A POLICY OF FISHERIES MANAGEMENT BASED ON CONTINUOUS FISHING EFFORT

2001 ◽  
Vol 09 (04) ◽  
pp. 247-254 ◽  
Author(s):  
M. JERRY ◽  
N. RAISSI
Keyword(s):  
Equilibrium Point ◽  
Fisheries Management ◽  
Optimal Strategy ◽  
Fishing Effort ◽  
Asymptotical Stability

This work is composed by two parts: the first part consists of the development and the analysis of a bioeconomical model of fisheries management, where the dynamic is controlled by the variation of the fishing effort; the second part of this work consists of the study of the asymptotical stability of the equilibrium point (stock/fishing effort) of the model; the optimal strategy is described briefly.

Benthic Habitats and the Effects of Fishing

2005 ◽  
Keyword(s):  
Fisheries Management ◽  
Large Scale ◽  
Scale Effects ◽  
Ecosystem Processes ◽  
Fishing Effort ◽  
Habitat Types ◽  
Benthic Habitats ◽  
Management Actions ◽  
Ecosystem Effects ◽  
Ecosystem Based Fisheries Management

<strong><em>Abstract. </em></strong>We review the impacts of towed gears on benthic habitats and communities and predict the consequences of these impacts for ecosystem processes. Our emphasis is on the additive and synergistic large-scale effects of fishing, and we assess how changes in the distribution of fishing activity following management action are likely to affect production, turnover time, and nutrient fluxes in ecosystems. Analyses of the large-scale effects of fishing disturbance show that the initial effects of fishing on a habitat have greater ecosystem consequences than repeated fishing in fished areas. As a result, patchy fishing effort distributions have lower total impacts on the ecosystem than random or uniform effort distributions. In most fisheries, the distribution of annual fishing effort within habitats is more patchy than random, and patterns of effort are maintained from year to year. Our analyses suggest that many vulnerable species and habitats have only persisted in heavily fished ecosystems because effort is patchy. Ecosystem-based fisheries management involves taking account of the ecosystem effects of fishing when setting management objectives. One step that can be taken toward ecosystem-based fisheries management is to make an a priori assessment of the ecosystem effects of proposed management actions such as catch controls, effort controls, and technical measures. We suggest a process for predicting the ecosystem consequences of management action. This requires information on habitat distributions, models to predict changes in the spatial distribution of fleets following management action, and models of the impacts of trawling disturbance on ecosystem processes. For each proposed management action, the change in disturbance affecting different habitat types would be predicted and used to forecast the consequences for the ecosystem. These simulations would be used to produce a decision table, quantifying the consequences of alternative management actions. Actions that minimize the ecosystem effects of fishing could then be identified. In data-poor situations, we suggest that management strategies that maintain or maximize the patchiness of effort within habitat types are more consistent with the precautionary approach than those that lead to more uniform fishing effort distributions.

scholarly journals Costs and Returns of Fishermen in the Massachusetts Inshore Lobster Fishery

1975 ◽  
Vol 4 (2) ◽  
pp. 195-210 ◽  
Author(s):  
J. M. Gates ◽  
J. M. D'Eugenio
Keyword(s):  
Fisheries Management ◽  
Fishing Effort ◽  
The State ◽  
Economic Factors ◽  
Sufficient Criterion ◽  
Fish Stocks ◽  
The Past ◽  
Resource Managers ◽  
Lobster Fishery

The inshore lobster fishery is one of the more important ones in the Commonwealth of Massachusetts, accounting for approximately 14 percent of the total landed value of all species in Massachusetts in 1971. Until recent years this fishery accounted for virtually all the pot landings in the state. Despite numerous attempts at conservation such as gear regulation, size restrictions, and prohibitions on harvesting egg-bearing females, the fishery has been subject to rapidly increasing effort and virtually constant landings. In the past decade it has become obvious to many fishery biologists and economists that conservation of fish stocks is a necessary but not sufficient criterion for fisheries management. Resource managers have become increasingly aware of the interdependence between economic factors and the intensity, location and composition of fishing effort.

A fisheries perspective of behavioural variability: differences in movement behaviour and extraction rate of an exploited sparid, snapper (Pagrus auratus)

2011 ◽  
Vol 68 (4) ◽  
pp. 632-642 ◽  
Author(s):  
Darren M. Parsons ◽  
Mark A. Morrison ◽  
Jeremy R. McKenzie ◽  
Bruce W. Hartill ◽  
Richard Bian ◽  
...  
Keyword(s):  
Population Size ◽  
Fisheries Management ◽  
Fishing Effort ◽  
Extraction Rate ◽  
Movement Behaviour ◽  
Pagrus Auratus ◽  
The Status ◽  
Likelihood Model ◽  
Lower Population ◽  
Fishery Species

Intraspecific variation in movement patterns are well established for many species, but poorly appreciated in fisheries management. In this study we dart-tagged snapper ( Pagrus auratus ), an important fishery species, across different areas and habitats in the Hauraki Gulf, New Zealand. Tag returns were used to quantify movement behaviour and extraction rates using a maximum likelihood model that corrected for spatial variability in population size and fishing effort. Residency was high (~90%) in two strata and lower (75%) in the remaining stratum. The stratum with the highest residency also appeared to experience the highest extraction rate (likely due to a lower population size). These results confirm the existence of differences in movement behaviour within the snapper population, suggesting that localized areas may become depleted regardless of the status of the overall stock. This has consequences for the scale of fisheries management and the size of marine reserves implemented in different regions. Understanding why variation in movement behaviour exists (i.e., genetic vs. environmental) is the next step in addressing the influence of animal behaviour on fisheries management.

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 Dinámica espacio-temporal del esfuerzo en una pesquería de buceo artesanal multiespecífica y sus efectos en la variabilidad de las capturas: Implicaciones para el manejo sostenible

2014 ◽  
Vol 62 (4) ◽  
pp. 1565 ◽  
Author(s):  
Helven Naranjo Madrigal ◽  
Silvia Salas Márquez
Keyword(s):  
Fisheries Management ◽  
Pacific Coast ◽  
Temporal Dynamics ◽  
Fishing Effort ◽  
The North ◽  
Fishing Strategies ◽  
Personal Consumption ◽  
Spatial And Temporal Dynamics ◽  
The North Pacific

Artisanal diving fisheries are a source of income, employment and food security of coastal areas in many countries. Understanding the dynamics of these fisheries, including the spatial and temporal dynamics of fishing effort, gears and species can help to address the challenges involved in fisheries management. We aimed to analyze the differences in fishing strategies undertaken by fishers that use two different diving methods (hookah and free diving), and the conditions and their potential impacts on catches when adjustments to those strategies are applied over time. For this, detailed information of fishing operations from artisanal boats in the North Pacific coast of Costa Rica was analyzed in two fishing seasons (2007-2008 and 2011-2012). Data were collected by onboard observers (fishing site, fishing time, species composition, depth and visibility). Additionally, interviews with divers were applied to obtain information of price per species, species volume and fishing operations. From the total number of trips during both seasons, hookah diving was represented by a sample size of 70.5%, while free diving, with a sample of 69.5%. More than 15 species were identified in each fishing season. Nevertheless, three categories had substantial contributions in both seasons with differences in the proportions for each case: green lobster (<em>Panulirus gracilis</em>), octopus (<em>Octopus</em> sp.) and parrotfish (<em>Scarus perrico</em> and <em>S. ghobban</em>). It is worth noting that an important proportion of catch was retained by fishers for personal consumption purposes, including species of high commercial value. Additional night diving activity, increased the number of dives from one season to another. Besides, cooperation processes in free diving fishing operations, and changes in fishing effort between seasons, defined important changes in fishing strategies. Potential causes of changes in fishing strategies and the implications for management to ensure the sustainability of these fisheries in the long term are discussed.

scholarly journals PERKEMBANGAN EKONOMI SUBSEKTOR PERIKANAN DI KABUPATEN MINAHASA SELATAN PROVINSI SULAWESI UTARA

2013 ◽  
Vol 1 (2) ◽  
pp. 81
Author(s):  
Aldy Adrianus Tatali ◽  
Eddy Mantjoro ◽  
Florence V. Longdong
Keyword(s):  
Economic Development ◽  
Fisheries Management ◽  
Driving Force ◽  
Fishing Effort ◽  
Salted Fish ◽  
Smoked Fish ◽  
Fisheries Resources ◽  
North Sulawesi ◽  
Fishery Products ◽  
The Government

PERKEMBANGAN EKONOMI SUBSEKTOR PERIKANAN DI KABUPATEN MINAHASA SELATAN PROVINSI SULAWESI UTARA1 Economic Development Fisheries Subsector in the South Minahasa Regency Aldy Adrianus Tatali2, Eddy Mantjoro3, Florence V Longdong3   ABSTRACT The Development of fisheries in North Sulawesi refers to fisheries subsector progress and national marine. Also look at the potential of natural resources, so that fisheries and marine sector to be one of the flagship program of economic development of North Sulawesi. By knowing the great potential of fisheries resources and the development of fishing effort, aquaculture and fisheries management efforts, the government set the fisheries subsector as one driving force of development. Fishermen fishing in coastal South Minahasa regency fishing along the coast and in the Celebes Sea. Most fishermen only catch about 2-3 miles away from the coast. For fishermen purse seine at a distance far enough from the coast 7-12 mill. Mariculture potential to be developed because it is supported by the marine and coastal areas of South Minahasa regency broad and potent. Some commodities, seeded mariculture in South Minahasa Regency is seaweed, grouper, giant travelly (bobara) and sea cucumbers. Production of processed fishery products in South Minahasa Regency is very diverse both in the traditional and modern though. Commodities processed fishery products in the form of wooden fish, salted fish, smoked fish/fufu and bakasang. Keywords : economic, development, fisheries   ABSTRAK Pengembangan usaha perikanan di Sulawesi Utara mengacu pada pembangunan subsektor perikanan dan kelautan nasional. Juga melihat potensi sumberdaya alam, sehingga dari sektor perikanan dan kelautan menjadi salah satu program unggulan pembangunan ekonomi Sulawesi Utara. Dengan mengetahui potensi sumberdaya perikanan yang besar dan perkembangan usaha penangkapan, budidaya dan usaha pengelolaan hasil perikanan maka pemerintah menetapkan subsektor perikanan sebagai salah satu motor penggerak pembangunan. Nelayan perikanan tangkap di pesisir Kabupaten Minahasa Selatan menangkap ikan sepanjang pantai maupun di Laut Sulawesi. Kebanyakan nelayan tradisional hanya menangkap ikan sekitar 2-3 mil jauhnya dari pantai. Bagi nelayan Purse Sein cukup jauh dengan jarak 7-12 mill dari pantai. Budidaya laut sangat potensial untuk dikembangkan karena di dukung oleh wilayah laut dan pesisir Kabupaten Minahasa Selatan yang luas dan potensial. Beberapa komoditi yang menjadi unggulan budidaya laut di Kabupaten Minahasa Selatan adalah rumput laut, ikan kerapu, ikan kuwe (bobara) dan teripang. Produksi olahan hasil perikanan di Kabupaten Minahasa Selatan sangat beragam baik yang di olah secara tradisonal maupun modern. Komoditas olahan hasil perikanan itu berupa ikan kayu, ikan asin, ikan asap/fufu dan bakasang.   Kata kunci : ekonomi, pengembangan, perikanan   1 Bagian dari skripsi 2 Mahasiswa Program Studi Agrobisnis Perikanan FPIK-UNSRAT 3 Staf pengajar Fakultas Perikanan dan Ilmu Kelautan Universitas Sam Ratulangi

scholarly journals Spatiotemporal Variation in the Catch Composition and Abundance of Precious Corals Around Taiwan: Implications for Fisheries Management

2021 ◽  
Vol 8 ◽  
Author(s):  
Chih-Shin Chen
Keyword(s):  
Fisheries Management ◽  
Regional Cooperation ◽  
Fishing Effort ◽  
Spatiotemporal Variation ◽  
Northwest Pacific ◽  
Fishing Gear ◽  
Fishery Resource ◽  
Religious Importance ◽  
Fishing Fleets ◽  
Catch Composition

Precious corals are a fishery resource of cultural and religious importance. Because of their high commercial value, precious corals have been exploited for several centuries in the Mediterranean and for almost one century in the Northwest Pacific. Taiwanese fishing fleets have harvested precious corals since the 1920s; however, management regulations have only been promulgated since January 2009, when the catch and effort data of fisheries began to be collected. This study examined spatiotemporal variation in the catch composition and abundance of precious corals Corallium, Hemicorallium, and Pleurocorallium spp. around Taiwan using fishery data from 2009 to 2018 and discussed its implications for fisheries management. Licenses are issued for 60 vessels annually, and the annual total catch was 2.9–3.5 t between 2009 and 2018, peaking in 2015 and then decreasing sharply in 2016. Because of the use of non-selective fishing gear, dead and fossilized colonies were included in the total catches of the fishery. Fossilized colonies were predominant (average 78.5%) in the total catches, whereas the proportion of live colony catches accounted for less than 5%. Pink coral (Momo) was predominant in the total and live colony catches during the 10-year period. The Taiwanese precious coral fishing fleets are restricted to harvesting precious corals in five designated fishing grounds (DFGs; A–E). The fishing effort (vessel⋅day) was mainly concentrated in DFG-A (average 56.6%), which accounted for an average of 63.9% of the total catches. However, the live colony catches were largest in DFG-E (average 39.9%) and DFG-A (average 39.6%). The annual catch rates of live colonies decreased in two major fishing grounds (DFGs-A and DFG-B), whereas it increased in two minor fishing grounds (DFGs-C and DFG-D). The temporal variation in occurrence rates of live colonies decreased between 2015 and 2018, indicating a declining trend for precious coral populations around Taiwan. These results indicate that an unsustainable condition may occur in the near future if the precious corals continue to be harvested at the current scale. Revised regulations for the Taiwanese precious coral fishery should contain proposals on fishing gear modifications, a rotational harvesting scheme, or both; such measures can contribute to the conservation of precious coral populations. Regional cooperation in fisheries management is necessary to achieve the sustainable development of precious corals and their fisheries in the Northwest Pacific.

Determining Optimal Strategy of a Micro-Grid through Hybrid Method of Nash Equilibrium –Genetic Algorithm

2019 ◽  
Vol 20 (3) ◽  
Author(s):  
Ehsan Jafari
Keyword(s):  
Genetic Algorithm ◽  
Nash Equilibrium ◽  
Equilibrium Point ◽  
Hybrid Method ◽  
Optimal Strategy ◽  
Energy Resource ◽  
Energy Resources ◽  
Optimal Planning ◽  
Nash Equilibrium Point ◽  
Micro Grid

Abstract Increasing the fossil fuels consumption, pollution and rising prices of these fuels have led to the expansion of renewable resources and their replacement with conventional sources. In this paper, a robust algorithm for a micro-grid (MG) planning with the goal of maximizing profits is presented in day-ahead market. The energy resources in MG are wind farms (WFs), photovoltaic (PV), fuel cell (FC), combined heat and power(CHP) units, tidal steam turbine (TST) and energy storage devices (ESDs). This algorithm is divided into two main parts: (1) Optimal planning of each energy resource; (2) Using the Nash equilibrium –genetic algorithm (NE-GA) hybrid method to determine the optimal MG strategy. In energy resources optimal planning, using a stochastic formulation, the generation bids of each energy resource is determined in such a way that the profit of each one is maximized. Also, the constraints of renewable and load demands and selection the best method of demand response (DR) program are investigated. Then the Nash equilibrium point is determined using the primary population produced in the previous step using the NE-GA hybrid method to determine the optimal MG strategy. Thus, using the ability of the genetic algorithm method, the Nash equilibrium point of the generation units is obtained at an acceptable time, and This means that none of the units are willing to change their strategy and that the optimal strategy is extracted. Comparison of results with previous studies shows that the expected profit in the proposed method is more than other method.

scholarly journals DYNAMICAL TRAPS CAUSED BY FUZZY RATIONALITY AS A NEW EMERGENCE MECHANISM

2012 ◽  
Vol 15 (08) ◽  
pp. 1250045 ◽  
Author(s):  
IHOR LUBASHEVSKY
Keyword(s):  
Phase Space ◽  
Equilibrium Point ◽  
Optimal Strategy ◽  
Complex Behavior ◽  
Main Attention ◽  
Emergent Phenomena ◽  
Long Time ◽  
A Chain ◽  
The Stability ◽  
Operator Control

A new emergence mechanism related to the human fuzzy rationality is considered. It assumes that individuals (operators) governing the dynamics of a certain system try to follow an optimal strategy in controlling its motion but fail to do this perfectly because similar strategies are indistinguishable for them. The main attention is focused on the systems where the optimal dynamics implies the stability of a certain equilibrium point in the corresponding phase space. In such systems the fuzzy rationality gives rise to some neighborhood of the equilibrium point, the region of dynamical traps, wherein each point is regarded as an equilibrium one by the operators. So, when the system enters this region and while it is located in it, maybe for a long time, the operator control is suspended. To elucidate a question as to whether the dynamical traps on their own can cause emergent phenomena, the stochastic factors are eliminated from consideration. In this case the system can leave the dynamical trap region only because of the mismatch between actions of different operators. By way of example, a chain of oscillators with dynamical traps is analyzed numerically. As demonstrated, the dynamical traps do induce instability and complex behavior of such systems.

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