scholarly journals Modelling the impacts of fish aggregating devices (FADs) and fish enhancing devices (FEDs) and their implications for managing small-scale fishery

2014 ◽  
Vol 71 (7) ◽  
pp. 1750-1759 ◽  
Author(s):  
Reniel B. Cabral ◽  
Porfirio M. Aliño ◽  
May T. Lim
Keyword(s):  
Phase Transition ◽  
Mean Field ◽  
Fishing Effort ◽  
Management Tool ◽  
Small Scale ◽  
Limited Area ◽  
Mean Field Model ◽  
Fish Catch ◽  
Fishery Collapse ◽  
Fish Aggregating Devices

Abstract Fish aggregating devices (FADs) are deployed to aggregate fish over a limited area to improve fish catch. Fish enhancing devices (FEDs), which are FADs deployed in no-fishing areas, are fast gaining popularity as a fisheries management tool in the western Pacific. Yet, the impacts of utilizing FADs and FEDs are not yet well understood. In this work, we used a mean-field model to assess the effects of utilizing FADs and FEDs on stock biomass and catch. Our results indicate that using FADs enhances catch per boat when total fishing pressure is low, but can exacerbate fishery collapse when fishing effort is high. On the other hand, a FED-based system can increase the resistance of the fishery to collapse. A FED-based fishery may thus serve as pelagic marine protected areas and/or refugia. In a quota-based system, where fishing time is tied to catch quota, a phase transition occurs: both catch and biomass abruptly shift to low levels without warning. Deploying FADs to act as FEDs in a high quota fishery can prevent this phase transition resulting to a stabilizing effect.

Efficiency and selectivity of the Anomalocardia brasiliana (Mollusca: Veneridae) hand dredge used in southern Brazil

2010 ◽  
Vol 90 (7) ◽  
pp. 1455-1464 ◽  
Author(s):  
Paulo R. Pezzuto ◽  
Caroline Schio ◽  
Tito C.M. Almeida
Keyword(s):  
Management Plan ◽  
Fishing Effort ◽  
Management Tool ◽  
Small Scale ◽  
Commercial Fisheries ◽  
Effective Management ◽  
Southern Brazil ◽  
Fishing Rights ◽  
Before And After ◽  
Experimental Plots

In Florianópolis, southern Brazil, the venerid clam Anomalocardia brasiliana has supported subsistence and small-scale commercial fisheries for decades. The introduction of a hand dredge (gancho) since 1987 led to the development of a significant fishery supplying both local and regional shellfish markets. In 1992 one of the main fishing areas in the region was designated as the first Brazilian Marine Extractive Reserve (Pirajubaé RESEX), a federal form of governance intended to promote sustainable exploitation of natural resources by assigning exclusive fishing rights to traditional users. However, excessive fishing effort, institutional shortcomings and lack of a negotiated management plan have resulted in the overexploitation of the species since 2000. This study was aimed at evaluating the efficiency and selectivity of the hand dredge currently in use at the RESEX, through a field experiment conducted in October 2006. Quantitative samples of A. brasiliana were collected before and after dredging 15 experimental plots. Additional samples were obtained inside the dredge (catch) and respective cover cod-end (discard) for selectivity analysis. A single haul of the hand dredge can dislocate up to 76% of the individuals present in the sediment irrespective of their size, and retain up to 69% of the commercial-sized organisms. The gear has a knife-edge selection pattern, which enables the use of the minimum spacing between the iron bars of the dredge's basket as an effective management tool.

scholarly journals Effects of Hadron-Quark Phase Transitions in Hybrid Stars within the NJL Model

Symmetry ◽  
2019 ◽  
Vol 11 (3) ◽  
pp. 425 ◽  
Author(s):  
Ignacio Ranea-Sandoval ◽  
Milva Orsaria ◽  
Germán Malfatti ◽  
Daniela Curin ◽  
Mauro Mariani ◽  
...  
Keyword(s):  
Phase Transition ◽  
Mean Field ◽  
Temperature Limit ◽  
Hadronic Matter ◽  
Transition Diagram ◽  
Mean Field Model ◽  
Relativistic Mean Field ◽  
Non Local ◽  
Gibbs Formalism ◽  
Hybrid Stars

We study local and non-local Polyakov Nambu-Jona-Lasinio models and analyze their respective phase transition diagram. We construct hybrid stars using the zero temperature limit of the local and non-local versions of Nambu-Jona-Lasinio model for quark matter and the modern GM1(L) parametrization of the non-linear relativistic mean field model for hadronic matter. We compare our models with data from PSR J1614-2230 and PSR J0343+0432 and also from GW170817 and its electromagnetic counterpart GRB170817A and AT2017gfo. We study observational signatures of the appearance of a mixed phase as a result of modeling a phase transition that mimics the Gibbs formalism and compare the results with the sharp first-order phase transition obtained using the Maxwell construction. We also study in detail the g-mode associated with discontinuities in the equation of state, and calculate non-radial oscillation modes using relativistic Cowling approximation.

scholarly journals Reconciling fisheries catch and ocean productivity

2017 ◽  
Vol 114 (8) ◽  
pp. E1441-E1449 ◽  
Author(s):  
Charles A. Stock ◽  
Jasmin G. John ◽  
Ryan R. Rykaczewski ◽  
Rebecca G. Asch ◽  
William W. L. Cheung ◽  
...  
Keyword(s):  
Climate Change ◽  
Net Primary Production ◽  
Trophic Transfer ◽  
Fishing Effort ◽  
Small Scale ◽  
Adaptation To Climate Change ◽  
Systems Model ◽  
Energy Flows ◽  
Consistent Manner ◽  
Fish Catch

Photosynthesis fuels marine food webs, yet differences in fish catch across globally distributed marine ecosystems far exceed differences in net primary production (NPP). We consider the hypothesis that ecosystem-level variations in pelagic and benthic energy flows from phytoplankton to fish, trophic transfer efficiencies, and fishing effort can quantitatively reconcile this contrast in an energetically consistent manner. To test this hypothesis, we enlist global fish catch data that include previously neglected contributions from small-scale fisheries, a synthesis of global fishing effort, and plankton food web energy flux estimates from a prototype high-resolution global earth system model (ESM). After removing a small number of lightly fished ecosystems, stark interregional differences in fish catch per unit area can be explained (r= 0.79) with an energy-based model that (i) considers dynamic interregional differences in benthic and pelagic energy pathways connecting phytoplankton and fish, (ii) depresses trophic transfer efficiencies in the tropics and, less critically, (iii) associates elevated trophic transfer efficiencies with benthic-predominant systems. Model catch estimates are generally within a factor of 2 of values spanning two orders of magnitude. Climate change projections show that the same macroecological patterns explaining dramatic regional catch differences in the contemporary ocean amplify catch trends, producing changes that may exceed 50% in some regions by the end of the 21st century under high-emissions scenarios. Models failing to resolve these trophodynamic patterns may significantly underestimate regional fisheries catch trends and hinder adaptation to climate change.

scholarly journals Phase transition in a mean-field model for sympatric speciation

2006 ◽  
Vol 369 (2) ◽  
pp. 612-618 ◽  
Author(s):  
V. Schwämmle ◽  
K. Luz-Burgoa ◽  
J.S. Sá Martins ◽  
S. Moss de Oliveira
Keyword(s):  
Phase Transition ◽  
Field Model ◽  
Mean Field ◽  
Sympatric Speciation ◽  
Mean Field Model

scholarly journals Detecting anchored fish aggregating devices (AFADs) and estimating use patterns from vessel tracking data in small-scale fisheries

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ahmad Catur Widyatmoko ◽  
Britta Denise Hardesty ◽  
Chris Wilcox
Keyword(s):  
Fisheries Management ◽  
Small Scale ◽  
Tracking Data ◽  
Use Patterns ◽  
Fishing Vessels ◽  
Vessel Tracking ◽  
Large Numbers ◽  
Fish Catch ◽  
Tracking Devices ◽  
Fish Aggregating Devices

AbstractMonitoring the use of anchored fish aggregating devices (AFADs) is essential for effective fisheries management. However, detecting the use of these devices is a significant challenge for fisheries management in Indonesia. These devices are continually deployed at large scales, due to large numbers of users and high failure rates, increasing the difficulty of monitoring AFADs. To address this challenge, tracking devices were attached to 34 handline fishing vessels in Indonesia over a month period each. Given there are an estimated 10,000–50,000 unlicensed AFADs in operation, Indonesian fishing grounds provided an ideal case study location to evaluate whether we could apply spatial modeling approaches to detect AFAD usage and fish catch success. We performed a spatial cluster analysis on tracking data to identify fishing grounds and determine whether AFADs were in use. Interviews with fishers were undertaken to validate these findings. We detected 139 possible AFADs, of which 72 were positively classified as AFADs. Our approach enabled us to estimate AFAD use and sharing by vessels, predict catches, and infer AFAD lifetimes. Key implications from our study include the potential to estimate AFAD densities and deployment rates, and thus compliance with Indonesia regulations, based on vessel tracking data.

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