scholarly journals Stock Assessment of Small Yellow Croaker (Larimichthys polyactis) Off the Coast of China Using Per-Recruit Analysis Based on Bayesian Inference

2021 ◽  
Vol 8 ◽  
Author(s):  
Lixin Zhu ◽  
Changzi Ge ◽  
Zhaoyang Jiang ◽  
Chunli Liu ◽  
Gang Hou ◽  
...  
Keyword(s):  
Bayesian Inference ◽  
Mortality Rate ◽  
Growth Parameters ◽  
Stock Assessment ◽  
Larimichthys Polyactis ◽  
Small Yellow Croaker ◽  
Spawning Stock ◽  
Key Factor ◽  
The Status ◽  
Spawning Potential Ratio

This paper presents a framework for quantifying uncertainty in per-recruit analysis for small yellow croaker (Larimichthys polyactis) fisheries in China, in which credible estimates of life history parameters from Bayesian inference were used to generate the distribution for a quantity of interest. Small yellow croakers were divided into five spatial groups. The status of each group was examined using a yield-per-recruit (YPR) model and a spawning stock biomass-per-recruit (SSBPR) model. The optimal length at first capture (Lcopt) was proposed to recover the biomass. The maximum observed age in the current stocks (3 years) and the maximum recorded age (≥20 years) were adopted in per-recruit analysis. Our results suggest that the framework can quantify uncertainty well in the output of per-recruit analysis for small yellow croaker. It is suited to other fish species. The SSBPR at FMSY (SSBPRMSY) is a better benchmark than the spawning potential ratio (SPR) at FMSY because SSBPRMSY had a unimodal distribution. The SSBPR analysis can lead to a more conservative Lcopt than the YPR analysis. The key factor influencing the assessment conclusions may be the growth parameters rather than the natural mortality rate for a stock with a younger maximum age. Overfishing likely occurred for all groups and recruitment overfishing may not occur if the maximum age is maintained at 3 years. Increasing lengths at first capture to the recommended values can help this population recover. However, Fcur is too high for small yellow croakers to attain the maximum recorded age. Both reducing fishing mortality rate and increasing length at first capture are needed to attain the maximum recorded age.

scholarly journals Length-Based Stock Assessment of Smith's Barb, Puntioplites proctozystron (Bleeker, 1865) (Cyprinidae) and Asian Redtail Catfish, Hemibagrus nemurus, (Valenciennes, 1840), (Bagridae) in a Multipurpose Reservoir in Thailand

2021 ◽  
Vol 34 (2) ◽  
Author(s):  
KAJITPAN CHARERNNATE ◽  
PAVAROT NORANARTTRAGOON ◽  
TUANTONG JUTAGATE ◽  
Keyword(s):  
Growth Parameters ◽  
Stock Assessment ◽  
Relative Yield ◽  
Mesh Size ◽  
Fish Stock ◽  
Fish Stocks ◽  
The Status ◽  
Curvature Parameter ◽  
Spawning Potential Ratio ◽  
Fish Stock Assessment

Catches from inland fisheries in Thailand are about 200,000 tonnes annually and plays an important role in food security and subsidiary income. However, fish stocks are seldom assessed because of the lack of catch and effort data. In this study, two fish stock assessment models, viz., relative yield per recruit and length-based spawning potential ratio, were used to evaluate the status of two species as well as to highlight their applications to datalimited situation in Thailand. The study was conducted at Kangkrajan Reservoir, Thailand, for two targeted species, viz., Smith's barb, Puntioplites proctozystron (Bleeker, 1865) and Asian redtail catfish, Hemibagrus nemurus (Valenciennes, 1840) using length frequency data. The data were collected throughout 2019. Both species showed isometric growth. Von Bertalanffy growth parameters were estimated. Asymptotic length, curvature parameter and theoretical age at length zero were 36.2 cm TL, 0.39 yr-1 and -0.28 yr for P. proctozystron, respectively, and 63.2 cm TL, 0.37 yr-1 and -0.32 yr for H. nemurus. The exploitation rates reveal that both species are slightly overfished. Sizes at 50 % maturity and 50 % selectivities were 17.8 and 23.5 cm TL for P. proctozystron, respectively, and 15.6 and 20.8 cm TL for H. nemurus. Considering both parameters, the size at first capture to sustain the fisheries of P. proctozystron and H. nemurus should be >18 cm and >30 cm, respectively, which can be achieved by mesh-size regulations.

Assessing the sensitivity of data-limited methods (DLMs) to the estimation of life-history parameters from length–frequency data

2018 ◽  
Vol 75 (10) ◽  
pp. 1563-1572 ◽  
Author(s):  
Ming Sun ◽  
Chongliang Zhang ◽  
Yong Chen ◽  
Binduo Xu ◽  
Ying Xue ◽  
...  
Keyword(s):  
Life History ◽  
Stock Assessment ◽  
Stock Management ◽  
Larimichthys Polyactis ◽  
Life History Parameters ◽  
Control Rules ◽  
Strategy Evaluation ◽  
Management Procedures ◽  
Spawning Potential Ratio ◽  
Harvest Control Rules

Data-limited methods (DLMs) in stock assessment may provide potential critical information for data-limited stock management. However, the sensitivity of those methods to life-history parameters is largely unknown, resulting in extra uncertainty and consequent risks. In the present study, we designed six parallel workflows (WFs) to incorporate classic and state-of-the-art methods of estimating life-history parameters and examined their influences on the assessment of small yellow croaker (Larimichthys polyactis) in Haizhou Bay, China. The sensitivity was evaluated with three objectives: (i) the evaluation of stock status with the spawning potential ratio following different assumptions; (ii) the length-based harvest control rules derived from three management procedures; and (iii) the management performance of these harvest control rules with simulation of management strategy evaluation. The results showed considerable sensitivity regarding the three objectives to the estimations with different WFs, indicating the previous practice of credulously accepting empirical values and indiscriminately selecting references are inadvisable. We also identified the most appropriate WFs used for different purposes with limited data, aiming to provide more reliable inputs for effective fisheries management.

Incorporating Uncertainty into Fishery Models

2002 ◽  
Keyword(s):  
Mortality Rate ◽  
Blue Crab ◽  
Stock Assessment ◽  
Probability Distributions ◽  
Mortality Rates ◽  
Fishing Mortality ◽  
Statistical Hypothesis Testing ◽  
Control Laws ◽  
Decision Confidence ◽  
The Status

<em>Abstract.—</em>Stock assessment methodology has increasingly employed statistical procedures as a means to incorporate uncertainty into assessment advice. Deterministic values of fishing mortality rates (<em>F<sub>t </sub></em>) estimated from assessment models have been replaced by empirical distributions that can be compared with an appropriate biological reference point (<em>F</em><sub>BRP</sub>) to generate statements of probability (e.g., Pr[<em>F<sub>t </sub></em>≥ <em>F</em><sub>BRP</sub>]) regarding the status of the resource. It must be recognized, however, that terminal year fishing mortality rates and the biological reference points to which they are compared are both estimated with error, which will impact the quality of decisions regarding the status of the stock. We propose a two-tier stochastic decision-based framework for a recently conducted stock assessment of the Delaware Bay blue crab stock that specifies not only the probability for the condition Pr(<em>F<sub>t </sub></em>≥ <em>F</em><sub>BRP</sub>), but also the statistical level of confidence (i.e., 90%) in that decision. The approach uses a mixed Monte Carlobootstrap procedure to estimate probability distributions for both the terminal year fishing mortality rate (<em>F<sub>t </sub></em>) and the replacement fishing mortality rate, approximated by <em>F</em><sub>MED</sub> as an overfishing definition. Probability density functions (PDFs) for <em>F<sub>t </sub></em>and <em>F</em><sub>MED</sub>, generated using the mixed Monte Carlo-bootstrap procedure, show that recent fishing mortality rates (80% CI from 0.6 to 1.2) are generally below the <em>F</em><sub>MED</sub> overfishing definition (80% CI from 0.9 to 1.6), with significant overlap in the PDFs. Using the PDFs, the stochastic decision-based approach then generates a probability profile by integrating the area under the <em>F<sub>t </sub></em>PDF for different decision confidence levels (e.g. 90%, 80%, 70%, etc.), which can be thought of as one-tailed <em>α</em>-probability from standard statistical hypothesis testing. For example, at the 80% decision confidence level (value of <em>F </em>corresponding to the upper 20% of the <em>F</em><sub>MED</sub> PDF), Pr(<em>F<sub>t </sub>> F</em>MED) is about 0.03. Thus, with high confidence (80%), we can state that the blue crab stock is not currently being overfished. This approach can be extended to decisions regarding control laws that specify both maximum fishing rate and minimum biomass thresholds.

scholarly journals Influence of Growth and Recruitment Parameters in the Assessment and Management Variables of the Yellow Squat Lobster (Cervimunida johni)

2020 ◽  
Vol 8 (6) ◽  
pp. 423
Author(s):  
T. Mariella Canales ◽  
Juan-Carlos Quiroz ◽  
Rodrigo Wiff ◽  
Dante Queirolo ◽  
Doris Bucarey
Keyword(s):  
Growth Parameters ◽  
Stock Assessment ◽  
Sensitivity Analyses ◽  
Fishery Resource ◽  
Squat Lobster ◽  
The Status ◽  
Fitting Length ◽  
Key Issues ◽  
Age Structured ◽  
The Impact

Fitting length data in age-structured stock assessment is a common method for evaluating hard-to-age animals, such as crustaceans. Growth specification and the uncertainty in the stock recruitment relationship are key issues in length-based assessment models. We conducted sensitivity analyses to evaluate the impact of growth and recruitment parameters on the stock assessment and management variables of the yellow squat lobster (Cervimunida johni) caught off the Chilean coast. Nine different scenarios of the length at first capture ( L a = 1 ) and the coefficient of variation at age ( c v a ) were tested for six combinations of values for the steepness parameter (h) and the recruitment variance ( σ R 2 ). We also investigated the reliability of these estimates using an operating model. Our findings indicate that the parameter related to growth, L a = 1 , has the greatest impact on the assessment and management variables of this fishery resource, with c v a having a lesser effect. Recruitment and fishing mortality estimates were the main variables affected. Parameters h and σ R 2 did not profoundly impact the variables assessed. In addition, L a = 1 was the most biased estimated parameter. We discuss that the high influence of growth parameters is related to model structure, and thus implications for determination of the status of yellow squat lobster should be addressed in the future. We recommended developing simulation protocols for the selection of growth parameters when using an age-structured model with length observations, and we believe that our findings are relevant for all Chilean fisheries with a similar stock assessment framework.

scholarly journals Multi-decadal trends in contingent mixing of Atlantic mackerel (Scomber scombrus) in the Northwest Atlantic from otolith stable isotopes

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Kohma Arai ◽  
Martin Castonguay ◽  
David H. Secor
Keyword(s):  
Stable Isotopes ◽  
Stock Assessment ◽  
Northwest Atlantic ◽  
Atlantic Mackerel ◽  
Scomber Scombrus ◽  
Stock Biomass ◽  
Oxygen Stable Isotopes ◽  
The Us ◽  
Spawning Stock ◽  
The Status

AbstractThe Atlantic mackerel (Scomber scombrus) in the Northwest Atlantic is comprised of northern and southern components that have distinct spawning sites off Canada (northern contingent) and the US (southern contingent), and seasonally overlap in US fished regions. Thus, assessment and management of this population can be sensitive to levels of mixing between contingents, which remain unknown. Multi-decadal trends in contingent mixing levels within the US fisheries region were assessed, and the contingent composition across seasons, locations, ages, and size classes were characterized using archived otoliths and developing a classification baseline based on juvenile otolith carbon and oxygen stable isotopes (δ13C/δ18O values). Classification of age ≥ 2 adults demonstrated that northern contingent mixing was prevalent within the US continental shelf waters during the past 2 decades (2000–2019), providing an important seasonal subsidy to the US winter fishery despite substantial depletion in spawning stock biomass of the dominant northern contingent. While the majority of older fish were of the northern contingent during the early 2000s, the southern contingent contribution increased with age/size class during the recent period (2013–2019). Spatial mixing was most prevalent during February and March when the northern contingent occurred as far south as the Delmarva Peninsula, but were mostly absent from US waters in May. A positive relationship (albeit not significant; r = 0.60, p = 0.07) occurred between northern contingent mixing and US fisheries landings, which could imply that higher contingent mixing levels might be associated with greater landings for the US winter mackerel fishery. The yield of the Northwest Atlantic mackerel depends upon the status of the northern contingent, with the southern contingent possibly more prone to depletion. Spatially explicit stock assessment models are recommended to conserve both productivity and stability in this two-component population.

scholarly journals Fluctuations in the spawning stock biomass and recruitment of the Brazilian sardine (Sardinella brasiliensis) 1977-1997

2002 ◽  
Vol 50 (unico) ◽  
pp. 13-26 ◽  
Author(s):  
Maria Cristina Cergole ◽  
Suzana Anita Saccardo ◽  
Carmen L. D. B. Rossi-Wongtschowski
Keyword(s):  
Growth Parameters ◽  
Stock Assessment ◽  
Total Mortality ◽  
Commercial Fishing ◽  
Total Length ◽  
Length Relationship ◽  
Stock Biomass ◽  
Historical Series ◽  
Spawning Stock ◽  
Acoustic Surveys

In the southeastern coast of Brazil, catches of the Brazilian sardine (Sardinella brasiliensis) have been decreasing from more than 200 thousand tons/year in the early '70s to about 32 thousand tons in 1990. From 1994 to 1997, catches recovered slightly (118 thousand tons), dropping then to about 20 thousand tons in 1999-2000. Extensive investigations on biology and stock assessment of Brazilian sardine have been developed in the '80s, providing stock biomass and recruitment estimates based on commercial fishing data obtained from 1977-1992. The present paper aims to update biological and stock assessment parameters from sardine data obtained during two acoustic surveys carried out in 1995 and commercial catches from the 1993-1997 period. Results from both cruises showed the weight-length relationship Wt=0.0000019. Lt3,26 (90-240 mm total length) and four age classes (mostly class II+). In the commercial catches, sardines belonged to ages 0+ and 3+ years old (mostly older than 1-year old) with 90-250 mm total length. Annual growth parameters were: Li=275 mm, K= 0.55 (1996), and Li=273 mm, K=0.50 (1997). Total mortality (Z) and natural mortality (M) coefficients were: Z= 3.8; M= 0.7 -1.2 (1996), and Z= 3.6; M= 0.6 - 1.1 (1997). The variation amplitude of M is due to the application of several different methods. Considering the historical series of 21 years of data (1977-1997), results showed that the stock went through two favorable periods (1980-84, 1989-94) and one unfavorable period (1985-89). 1997 seems to have been the beginning of a new unfavorable period, revealing recruitment cycles likewise other stocks from California and Japan.

scholarly journals Improving assessment of Pandalus stocks using a seasonal, size-structured assessment model with environmental variables. Part II: Model evaluation and simulation

2017 ◽  
Vol 74 (3) ◽  
pp. 363-376 ◽  
Author(s):  
Jie Cao ◽  
Yong Chen ◽  
R. Anne Richards
Keyword(s):  
Growth Parameters ◽  
Stock Assessment ◽  
Assessment Model ◽  
Annual Growth ◽  
Estimation Bias ◽  
Environmental Signals ◽  
Stock Biomass ◽  
Model Configuration ◽  
Spawning Stock ◽  
And Performance

Integrated, size-structured stock assessment models are now being used widely for assessment and management of hard-to-age species. However, few studies have attempted to evaluate their performance. A seasonal, size-structured assessment model with environmental covariates has been developed for hermaphroditic Pandalidae. We conducted simulations to evaluate its sensitivity to model configuration and performance with various misspecifications. Ignoring the seasonal fishing pattern (half-year closure) led to risk-prone assessment results of overestimating spawning stock biomass (SSB) and recruitment (R) and underestimating fishing mortality (F). Failure to incorporate environmental signals when the recruitment dynamics was environmentally driven led to bias in recent estimates of SSB, R, and F in the simulation. Ignoring annual variability in growth resulted in large estimation bias. Failing to account for time-varying natural mortality (M) led to strong biases; however, misspecifying size-specific M produced even stronger estimation bias. This result may depend on the variation of M among size classes. Under no model misspecifications, an unbiased estimate of M could be obtained by taking advantage of the seasonal fishery closure. Annual growth parameters were also estimable, but the large number of parameters with annual growth made it difficult for the model to converge.

scholarly journals Stock collapse or stock recovery? Contrasting perceptions of a depleted cod stock

2019 ◽  
Vol 76 (4) ◽  
pp. 787-793 ◽  
Author(s):  
R M Cook
Keyword(s):  
Mortality Rate ◽  
Gadus Morhua ◽  
Fishing Effort ◽  
Assessment Model ◽  
Fishing Mortality ◽  
Benchmark Assessments ◽  
Spawning Stock ◽  
The Status ◽  
Fishery Exploitation ◽  
Management Advice

Abstract ICES assessments of cod (Gadus morhua) in the west of Scotland (ICES Division 6a) suggest the biomass has collapsed and that fishing mortality rate (F) has remained high. In contrast, other stocks in the same fishery, and adjacent cod stocks all show marked declines in fishing mortality and some recovery of the biomass. The perception of the status of 6a cod appears to be dependent on the assumption that the fishery exploitation pattern is flat topped. An assessment that allows the exploitation to take a domed shape produces results that suggest a marked decline in fishing mortality rate and that the spawning stock biomass has recovered to the minimum biomass reference point, Blim. The reduction in F is consistent with substantial reductions in fishing effort and shows a similar pattern to stocks taken within the same fishery. The management implications arising from the two assessments differ substantially. The analysis indicates that benchmark assessments need to test assessment model conditioning assumptions more widely and that management advice needs to consider a more comprehensive range of information about the stock and fishery.

Reference points for the length-based indicator Lmax5% for use in the assessment of data-limited stocks

2019 ◽  
Vol 76 (7) ◽  
pp. 2125-2139 ◽  
Author(s):  
Tanja Miethe ◽  
Yves Reecht ◽  
Helen Dobby
Keyword(s):  
Life Histories ◽  
Stock Assessment ◽  
Reference Points ◽  
Length Frequency ◽  
Frequency Distributions ◽  
Simulation Tools ◽  
Spawning Potential Ratio ◽  
The Mean ◽  
Commercial Sources ◽  
Length Frequency Data

Abstract In the absence of abundance indices from scientific surveys or commercial sources, reliable length frequency data from sampled commercial catches can be used to provide an indirect assessment of fishing mortality. Length-based indicators are simple metrics which describe length frequency distributions. The length-based indicator Lmax5%, the mean length of the largest 5% of individuals in the catch, combined with appropriately selected reference points, can be used to evaluate the presence of very large individuals in the catch and hence determine exploitation level. Using analytical per-recruit models, we derive reference points consistent with a spawning potential ratio of 40%. The reference points depend on the life history parameters for natural mortality, maturity, and growth (M, Lmat, L∞, k, CVL∞). Using available simulation tools, we investigate the sensitivity of the reference points to errors in these parameters and explore the usefulness of particular reference points for management purposes for stocks with different life histories. The proposed reference points are robust to uncertainty in length at first capture, Lc, and take into account the maturation schedule of a species. For those stocks with high M/k ratios (&gt;1), Lmax5%, combined with the appropriate reference point, can be used to provide a data-limited stock assessment.

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