Evaluation of quota management policies for developing fisheries

1998 ◽  
Vol 55 (12) ◽  
pp. 2691-2705 ◽  
Author(s):  
Carl Walters
Keyword(s):  
Mortality Rate ◽  
Relative Abundance ◽  
Cumulative Effect ◽  
Mortality Rates ◽  
Reference Trajectory ◽  
Fishing Mortality ◽  
Small Probability ◽  
Abundance Indices ◽  
Management Policies ◽  
Quota Management

Losses can be measured as deviations from a desired reference trajectory of quotas that would be taken if there were no uncertainty and are highly dependent on assessments prior to and during development. Simulations of assessment and quota setting under various quota setting rules indicate that variability in relative abundance indices can cause substantial losses, especially considering cumulative effect of early quota errors on later departures of biomass from that needed to produce the desired quotas, even if optimum fishing mortality rate is known in advance. Conservative assessments (low biomass estimates for which there is only a small probability that biomass is actually lower) are favored during development when loss is measured as the relative departure from the best quota for each year. But if loss is measured as absolute departure from the best quota, it is generally better to base the quota on the biomass estimate for which there is nearly a 50% chance that the stock is smaller. Deliberate overfishing (probing) is not favored under either loss measure. Losses can be reduced with minimum biomass surveys and closed areas that directly cushion fishing mortality rates from being more than 50% too low or high.

scholarly journals Optimal fishing mortality assignment for southern hake Merluccius australis in Chile

2020 ◽  
Vol 48 (4) ◽  
pp. 613-625
Author(s):  
Felipe Lopez ◽  
Jorge Jimenez ◽  
Cristian Canales
Keyword(s):  
Mortality Rate ◽  
Economic Benefit ◽  
Mortality Rates ◽  
Fish Population ◽  
Fishing Effort ◽  
Economic Benefits ◽  
Historical Background ◽  
Total Catch ◽  
Fishing Mortality ◽  
Objective Functions

Since 1979, southern hake (Merluccius australis) has been exploited in Chile from the Bio Bio to the Magallanes regions, between the parallels 41°28.6'S and 57°S. There is evidence of a constant fishing effort and a sustained reduction of the fish population, consistent with a progressive decrease in total annual catches. Management strategies based on the maximum sustainable yield (MSY) and quota assignment/ distribution criteria have not been able to sustain acceptable biomass levels. A non-linear optimization model with two objective functions was proposed to determine an optimal total catch quota for more sustainable exploitation of this fishery. The first function maximizes the total catch over time in response to an optimal assignment of fishing mortality rates per fleet; the second function maximizes the total economic benefit associated with the total catch. The dynamics of the fish population were represented with the equations of a predictive age-structured model. Decision variables were fishing mortality rates and annual catch quotas per fleet, subject to constraints that guarantee a minimum level of biomass escape over a long-term period. The input parameters were obtained from the last stock evaluation report carried out by the Instituto de Fomento Pesquero (IFOP) of Chile. The historical background data of the fishery and the regulatory framework were relevant aspects of the methodology. Five scenarios were evaluated with the two objective functions, including a base scenario, which considered the referential mortality rate as input data as the average mortality rate per fleet from 2007 to 2012. Total economic benefits fluctuate between 102 and USD 442 million for total catches in the range of 108 to 421 thousand tons, which were obtained from maximizing the economic and biological objective functions. Economic benefit/catch ratios were reduced for scenarios with higher constraints on catch limits, and they were more efficient from a biological point of view. Situations with lighter constraints showed in general higher economic benefits and better performance ratios than those with stronger restrictions. The use of optimization models may provide a useful tool to evaluate the effect of regulations for adequate conservation and economical utilization of a limited resource.

Sustainability assessment for fishing effects (SAFE) on highly diverse and data-limited fish bycatch in a tropical prawn trawl fishery

2009 ◽  
Vol 60 (6) ◽  
pp. 563 ◽  
Author(s):  
Shijie Zhou ◽  
Shane P. Griffiths ◽  
Margaret Miller
Keyword(s):  
Mortality Rate ◽  
Fishery Management ◽  
Sustainability Assessment ◽  
Cost Effective ◽  
Mortality Rates ◽  
Assessment Method ◽  
Reference Points ◽  
Fishing Mortality ◽  
Point Estimates ◽  
Large Numbers

A new sustainability assessment for fishing effects (SAFE) method was used to assess the biological sustainability of 456 teleost bycatch species in Australia’s Northern Prawn Fishery. This method can quantify the effects of fishing on sustainability for large numbers of species with limited data. The fishing mortality rate of each species based on its spatial distribution (estimated from detection/non-detection data) and the catch rate based on fishery-dependent or fishery-independent data were estimated. The sustainability of each species was assessed by two biological reference points approximated from life-history parameters. The point estimates indicated that only two species (but 21 when uncertainty was included) had estimated fishing mortality rates greater than a fishing mortality rate corresponding to the maximum sustainable yield. These two species also had their upper 95% confidence intervals (but not their point estimates) greater than their minimum unsustainable fishing mortality rates. The fact that large numbers of species are sustainable can be attributed mainly to their wide distributions in unfished areas, low catch rates within fished areas and short life spans (high biological productivity). The present study demonstrates how SAFE may be a cost-effective quantitative assessment method to support ecosystem-based fishery 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.

Estimating reference fishing mortality rates from noisy spawner–recruit data

2004 ◽  
Vol 61 (9) ◽  
pp. 1771-1783 ◽  
Author(s):  
A Jamie F Gibson ◽  
Ransom A Myers
Keyword(s):  
Maximum Likelihood ◽  
Mortality Rate ◽  
Mortality Rates ◽  
Maximum Sustainable Yield ◽  
Maximum Likelihood Estimates ◽  
Organizational Level ◽  
Likelihood Method ◽  
Parameter Estimates ◽  
Fishing Mortality ◽  
Over Exploitation

We review and evaluate methods of estimating reference fishing mortality rates from spawner–recruit (SR) data to obtain maximum sustainable yield. Using Monte Carlo simulations, we found that a reference fishing mortality rate derived from the maximum likelihood estimates of the SR parameters was less biased than reference fishing mortality rates obtained using the mode of the marginal probability distribution for the maximum rate that spawners produce recruits or by finding the fishing mortality rate that maximizes the expected yield. However, the maximum likelihood method produced the most variable estimates, at times leading to substantial under- or over-exploitation of the population. In contrast, the decision theoretic method of maximizing the expected yield exhibited less variability, produced higher yields, and substantially reduced the risk of overexploiting the population. We show how these methods can be extended to include information from other populations. Bayesian priors for the SR parameters, obtained through meta-analyses of population dynamics at some higher organizational level (e.g., the species), may be used to assess the plausibility of parameter estimates obtained for a single population or combined with the data for the population of interest. Reference fishing mortality rates are then estimated from the resulting joint posterior distribution.

Initial Report of Off-Pump Coronary Artery Bypass Surgery as Sole Therapy for Moderate Ischemic Mitral Regurgitation: Operative and Intermediate-Term Outcome

2005 ◽  
Vol 8 (2) ◽  
pp. 89 ◽  
Author(s):  
Kevin M. Harris ◽  
Avinash Reddy ◽  
Dorothee Aepplii ◽  
Betsy Wilson ◽  
Robert W. Emery
Keyword(s):  
Coronary Artery ◽  
Mortality Rate ◽  
Mitral Regurgitation ◽  
Coronary Artery Bypass Surgery ◽  
Bypass Surgery ◽  
Artery Bypass ◽  
Mortality Rates ◽  
Off Pump ◽  
Moderate Ischemic Mitral Regurgitation ◽  
Pump Coronary Artery Bypass

Background: Patients undergoing on-pump coronary artery bypass surgery (CAB) with coexistent moderate ischemic mitral regurgitation (IMR) have a significant mortality rate compared to patients without MR. The mortality rate is elevated both perioperatively (0%-12% mortality), as well as over a 1- and 2-year postoperative period (15%-25%). It is thought that some patients are best served by off-pump CAB (OPCAB); however, outcomes have not been reported for such patients with coexistent moderate IMR. Methods: We reviewed the independent database of patients undergoing OPCAB between 1995 and 2002 to find 989 patients, 17 (1.7%) of whom had moderate or moderately severe MR. Patients were contacted and clinical and echocardiographic data were obtained. Results: The patient group consisted of 11 men and 6 women (age, 65 15 years). The study group had a PA pressure of 52 14, creatinine of 1.6 0.7, and left ventricular ejection fraction of 43 18. Nine patients (53%) had advanced New York Heart Association (class III-IV) heart failure. Mortality rates perioperatively and at 1, 2, and 3 years were 0%, 6.25% (1/16), 12.5% (2/16), and 38% (4/8), respectively. At the time of this report, no patient had returned for a reparative procedure. Conclusion: In patients felt to be best served by OPCAB with ischemic MR, operative and intermediate mortality rates are remarkably similar to those previously reported for on-pump series. These data underscore the continued need to understand which patients undergoing CAB require mitral valve problems to be addressed at the time of surgery.

scholarly journals Effects of some bioinsecticides on the tomato leaf miner, Tuta absoluta (Meyrick, 1917) (Lepidoptera: Gelechiidae)

2021 ◽  
Vol 31 (1) ◽  
Author(s):  
Alime Bayindir Erol ◽  
Oktay Erdoğan ◽  
İsmail Karaca
Keyword(s):  
Mortality Rate ◽  
Active Ingredient ◽  
Metarhizium Anisopliae ◽  
Mortality Rates ◽  
Tomato Leaf ◽  
Tuta Absoluta ◽  
Leaf Miner ◽  
Verticillium Lecanii ◽  
Main Body ◽  
Tomato Leaf Miner

Abstract Background In this study, commercial bioinsecticides including entomopathogenic fungi, Beauveria bassiana, Metarhizium anisopliae, and Verticillium lecanii, and Spinetoram active ingredient insecticide were evaluated against the tomato leaf miner, Tuta absoluta (Meyrick, 1917) (Lepidoptera: Gelechiidae) larvae. Main body The active ingredients were prepared at the recommended concentrations under laboratory conditions and applied to the 2nd instar larvae of T. absoluta by spraying with a hand sprayer. On the 1st, 3rd, 5th, and 7th days of the application, evaluations were made by counting survived individuals. The findings showed that the highest mortality rates were detected in the case of Spinetoram with 56, 60, 88, and 100% on all counting days of the experiments, respectively. The highest mortality rate among bioinsecticides was recorded for M. anisopliae, with 87% mortality on the 7th day of application. Short conclusion As a result, Spinetoram was found the most effective insecticide when applied to T. absoluta, followed by M. anisopliae.

scholarly journals Long-Term Exposure to Fine and Coarse Particulate Matter and COVID-19 Incidence and Mortality Rate in Chile during 2020

2021 ◽  
Vol 18 (14) ◽  
pp. 7409
Author(s):  
Macarena Valdés Salgado ◽  
Pamela Smith ◽  
Mariel Opazo ◽  
Nicolás Huneeus
Keyword(s):  
Mortality Rate ◽  
Incidence Rate ◽  
Air Pollutants ◽  
Negative Binomial ◽  
Transport Model ◽  
Surface Concentration ◽  
Mortality Rates ◽  
Incidence And Mortality ◽  
Pm2.5 And Pm10

Background: Several countries have documented the relationship between long-term exposure to air pollutants and epidemiological indicators of the COVID-19 pandemic, such as incidence and mortality. This study aims to explore the association between air pollutants, such as PM2.5 and PM10, and the incidence and mortality rates of COVID-19 during 2020. Methods: The incidence and mortality rates were estimated using the COVID-19 cases and deaths from the Chilean Ministry of Science, and the population size was obtained from the Chilean Institute of Statistics. A chemistry transport model was used to estimate the annual mean surface concentration of PM2.5 and PM10 in a period before the current pandemic. Negative binomial regressions were used to associate the epidemiological information with pollutant concentrations while considering demographic and social confounders. Results: For each microgram per cubic meter, the incidence rate increased by 1.3% regarding PM2.5 and 0.9% regarding PM10. There was no statistically significant relationship between the COVID-19 mortality rate and PM2.5 or PM10. Conclusions: The adjusted regression models showed that the COVID-19 incidence rate was significantly associated with chronic exposure to PM2.5 and PM10, even after adjusting for other variables.

scholarly journals Mortality in Patients with Brainstem Cavernous Malformations

2021 ◽  
pp. 1-7
Author(s):  
Julia Velz ◽  
Marian Christoph Neidert ◽  
Yang Yang ◽  
Kevin Akeret ◽  
Peter Nakaji ◽  
...  
Keyword(s):  
Mortality Rate ◽  
Literature Review ◽  
Systematic Literature Review ◽  
Postoperative Mortality ◽  
Mortality Rates ◽  
Cavernous Malformations ◽  
Patient Cohort ◽  
Actual Risk ◽  
Single Center Study

<b><i>Objective:</i></b> Brainstem cavernous malformations (BSCM)-associated mortality has been reported up to 20% in patients managed conservatively, whereas postoperative mortality rates range from 0 to 1.9%. Our aim was to analyze the actual risk and causes of BSCM-associated mortality in patients managed conservatively and surgically based on our own patient cohort and a systematic literature review. <b><i>Methods:</i></b> Observational, retrospective single-center study encompassing all patients with BSCM that presented to our institution between 2006 and 2018. In addition, a systematic review was performed on all studies encompassing patients with BSCM managed conservatively and surgically. <b><i>Results:</i></b> Of 118 patients, 54 were treated conservatively (961.0 person years follow-up in total). No BSCM-associated mortality was observed in our conservatively as well as surgically managed patient cohort. Our systematic literature review and analysis revealed an overall BSCM-associated mortality rate of 2.3% (95% CI: 1.6–3.3) in 22 studies comprising 1,251 patients managed conservatively and of 1.3% (95% CI: 0.9–1.7) in 99 studies comprising 3,275 patients with BSCM treated surgically. <b><i>Conclusion:</i></b> The BSCM-associated mortality rate in patients managed conservatively is almost as low as in patients treated surgically and much lower than in frequently cited reports, most probably due to the good selection nowadays in regard to surgery.

Outcome in an Urban Pediatric Trauma System with Unified Prehospital Emergency Medical Services Care

1995 ◽  
Vol 10 (1) ◽  
pp. 19-23 ◽  
Author(s):  
Michael J. VanRooyen ◽  
Edward P. Sloan ◽  
John A. Barrett ◽  
Robert F. Smith ◽  
Hernan M. Reyes
Keyword(s):  
Head Injury ◽  
Mortality Rate ◽  
Trauma Center ◽  
Pediatric Trauma ◽  
Trauma System ◽  
Age Groups ◽  
Mortality Rates ◽  
Trauma Centers ◽  
Field Triage ◽  
Pediatric Trauma Center

AbstractHypothesis:Pediatric mortality is predicted by age, presence of head trauma, head trauma with a low Glasgow Coma Scale (GCS) score, a low Pediatric Trauma Score (PTS), and transport directly to a pediatric trauma center.Population:Studied were 1,429 patients younger than 16 years old admitted to or declared dead on arrival (DOA) in a pediatric trauma center from January through October, 1988. The trauma system, which served 3-million persons, included six pediatric trauma centers.Methods:Data were obtained by a retrospective review of summary statistics provided to the Chicago Department of Health by the pediatric trauma centers.Results:Overall mortality was 4.8% (68 of 1429); 32 of the patients who died (47.1%) were DOA. The in-hospital mortality rate was 2.6%. Head injury was the principal diagnosis in 46.2% of admissions and was a factor in 72.2% of hospital deaths. The mortality rate was 20.3% in children with a GCS≤10 and 0.4% when the GCS was >10 (odds ratio [OR] = 67.0, 95% CI = 15.0–417.4). When the PTS was ≤ 5, mortality was 25.6%; with a PTS > 5, the mortality was 0.2% (OR = 420.7, 95% CI = 99.3–2,520). Although transfers to a pediatric trauma center accounted for 73.6% of admissions, direct field triage to a pediatric trauma center was associated with a 3.2 times greater mortality risk (95% CI = 1.58–6.59). Mortality rates were equal for all age groups. Pediatric trauma center volume did not influence mortality rates.Conclusions:Head injury and death occur in all age groups, suggesting the need for broad prevention strategies. Specific GCS and PTS values that predict mortality can be used in emergency medical services (EMS) triage protocols. Although the high proportion of transfers mandates systemwide transfer protocols, the lower mortality in these patients suggests appropriate EMS field triage. These factors should be considered as states develop pediatric trauma systems.

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