, is unacceptable. Both our review and our approach to uncertainty are generally applicable to nonlinear estimation, and not solely restricted to growth models. We illustrate our approach with length-at-age data for female Pacific hake (Merluccius productus) from Georgia Strait, British Columbia. Between-year variation in somatic growth seems to be restricted to the two von Bertalanffy growth parameters K and L∞. Mean asymptotic length declined by about 10% since the late 1970's while the parameter K nearly tripled in value. Closer examination showed that the decline in somatic growth was restricted to the maximum size attained. We argue that the changes are most consistent with selective removal of the largest individuals from the population by the fishery, rather than a response of growth rates to either environmental or density-dependent factors.

A Bayesian approach for overcoming inconsistencies in mortality estimates using, as an example, data for Acanthopagrus latus

2004 ◽  
Vol 61 (7) ◽  
pp. 1202-1211 ◽  
Author(s):  
Norman G Hall ◽  
S Alex Hesp ◽  
Ian C Potter
Keyword(s):  
Life History ◽  
Bayesian Approach ◽  
Growth Parameters ◽  
Probability Distributions ◽  
Total Mortality ◽  
Growth Parameter ◽  
Life History Parameters ◽  
Acanthopagrus Latus ◽  
Marine Embayment ◽  
Mortality Estimates

Reliable estimates of natural (M) and total mortality (Z) are essential for effective fisheries management. However, estimates of M, which are frequently determined from life history parameters, are imprecise and often inconsistent with the values of Z derived from life history parameters and other analyses. This is exemplified by the mortality estimates derived for Acanthopagrus latus in a large marine embayment. Thus, such estimates, calculated for M for this population from a growth parameter and from growth parameters and water temperature, were both 0.70·year–1, whereas those for Z, calculated from maximum recorded age, relative abundance analysis, and a simulation based on maximum age and sample size, ranged from 0.18 to 0.30·year–1. These results are clearly inconsistent. A Bayesian approach was therefore developed that combines the posterior probability distributions of the various mortality estimates and thereby produces integrated and consistent estimates for M and Z. The application of our Bayesian approach to the data for A. latus yielded lower values for M than for Z. Our approach is equally applicable to other fish species.

Sign in / Sign up

Export Citation Format

Share Document