scholarly journals Aspects of Stock Assessment of Klunzinger's Mullet, Planiliza klunzengeri (Day, 1888) from Northwest Arabian Gulf, Iraq

2021 ◽  
pp. 25-36
Author(s):  
Ali H. Al-Hassani ◽  
Abdul-Razak M. Mohamed
Keyword(s):  
Stock Assessment ◽  
Population Analysis ◽  
Arabian Gulf ◽  
Total Mortality ◽  
Landing Site ◽  
Fishing Effort ◽  
Reference Points ◽  
Recruitment Pattern ◽  
Virtual Population Analysis ◽  
Virtual Population

The stock assessment of Klunzinger's mullet, Planiliza klunzengeri was conducted, to estimate its some aspects viz. growth, mortality, recruitment, yield-per-recruit and virtual population analysis in Iraqi marine waters, northwest Arabian Gulf, Iraq, from February 2020 and January 2021. The population parameters were analyzed by the FiSAT software using monthly length-frequency data collected by the Shaheen dhow and from the artisanal fishermen at the fish landing site in Al-Fao city to derive information required for their management. A total of 3319 individuals of P. klunzingeri ranged from 11.0 to 27.0 cm have been collected. Length-weight relationship was calculated as W= 0.026L2.716. The asymptotic length (L∞), growth rate (K) and the growth performance index (Ø') were 29.8 cm, 0.34 and 2.48, respectively. The rates of annual instantaneous of total mortality (Z), fishing mortality (F), natural mortality (M) and present exploitation (Epresent) were 1.19, 0.84, 0.36 and 0.30, respectively. The recruitment pattern of P. klunzingeri was continuous throughout the year, with one peak during May. The results of virtual population analysis revealed that the majority of P. klunzingeri were harvested between 14 cm and 19 cm. The length at first capture (L50) in the current study was higher than the length at first maturity (Lm) of the species in the region. The Epresent was below the biological target reference points (E0.1= 0.770 and Emax= 0.903), referred to the stock of P. klunzingeri is underexploited. Therefore, the harvest level should increase to its maximum sustainable yield level by increasing fishing effort level with monitoring surveys and evaluate the risk associated with fishing effort increases as fishing precautionary approaches.

scholarly journals Aspects of Population Dynamics of Tiger Tooth Croaker, Otolithes ruber (Bloch and Schneider, 1801) from Northwest Arabian Gulf, Iraq

2021 ◽  
pp. 9-21
Author(s):  
Abdul-Razak M. Mohamed ◽  
Ali H. Al-Hassani
Keyword(s):  
Population Dynamics ◽  
Population Analysis ◽  
Arabian Gulf ◽  
Relative Yield ◽  
Total Mortality ◽  
Reference Points ◽  
Virtual Population Analysis ◽  
Virtual Population ◽  
Exploitation Rate ◽  
Otolithes Ruber

The present study consists of the growth, mortality, relative yield recruit and virtual population analysis of tigertooth croaker, Otolithes ruber from Iraqi marine waters, northwest Arabian Gulf between February 2020 and January 2021. Analysis of population dynamics employed methods fitted in FiSAT II software using pooled length-frequencies. A total of 3835 individuals of O. ruber ranged from 17.0 to 60.0 cm have been collected. The exponent (b) of the length-weight relationship was found to be 2.755. The von Bertalanffy growth parameters (L∞ and K) were estimated as 68.5 cm and 0.36, respectively, while the growth performance index (Ø') was 3.228.  The total mortality (Z) was calculated as 1.10, while the natural and fishing mortality rates were 0.69 and 0.41, respectively, and the current exploitation rate (Ecurrent) was 0.38. Fish were recruited to the fishery at a mean size of L50= 20.55 cm. The recruitment pattern of O. ruber was continuous throughout the year with two major peaks. The analysis of yield-per-recruit (Y/R’) indicates that the current exploitation rate was below the biological target reference points (E0.1 = 0.40 and Emax= 0.53), refer to the stock of O. ruber is underexploited. The 27 cm length group was more vulnerable to fishing and more harvested according to virtual population analysis. sLength at first capture was higher than the length at first maturity of the species in the region. For management purposes, more yields could be obtained by increasing the mesh sizes of the nets employed in the fishing of the species. 

scholarly journals Accounting for uncertainty due to data processing in virtual population analysis using Bayesian multiple imputation

2018 ◽  
Vol 75 (6) ◽  
pp. 883-896 ◽  
Author(s):  
Thomas Carruthers ◽  
Laurence Kell ◽  
Carlos Palma
Keyword(s):  
Data Processing ◽  
Multiple Imputation ◽  
Stock Assessment ◽  
Population Analysis ◽  
Reference Points ◽  
Observation Error ◽  
Predictive Capacity ◽  
Data Set ◽  
Virtual Population Analysis ◽  
Virtual Population

Virtual population analysis (VPA) is used in many stock assessment settings and requires a total catch-at-age data set where an age is assigned to each fish that has been caught. These data sets are typically constructed using ad hoc methods that rely on numerous assumptions. Although approaches are available to account for observation error in these data, no statistically rigorous methods have been developed to account for uncertainty from data processing. To address this, we investigated a Bayesian multiple imputation approach to filling missing size data. Using Atlantic yellowfin tuna (Thunnus albacares) and bigeye tuna (Thunnus obesus) as case studies, we evaluated the hypothesis that data processing is as important in determining management reference points in stock assessments as conventional sources of uncertainty. Size imputation models accounting for location, season, and year provided good predictive capacity. Uncertainty from data processing could be large; however, the circumstances for this were unpredictable and varied depending on the stock. These results indicate that VPA assessments should attempt to account for uncertainty in data processing to avoid potentially large compression of uncertainty in assessment results.

scholarly journals Growth, mortality and stock assessment of greenback mullet, Planiliza subviridis from northwest Arabian Gulf, Iraq

2021 ◽  
Vol 6 (2) ◽  
pp. 142-148
Author(s):  
Abdul-Razak M. Mohamed ◽  
Ali H. Al-Hassani
Keyword(s):  
Mortality Rate ◽  
Stock Assessment ◽  
Population Analysis ◽  
Arabian Gulf ◽  
Total Mortality ◽  
Reference Points ◽  
Fishing Mortality ◽  
Fish Samples ◽  
Exploitation Rate ◽  
First Maturity

The growth, mortality and stock parameters of greenback mullet, Planiliza subviridis from Iraqi marine waters, northwest Arabian Gulf was assessed using FiSAT II software for length-frequency data collected from February 2020 to January 2021. P. subviridis is one of the species caught in large quantities as commercial by artisanal fishers. Fish samples were collected by the Shaheen steel-hulled dhow and from the artisanal fishermen. The total length and body weight relationship of fish was estimated as W= 0.034L2.670, indicating negative allometric growth. Of 3350 specimens, growth and mortality parameters were evaluated. The asymptotic length (L∞), growth rate (K) and growth performance index (Ø') were 33.8 cm, 0.30 and 2.535, respectively. The total mortality rate (Z), natural mortality rate (M), and fishing mortality rate (F) were 1.11, 0.74 and 0.38, respectively. The present exploitation rate (Epresent) of P. subviridis computed as 0.34. Length at first capture (L50) was 17.47 cm. Recruitment of P. subviridis was observed throughout the year, with a peak during July. The yield per recruit analysis indicates that the current exploitation rate was below the biological target reference points (E0.1 and Emax), which refers to the stock of P. subviridis is underexploited. Virtual population analysis results showed that mid-lengths (16-22 cm) experienced the highest fishing mortality. The length at first capture (L50) was higher than the length at first maturity (Lm) of the species. So, for management purposes, more yields could be obtained by increasing the fishing activities on this species for a substantial harvest.

Population dynamics and stock assessment of Hilsa shad, Tenualosa ilisha (Hamilton, 1822) along the coast of Bangladesh

2021 ◽  
Vol 48 (2) ◽  
pp. 231-241
Author(s):  
Md Khairul Islam ◽  
Md Humayun ◽  
Manmatha Nath Sarker ◽  
Md Sharifuddin ◽  
M Niamul Naser
Keyword(s):  
Growth Parameters ◽  
Stock Assessment ◽  
Population Analysis ◽  
Total Mortality ◽  
Maximum Sustainable Yield ◽  
Fishing Mortality ◽  
Recruitment Pattern ◽  
Weight Relationship ◽  
Tenualosa Ilisha ◽  
Highly Correlated

Stock Assessment of Tenualosa ilisha (Hamilton, 1822) were estimated using FiSAT-II software with length-frequency data collected from different landing centers. The Southeast Coast of Bay Of Bengal, Cox's Bazar. The Von Bertalanffy growth parameters Land K for the species were asymptotic length (L∞) was 51.41 cm, growth rate (K) was 0.75 year-1 and t0 = -0.2 year respectively. The estimated value of total mortality (Z) based on length converted catch curve using these growth parameters was 2.35 year-1.Natural mortality (M) based on growth parameters and mean environmental temperature (T = 27° C) was 1.00 year-1 and fishing mortality (F) was 1.35 year-1. Optimum length of hilsa at first capture (Lc=L50) was 28.36 cm TL. Growth performance indices (ϕ') was 3.30. The estimated value of the exploitation rate (E) using the length-converted catch curve was 0.57. The recruitment pattern of this species was continuous and two peaks per year. The present investigation clearly showed the over fishing (E > 0.50) condition for T. ilisha in Bangladesh. The estimated length-weight relationship for the combined sex was found to be W = 0.0109 L3. Virtual population analysis (VPA) showed that the maximum fishing mortality occurring in the length between 30 to 35 cm with a maximum value in the length of 32 cm that repeatedly indicate high fishing mortality in the T. ilisha. The generalized length-weight relationship was fitted with the pooled data of all monthly samples were BW = 0.029 TL2.718 (R2= 0.833) respectively. The results revealed that all length-weight relationships were highly correlated (r > 0.993). Maximum sustainable yield (MSY) was estimated as 435,554 t. Bangladesh J. Zool. 48(2): 231-241, 2020

Estimating some population parameters and stock assessment of Dark Sleeper Odontobutis potamophila in the Gaosha River, Wuyuan County, Jiangxi Province, China

2017 ◽  
Author(s):  
Wu Bin Wang Haihua ◽  
Fu Huiyun Zhang Yanping
Keyword(s):  
Growth Parameters ◽  
Stock Assessment ◽  
Total Mortality ◽  
Landing Site ◽  
Jiangxi Province ◽  
Recruitment Pattern ◽  
Growth Coefficient ◽  
West Part ◽  
Exploitation Rate ◽  
Odontobutis Potamophila

A study was conducted to investigate the growth parameters, mortality and recruitment pattern of Odontobutis potamophila collected in the Gaosha river fish landing site, west part of Wuyuan County (Latitude: 29° 14' 29" N, Longitude: 117° 45' 49" E). O.potamophila were collected from November, 2013 to October, 2014. Growth parameters, asymptotic length (L) = 192mm and growth coefficient (k) = 0.22 year-1. Growth performance index(Ø’) =3.91, total mortality (Z) = 0.72 year-1, natural mortality (M) = 0.32 year-1, fishing mortality (F) = 0.40 year-1 and exploitation rate (E) = 0.55year-1.The estimated exploitation rate (E) has slightly exceeded the optimum value of E indicating this species was sustainable exploitation in the study area. The exploitation ratios were computed as Emax= 0.61, E10= 0.52, E50= 0.34. The length at first capture at 50%, (Lc) was 77 mm. The recruitment pattern of the species was found continuous all-round the year with one peak. The observation of the annual recruitment of O.potamophila found to occur from May to July. Steady biomass also increased with length class until 121-125 mm, and the total steady state biomass was found to be 2240 kg.

Incorporating predation interactions in a statistical catch-at-age model for a predator-prey system in the eastern Bering Sea

2005 ◽  
Vol 62 (8) ◽  
pp. 1865-1873 ◽  
Author(s):  
Jesús Jurado-Molina ◽  
Patricia A Livingston ◽  
James N Ianelli
Keyword(s):  
Bering Sea ◽  
Stock Assessment ◽  
Population Analysis ◽  
Adult Population ◽  
Single Species ◽  
Virtual Population Analysis ◽  
Virtual Population ◽  
Statistical Assumptions ◽  
The Difference ◽  
Management Advice

Virtual population analysis and the statistical catch-at-age methods are common stock assessment models used for management advice. The difference between them is the statistical assumptions allowing the fitting of parameters by considering how errors enter into the models and the data sources for the estimation. Fishery managers are being asked to consider multispecies interactions in their decisions. One option to achieve this goal is the multispecies virtual population analysis (MSVPA); however, its lack of statistical assumptions does not allow the use of tools used in single-species stock assessment. We chose to use a two-species system, walleye pollock (Theragra chalcogramma) and Pacific cod (Gadus macrocephalus), to incorporate the predation equations from MSVPA into an age-structured multispecies statistical model (MSM). Results suggest that both models produced similar estimates of suitability coefficients and predation mortalities. The adult population estimates from the single-species stock assessment and MSM were also comparable. MSM provides a measure of parameter uncertainty, which is not available with the MSVPA technologies. MSM is an important advancement in providing advice to fisheries managers because it incorporates the standard tools such as Bayesian methods and decision analysis into a multispecies context, helping to establish useful scenarios for management in the Bering Sea.

Sensitivities and Variances of Virtual Population Analysis As Applied to the Mackerel, Scomber japonicus

1988 ◽  
Vol 45 (3) ◽  
pp. 539-547 ◽  
Author(s):  
Michael H. Prager ◽  
Alec D. MacCall
Keyword(s):  
Stock Assessment ◽  
Population Analysis ◽  
Error Variance ◽  
Quantitative Model ◽  
Fish Stock ◽  
Scomber Japonicus ◽  
Virtual Population Analysis ◽  
Virtual Population ◽  
Coefficients Of Variation ◽  
Fish Stock Assessment

Virtual population analysis (VPA) is widely used in fish stock assessment. However, VPA results are generally presented as point estimates, without error variance. Using numerical methods, we estimated the total variance of historical (1929–65) biomass estimates of mackerel, Scomber japonicus, off southern California. In the years before 1940, coefficients of variation (CV's) approached 100%; later, when weights at age and the age structure of the catch were better known, the CV's were about 25%. Most of the variability derives from uncertainties in estimates of natural mortality (M) and of weights at age. We also developed dimensionless coefficients (sensitivities) to examine the effects of errors in the inputs on the VPA biomass estimates. The largest sensitivities were to M and the total catch and varied substantially from year to year. As expected, sensitivity to M decreased with increasing exploitation, and sensitivity to catch increased with increasing exploitation. Using such sensitivities, one could estimate the error in a biomass estimate for a past year when M (or any other input) was thought to be unusually high or low. Thus, retrospective corrections can be made. Also, such sensitivities form an analytic tool for examining the properties of VPA, or any quantitative model.

Estimation of Population Parameters and Stock Assessment of Mastacembelus armatus in the Taojiang River, Xinfeng County, Jiangxi Province, China

2019 ◽  
Author(s):  
Wu Bin ◽  
Wang Haihua ◽  
Ma Benhe ◽  
Xu Xiandong ◽  
Zeng Qingxiang
Keyword(s):  
Growth Parameters ◽  
Stock Assessment ◽  
Total Mortality ◽  
Landing Site ◽  
Jiangxi Province ◽  
Recruitment Pattern ◽  
Growth Coefficient ◽  
Exploitation Rate ◽  
Mastacembelus Armatus ◽  
River Fish

A study was conducted to investigate the growth parameters, mortality and recruitment pattern of Mastacembelus armatus collected in the Taojiang River fish landing site, Xinfeng County. M. armatus were collected from March, 2018 to February, 2019. Growth parameters, asymptotic length (L¥) = 58.8cm and growth coefficient (k) = 0.13 year-1. Growth performance index(Ø2 ) =2.65, total mortality (Z) = 0.75 year-1, natural mortality (M) = 0.32 year-1, fishing mortality (F) = 0.43 year-1 and exploitation rate (E) = 0.57year-1.The estimated exploitation rate (E) has slightly exceeded the optimum value of E indicating this species was over exploited mainly due to fishing in the study area. The exploitation ratios were computed as Emax= 0.59, E10= 0.45, E50= 0.31. The length at first capture at 50%, (Lc) was 19.51 cm. The Steady biomass also increased with length class until 36.0-36.9 cm and the total steady state biomass was found to be 19.12 tons.

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