scholarly journals Evaluating deepwater fisheries management strategies using a mixed-fisheries and spatially explicit modelling framework

2013 ◽  
Vol 70 (4) ◽  
pp. 768-781 ◽  
Author(s):  
Paul Marchal ◽  
Youen Vermard
Keyword(s):  
Fisheries Management ◽  
Management Strategies ◽  
Spatially Explicit ◽  
Catch Per Unit Effort ◽  
Modelling Framework ◽  
Control Rules ◽  
Bioeconomic Modelling ◽  
Stock Assessments ◽  
Fleet Dynamics

Abstract Marchal, P., and Vermard, Y. 2013. Evaluating deepwater fisheries management strategies using a mixed-fisheries and spatially explicit modelling framework. – ICES Journal of Marine Science, 70: 768–781. We have used in this study a spatially explicit bioeconomic modelling framework to evaluate management strategies, building in both data-rich and data-limited harvest control rules (HCRs), for a mix of deepwater fleets and species, on which information is variable. The main focus was on blue ling (Molva dypterygia). For that species, both data-rich and data-limited HCRs were tested, while catch per unit effort (CPUE) was used either to tune stock assessments, or to directly trigger management action. There were only limited differences between the performances of both HCRs when blue ling biomass was initialized at the current level, but blue ling recovered more quickly with the data-rich HCR when its initial biomass was severely depleted. Both types of HCR lead, on average, to a long-term recovery of both blue ling and saithe (Pollachius virens) stocks, and some increase in overall profit. However, that improvement is not sufficient to guarantee sustainable exploitation with a high probability. Blue ling CPUE did not always adequately reflect trends in biomass, which mainly resulted from fleet dynamics, possibly in combination with density-dependence. The stock dynamics of roundnose grenadier (Coryphaenoides rupestris), black scabbardfish (Aphanopus carbo) and deepwater sharks (Centrophorus squamosus and Centroscymnus coelolepis) were little affected by the type of HCR chosen to manage blue ling.

scholarly journals Implementing the precautionary approach into fisheries management: Making the case for probability-based harvest control rules

2020 ◽  
Author(s):  
Tobias K. Mildenberger ◽  
Casper W. Berg ◽  
Alexandros Kokkalis ◽  
Adrian R. Hordyk ◽  
Chantel Wetzel ◽  
...  
Keyword(s):  
Fisheries Management ◽  
Management Strategies ◽  
Reference Points ◽  
Production Model ◽  
Scientific Uncertainty ◽  
Precautionary Approach ◽  
Control Rules ◽  
Stock Biomass ◽  
Harvest Control Rules

AbstractThe precautionary approach to fisheries management advocates for risk-averse management strategies that include biological reference points as well as decision rules and account for scientific uncertainty. In this regard, two approaches have been recommended: (i) harvest control rules (HCRs) with threshold reference points to safeguard against low stock biomass, and (ii) the P* method, a ‘probability-based HCR’ that reduces the catch limit as a function of scientific uncertainty (i.e. process, model, and observation uncertainty). This study compares the effectiveness of these precautionary approaches in recovering over-exploited fish stocks with various life-history traits and under a wide range of levels of scientific uncertainty. We use management strategy evaluation based on a stochastic, age-based operating model with quarterly time steps and a stochastic surplus production model. The results show that the most effective HCR includes both a biomass threshold as well as the P* method, and leads to high and stable long-term yield with a decreased risk of low stock biomass. For highly dynamics stocks, management strategies that aim for higher biomass targets than the traditionally used BMSY result in higher long-term yield. This study makes the case for probability-based HCRs by demonstrating their benefit over deterministic HCRs and provides a list of recommendations regarding their definition and implementation.

scholarly journals Leopard Density Estimation within an Enclosed Reserve, Namibia Using Spatially Explicit Capture-Recapture Models

Animals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 724
Author(s):  
Noack ◽  
Heyns ◽  
Rodenwoldt ◽  
Edwards
Keyword(s):  
Management Strategies ◽  
Camera Traps ◽  
Spatially Explicit ◽  
Conservation Areas ◽  
Term Survival ◽  
New Class ◽  
Capture Recapture ◽  
Wildlife Populations ◽  
Effective Conservation

The establishment of enclosed conservation areas are claimed to be the driving force for the long-term survival of wildlife populations. Whilst fencing provides an important tool in conservation, it simultaneously represents a controversial matter as it stops natural migration processes, which could ultimately lead to inbreeding, a decline in genetic diversity and local extinction if not managed correctly. Thus, wildlife residing in enclosed reserves requires effective conservation and management strategies, which are strongly reliant on robust population estimates. Here, we used camera traps combined with the relatively new class of spatially explicit capture-recaptured models (SECR) to produce the first reliable leopard population estimate for an enclosed reserve in Namibia. Leopard density was estimated at 14.51 leopards/100 km2, the highest recorded density in Namibia to date. A combination of high prey abundance, the absence of human persecution and a lack of top-down control are believed to be the main drivers of the recorded high leopard population. Our results add to the growing body of literature which suggests enclosed reserves have the potential to harbour high densities and highlight the importance of such reserves for the survival of threatened species in the future.

scholarly journals Evaluation of current and alternative fisheries management scenarios based on spawning-per-recruit (SPR), revenue-per-recruit (RPR), and yield-per-recruit (YPR) diagrams

2005 ◽  
Vol 62 (5) ◽  
pp. 841-846 ◽  
Author(s):  
T. Katsukawa
Keyword(s):  
Fisheries Management ◽  
Numerical Optimization ◽  
Management Strategy ◽  
Management Strategies ◽  
Management Scenarios ◽  
Trade Off ◽  
Contour Lines ◽  
Stock Assessments ◽  
Optimal Harvest ◽  
Yield Per Recruit

Abstract Spawning-per-recruit (SPR) and yield-per-recruit (YPR) analyses are widely used in stock assessments of exploited fish populations. In decision-making for fisheries management, the trade-off between fisheries production (YPR) and stock reproduction (SPR) is important. The general outputs of SPR and YPR analysis, such as single variate plots with contour lines or optimal harvest strategies estimated by numerical optimization, are inappropriate in obtaining an overview of the trade-off. This paper introduces a diagram that expresses graphically the bivariate trade-off between YPR and SPR. The method was applied to chub mackerel (Scomber japonicus) data, and two management scenarios were compared using the SPR–YPR diagram. Differences between YPR and revenue-per-recruit (RPR) were also considered. The results showed that: (i) current estimated fishing mortality is suggestive of growth-overfishing, and there is room for improving SPR and YPR simultaneously; (ii) increasing the age at first capture is more effective than effort control; (iii) management strategies that maximize landing weight or revenue are significantly different. The management strategy that maximizes landing weight, when considered from the viewpoint of maximizing revenue, results in growth-overfishing.

Diversity and complexity of angler behaviour drive socially optimal input and output regulations in a bioeconomic recreational-fisheries model

2010 ◽  
Vol 67 (9) ◽  
pp. 1507-1531 ◽  
Author(s):  
Fiona D. Johnston ◽  
Robert Arlinghaus ◽  
Ulf Dieckmann
Keyword(s):  
Fisheries Management ◽  
Fish Population ◽  
Integrated Modelling ◽  
The Novel ◽  
Recreational Fisheries ◽  
Optimal Input ◽  
Modelling Framework ◽  
Management Objectives ◽  
Input And Output ◽  
Bioeconomic Modelling

In many areas of the world, recreational fisheries are not managed sustainably. This might be related to the omission or oversimplification of angler behaviour and angler heterogeneity in fisheries-management models. We present an integrated bioeconomic modelling approach to examine how differing assumptions about angler behaviour, angler preferences, and composition of the angler population altered predictions about optimal recreational-fisheries management, where optimal regulations were determined by maximizing aggregated angler utility. We report four main results derived for a prototypical northern pike ( Esox lucius ) fishery. First, accounting for dynamic angler behaviour changed predictions about optimal angling regulations. Second, optimal input and output regulations varied substantially among different angler types. Third, the composition of the angler population in terms of angler types was important for determining optimal regulations. Fourth, the welfare measure used to quantify aggregated utility altered the predicted optimal regulations, highlighting the importance of choosing welfare measures that closely reflect management objectives. A further key finding was that socially optimal angling regulations resulted in biological sustainability of the fish population. Managers can use the novel integrated modelling framework introduced here to account, quantitatively and transparently, for the diversity and complexity of angler behaviour when determining regulations that maximize social welfare and ensure biological sustainability.

scholarly journals The dual role of indicators in optimal fisheries management strategies

2007 ◽  
Vol 64 (4) ◽  
pp. 775-778 ◽  
Author(s):  
Jake C. Rice ◽  
Denis Rivard
Keyword(s):  
Fisheries Management ◽  
Integrated Management ◽  
Management Strategies ◽  
Management Plan ◽  
Dual Role ◽  
Management Tools ◽  
Control Functions ◽  
Control Rules ◽  
Spawning Stock

Abstract Rice, J. C., and Rivard, D. 2007. The dual role of indicators in optimal fisheries management strategies. – ICES Journal of Marine Science, 64: 775–778. Indicators are used in two different ways in the assessment and advisory cycle. One is to audit performance of the management plan relative to achieving the objectives for the fishery. The second is to trigger control rules to manage the subsequent harvest. Traditionally, the assessment and management community has used spawning-stock biomass and fishing mortality for these functions, and as management strategies are being developed, generally continues to test the same indicators in both the audit and control functions. There is no reason to use the same indicators in both functions, and management of a few specialized commercial fisheries has recognized this, using different indicators in different roles for many years. That different indicators may be optimal for both roles presents a richer range of opportunities for exploring robust management strategies, and will be essential as ecosystem considerations and integrated management tools are included in assessment and management.

It’s time to sharpen our definition of sustainable fisheries management

2008 ◽  
Vol 65 (10) ◽  
pp. 2305-2314 ◽  
Author(s):  
Peter A. Shelton ◽  
Alan F. Sinclair
Keyword(s):  
Fisheries Management ◽  
Management Practices ◽  
Management Strategies ◽  
Governance Structure ◽  
Maximum Sustainable Yield ◽  
Sustainable Fisheries ◽  
International Obligations ◽  
Harvest Strategy ◽  
Definition Of

We review and evaluate the sustainability paradigm as it applies to wild capture fisheries in the context of a recently developed harvest strategy framework that, if implemented, will meet Canada’s national and international obligations with regard to sustainable fisheries. This framework is based on an operationally explicit definition of sustainability that includes a commitment to managing for maximum sustainable yield. Although Canadian policy strongly supports sustainable fisheries management in principle, usage of the term has been vague and implementation of sustainable fisheries management strategies has lagged. Fisheries managed under the recently developed framework would be better able to meet new ecocertification and ecolabelling standards. An emerging governance structure discussed herein with respect to fisheries management is conducive to implementing sustainable management practices that meet long-term public good objectives.

scholarly journals Predicting sustainable shark harvests when stock assessments are lacking

2018 ◽  
Vol 75 (5) ◽  
pp. 1591-1601 ◽  
Author(s):  
Corey J A Bradshaw ◽  
Thomas A A Prowse ◽  
Michael Drew ◽  
Bronwyn M Gillanders ◽  
Steven C Donnellan ◽  
...  
Keyword(s):  
Fisheries Management ◽  
Population Change ◽  
Population Decline ◽  
Life Tables ◽  
Stochastic Simulations ◽  
Sufficient Information ◽  
Natural Mortality ◽  
Boosted Regression Tree ◽  
Stock Assessments

Abstract Effective fisheries management generally requires reliable data describing the target species’ life-history characteristics, the size of its harvested populations, and overall catch estimates, to set sustainable quotas and management regulations. However, stock assessments are often not available for long-lived marine species such as sharks, making predictions of the long-term population impacts of variable catch rates difficult. Fortunately, stage- or age-structured population models can assist if sufficient information exists to estimate survival and fertility rates. Using data collected from the bronze whaler (Carcharhinus brachyurus) fishery in South Australia as a case study, we estimated survival probabilities from life tables of harvested individuals, as well as calculated natural mortalities based on allometric predictions. Fertility data (litter size, proportion mature) from previous studies allowed us to build a fertility vector. Deterministic matrices built using estimates of life-table data or natural mortality (i.e. harvested-augmented and natural mortality) produced instantaneous rates of change of 0.006 and 0.025, respectively. Assuming an incrementing total catch at multiples of current rates, stochastic simulations suggest the relative rate of population decline starts to become precipitous around 25% beyond current harvest rates. This is supported by a sharp increase in weighted mean age of the population around 25% increase on current catches. If the catch is assumed to be proportional (i.e. a constant proportion of the previous year’s population size), the relative r declines approximately linearly with incrementing harvest beyond the current rate. A global sensitivity analysis based on a Latin-hypercube sampling design of seven parameters revealed that variation in the survival estimates derived from the life tables was by far the dominant (boosted-regression tree relative influence score = 91.14%) determinant of model performance (measured as variation in the long-term average rate of population change r). While current harvest rates therefore appear to be sustainable, we recommend that fisheries-management authorities attempt to sample a broader size range of individuals (especially older animals) and pursue stock assessments. Our models provide a framework for assessing the relative susceptibility of long-lived fishes to harvest pressure when detailed stock data are missing.

scholarly journals “Crash landing” obligation for Mediterranean mixed fisheries: Evaluation of management strategies using bioeconomic modelling in the Aegean Sea

2019 ◽  
Vol 83 (2) ◽  
pp. 143 ◽  
Author(s):  
Maria Christou ◽  
Francesc Maynou ◽  
George Tserpes ◽  
Konstantinos I. Stergiou ◽  
Christos D. Maravelias
Keyword(s):  
Juvenile Fish ◽  
Management Strategies ◽  
Aegean Sea ◽  
Sustainable Fisheries ◽  
Management Measures ◽  
Bioeconomic Modelling ◽  
Fisheries Policy ◽  
Ne Mediterranean ◽  
The Common

Minimizing unwanted catches is a major milestone for achieving sustainable fisheries. In the framework of the Common Fisheries Policy, a landing obligation is being established progressively in European waters (Article 15, EU Regulation 1380/2013). Supplementary management measures have been proposed to support and enhance the effectiveness of this new regime. In this context, the effect of the landing obligation on a demersal mixed fishery (coastal and trawl fleet) in the Aegean Sea (NE Mediterranean Sea) was assessed in terms of both biological and economic sustainability. Our results show that the landing obligation alone does not ensure sustainable fisheries. Management action should be directed to the introduction of additional measures. Evidence suggests that improving selectivity and protecting the nursery grounds are possible solutions to decrease discards and ensure sustainable fisheries in the long term. The landing obligation can have a role in incentivizing the adoption of these management measures that ensure lower fishing mortality on juvenile fish.

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