scholarly journals Immediate maximum economic yield; a realistic fisheries economic reference point

2009 ◽  
Vol 67 (3) ◽  
pp. 577-582 ◽  
Author(s):  
Jordi Lleonart ◽  
Gorka Merino
Keyword(s):  
Reference Point ◽  
Fishing Effort ◽  
Reference Points ◽  
Economic Rent ◽  
Short Term ◽  
Fishing Season ◽  
Shrimp Fishery ◽  
Maximum Economic Yield ◽  
Nw Mediterranean ◽  
Definition Of

Abstract Lleonart, J., and Merino, G. 2010. Immediate maximum economic yield; a realistic fisheries economic reference point. – ICES Journal of Marine Science, 67: 577–582. Unregulated or poorly managed fisheries tend towards overexploitation, but fisheries rent does not completely dissipate when immediate rent maximization is sought. The principle of immediate economic rent maximization is the basis of the derivation of a classic model and has led to the definition of a relationship in a catch-and-effort diagram termed the dynamic immediate maximum economic yield (DIMEY) curve. For any initial biomass, if the economic rent in the immediate fishing season is maximized, then the fishing effort and catch strategy that follows will be located on the DIMEY curve. The DIMEY curve is not only used for dynamic simulation but also used to identify a new reference point, the immediate maximum economic yield (IMEY), which is proposed as more realistic than the classic open-access solution for unregulated fisheries. IMEY is proposed as an asymptotic outcome for unregulated or poorly managed fisheries when short-term economic objectives drive fleet activities. IMEY properties are described and compared with traditional fisheries reference points in the yield-and-effort diagram. Theoretical conclusions are compared with empirical evidence provided by the red shrimp fishery off Blanes, Spain (NW Mediterranean). Observed catch-and-effort records are plotted and were positively correlated with the DIMEY curve and IMEY.

An Alternative Perspective on Recruitment Overfishing and Biological Reference Points

1987 ◽  
Vol 44 (4) ◽  
pp. 913-918 ◽  
Author(s):  
M. P. Sissenwine ◽  
J. G. Shepherd
Keyword(s):  
Fisheries Management ◽  
Reference Point ◽  
Reference Points ◽  
Fishing Mortality ◽  
Alternative Perspective ◽  
Conventional Models ◽  
Definition Of ◽  
Yield Per Recruit ◽  
Spawning Biomass

Biological reference points are used to guide fisheries management decisions. The reference points most often used are expressed in terms of fishing mortality rate (F). Fmsy relates to the maximization of sustainable yield. In principle, it is a most useful reference point, but in practice it is difficult to estimate. Fmax and F0.1 relate to certain levels of yield per recruit and are easily estimated, but they ignore conservation of the resource. Recruitment overfishing has usually been understood to occur when a population has been fished down to a point where recruitment is substantially reduced or fails. It has not been used as a basis for a biological reference point because the definition is vague and cannot be readily related to fishing mortality. Levels of spawning biomass below which recruitment seems to be reduced have been used, but their determination from available data is usually difficult and controversial. We propose an alternative definition of recruitment overfishing in terms of the level of fishing pressure that reduces the spawning biomass of a year class over its lifetime below the spawning biomass of its parents on average. Conventional models and types of data can be used to determine this level of F, denoted as Frep, which clearly relates to the replacement of spawning biomass and thus to sustainability of a population and yield in the long term.

Biological reference points for sea scallops (Placopecten magellanicus): the benefits and costs of being nearly sessile

2004 ◽  
Vol 61 (8) ◽  
pp. 1338-1354 ◽  
Author(s):  
Stephen J Smith ◽  
Paul Rago
Keyword(s):  
Management Strategies ◽  
Fishing Effort ◽  
Reference Points ◽  
Placopecten Magellanicus ◽  
Nonlinear Mixed Effects Models ◽  
Lower Productivity ◽  
Boom And Bust ◽  
Sea Scallops ◽  
Habitat Damage ◽  
Definition Of

In this paper, we concentrate on spatial aspects of growth and reproduction for sea scallops (Placopecten magellanicus) to advance the general theory for development of reference points for sessile animals and to illustrate the general points with several specific examples. Nonlinear mixed effects models can be used to define the spatial distribution of growth rates and their implications for the definition of growth overfishing. We develop a basin model to illustrate that the typical "boom and bust" effects, often attributed to environmental factors, are explained equally well by spatial variations in habitat quality, spatial concentration of fisheries, and dispersal of larvae among areas. Results suggest that incentives to concentrate fishing effort in lower productivity areas may be an effective tool for reducing recruitment variation and improving yields. Reductions in fishing mortality might be possible with closed areas as they can be used to reduce the concentration of effort on high scallop densities. Further, rotational area management strategies can offer the promise of balancing demands for increased yield, prevention of recruitment overfishing, maintaining spawning reserves, and reducing habitat damage and bycatch.

scholarly journals ANGKA ACUAN SASARAN UNTUK PENGELOLAAN PERIKANAN UDANG LAUT ARAFURA DENGAN TUJUAN BERAGAM

2013 ◽  
Vol 5 (2) ◽  
pp. 73
Author(s):  
Purwanto Purwanto
Keyword(s):  
Fisheries Management ◽  
Programming Model ◽  
National Development ◽  
Fishing Effort ◽  
Optimal Number ◽  
Reference Points ◽  
Shrimp Fishery ◽  
Fishing Vessels ◽  
Conflicting Objectives ◽  
Arafura Sea

<p>Kriteria pengelolaan perikanan dalam kerangka pembangunan nasional, yaitu pro-growth, pro-poor, pro-job dan pro-environment, mengarahkan pengelolaan perikanan udang di Laut Arafura untuk mengoptimumkan produksi lestari dan keuntungan perikanan, serta meningkatkan keuntungan per kapal dan peluang kerja sebagai nelayan. Masing-masing tujuan tersebut perlu ditetapkan angka acuan sasarannya yang diharapkan dicapai dalam pengelolaan perikanan. Mengingat tujuan tersebut saling bertentangan, sehingga tidak dapat dicapai bersamaan, perlu ditentukan tingkat kompromi optimal diantara tujuan tersebut dan angka acuan sasarannya. Tulisan ini menyajikan model pemrograman matematika untuk optimisasi dengan empat tujuan pengelolaan, serta menggunakannya untuk mengestimasi angka acuan sasaran dan jumlah optimal kapal penangkap. Hasil optimisasi dengan pemberian bobot prioritas yang sama terhadap empat tujuan pengelolaan perikanan dalam kerangka pembangunan nasional menunjukkan bahwa angka acuan sasaran pada tingkat kompromi optimal dicapai dengan pengendalian upaya penangkapan pada tingkat yang setara dengan daya tangkap 512 kapal pukat udang 130 GT. Angka acuan sasaran yang sama dihasilkan dari optimisasi dengan pemberian bobot prioritas yang lebih tinggi terhadap dua tujuan pengelolaan perikanan sesuai dengan Pasal 6 Undang Undang Perikanan tahun 2004.</p><p>The criteria of fisheries management undertaken in a framework of national development, particularly pro-growth, pro-poor, pro-job and pro-environment, guide the management of shrimp fishery in the Arafura Sea to optimising shrimp production and fishery profit, and increasing per vessel profit and job opportunity as fishers. As those objectives were conflicting that could not be achieved simultaneously, it is necessary to seek an optimal compromise amongst several conflicting objectives and to estimate their target reference points. This paper presents a mathematical programming model accommodating four objectives of fisheries management, and the utilisation of this for estimating the target reference points and the optimal number of fishing vessels. The result of optimisation shows that target reference points at the optimal compromise levels for the four conflicting objectives, with equal priority, of fisheries management supporting the national development could be achieved by controlling fishing effort at the level equal to fishing power of 512 shrimp trawlers of 130 GT. The same target reference points resulted from the analysis providing higher priority to the objectives of fisheries management stated in Article 6 of Fisheries Act of 2004.</p>

scholarly journals Delineating the continuum of marine ecosystem-based management: a US fisheries reference point perspective

2015 ◽  
Vol 73 (4) ◽  
pp. 1042-1050 ◽  
Author(s):  
Tara E. Dolan ◽  
Wesley S. Patrick ◽  
Jason S. Link
Keyword(s):  
Fisheries Management ◽  
Ecosystem Management ◽  
Reference Point ◽  
Marine Ecosystem ◽  
Single Species ◽  
Reference Points ◽  
Current State ◽  
Definition Of ◽  
Compare And Contrast ◽  
The Continuum

Abstract Ecosystem management (EM) suffers from linguistic uncertainty surrounding the definition of “EM” and how it can be operationalized. Using fisheries management as an example, we clarify how EM exists in different paradigms along a continuum, starting with a single-species focus and building towards a more systemic and multi-sector perspective. Focusing on the specification of biological and other systemic reference points (SRPs) used in each paradigm and its related regulatory and governance structures, we compare and contrast similarities among these paradigms. We find that although EM is a hierarchical continuum, similar SRPs can be used throughout the continuum, but the scope of these reference points are broader at higher levels of management. This work interprets the current state of the conversation, and may help to clarify the levels of how EM is applied now and how it can be applied in the future, further advancing its implementation.

scholarly journals Can we fish on stocks that need rebuilding? Illustrating the trade-offs between stock conservation and fisheries considerations

2021 ◽  
Author(s):  
Vanessa Trijoulet ◽  
Casper W Berg ◽  
Claus R Sparrevohn ◽  
Anders Nielsen ◽  
Martin A Pastoors ◽  
...  
Keyword(s):  
North Sea ◽  
Reference Point ◽  
Reference Points ◽  
Lower Probability ◽  
Medium Term ◽  
Short Term ◽  
Fish Stocks ◽  
Control Rules ◽  
Trade Offs ◽  
Harvest Control Rules

In the Northeast Atlantic, advice for many fish stocks follows the ICES MSY approach, where a zero catch will be recommended if the stock is below its limit reference point, Blim, and cannot rebuild in the short-term. However, zero catch advice are rarely implemented by managers. This study used medium-term stochastic forecasts with harvest control rules (HCRs) to investigate the consequences of allowing reduced fishing below Blim. We applied the method to western Baltic herring and North Sea cod, two contrasting species currently estimated below Blim. We show that the minimum rebuilding probability of 95% required by the MSY approach could be impossible to reach in the short-to medium-term. When this is the case, a lower probability may need to be considered instead in the short-term. Recruitment is the largest source of uncertainty in stock response to management, and can exceed differences between HCRs. Reference points should be estimated in accordance with current recruitment levels if they are to be used for short-term advice or as realistic rebuilding targets. For both stocks, it is possible to keep fishing at reduced levels for similar cumulative catch, SSB and risk on the stock in the medium-term compared to no catch below Blim. Medium-term trade-offs between stock conservation and fisheries considerations may be needed when fishery closure cannot be implemented in practice.

On modal grounding, reference points, and subjectification

2005 ◽  
Vol 3 ◽  
pp. 56-77 ◽  
Author(s):  
Bert Cornillie
Keyword(s):  
Reference Point ◽  
Epistemic Modals ◽  
Reference Points ◽  
Epistemic Modality ◽  
Point Function ◽  
Theoretical Underpinning ◽  
Modal Verbs ◽  
Epistemic Modal ◽  
Modal Auxiliaries ◽  
Definition Of

In this paper it is argued that Langacker’s definition of grounding predications is problematic for languages other than English. The idea that in English tense and modal auxiliaries are mutually exclusive grounding elements leads Langacker (1990, 2003) to consider both deontic and epistemic modal auxiliaries as grounding predications, whereas he excludes German modals from being so on the basis of their tense inflection. In this paper I contend that, unlike the deontic modal verbs, and despite their tense marking, Spanish epistemic modals deber ‘must’, poder ‘may’ and tener que ‘have to’ are certainly appropriate for modal grounding due to their reference point function and to the subjectification they undergo. I show that deontic modality is more affected by temporal grounding than epistemic modality. Moreover, the impossibility of inserting an inchoative verb such as ir a ‘to be going to’ corroborates the theoretical underpinning that Spanish epistemic modals effect an epistemic grounding similar to that of the grounding predications in English.

scholarly journals Bioeconomics of Commercial Marine Fisheries of Bay of Bengal: Status and Direction

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Ahasan Habib ◽  
Md. Hadayet Ullah ◽  
Nguyen Ngoc Duy
Keyword(s):  
Bay Of Bengal ◽  
Legal Framework ◽  
Fishing Effort ◽  
Maximum Sustainable Yield ◽  
Reference Points ◽  
Production Model ◽  
Marine Fishery ◽  
Maximum Economic Yield ◽  
Surplus Production Model ◽  
Marine Realm

The fishery of the Bay of Bengal (BOB) is assumed to be suffering from the overexploitation. This paper aims to assess the sustainability of current level of fishing effort as well as possible changes driven by anthropogenic and climate driven factors. Therefore, the commercial marine fishery of BOB for the period of 1985/86 to 2007/08 is analyzed by applying Gordon-Schaefer Surplus Production Model on time series of total catch and standardized effort. Static reference points such as open-access equilibrium, maximum economic yield, and maximum sustainable yield are established. Assumptions about potential climatic and anthropogenic effects on r (intrinsic growth rate) and K (carrying capacity) of BOB fishery have been made under three different reference equilibriums. The results showed that the fishery is not biologically overexploited; however, it is predicted to be passing a critical situation, in terms of achieving reference points in the near future. But, on the other hand, economic overfishing started several years before. Higher fishing effort, and inadequate institutional and legal framework have been the major bottlenecks for the proper management of BOB fisheries and these may leads fishery more vulnerable against changing marine realm. Thus, the present study calls for policy intervention to rescue the stock from the existing high fishing pressure that would lead to depletion.

scholarly journals Subjective judgement in data subsetting: implications for CPUE standardisation and stock assessment of non-target chondrichthyans

2011 ◽  
Vol 62 (6) ◽  
pp. 734 ◽  
Author(s):  
J. M. Braccini ◽  
M.-P. Etienne ◽  
S. J. D. Martell
Keyword(s):  
Ad Hoc ◽  
Stock Assessment ◽  
Fishing Effort ◽  
Reference Points ◽  
Fish Stock ◽  
Model Parameters ◽  
Total Allowable Catch ◽  
Subjective Judgement ◽  
Definition Of ◽  
Catch Per Effort

Standardisation of catch-per-effort (CPUE) data is an essential component for nearly all stock assessments. The first step in CPUE standardisation is to separate the comparable from the non-comparable catch and effort records and this is normally done based on subjective rules. In the present study, we used catch-and-effort data from the elephant fish (Callorhinchus milii) to illustrate the differences in CPUE when using expert judgement to define different ad hoc selection criteria used to subset these data. The data subsets were then used in the standardisation of CPUE and the stock assessment of elephant fish. The catch-and-effort subsets produced different patterns of precision and trends, each of which led to different estimates (and related uncertainty) of model parameters and management reference points. For most CPUE series, there was a very high probability that the elephant fish stock is overexploited and that overfishing is occurring. The estimates of total allowable catch (TAC) and the uncertainty around these estimates also varied considerably depending on the CPUE series used. Our study shows how sensitive TAC estimation is when there is high uncertainty in the definition of the fishing effort targeted at the species analysed.

scholarly journals Implications of climate change for the management of North Sea cod (Gadus morhua)

2005 ◽  
Vol 62 (7) ◽  
pp. 1483-1491 ◽  
Author(s):  
Laurence T. Kell ◽  
Graham M. Pilling ◽  
Carl M. O'Brien
Keyword(s):  
Climate Change ◽  
North Sea ◽  
Gadus Morhua ◽  
Stock Assessment ◽  
Management Strategies ◽  
Fishing Effort ◽  
Reference Points ◽  
Fishing Mortality ◽  
Short Term ◽  
Management Procedures

Abstract Robustness of both short-term stock biomass recovery and longer-term sustainable management strategies to different plausible climatic change scenarios were evaluated for North Sea cod (Gadus morhua), where climate was assumed to impact growth and recruitment. In the short term, climate change had little effect on stock recovery, which depends instead upon reducing fishing effort to allow existing year classes to survive to maturity. In the longer term, climate change has greater effects on stock status, but higher yields and biomass can be expected if fishing mortality is reduced. Incorporating environmental covariates in stock assessment predictions will not achieve sustainable resource use. The implications of climate change for biological reference points depend upon the mechanism through which temperature acts on recruitment, i.e. on juvenile survival or carrying capacity. It is not possible to distinguish between these processes with stock assessment data sets alone. However, this study indicates that reference points based on fishing mortality appear more robust to uncertainty than those based on biomass. Ideally, simpler management procedures are required that meet pre-agreed management objectives and are robust to uncertainty about the true dynamics.

Cognitive Reflection Effects on Time Discounting

2018 ◽  
Vol 39 (2) ◽  
pp. 99-106 ◽  
Author(s):  
Michał Białek ◽  
Przemysław Sawicki
Keyword(s):  
Individual Differences ◽  
Individual Difference ◽  
Delay Discounting ◽  
Reference Point ◽  
Reference Points ◽  
Cognitive Reflection Test ◽  
Process Information ◽  
Time Discounting ◽  
Cognitive Reflection ◽  
The Way

Abstract. In this work, we investigated individual differences in cognitive reflection effects on delay discounting – a preference for smaller sooner over larger later payoff. People are claimed to prefer more these alternatives they considered first – so-called reference point – over the alternatives they considered later. Cognitive reflection affects the way individuals process information, with less reflective individuals relying predominantly on the first information they consider, thus, being more susceptible to reference points as compared to more reflective individuals. In Experiment 1, we confirmed that individuals who scored high on the Cognitive Reflection Test discount less strongly than less reflective individuals, but we also show that such individuals are less susceptible to imposed reference points. Experiment 2 replicated these findings additionally providing evidence that cognitive reflection predicts discounting strength and (in)dependency to reference points over and above individual difference in numeracy.

Sign in / Sign up

Export Citation Format

Share Document