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seeks to reduce the number ! fish that escape "om European aquaculture through research to improve fish farming techniques and technologies.

PREVENT ESCAPE is financially supported by the Commission of the European Communities, under the 7th Research Framework Program.

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Cite this article as: Jensen Ø (2013) Preventing and mitigating escapes through research to underpin technological and operational improvements for seacage farming and recapture technologies. In: PREVENT ESCAPE Project Compendium. Chapter 6.1. Commission of the European Communities, 7th Research Framework Program. www.preventescape.eu

authors: Østen Jensen1

1 SINTEF Fisheries & Aquaculture, Norway

6.1. PREVENTING AND MITIGATING ESCAPES THROUGH RESEARCH TO UNDERPIN TECHNOLOGICAL AND OPERATIONAL IMPROVEMENTS FOR SEACAGE FARMING AND RECAPTURE TECHNOLOGIES

ISBN: 978-82-14-05565-8

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Much of the state-of-the-art of knowledge for ensuring that fish farms do not fail structurally, and that operations do not cause escapes, is contained in technical standards. Such standards are well developed in some European countries, but non-existent in others. Even though Norway has a comprehensive technical standard, escapes still occur at a level which is regarded by many to be detrimental to wild stocks, indicating that the knowledge which forms the basis of technical standards is in constant need of improvement. Work is ongoing to develop an ISO standard that can apply to all sea-cage fish farm installations.

The main objective of WP6: Prevent Escape was to extend the knowledge on culture operations and technology, to improve technical and operational guidelines, to prevent fish escape and to increase the recapture success of escaped fish on the basis of integrated biological and technological research. The work consisted of full scale tests, physical and numerical modelling of farms and structures, material and component testing as well as developing recommendations and guidelines for the design an operation of marine fish farms.

The specific objectives of WP6 were: (1) integrate biological and technological research to facilitate knowledge-based development of robust containment technology, (2) generate fundamental knowledge on the properties of component aquaculture technologies to help improve design and production of sea-cage equipment components, (3) develop guidelines for the design and use of sea-cage technologies and equipment to minimize the risk of escapes, (4) test recapture technologies to improve recapture rates of escapees based on knowledge of the post escape behaviour of fish, and (5) disseminate the results to fish farmers, aquaculture technology manufacturers and suppliers, standards organisations, government agencies and the wider scientific community.

Net cages used to farm cod, salmon, seabass and seabream were inspected for holes throughout a production cycle. A higher number of holes were found in nets used to farm seabream and cod compared to nets used to farm salmon and seabass, due to the cod and seabream biting the

INTRODUCTION

net. Measurements performed during laboratory tests confirmed that even small to medium sized cod were able to pull the net with a force sufficient to tear a single nylon filament in the net. To avoid the farmed fish creating holes in the net, the strength of a single filament should be higher than the strength of the fish. Numerous tests have been performed on new virgin material as well as on net materials used to farm cod, salmon, seabass and seabream. Different mesh types and different materials have been tested using different procedures to determine the strength, flexibility, resistance to abrasion, weakening due to washing and other operations on the net. The net strength declines with use, but it was not possible to directly relate the remaining strength of the material to the age or number of productions cycles for the net. Some of the tests performed (high pressure cleaning, cyclic tests, creep tests) had a minor if any effect on the strength of the material whereas others (e.g. washing in tumble washers and abrasion) had larger impact on the net strength.

Environmental conditions along the coast of Spain (mainland and Canary Islands), Ireland, and Norway were determined and served as valuable input for numerical and physical modelling of commonly used aquaculture structures.

Several methods for recapturing escaped fish were tested, but none of them gave recapture rates at a satisfactory level. In addition the by-catch was significant and often orders of magnitude larger than the recapture. Thus effort should be placed on preventing fish from escaping. However, natural- and human-induced mitigation occurs in the Mediterranean Sea, because predation pressure could reduce survival as well as the capture during the next days by commercial and sport fisheries at scale of kilometres around the fish farms.

The results from the project has served as valuable input in the process of developing a Scottish Technical Standard as well as a ISO standard for fish farms, SINTEF Fisheries and Aquaculture has been involved in the development of both.

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