112 research outputs found
Comment on "Fisheries Management"
No full textThe recent article by O’Leary et al. (2011) raises an important question about the relationship between science and those who manage fisheries. They contend that fishery managers do not give due cognisance to scientific advice and consistently set Total Allowable Catches (TACs) above values advised by scientists (which they define as ‘‘political adjustment’’). The authors claim that the consequence of this is that there is a high probability of stock collapse in the next 40 years. They use a simulation model to argue that this probability may exceed 80% at the mean level of political adjustment adopted by managers, depending on the degree of environmental variability and life history strategy of the fish
Hermits and the Wells
No full textAn interview with children\u27s author Coby McKenzie on her background and illustration and publication process by Tess Hart
Evaluating the effect of real-time closures on cod targeting
No full textAbstract
Needle, C. L., and Catarino, R. 2011. Evaluating the effect of real-time closures on cod targeting. – ICES Journal of Marine Science, 68: 1647–1655. Under its Conservation Credits scheme to reduce cod mortality, the Scottish Government has implemented a system of real-time closures (RTCs) since 2008. These are relatively small, temporarily closed areas (50–225 square nautical miles per RTC, closed for 21 d) that are triggered by high cod catches. An important step in evaluating their effectiveness is to determine the response of vessels to RTCs, because the conservation benefit would be reduced if vessels moved to areas of greater cod abundance following closures. Abundance indices from research-vessel surveys and commercial-vessel observer trips are combined to create a time- and space-dependent relative cod-importance index (RCII). Vessel monitoring system data from Scottish vessels fishing during 2008/2009 are used to construct RCII profiles for each vessel, which are then used to determine whether the areas to which vessels move have a higher or a lower RCII, and how far away they move when an RTC is activated. We show that the RCII of the areas moved to tends to be lower than that of the RTC and that vessels travel farther when moving away from a closure than when moving back after reopening. Although not conclusive, this result indicates that RTCs may impact beneficially on cod mortality.</jats:p
Fleet dynamics in fisheries management strategy evaluations
No full textFisheries managers use scientific evaluations of management plans to determine whether such plans will be sustainable. Most extant evaluations do not account for changes in fleet dynamics in response to management measures, and are likely to be flawed as a result. In this thesis, I develop a new simulation model to address this issue. I present motivating case studies of management strategy evaluations for haddock, survey-based management approaches, and multi-species catch quotas, in order to highlight the need for an improved spatio-temporal fishery modelling framework. I characterise the response of the Scottish whitefish fleet to short-term real-time area closures, as an example of the type of fleet dynamics that a new model would need to be able to simulate for cod in the North Sea. I demonstrate using two complementary methods that such closures are unlikely to have directly encouraged skippers to avoid cod-important areas, and are therefore unlikely to have reduced cod mortality. I develop and implement a new spatio-temporal fishery simulation model which is flexible and powerful enough to account for fleet responses and thereby enable insightful quantitative analysis and evaluation of the wide range of management approaches. Finally, I report initial tests of the model, which demonstrate that a vessel seeking to maximise weekly profit will act differently (and with different fish stock implications) to one that is allowed a maximum weekly catch. With this model and the further future developments of it that I outline, scientists will be in a much better position to advise fisheries managers on stock sustainability over long-term time scales.Fisheries managers use scientific evaluations of management plans to determine whether such plans will be sustainable. Most extant evaluations do not account for changes in fleet dynamics in response to management measures, and are likely to be flawed as a result. In this thesis, I develop a new simulation model to address this issue. I present motivating case studies of management strategy evaluations for haddock, survey-based management approaches, and multi-species catch quotas, in order to highlight the need for an improved spatio-temporal fishery modelling framework. I characterise the response of the Scottish whitefish fleet to short-term real-time area closures, as an example of the type of fleet dynamics that a new model would need to be able to simulate for cod in the North Sea. I demonstrate using two complementary methods that such closures are unlikely to have directly encouraged skippers to avoid cod-important areas, and are therefore unlikely to have reduced cod mortality. I develop and implement a new spatio-temporal fishery simulation model which is flexible and powerful enough to account for fleet responses and thereby enable insightful quantitative analysis and evaluation of the wide range of management approaches. Finally, I report initial tests of the model, which demonstrate that a vessel seeking to maximise weekly profit will act differently (and with different fish stock implications) to one that is allowed a maximum weekly catch. With this model and the further future developments of it that I outline, scientists will be in a much better position to advise fisheries managers on stock sustainability over long-term time scales
Convolutional Neural Networks for Counting Fish in Fisheries Surveillance Video
No full textWe present a computer vision tool that analyses video from a CCTV system installed on fishing trawlers to monitor discarded fish catch. The system aims to support expert observers who review the footage and verify numbers, species and sizes of discarded fish. The operational environment presents a significant challenge for these tasks. Fish are processed below deck under fluorescent lights, they are randomly oriented and there are multiple occlusions. The scene is unstructured and complicated by the presence of fishermen processing the catch. We describe an approach to segmenting the scene and counting fish that exploits the -Fields algorithm. We performed extensive tests of the algorithm on a data set comprising 443 frames from 6 belts. Results indicate the relative count error (for individual fish) ranges from 2\% to 16\%. We believe this is the first system that is able to handle footage from operational trawlers
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Evaluating the Bio-economic Performance of the Northern Shelf Haddock (Melanogrammus aeglefinus) Fishery Using Age-structured Harvesting Strategies and Variable Growth Trajectories
No full textOne way to evaluate the bio-economic performance of fisheries is to base the decision to harvest on whether there is a benefit from leaving particular sizes of fish to reproduce or sell them today at market price. This takes into account both size-dependent fecundity and size-dependent pricing, two commonly overlooked features in bio-economic stock assessments. Here, this construct was applied in a bio-economic model that simulated the Northern Shelf Melanogrammus aeglefinus fishery and was evaluated against different age-at-first-capture selectivity policies under two individual growth types. The first growth type was the individual growth type seen in the Northern Shelf stock based on 2014 data and the second was a theoretical, linear growth type, which was designed to simulate a stock which contains larger, mature haddock. Furthermore, parameters from growth types corresponding to the historical cohorts from the years 1970-2006 were used to assess the economic consequences of changes in growth types throughout time. It was found that the construct which compared reproductive values against market values was not significantly worse than any of the age-at-first-capture, and therefore more practical, fishing approaches simulated, for both individual growth types. The construct also consistently produced some of the highest profit estimations for the fishery. Hence the construct is a resilient theoretical fishing strategy and movement towards this type of fishing should be encouraged. The fishery may also have experienced economic losses in performance attributable to changes in individual growth types seen over time, commonly referred to as the shrinking of larger haddock.Proceedings of the Eighteenth Biennial Conference of the International Institute of Fisheries Economics and Trade, held July 11-15, 2016 at Aberdeen Exhibition and Conference Center (AECC), Aberdeen, Scotland, UK
Identification and recommendations on innovative, applicable and practical solutions for on-board handling of unavoidable unwanted catches
No full textExecutive Summary
This document is the second deliverable in work package 5 of the DiscardLess project. The project is intended to contribute to a successful implementation of the landing obligation of the reformed Common Fisheries Policy of the EU. The work package 5 addresses how unwanted, unavoidable catches can be handled on-board the fishing vessels i.e. from catch to first sale. The objective of this deliverable is to identify available alternatives and recommend the most applicable solutions for on-board handling of these unwanted, unavoidable catches for four different fleet segments in three case studies. The case studies are North Sea, Bay of Biscay and Northeast Atlantic (Iceland and UK), but the selection of vessels has taken into consideration transferability to other European fleets and areas. Practical and cost efficient solutions are identified, adapted and developed for four different fleet segments based on input from different tasks in the project (1.4, 5.1, 6.1 & 6.2) and stakeholder interaction. The fleet segments selected are 10-15 meter hook & line coastal vessels typically operated in Northeast Atlantic, 18-30 meter Danish seine/bottom trawl vessels typically operated in the North Sea and adjacent areas, 34-44 meter Bay of Biscay bottom trawlers typically operated by the Spanish fleet and finally 40-60 meter fresh-fish bottom trawlers used by most EU offshore fleets.
Solutions for sorting, bleeding, cleaning, chilling, pre-processing, storing and other on-board handling are suggested and evaluated based on need, cost and applicability. Some parts of the work include elements of technological innovation, but most rely on exploiting currently available solutions, applying “best practice” technology and knowledge. Recommended solutions are presented on deck-plans (drawings) in order for stakeholders to get a clearer picture of the suggested changes.
The work presented in this report focuses on the four previously mentioned fleet types that provide a relatively good cross-section of important EU fleets that are to be heavily affected by the landing obligation. It includes reviewing current setup of on-board handling where discarding is allowed and then identifies solutions applicable for those fleet types under a discard ban. The main challenges are connected to catches of juvenile fish, which cannot be utilised for direct human consumption. A number of alternatives are identified for each fleet segment and the most applicable solutions are discussed and demonstrated in detail e.g. in deck-plans, mas-balance calculations, cost/benefit assessment etc.This is DiscardLess Project Delliverable Report 5.2 towards Strategies for the gradual elimination of discards in European fisheries
Stock Annex: Lemon sole (Microstomus kitt) in Subarea 4 and divisions 3.a and 7.d (North Sea, Skagerrak and Kattegat, eastern English Channel)
No full text
Stock-specific documentation of standard assessment procedures used by ICES.
Stock Lemon sole in Subarea 4 and Division 3.a and 7.d (North Sea)
Working Group Working Group on the Assessment of Demersal Stocks in the North Sea and Skagerrak (WGNSSK)
Created April 2018
Authors Coby Needle (WGNSSK)
Last updated 26/04/2023
Last updated by Tanja Miethe</p
Urban environmental geochemistry of trace metals
No full textAuthor name used in this publication: Coby S. C. Wong2005-2006 > Academic research: refereed > Publication in refereed journalAccepted ManuscriptPublishedGreen (AAM
Analysis of heavy metal contaminated soils
No full textAuthor name used in this publication: Coby S. C. Wong2002-2003 > Academic research: refereed > Publication in refereed journalAccepted ManuscriptPublishedGreen (AAM
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