scholarly journals Diversification insulates fisher catch and revenue in heavily exploited tropical fisheries

2020 ◽  
Vol 6 (8) ◽  
pp. eaaz0587 ◽  
Author(s):  
James P. W. Robinson ◽  
Jan Robinson ◽  
Calvin Gerry ◽  
Rodney Govinden ◽  
Cameron Freshwater ◽  
...  
Keyword(s):  
High Resolution ◽  
Fisheries Management ◽  
Management Strategies ◽  
Fishing Effort ◽  
Marine Resources ◽  
Nutritional Security ◽  
Fishing Vessels ◽  
Species Groups ◽  
Catch Rates ◽  
Average Catch

Declines in commercial landings and increases in fishing fleet power have raised concerns over the continued provisioning of nutritional and economic services by tropical wild fisheries. Yet, because tropical fisheries are often data-poor, mechanisms that might buffer fishers to declines are not understood. This data scarcity undermines fisheries management, making tropical fishing livelihoods particularly vulnerable to changes in marine resources. We use high-resolution fisheries data from Seychelles to understand how fishing strategy (catch diversification) influences catch rates and revenues of individual fishing vessels. We show that average catch weight decreased by 65% over 27 years, with declines in all nine species groups coinciding with increases in fishing effort. However, for individual vessels, catch diversity was associated with larger catches and higher fishing revenues and with slower catch declines from 1990 to 2016. Management strategies should maximize catch diversity in data-poor tropical fisheries to help secure nutritional security while protecting fishing livelihoods.

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>

Deriving high-resolution spatiotemporal fishing effort of large-scale longline fishery from vessel monitoring system (VMS) data and validated by observer data

2014 ◽  
Vol 71 (9) ◽  
pp. 1363-1370 ◽  
Author(s):  
Shui-Kai Chang ◽  
Tzu-Lun Yuan
Keyword(s):  
High Resolution ◽  
Fisheries Management ◽  
Large Scale ◽  
Fishing Effort ◽  
Time Of Day ◽  
Performance Measure ◽  
Classification Criteria ◽  
Monitoring Systems ◽  
Longline Fishery ◽  
Main Challenge

Estimating geo-referenced fishing effort is vital to develop advice for effective fisheries management. Many studies in recent decades have attempted to obtain complete, high-resolution effort data from vessel monitoring systems (VMSs). The main challenge in this regard is to develop a classification method for differentiating fishing activities (e.g., fishing days) from nonfishing activities in VMS data. This study developed a simple, novel classification criterion for a large-scale tuna longline (LTLL) fishery that has not been studied before. LTLL operations were first explored using observer data. Three approaches were designed for developing fishing-day classification criteria, using maximizing sum of sensitivity and specificity (SS) as the major performance measure and minimizing difference of SS as a reference. At least one VMS report with speed in the range of 2–5 kn (1 kn = 1.852 km·h–1) detected during the time-of-day period of 14:00–23:00 h was recommended as the criterion for defining a fishing day. Possible explanations for the differences between the estimated fishing days from VMS data and those reported on logbooks are discussed; most causes were related to specific features of the fishery.

A Robust Approach to Equilibrium Yield Curves

1986 ◽  
Vol 43 (7) ◽  
pp. 1332-1339 ◽  
Author(s):  
Gilbert G. Walter
Keyword(s):  
Fisheries Management ◽  
Management Strategies ◽  
Real Data ◽  
Concave Function ◽  
Fishing Effort ◽  
Approach To Equilibrium ◽  
Yield Curves ◽  
Fish Stocks ◽  
Robust Approach ◽  
Equilibrium Yield

The surplus yield models of fisheries management usually assume that a concave function of equilibrium yield versus fishing effort exists. However, this function is notoriously difficult to fit to real data for a number of reasons, including the fact that few fisheries are in equilibrium. A procedure for obtaining rough estimates of these equilibrium curves is introduced. Management strategies based on these estimates and the annual yield curves are also presented. The procedures are then applied to several fish stocks.

scholarly journals Scenario testing of fisheries management strategies using a high resolution ERSEM–POM ecosystem model

2007 ◽  
Vol 64 (9) ◽  
pp. 1627-1640 ◽  
Author(s):  
G. Petihakis ◽  
C. J. Smith ◽  
G. Triantafyllou ◽  
G. Sourlantzis ◽  
K-N. Papadopoulou ◽  
...  
Keyword(s):  
High Resolution ◽  
Fisheries Management ◽  
Management Strategies ◽  
Ecosystem Model ◽  
Ecosystem Models ◽  
Management Scenarios ◽  
Management Tools ◽  
Cost Impact ◽  
The Cost ◽  
Scenario Testing

Abstract Petihakis, G., Smith, C. J., Triantafyllou, G., Sourlantzis, G., Papadopoulou, K-N., Pollani, A., and Korres, G. 2007. Scenario testing of fisheries management strategies using a high resolution ERSEM–POM ecosystem model. – ICES Journal of Marine Science, 64: 1627–1640. Ecosystem models are just beginning to be considered as management tools. In terms of fishery impacts, dynamic ecosystem models provide an opportunity to make advances because they can both evaluate the state of the system and make predictions about the ecosystem under various fishing scenarios. In the framework of the Cost Impact project, a complex high-resolution (500 × 500 m grid) ecosystem model was implemented in Iraklion Bay, Crete. Several management scenarios were simulated to investigate the impacts of trawling on this particular ecosystem (reductions in fishing area, effort, and mortality). Introducing trawling impacts into the model led to increases in pelagic production. All scenarios also resulted in net increases in pelagic production, the level of which, and the degree of spatial variability, was dependent on the particular scenario. Changes in pelagic variables were often noted in areas well away from trawled areas. It was also clear that for pelagic variables and processes, depth of trawling is more important than reduction in trawling area, i.e. a scenario banning fishing in waters shallower than 100 m seems to lead to less change in the pelagic system than a scenario that reduces direct mortality to the benthos.

scholarly journals Analysis of the second generation buy-back program for fishing vessels in Turkey

2019 ◽  
Vol 36 (3) ◽  
pp. 229-243 ◽  
Author(s):  
Betül Ekmekci ◽  
Vahdet Ünal
Keyword(s):  
Fisheries Management ◽  
Sampling Method ◽  
Telephone Interview ◽  
Sustainable Use ◽  
Marine Resources ◽  
Fish Stocks ◽  
Fishing Vessels ◽  
Mediterranean Regions ◽  
Management Implication ◽  
Buy Back

Many implementations are put into practice on the national and international scale for the purpose of enabling the sustainable use of living marine resources. The Ministry of Food, Agriculture and Livestock published a notification in 2012 and the buy-back program for fishing vessels was initiated to keep the balance between the fish stocks and fishing capacity, prevent overfishing and enable sustainable fishing. While 12 m and larger vessels were considered in the first program, length of the vessels was reduced 10 m in the second. The aim of this study is to reveal the results of the related program. A telephone interview was applied to the owners of 207 fishing vessels determined through the stratified sampling method among 446 fishing vessels in 2014. In the 2nd program, 446 fishing vessels were withdrawn from the fleet by paying 51 million TL in total. Mostly the buy-back of the fishing vessels with the length of 10-20 meters (440 vessels) was carried out, and the fishing vessels with the length of 21-30 meters (6 vessels) were bought back at the least. Most of the vessels (44%) were from the Marmara and the least was from the Mediterranean Regions (19%). Only 9% of the vessels bough-back was trawl or purse seine vessels. It was found that 28% of vessel owners have a second vessel and gave the inactive or unprofitable vessels they had to the buy-back program. Furthermore, 62% of the individuals who gave their vessels stated that they will continue working in the fishing industry, and 27% of respondents stated that they will buy a new fishing vessel. As a result; buy-back program is one of the most important management implication of fisheries management authority in recent years. However, it should be considered by the managers that the large vessel owners have not shown interest in the program. One of every four fishermen giving his vessel is also a second vessel owner, and he gives his inactive vessel to the program, and the fishers have a similar tendency to buy a second vessel with the money they receive from the program. However, it is the basic approach that should be taken into account by the fisheries management authority to take advantage of relevant global experiences to ensure the highest possible benefit from the buy-back programs. This approach should at least be followed in future buy-back programs.

scholarly journals Balancing indigenous and non-indigenous commercial objectives in a coral reef finfish fishery

2011 ◽  
Vol 68 (5) ◽  
pp. 834-847 ◽  
Author(s):  
Ashley J. Williams ◽  
L. Richard Little ◽  
Gavin A. Begg
Keyword(s):  
Coral Reef ◽  
Management Strategies ◽  
Fishing Effort ◽  
Management Options ◽  
Alternative Management ◽  
Coral Trout ◽  
Evaluation Of Performance ◽  
Indigenous Participation ◽  
Torres Strait ◽  
Catch Rates

Abstract Williams, A. J., Little, L. R., and Begg, G. A. 2011. Balancing indigenous and non-indigenous commercial objectives in a coral reef finfish fishery. – ICES Journal of Marine Science, 68: 834–847. Indigenous participation in commercial fisheries is poorly established in Australia, except in Torres Strait where indigenous and non-indigenous commercial fishers participate in the Torres Strait Finfish Fishery (TSFF). TSFF stakeholders helped identify specific objectives and alternative management strategies for the fishery at a time when new management strategies were under consideration. A metapopulation and fishing simulation model was used to evaluate alternative management strategies related to harvest and conservation of coral trout (Plectropomus spp.), the main target species. Stakeholders identified objectives relating to conservation of unfished populations, maintenance of harvestable stock, and economic performance. In terms of management options, spatial closures decreased the prospects of meeting nearly all stakeholder objectives. A seasonal closure and larger minimum capture size increased the probability of meeting conservation and harvest objectives, but decreased the probability of meeting most economic objectives for both sectors. Increasing fishing effort increased harvest but decreased the catch rates for both sectors, so had varied effects on the probability of achieving harvest objectives. The research provides a case study of productive engagement with indigenous and non-indigenous stakeholders to address fisheries management needs and provides a framework for impartial evaluation of performance of alternative management strategies against stakeholder objectives.

Monitoring the recreational gamefish fishery off south-eastern Australia

2003 ◽  
Vol 54 (4) ◽  
pp. 425 ◽  
Author(s):  
Michael Lowry ◽  
Jeff Murphy
Keyword(s):  
Spatial Distribution ◽  
Monitoring Program ◽  
Fishing Effort ◽  
Target Species ◽  
Eastern Australia ◽  
Species Groups ◽  
Catch Rates ◽  
Catch Composition ◽  
The Impact ◽  
Integrated Program

The east coast Australian gamefish fishery is a diverse, multi-species fishery that targets billfish, sharks, tuna and other pelagic fish along the east Australian seaboard. A Gamefish Tournament Monitoring Program (GTMP) was undertaken, and 39021 angler trips from 1996 to 2000 were analysed. The program reports on trends in fishing effort, catch rates, catch composition, proportions of captures tagged and released and spatial distribution of catches for the principal recreational billfish species: black marlin (Makaira indica), striped marlin (Tetrapterus audax) and blue marlin (Makiara nigricans).The GTMP was principally designed as part of an integrated program to monitor the recreational gamefish fishery. The spatial and temporal design of the program restricted statistical analyses however, there were trends in fishing effort, directed effort, catch rates, catch composition, proportions of fish tagged and spatial distribution of catches for the principal recreational billfish species over seven successive years (1994–2000). Analysis of catch data, stratified by directed effort, indicated significant differences in catches of target species, demonstrating the importance of calculating catch rate estimates according to the main target preference. Analysis of tournament based tagging information indicated that while overall tournament tagging rates remained high (88%) there were significant differences in the number of fish tagged between species groups highlighting the impact that angler attitude and the competition point score structure has on the harvest of gamefish target species.

Variation in the Competitive Abilities of Fishermen and its Influence on the Spatial Distribution of the British Columbia Salmon Troll Fleet

1990 ◽  
Vol 47 (6) ◽  
pp. 1116-1121 ◽  
Author(s):  
M. V. Abrahams ◽  
M. C. Healey
Keyword(s):  
British Columbia ◽  
Ideal Free Distribution ◽  
Fishing Effort ◽  
Catch Rate ◽  
Fish Distribution ◽  
Fish Stocks ◽  
Fishing Vessels ◽  
Catch Rates ◽  
Ideal Free ◽  
The Ideal

We estimated the catch rates of individual fishing vessels within the British Columbia salmon troll fleet from the data of a 7-yr log book program. Catch rates varied considerably among vessels. A portion of the variation could be attributed to environmental variation. However, there were also significant differences in competitive ability among vessels. The top ranked vessels had a catch rate 3.6 times that of the lowest ranked vessels. Top ranked vessels distributed their fishing effort among more fishing areas than bottom ranked vessels, but were also more successful at catching fish when fishing in the same areas as bottom ranked vessels. This information, through an application of the ideal free distribution theory, can be used to develop a model that will describe the expected relationship between vessel distribution, vessel catch rate, and fish distribution, potentially allowing vessel distributions to be used as a tool for assessing fish stocks.

scholarly journals The global network of ports supporting high seas fishing

2021 ◽  
Vol 7 (9) ◽  
pp. eabe3470
Author(s):  
Jorge P. Rodríguez ◽  
Juan Fernández-Gracia ◽  
Carlos M. Duarte ◽  
Xabier Irigoien ◽  
Víctor M. Eguíluz
Keyword(s):  
Fishing Effort ◽  
Global Network ◽  
Automatic Identification ◽  
Identification System ◽  
Middle Income ◽  
Middle Income Countries ◽  
Fishing Vessels ◽  
National Jurisdiction ◽  
The Commons ◽  
High Seas

Fisheries in waters beyond national jurisdiction (“high seas”) are difficult to monitor and manage. Their regulation for sustainability requires critical information on how fishing effort is distributed across fishing and landing areas, including possible border effects at the exclusive economic zone (EEZ) limits. We infer the global network linking harbors supporting fishing vessels to fishing areas in high seas from automatic identification system tracking data in 2014, observing a modular structure, with vessels departing from a given harbor fishing mostly in a single province. The top 16% of these harbors support 84% of fishing effort in high seas, with harbors in low- and middle-income countries ranked among the top supporters. Fishing effort concentrates along narrow strips attached to the boundaries of EEZs with productive fisheries, identifying a free-riding behavior that jeopardizes efforts by nations to sustainably manage their fisheries, perpetuating the tragedy of the commons affecting global fishery resources.

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