A new likelihood for simultaneously estimating von Bertalanffy growth parameters, gear selectivity, and natural and fishing mortality

2005 ◽  
Vol 62 (1) ◽  
pp. 215-223 ◽  
Author(s):  
Nathan G Taylor ◽  
Carl J Walters ◽  
Steven J.D. Martell
Keyword(s):  
Growth Parameters ◽  
Fork Length ◽  
Simulated Data ◽  
Data Sets ◽  
Von Bertalanffy ◽  
Fishing Mortality ◽  
Size Selectivity ◽  
Gear Selectivity ◽  
History Of ◽  
Size At Age

Gear selectivity and the cumulative effects of size-selective fishing produce bias in the length-at-age samples used to estimate the von Bertalanffy growth parameters. In fished populations, fast-growing young fish and slow-growing old fish are overrepresented in size–age samples. To account for such effects, we treated size-at-age observations as multinomial samples, with expected catches in each size–age category dependent on growth parameters, growth variation, size selectivity, abundance at age, and the history of exploitation. Using simulated data sets, estimated growth parameters using the multinomial likelihood were unbiased when fishing mortality was not too high and the shape of the vulnerability function was correct. In contrast, estimated growth parameters using a least squares approach overestimated the metabolic growth coefficient (K) and underestimated mean asymptotic length (L∞). Models that do not explicitly account for the effects of fishing and size selectivity underestimated L∞ and overestimated K. We estimate growth parameters for northern pikeminnow (Ptychocheilus oregonensis) as an example of the method and document a stunted "pigmy" population with an L∞ of 175-mm fork length, attributing its small size to effects of high density and (or) a short growing season.

Age, growth and mortality of the garfish, Belone belone (L. 1761) in the Adriatic Sea

2012 ◽  
Vol 93 (2) ◽  
pp. 365-372 ◽  
Author(s):  
Barbara Zorica ◽  
Vanja Čikeš Keč
Keyword(s):  
Adriatic Sea ◽  
Growth Parameters ◽  
Fork Length ◽  
Mortality Rates ◽  
Von Bertalanffy ◽  
Positive Allometry ◽  
Von Bertalanffy Model ◽  
Total Length ◽  
Belone Belone ◽  
Conservation And Management

A sample of 3393 garfish, Belone belone (Linnaeus, 1761) was captured using a seine net between January 2003 and December 2008, along the eastern Adriatic Sea. The range in total length was 20.8–75.4 cm and in weight was 12.21–639.25 g. Length–length equations for converting size measurements (standard length and fork length to total length (TL)) were linear. In the length–weight relationship, positive allometry was established (b = 3.4818). Age, determined from sagittal otoliths, ranged from 1+ to 8+ years. The estimated von Bertalanffy model growth parameters for garfish were L∞ = 90.3 cm, K = 0.158 year−1, t0 = −0.109. Otolith weight was endorsed as a possible age predictor, as it showed highly exponential correlation with total garfish length and age (Wo = 0.0012 TL2.189; Wo = 0.568t1.486). These findings were used to examine mortality rates and exploitation in order to improve conservation and management of this pelagic species.

scholarly journals Age, growth and mortality of the European Seabass, (Dicentrarchus Labrax) in Bardawil lagoon, North Sinai, Egypt

2021 ◽  
pp. 042-046
Author(s):  
El-Desoki Menna O ◽  
Younis Younis M ◽  
A Youssef El-Dakar ◽  
Ahmed Salem M ◽  
Ahmed Kassem S ◽  
...  
Keyword(s):  
Growth Parameters ◽  
Age Groups ◽  
Dicentrarchus Labrax ◽  
Mortality Rates ◽  
Von Bertalanffy ◽  
Fishing Mortality ◽  
European Seabass ◽  
Exploitation Rate ◽  
The Relationship ◽  
North Sinai

Age, growth, and mortality of European Seabass (Dicentrarchus labrax) were studied from a small-scaled fishery of Bardawil lagoon, (North Sinai, Egypt). 181 specimens (16.6 to 35 cm total Length and 39.8 to 367.2 g total weight). The relationship between length and weight was W = 0.0054L3.1428. Age was determined by otoliths and age groups I to IV years were observed. Growths in length and weight at the end of each year were calculated. The growth parameters of von Bertalanffy equation were calculated as (L∞ = 48.69 cm, K = 0.1677 yr -1 and t0 = -0.447 yr -1). Growth performance index was calculated (φ = 2.60 for length and 1.25 for weight). Mortality rates were 0.867 yr-1, 0.25 yr1and 0.617 yr-1 for total, natural and fishing mortality, respectively. The currently exploitation rate E = 0.712 yr-1 indicating that, the population of this species is being heavily exploited.

scholarly journals Population networks from DNA sequences: methodological developments

2017 ◽  
Author(s):  
B. Schaeffer ◽  
V. Nicolas ◽  
F. Austerlitz ◽  
C. Larédo
Keyword(s):  
Graphical Models ◽  
Dna Sequences ◽  
Genetic Material ◽  
Simulated Data ◽  
Original Method ◽  
Population History ◽  
Data Sets ◽  
Key Factor ◽  
History Of ◽  
Simulated Data Sets

AbstractSeveral classes of methods have been proposed for inferring the history of populations from genetic polymorphism data. As connectivity is a key factor to explain the structure of populations, several graph-based methods have been developed to this aim, using population genetics data. Here we propose an original method based on graphical models that uses DNA sequences to provide relationships between populations. We tested our method on various simulated data sets, describing typical demographic scenarios, for different parameters values. We found that our method behaved noticeably well for realistic demographic evolutionary processes and recovered suitably the migration processes. Our method provides thus a complementary tool for investigating population history based on genetic material.

Life history parameters of blue jack mackerel Trachurus picturatus (Teleostei: Carangidae) from north-east Atlantic

2014 ◽  
Vol 95 (2) ◽  
pp. 401-410 ◽  
Author(s):  
Alexandra Garcia ◽  
João g. Pereira ◽  
Ângela Canha ◽  
Dália Reis ◽  
Hugo Diogo
Keyword(s):  
Growth Parameters ◽  
Fork Length ◽  
Biological Information ◽  
Von Bertalanffy ◽  
Jack Mackerel ◽  
East Atlantic ◽  
Calculated Length ◽  
North East ◽  
Growth Bands ◽  
Marginal Increment

Blue jack mackerel Trachurus picturatus monthly samples were collected between 1998 and 2011 to determine morphometric relationships, maturity, growth rates, reproduction and spawning seasonality in north-east Atlantic waters (ICES area Xa2). A total of 2895 specimens were sampled, ranging from 98 to 542 mm in fork-length (LF). The morphometric relationships (length-length and length-weight) showed statistically significant differences between sexes. Ages were estimated by counting growth bands on otoliths and verified by marginal increment analysis, with specimens ranging from 0 to 18 years. The von Bertalanffy models used to estimate growth parameters for both observed and back-calculated length-at-age data gave good fits. The gonads were analysed macroscopically and the spawning season found to occur from December to May. The length at 50% maturity for females and males occurred at 277 mm LF (4.3 years) and 288 mm LF (5.1 years), respectively. The results provide important biological information for fisheries assessment of a species that plays an important key role in the surrounding ecosystem.

Are Growth Parameters Estimated from Tagging and Age–Length Data Comparable?

1988 ◽  
Vol 45 (6) ◽  
pp. 936-942 ◽  
Author(s):  
R. I. C. C. Francis
Keyword(s):  
Growth Rate ◽  
Growth Rates ◽  
Growth Parameters ◽  
Growth Models ◽  
Maximum Length ◽  
Fish Growth ◽  
Data Sets ◽  
Von Bertalanffy ◽  
Length Data ◽  
The Mean

The two most common ways of estimating fish growth use age–length data and tagging data. It is shown that growth parameters estimated from these two types of data have different meanings and thus are not directly comparable. In particular, the von Bertalanffy parameter l∞ means asymptotic mean length at age for age–length data, and maximum length for tagging data, when estimated by conventional methods. New parameterizations are given for the von Bertalanffy equation which avoid this ambiguity and better represent the growth information in the two types of data. The comparison between growth estimates from these data sets is shown to be equivalent to comparing the mean growth rate of fish of a given age with that of fish of length equal to the mean length at that age. How much these growth rates may differ in real populations remains unresolved: estimates for two species of fish produced markedly different results, neither of which could be reproduced using growth models. Existing growth models are shown to be inadequate to answer this question.

Demographics of the endemic and threatened small cyprinid Pethia setnai from the Northern Western Ghats, India

2020 ◽  
Vol 71 (7) ◽  
pp. 810
Author(s):  
M. SriHari ◽  
Y. Gladston ◽  
S. M. Ajina ◽  
G. B. Sreekanth ◽  
Rajeev Raghavan ◽  
...  
Keyword(s):  
Western Ghats ◽  
Growth Parameters ◽  
Local Population ◽  
Natural Mortality ◽  
Von Bertalanffy ◽  
Fishing Mortality ◽  
Length Frequency ◽  
Growth Coefficient ◽  
First Time ◽  
The Western Ghats

The indigo barb Pethia setnai is a threatened small cyprinid endemic to the Western Ghats biodiversity hotspot of India. In this study, the length–weight relationship and length–frequency-based population dynamics of this species, which are important prerequisites for effective fisheries management, were investigated for the first time based on specimens collected from the Mhadei River in the northern part of the Western Ghats. Estimated von Bertalanffy growth parameters were as follows: theoretical maximum length, L∞, 70.88 mm; growth coefficient, k, 1.50 year–1; and theoretical age at length 0, t0, –0.016 years. Natural mortality of P. setnai was higher than fishing mortality, and the present exploitation level (0.37) was less than 60% of the predicted maximum exploitation, suggesting that the species is not exploited to a level that is detrimental to the local population.

scholarly journals Age, growth, mortality, and exploitation rate of blueline snapper, Lutjanus coeruleolineatus (Actinopterygii: Perciformes: Lutjanidae), from Dhofar Governorate, Sultanate of Oman

2021 ◽  
Vol 51 (2) ◽  
pp. 159-166
Author(s):  
Dawood Almamari ◽  
Said Rabia ◽  
Joo Myun Park ◽  
Laith A. Jawad
Keyword(s):  
Fishery Management ◽  
Growth Parameters ◽  
Total Mortality ◽  
Natural Mortality ◽  
Von Bertalanffy ◽  
Fishing Mortality ◽  
Sultanate Of Oman ◽  
Commercial Fish ◽  
Exploitation Rate ◽  
Reported Study

The blueline snapper, Lutjanus coeruleolineatus (Rüppell, 1838), is a significant commercial fish species harvested from the traditional fishery in the Sultanate of Oman. Deficient data on this species, however, make the management strategies challenging, especially in fisheries ecology. A total of 978 specimens were obtained from Dhofar Governorate off the coast of the Arabian Sea during the period between February 2015 and March 2016. In total, 296 sectioned otoliths were analyzed and growth was estimated from non-seasonal growth by using von Bertalanffy method. The parameters of von Bertalanffy growth function, total mortality (Z), natural mortality (M), fishing mortality (F), and exploitation rate (E) were determined and compared with those for Lutjanidae fishes elsewhere. The age structure of male fishes was between 1 and 14 years for males while the age of females ranged from 1 to 18 years. Growth rate (K) was 0.21 y–1 and 0.16 y–1 for males and females, respectively. The hypothetical length of female (L∞ = 46 cm) was relatively higher than that of male (L∞ = 42 cm). The natural mortality (M) was 0.296, total mortality (Z) was 0.372, fishing mortality was 0.076, and exploitation rate (E) was estimated as 0.2. The presently reported study is conducted to examine this fish in relation to growth parameters by analyzing otolith structure. The results of the presently reported study will contribute towards planning the regional fishery management policies in Oman.

scholarly journals The Variation of Several Biological Characteristics of the Chub, Squalius cephalus (L., 1758), in the Orenler Dam Lake, Northwest Anatolia, Turkey

2012 ◽  
Vol 4 (3) ◽  
pp. 27-32 ◽  
Author(s):  
Sait BULUT ◽  
Ramazan MERT ◽  
Muhsin KONUK ◽  
Beklan ALGAN ◽  
Ali ALAŞ ◽  
...  
Keyword(s):  
Condition Factor ◽  
Growth Parameters ◽  
Fork Length ◽  
Biological Characteristics ◽  
Von Bertalanffy ◽  
Calculated Length ◽  
Weight Relationship ◽  
Average Condition ◽  
Squalius Cephalus

In the present study, several growth parameters of 338 Squalius cephalus (L., 1758) specimens collected from the Orenler dam lake (Turkey) between July 2005 and June 2006 were studied. The population comprised 50.74% males, 46.29% females, and 2.97% males+females. In the examined samples, the age of females and males ranged from I to VII and I to VI, respectively. The fork length and weight of females were 14.7-38.0 cm and 40.68-27.0 g, respectively; these values were 16.3-33.7 cm and 57.7-560.0 g, respectively, for males. The age-length and age-weight relationships at time t were calculated by the von Bertalanffy equation for females, and the following results were obtained: Lt = 37.12[1–e–0.36(t–(–0.96))], Wt = 775.6[1–e–0.36(t–(–0.96))]3.27, Lt = 43.59[1–e–0.3356(t–(–0.719))], and Wt = 1123.2[1–e–0.3356(t–(–0.719))]3.08. The calculated length-weight relationship was W = 0.36L3.27 for females and W = 0.03356L3.08 for males. The average condition factor was 1.412 for females and 1.284 for males. Consequently, in the Orenler dam lake, S. cephalus grows very well according to the study’s results.

scholarly journals Bioeconomic consequences of fishing-induced evolution: a model predicts limited impact on net present value

2015 ◽  
Vol 72 (4) ◽  
pp. 612-624 ◽  
Author(s):  
Fabian Zimmermann ◽  
Christian Jørgensen
Keyword(s):  
Net Present Value ◽  
Management Strategies ◽  
Fishing Mortality ◽  
Size Selectivity ◽  
Present Value ◽  
Maximum Economic Yield ◽  
Evolutionary Changes ◽  
Sole Criterion ◽  
And Shifts ◽  
Size At Age

Fishing reduces stock size and shifts demographics, and selective mortality may also lead to evolutionary changes. Previous studies suggest that traits may change evolutionarily because of fishing on decadal time scales. Here we examine the potential bioeconomic impacts of fishing-induced evolutionary change. We used a life-history model with stock dynamics based on evolving maturation age, which has consequences for size-at-age, coupled with a fishing module that describes costs and economic yield. Size-dependent natural mortality and trawl-like fishing mortality are drivers of selection, and in the analysis we varied fishing mortality and size-selectivity of the fishing gear to determine trait evolution as well as economic yield. Comparison of two scenarios — allowing for evolution and assuming no evolution — shows that under current size selectivity, the fishing regimes generating maximum economic yield are not different when evolution is accounted for. However, ignoring evolution overestimates long-term yield under optimal fishing regimes and underestimates resilience to overfishing. Whether fishing-induced evolution matters for management strategies depends on size selectivity, stock state, how it acts on specific traits, and its sensitivity to the assumed discount rate, calling for a cautious use of net present value as sole criterion for management of evolving resources.

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