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Bericht / Forschungsbericht / Abhandlung zugänglich unter
URL: https://epub.sub.uni-hamburg.de/epub/volltexte/2008/1444/
GHOST FISHING BY LOST FISHING GEAR: Final Report August 2005
INSTITUTE FOR EUROPEAN ENVIRONMENTAL POLICY; POSEIDON AQUATIC RESOURCE MANAGEMENT
| Originalveröffentlichung: |
| (2005) http://ec.europa.eu/fisheries/publications/factsheets/legal_texts/ghostfishing_en.pdf |
| pdf-Format:
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| BK - Klassifikation: |
| 48.67 |
| Sondersammelgebiete: |
| 21.3 Küsten- und Hochseefischerei |
| DDC-Sachgruppe: |
| Biowissenschaften, Biologie |
| Dokumentart: |
| Bericht / Forschungsbericht / Abhandlung |
| Sprache: |
| Englisch |
| Erstellungsjahr: |
| 2005 |
| Publikationsdatum: |
| 28.08.2008 |
| Kurzfassung auf Deutsch: |
| ‘Ghost fishing’ is the term given to the continued fishing by fishing gear that has been lost or abandoned. It is largely confined to ‘passive gears’ such as gillnets, trammel nets, wreck nets, and traps. It is a phenomenon that has attracted attention over the past two decades given the sometimes graphic images of fish and other marine life entangled in lost nets, illustrating the potentially wasteful and destructive impacts of lost fishing gear. However, the real extent of the problem is not well known at the present time.
This report is the output of a six-month research project funded by the Environment Unit of DG Fisheries and Maritime Affairs of the European Commission. Evidence suggests that ghost fishing from ‘active’ fishing gears such as trawl nets and from ‘static’ pot fishing is not significant in European Union (EU) waters, and the focus of this project is therefore on ghost fishing in static set-net fisheries.
The work was carried out by the Institute for European Environmental Policy (IEEP) and Poseidon Aquatic Resource Management Ltd. It was based on detailed terms of reference, but in essence attempted to answer the following three questions:
1. What are the main gaps in our knowledge about the extent of ghost fishing?
2. Based on what we do know, to what extent is ghost fishing a serious issue in European Union waters?
3. If it is a problem, how effective are gear retrieval programmes and other management options in dealing with it?
The project involved a detailed literature review, brief surveys with selected fisheries in the EU, a workshop of industry participants and specialist fisheries researchers, and desk-based analysis and report writing.
Why is gear lost, and what happens to lost fishing gear
The causes of gear loss vary between and within different fishing areas and types of vessels. However some of the common causes, in decreasing order of relative importance, are:
• conflict with other sectors, principally towed gear operators;
• working in deep water;
• working in poor weather conditions and/or on very hard ground;
• working very long nets or fleets of nets; and
• working more gear than can be hauled regularly.
Once fishing nets are outside of the control of fishermen their ability to catch fish and crustacea declines over time, usually quickly at first and then more slowly but this can be highly variable. The extent and pattern of this decline depends strongly on environmental conditions. In shallow areas, wind and tidal currents result in nets being more quickly self-entangled and rolled up than in deep water areas where tides/currents are low, thereby reducing the ability of nets to catch fish more quickly. Marine fouling by colonising organisms also increases the visibility of nets to fish, so reducing their catching efficiency over time. The way in which nets are lost is also an important determinant of the extent to which nets continue to fish. Nets lost because of gear conflict (eg when trawlers tow through set-nets) may have little catching capacity if they are rolled up when towed through
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When lost in shallow water on rocky ground conditions or on wrecks, it is believed that nets are generally fouled, broken up or rolled up within a year, and in many cases catch rates decline to less than 5 per cent of commercial catch rates within just a few months. In waters with weaker tidal currents, such as the Baltic, ghost catches of 4-5 per cent of commercial levels have been recorded after 27 months. The most extreme case is in the deep water net fisheries (where nets are set at a depth of more than 500 metres) in the northeast Atlantic where vessels fish for shark and monkfish. Research on this fishery suggests that the catching efficiency of ghost nets stabilises at 20-30 per cent of commercial catch rates after 45 days, and that some nets may continue to catch lower amounts of fish and crustacean more than eight years after being lost.
How significant is ghost fishing in EU waters, and what are the environmental impacts of lost gear
In relation to the total number of nets being used in EU waters, the rates of permanent net loss appear to be rather low – well below one per cent of nets deployed. This is largely because most nets are deployed in shallow waters, and after they are first lost a significant proportion of nets are then recovered through the use of global position systems (GPS); fishermen typically go to considerable lengths to recover nets given their cost. However, because the total length of nets being set is high, the total length of netting permanently lost may be significant, although exact figures are not available.
An exception to the low loss rates seen in most European fisheries is in the deep water net fishery in the north east Atlantic. Preliminary research suggests that around 25,000 nets may be lost or deliberately discarded in this fishery each year, with a total length of around 1,250 km. The water depths being fished and conflict with trawlers are conducive to net loss, while vessels use more nets than can be stowed upon retrieval. It is believed that the high level of net loss in this fishery is also a symptom of unsustainable fishing practices and fishing effort levels in the fishery more broadly, rather than a result of fishing in deep waters alone.
Given the fact that many static-net fisheries take place in shallow waters where catch rates of lost gear decline quickly, and rates of net loss are typically low, it is not felt that ghost fishing is a serious issue in most net fisheries in the EU. However, given the total length of netting that may be lost each year, such a statement should not be taken to mean that ghost fishing does not occur, or that steps should not be taken to reduce it. When considering a fishery as a whole, even if losses of fishing gear by individual vessels are small, the environmental and economic costs of ghost fishing across the fishery may be significant.
Furthermore, it is extremely important to note that the cause and extent of ghost fishing is very fishery specific, and one should not generalise about either the extent of the problem for set-net fisheries as a whole, or the solutions, given the wide range of different types of net fisheries within EU waters. However, ghost fishing in the deepwater net fisheries in the north east Atlantic appears to be of a different magnitude to all other net fisheries in the EU. The practices of deliberate dumping of nets, excessively long soak times (the time that the net is left in the water to fish), plus weak currents at the depths fished, all point towards significant levels of ghost fishing in these waters. It would certainly not be fair if in the minds of the public other net fisheries were tarnished with this same picture, given the generally wide awareness of the need to continually minimise net loss in many fisheries in the EU.
As well as considering the absolute environmental impacts of lost static gear, they must also be considered in the broader context, and as compared to the environmental impacts of other fishing methods. Mobile gears such as trawls have much greater impacts in terms of non-target species, catch and discards, as well as habitat and biodiversity damage than static gears. Static gears tend to be very selective; while marine habitat impacts are increased when nets are lost and marine mammals may occasionally become caught in certain situations, impacts
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are not considered profound or extensive and are certainly of an order of magnitude less than the impacts of trawl gear. However, lost static nets can be washed ashore causing negative aesthetic impacts along coastlines, and presenting a risk to birds which can become entangled.
The need for management measures to reduce ghost fishing
The need to reduce the amount of fishing gear that is lost is recognised in the international Codes of Conduct for Responsible Fisheries developed by the Food and Agriculture Organisation (FAO) of the United Nations. Furthermore, within the EU’s Common Fisheries Policy (CFP) there is a clear legal basis for taking measures to address ghost fishing given that it impacts on fish stocks and the wider marine environment. In June 2004 the European Commission committed itself to addressing ghost fishing, and the European Council subsequently invited the Commission to take forward these commitments.
The management options for addressing lost gear can be classified into two groups: firstly those that are ‘curative’ and attempt to reduce the extent of ghost fishing once a net has been lost; and secondly, those that are ‘preventative’ and attempt to reduce net loss in the first place.
Curative initiatives include: reporting of gear loss prior to subsequent gear recovery campaigns; gear recovery/retrieval campaigns; or opportunistic gear recovery by demersal trawl surveys. Preventative initiatives include: the marking of gear; acoustic detection devices; zoning of fishing activities to avoid conflict; the use of bio-degradable gear; limiting gear use (eg restricting the length of nets used based on vessel size, placing limits on soak times); encouraging static net fishermen to switch to other fishing methods; requirements to register gear tied to onshore disposal and information about any gear lost at sea; and, increasing communication between different types of fishing vessels fishing in the same area. A broader strategic approach of establishing codes of good practice is considered to be especially important in linking different types of measures. While all measures have their relative merits, a clear management message to come from this project is that prevention is better than cure.1
There are already a number of voluntary and legislative measures in the EU to prevent and cure both net loss and abandonment. These include good communication between English net fishermen and French trawlers operating in the Western English Channel about gear location, Swedish gear retrieval programmes in the Baltic, and limitations on soak times in the Baltic cod fishery. However, there is certainly much scope for further improvement.
Costs and benefits of management options
This project has highlighted that management measures for reducing ghost fishing are rarely, if ever, based on an assessment of the costs and benefits of different management options. A ‘knee-jerk’ and politically appealing reaction to ghost fishing in both the EU and elsewhere in the world, is to undertake retrieval programmes to remove lost gear from the sea. However, the effectiveness of such exercises and the economic justification has never been fully demonstrated. This project has therefore developed a model for adaptation by fisheries administrations. The model can be used to assess many of the costs and benefits of retrieval programmes, as well as of other management measures. It is recommended that in association with other costs and benefits that are identified but less easily quantified, the model be used
1 The use of biodegradable gear however is unlikely to be effective in the short term because of the lack of available appropriate technology and lack of faith in the concept from industry. As a long-term measure however, based on research and development work with the industry and appropriate levels of finance, technical solutions could probably be found to current limitations.
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by administrations when deliberating on how to reduce ghost fishing and which management measures should be adopted.
The model suggests that even if individual vessels lose small amounts of nets, total costs across a fishery could be significant. This is mainly because of potentially large numbers of vessels losing valuable fishing gear, and the loss of profits from the ghost catches themselves that could otherwise be made by the fishing fleet.
The sensitivity analysis conducted on the model suggests that key variables in net benefit/cost calculations are likely to be the number of vessels in the fishery, the cost of the retrieval programme, the number of nets lost, the value of the gear lost, and the percentage of lost nets that retrieval programmes are successfully able to recover. Less important appears to be the rate of decline of ghost catches over time, because retrieval programmes are always unlikely to prevent the high levels of ghost fishing immediately after fishing gear is lost, unless they take place very frequently.
The analysis supports two main arguments. Firstly that gear retrieval programmes may only be cost effective in a limited number of situations. And secondly, that preventative measures are generally preferable to curative measures because, by preventing gear loss, they can prevent the potentially high costs associated with ghost catches immediately after gear loss from occurring in the first place. This conclusion is likely to be valid regardless of the accuracy of the data used in the model, and even if a retrieval programme may itself result in a net benefit.
Future research
Knowledge about the extent of ghost fishing is still very limited. Some fisheries have not yet been researched at all (eg Greece where more than 16,000 vessels are engaged in net fisheries), and due to the costs and practical difficulties of underwater survey work and of simulating ghost catches through experiments, estimates of ghost catch rates are imprecise. These factors, combined with only partial knowledge about the amount of gear that is lost, means there are no overall estimates of the extent of the problem for the EU as a whole. There are also research gaps on the environmental impacts of ghost gear, for example on the impacts and extent of particulate matter from decaying nets entering the food chain. The environmental impacts of management responses, notably gear retrieval programmes, have also not been quantified. Of the information that is available on ghost fishing, the majority is largely biological and technical in nature with very little economic research available on the costs of gear loss and ghost fishing, or on the relative costs and benefits of different management responses.
Headline messages
This summary started by asking three questions. In attempting to answer them and to summarise the outputs of the project, several key messages from the study are:
• There remain significant gaps in knowledge about ghost fishing in EU waters. Priority research areas include a) quantifying the amounts of lost gear; b) assessing the extent to which lost nets continue to catch fish; c) assessing those fisheries for which there is virtually no information; d) estimating total ghost fishing catches in the EU; e) assessing the different types of environmental impacts of ghost fishing and management responses; and f) collecting economic data on ghost fishing and management responses.
• With the proviso about existing knowledge being imperfect, ghost fishing in set-net fisheries in the EU is probably not a significant problem, either in terms of its total ix
impact, or its environmental impact in comparison with ‘active’ fishing methods such as trawling.
• However, net fisheries in the EU are each very different and should therefore be judged individually. In deep water fisheries conditions are more conducive to net loss, and there is strong evidence of net dumping and significant levels of ghost fishing in the deep water north east Atlantic fishery for shark and monkfish. The problem of ghost fishing in this fishery appears to be of a different order of magnitude compared to other fisheries in the EU, and as such warrants immediate action and research by the EU, Member States and the industry involved.
• Appropriate management responses are likely to be variable for different fisheries, as are the research gaps, but prevention (ie Codes of Practices, improved communication between active and passive gear users) is almost certainly better than cure (retrieval programmes). Management responses should be better justified on the basis of the relative costs and benefits of different management options.
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