Scottish Aquaculture Research Forum

Transcription

1 Scottish Aquaculture Research Forum Assessment of Protocols and Development of Best Practice Contingency Guidance to Improve Stock Containment at Cage and Land-based Sites Volume 2: Supporting Information SARF054 Mark Taylor and Robert Kelly A REPORT COMMISSIONED BY SARF Prepared By Thistle Environmental Ltd July 2010

2 Published by the: Scottish Aquaculture Research Forum (SARF) This report is available at: Dissemination Statement This publication may be re-used free of charge in any format or medium. It may only be reused accurately and not in a misleading context. For material must be acknowledged as SARF copyright and use of it must give the title of the source publication. Where third party copyright material has been identified, further use of that material requires permission from the copyright holders concerned. Disclaimer The opinions expressed in this report do not necessarily reflect the views of SARF and SARF is not liable for the accuracy of the information provided or responsible for any use of the content. Suggested Citation Title ISBN: First published: SARF 2009

3 Assessment of Protocols and Development of Best Practice Contingency Guidance to Improve Stock Containment at Cage and Land-based Sites Volume 2: Supporting Information Scottish Aquaculture Research Forum Report May 2010 Thistle Environmental Partnership

4 Acknowledgements Acknowledgements This project was commissioned and funded by the Scottish Aquaculture Research Forum (SARF). The generous financial support of SARF for this project is acknowledged. The project steering group included SARF as well as representatives of the Scottish Salmon Producers Organisation (SSPO), the British Trout Association (BTA) and the Scottish Government. The steering group performed a valuable and supportive role and their participation is much appreciated. Consultations and discussions were undertaken with a range of organisations and individuals throughout the supply chain including feed companies, fish farmers, processors and supermarkets as well as wider stakeholders such as non-governmental organisations (NGOs) and academics. They all engaged with interest and their contributions were essential to the successful conclusion of this project. Valuable assistance was provided by Robin Turner of Seawork (Scotland) Ltd in respect of the engineering aspects of moorings, cages and closed containment systems. It should be noted that this is an independent report which is presented in good faith and represents the views of the authors. Thistle Environmental

5 Contents CONTENTS VOLUME 1: REPORT (bound separately) Executive summary 1 1. Introduction 6 2. Methodology 8 3. Escape incidents: magnitude, tends and causes Addressing cage and mooring failure Maintaining net integrity Land-based farms and stock transfers Addressing other causes of escape incidents Protocols Conclusions and recommendations 50 References 64 Appendices: A List of Consultees 65 VOLUME 2: SUPPORTING INFORMATION (bound separately) Annexes: 1. Literature review 1 2. Aquaculture containment protocols (worldwide) Finfish escape statistics: worldwide Causes of escapes in Scottish finfish farming Consultations with Scottish fish farmers Consultations with suppliers to the Scottish aquaculture industry 163 Thistle Environmental

6 Literature Review Annex 1: Literature Review A1.1 Introduction The purpose of the literature review is to reflect the current status of research into the containment of farmed finfish. The review included published journal articles, books, non-government organisation materials, conference reports, UK and other national and state government websites and other miscellaneous sources. The protocols relating to containment, in Scotland and elsewhere, are considered in Annex 2. The literature was obtained through internet based research and from discussion with consultees, as well as covering existing documents known to the authors. Whilst allowing a reasonable coverage of the topic, this element of the project was relatively brief and hence this review should not be considered exhaustive. Further, documents in languages other than English were not included; consideration of Norwegian documents in particular would be useful, especially technical investigations into the causes of escapes, and this might be considered in future studies. There appears to have been greater research effort into the numbers and impacts of escapes on wild fisheries than on the causes of escapes and their prevention. Whilst the impacts of escapes are outwith the scope of this report, the subject has been covered briefly to provide a background for the project. The focus is, however, on escape prevention. A1.2 Numbers and Causes of Escapes In most of the key salmon farming countries the reporting of escapes is obligatory either as a legal requirement or as a farming licence condition (see Annex 2). However, as Thorstad et al (2008) note, information on why, when and from where salmon escape is not provided by all salmon producing countries. With the exception of Norway, no research was identified which considered whether there was a history of escape incidents being unreported. In Norway, there have been claims that the real total of escaped fish is far higher than the reported figure and that only 12-29% of the actual number of escaped farmed salmon is reported (Thorstad et al 2008). However, this suggestion has been strongly refuted on the basis of research into the numbers of farmed salmon caught in the wild (2009, Fiskeri- og havbruksnæringens landsforening (FHL), pers. comm.). The Genimpact project stated that around million salmon ( % of farmed production) escape each year into the North Atlantic (Genimpact, 2007). As well as escape incidents, some stakeholders suggest that there may be some small numbers of more frequent escapes, often termed low-level leakage, either through handling errors at cage sites or through inadvertent discharge from freshwater tank sites. Again, no references were identified in this regard. In Scotland, companies experiencing an escape are required to provide information on the event on a specific form to the Government. In 2007 the Scottish Executive summarised escape report information into six categories of cause. Thistle Environmental 1

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8 Literature Review Table A1.1 Scottish Finfish Farming (All Species): Number of reported escape incidents and fish lost by cause for the period Cause No. Incidents % No. Fish Escaped % of Total Weather , Predation , Equipment failure , Human error , Hole in the net , Other , Totals , Source: Scottish Executive 2007a. Whilst information on escape causes are also available in Norway and Canada (see Annex 3) Thorstad et al (2008) suggest that this may not be accurate as incidents have not always been investigated. A Norwegian study (Rist et al, 2004) based on indepth interviews with Norwegian fish farmers concluded that inadequate operation procedures and lack of appropriate training were the cause of 80% of escapes in Norway and lack of equipment or poorly maintained equipment were responsible for a further 15%. Such causes are not identified on Norwegian escape report forms. Where escapes were caused by circumstances beyond human control most commonly storm events the study found that the number of escape episodes and number of escapees during each episode would have been reduced if best operational practice had been followed (Thorstad et al, 2008). A recent study in Chile states that in 2008, 19 escape events took place with 1,646,817 (Atlantic salmon, Coho salmon and Rainbow trout) escapees and in 2007 there were 1,726,919 escapees from seven large-scale escape events (Sepulveda et al, 2009). Coho and Atlantic salmon escapes have been declining since 2004 and Rainbow Trout escapes have been increasing. No freshwater escapes are reported and therefore escape figures are underestimated. Causal data is unreliable and the authors concluded that the main causes of escapes appear to be human error, technical failures or theft and that there may be unreported escape incidents. There have also been some severe weather events, such as the tsunami in April 2008 in which more than 1 million fish were reported to have escaped. Net ruptures during crowding for harvests and net changing are identified as a major human error cause (Sepulveda et al, 2009). Non-Salmonid Species Spain, Greece and Turkey are the main producers of sea bream and sea bass. There are no requirements to report escapes nor are official figures for escapes available. 1 Not including 14 incidents during the Western Isles storm in January 2005, resulting in 893,270 escaped salmon. Thistle Environmental 3

9 Literature Review Escapes from Mediterranean farms are attributed to storms, handling and harvesting errors, holes caused by operations or by predators (Dempster et al, 2007). Sea bream (and cod) are thought to nibble at cage nets and create holes, which may lead to under-reporting as the holes may not be spotted. Manual harvesting techniques provide another escape opportunity and tens to hundreds of escapees have been visually observed (Dempster et al, 2007). The hypothesis that cod bite netting and create holes has been tested and confirmed (Moe et al, 2007). The same research proposed the following operational practices to avoid escapes: 1. Use good quality cage nets. 2. Avoid minor damage to nets from handling and abrasion. 3. Inspect the net cage frequently for holes. 4. Ensure net repairs are good quality. 5. Keep the cage nets clean. Biofouling may attract cod. 6. Make sure that cage nets are taut. 7. Check that the mesh width is suitable for the fish size. 8. Make sure that the cod is fully fed at all times. 9. Grade fish for size frequently. The authors suggest that for cod (and perhaps therefore, other species known to be aggressive to the net) the solution for an escape-free cage net lies within the following three areas or a combination thereof: 1. Using stronger net cage constructions. 2. Developing an uninteresting or repulsive net cage wall. It may be possible to use taste, smell, sound, colour and shape to prevent biting at the net cage. 3. Providing a stimulating cage environment to distract the fish from biting. The use of submersible cages (as most surface wave energy is dissipated within 10m), stronger nets, as well as a more interesting cage environment and a repulsive net cage wall are preventive measures suggested elsewhere for sea bream and sea bass (Dempster et al, 2007). In respect of sea bream and sea bass, Dempster et al (2007) suggested that the mandatory reporting of escapes, the establishment of an equivalent of the Norwegian Escapes Commission 2, and the implementation of the Norsk Standard NS 9415 would help prevent escapes. A1.3 Impacts of Escapes The relationship between escapes and wild fish is the main environmental concern regarding escapes and has been the subject of several studies. The Scottish Executive study of the impacts of aquaculture concluded that the number of escapes was probably unsustainable and represented a major threat to wild population (Scottish 2 See Annex 2 for further details of the work of the Commission. Thistle Environmental 4

10 Literature Review Executive, 2002). However, it should be noted that this report was published just prior to the time when escapes were first reported in Scotland and hence there would have been little information available on the incidence and magnitude of Scottish finfish escapes. It should also be noted that this report reflects the predominance of research material regarding the escape impacts of salmon and the relative lack of material regarding the escape of Rainbow trout. In Northwest Ireland it has been shown conclusively that escaped parr from a hatchery can home to the site of the escape and complete their life cycle, breeding and/or interbreeding with native fish as returning adults (Thorstad et al, 2008). Homing is much higher from escaped juveniles than from sea water escapes (Genimpact 2007). Escaped fish can, however, travel far from the location of the escape (FRS pers. comm.). An experiment to track 700 farmed salmon released near Ullapool in 2006 aimed to assess their ability to survive. Of five tags recovered one tag has been recovered in North Yell in Scotland and one from a beach at the mouth of the Laxford River. One tagged fish was caught in a river in western Sweden. Two fish were caught in Norway, one in a net in Harganger fjord and another from the sea near Lofoten in northern Norway, demonstrating the ability of escapees to travel great distances (FRS pers. comm.). While this study indicates that escaped salmon may travel considerable distances, the fact that such a small percentage of tags were recovered suggests that many escaped salmon do not survive. The relationship between escapees and wild salmonids can be summarised as follows: The numbers of escaped farmed salmonids are low relative to the numbers stocked (Genimpact, 2007). The numbers of escaped fish are high relative to the wild salmon population McGinnity et al 2003). Up to 80% of the salmon in some Norwegian rivers are farmed (Genimpact, 2007). Diseased farmed fish escapes have the potential to infect wild populations (and vice versa) (Genimpact, 2007). The genetic effects from interbreeding are typically unpredictable; they vary from no detectable effect to complete introgression or displacement. Where genetic effects are detected they are always negative in comparison with the native wild salmon (Verspoor et al, 2007). Interbreeding between wild and farmed salmon and competition for habitat (and therefore food) results in negative effects on the wild salmon. These effects can be a reduced genetic variety, reduced wild population, reduced fitness and therefore reduced spawning success. In turn, reduced spawning success has the knock-on effect of further reduction in genetic variety. Should there be repeated escapee river entry, these effects would be cumulative (McGinnity et al 2003). Thistle Environmental 5

11 Literature Review Because escaped post-smolts appear to move away from the release site within a few hours, even a huge effort over large areas may not effectively recapture them (Thorstad, et al 2008). The Genimpact report recommended research priorities relating to improving knowledge of wild fisheries, adaptive abilities of escapees and hybrids, environmental factors influencing the effects of escapes on wild fish and building reliable models to predict effects (Genimpact, 2007). Although the majority of work on escaped Atlantic salmon considers them to have a negative impact, this is not a universal view as one study presented escapes in positive light. In Tasmania, where there are no native Atlantic salmon and hence escapees are not considered a threat to wild salmon, the Department of Primary Industries, Parks, Water and Environment website recommends where to fish for the highly prized catch of farmed Atlantic salmon. A1.4 Escape Prevention and Impact Mitigation In the literature there are, in summary, four methods of escape prevention and mitigation. Firstly, there is the use of sterile fish as a method of mitigating the effects of escapes rather than preventing them. The use of exclusion zones is a second, mitigatory method which seeks to exclude any escapees from sensitive areas and hence neutralise their impact on wild fish. Farmers preventative methods are the third method, examined in more detail below. The ability to fully domesticate fish is another long term method. The recapture of escaped fish and its effectiveness is outwith the scope of this report, but recapture rates (of salmon) are reportedly low at less than 3% (Thorstad et al, 2008) 3. Sterile Fish Sterilisation is seen by some as a promising method of preventing escape impacts (Thorstad et al, 2008). For Atlantic salmon, triploidy is considered the most effective way of producing sterile fish Atlantic salmon (NASCO, 2005). Triploids have been produced in a commercial context, and are grown in Tasmania to fill a production gap, but farmers experience of Atlantic salmon triploids is generally negative (NASCO, 2005). Variable growth, poorer survival and deformities have resulted in their virtual absence from current aquaculture production. It is also difficult to consistently induce and verify triploidy in large commercial populations of fish. There are possible risks that escaped triploid females, behaving as if reproductively normal, would consort with wild diploid males, as well as competing with wild fish for habitat, although it has been suggested that escaped triploid returns to coast and freshwater are reduced relative to diploid escapes (Verspoor et al, 2007). There is also market resistance to the use of triploids, firstly because they are perceived as genetically modified (Genimpact 2007) and secondly, because of the observed increase in deformities amongst triploid populations, there are animal welfare issues (NASCO 2005). A review of the current methods of physical and biological containment of farmed fish considered their applicability and effectiveness for the containment of transgenic 3 Note that the research did not specify whether freshwater or sea water. Thistle Environmental 6

12 Literature Review fish (Wonget al, 2008). The authors argue that the impacts from escaped transgenic fish are, in principle, the same as those from the currently used selected strains and that complete physicochemical containment is only possible in closed systems. The paper discusses several approaches to transgenic containment, ranging from the induction of sterility by disrupting sexual reproduction through targeting hormone genes, to gonad-specific transgene excision. No successful experiments were identified in the literature by the authors and they point out that, even if the technical challenges of these approaches were overcome, they would then have to be taken through the regulatory process. Furthermore, industry and market resistance would likely be an additional severe challenge to the possibility of the commercialisation of transgenic approaches. A long term preventative measure would be the development of a fully domesticated farmed fish which was unable to successfully breed and/or survive in the wild environment. This is a theoretical solution only and would be a long term and complex strategy. In selecting for domestication, other favourable farming characteristics such as feeding aggression, disease resistance and yield, may be lost (Thorstad et al, 2008). Exclusion Areas or Farm-Free Zones. Protection or exclusion zones where salmon farming is prohibited may be an effective way of protecting wild salmon populations from potential impacts from escapes and also disease. This has been tried in Norwegian and Icelandic fjords with varying success. The largest exclusion zones appear to have been more effective than smaller zones but further research on the characteristics of rivers is needed in order to find out why some rivers attract more escaped salmon than others (Thorstad et al, 2008). In Scotland, a simple approach would be to site farms well away from the head of sea lochs and associated salmonid runs; a figure of 18km from a river mouth has been suggested (Hambrey Consulting, 2005) and also a suggestion of 30km (Verspoor et al, 2007). Escaped salmon have, however been found at great distances from source (FRS pers. comm.). The location or relocation of Scottish farms in relation to other stakeholders including wild fisheries was considered at length by the Location/Relocation Working Group (LRWG). The LRWG examined different location strategies including establishing priority zones, building on existing Special Areas of Conservation, where there would be a presumption against and/or relocation of aquaculture developments (Scottish Executive, 2006). The results of this work have fed into the renewed Strategic Framework for Scottish Aquaculture and the planning controls for fish farming (Marine Scotland, 2009). With reference to Scottish development planning policy, local authorities should identify areas which are sensitive and unlikely to be appropriate for fish farming (e.g. where escapes and sea lice would impact wild fisheries) and potential development areas where development is more appropriate (Scottish Executive, 2007 b). Prevention and Contingency In 2007 the Scottish Executive suggested that farmers should not only have sitespecific contingency plans for escapes but should also be familiar with their content (Scottish Executive, 2007a). Thistle Environmental 7

13 Literature Review Most salmonid producing areas have legal and non-regulatory protocols for the prevention of escapes and for impact mitigation. These are discussed in Annex 2. If fish could be conditioned by associating feeding with a specific acoustic tone then recapture may be facilitated. This possibility has been researched (Tlusty, et al, 2008). The trials took place in fresh and sea water tanks. The factors assessed included training period, retention of conditioning the ability to discriminate tones and recall fish to a pen within a tank. Juvenile trout and salmon were used. To condition the fish food was made available and consumed during the duration of a repeated tone. When the tone was played without a food reward, the fish were considered conditioned. After conditioning neither salmon nor trout exhibited a decrease in the response to the signal over a period of 7 months, but the fish did not readily enter the pen within the tank. A1.5 Technical Issues Finfish aquaculture has rapidly developed since its infancy in the 1970s. This section considers the literature on fish farm technology in relation to containment. Location The suitability of a location for cage fish farming depends on several environmental variables in addition to those related to water quality. The former are particularly valid from the perspective of containment issues and include shelter from wind, potential for icing, fetch (the distance of open unobstructed water between the site and land in all directions), wave climate (including wave height, length and period), current (tidal, wind induced and freshwater flows), depth (taking account of tidal fluctuations) and nature of substrate which can affect mooring design (Beveridge, 1987). Most, but not all, of the above information is required by Scottish farmers to meet differing regulatory requirements (e.g. for planning permission or consent to discharge) but not necessarily for the purpose of identifying suitable farm systems of cages, nets and moorings. It has been argued that a national marine aquaculture data base survey would provide normative data generally available to all stakeholders, including the wind, wave, current, depth and substrate data required for proper mooring design (Turner, 2000). In 2007 the Scottish Executive wrote an informal paper on containment which suggested several areas for consideration, including that all new or existing cages are subject to wave height analysis to meet the manufacturers recommendations (Scottish Executive, 2007 a). With regard to current forces one study concluded that farm sites should not be situated in areas where the current speed exceeds 1 m/s, unless net deformation can be overcome by technological devices (Huan et al, 2008). Thistle Environmental 8

14 Literature Review Cage Moorings Mooring systems have largely borrowed technology from other marine industries and, in common with them, use a combination of anchor (or other fixing such as rockpin or concrete block) chain and rope to complete a mooring leg. Close to land a mooring leg can be fixed to the ground. Tension leg cages are also in use elsewhere. In this case the cage is secured to the substrate by spars with vertical moorings. The cage can be semi or completely submersible having the advantage of avoiding surface forces from wind and waves (Lisac, 2000) discussed in more detail below. The Scottish Executive s paper on containment (2007a) suggested that it should be ascertained that moorings are suitable prior to deployment and that a properly designed inspection and maintenance schedule is adhered to. Cage Systems Cage technology in Scotland can be summarised into three types: 1. Wooden cages with steel connecting brackets and polystyrene floatation. While these are still used on occasion in sea water and (more frequently) freshwater sites, they have largely been replaced by steel or plastic cages. 2. Steel section cages with plastic foam or polystyrene filled floatation. These have the advantage of a stable centre and cage walkway on which to work. 3. Plastic cages with one to three rings which are sometimes filled with polystyrene and which sometimes have steel fittings and fixtures. These are now the dominant type of cage system but currently many systems do not have walkways. Neoprene or rubber cages with steel connections have been used in Scotland in the past, and are still used elsewhere, such as in Ireland. Cages and nets are subject to forces from moorings, boats, tidal and wind driven currents, waves, gravity and buoyancy. On steel cages these forces cause fatigue and possibly cracks and failure (Cairns and Linfoot, 1990). As the industry turns its attention to offshore farming the following cage design objectives have been identified in relation to containment: Providing a reasonably stable cage shape, to avoid stressing the stock, and to provide a stable working environment. Absorbing or deflecting environmental forces, to maintain the structural soundness of the system. Providing an efficient working environment, for routine husbandry, and where equipment and materials (harvested fish, feed, tanks and bins, etc.) can be handled if necessary. Maintaining position, to provide a secure location, free from navigation hazards, etc. (Scott & Muir 2000) It has been suggested that the use of submersible cages could diminish the risks of escape incidents (as well as lice infestation and the impacts from algal and jellyfish Thistle Environmental 9

15 Literature Review blooms) at salmon farms (Dempster et al, 2008). Short term submergence could be useful in avoiding storm or ice damage which can lead to escape incidents and may also be useful in avoiding other farming challenges where surface conditions are suboptimal. Whilst submergence has been shown to have a negative affect on growth in the short term, it was also shown that salmon adapt to submergence and to reemergence to the surface. Previous studies documented negative effects on behaviour and/or growth which were put down to the physiological requirement of swim bladder adjustment. Salmon fill their swim bladder by gulping air in order to remain buoyant. This study showed that salmon can compensate for the inability to obtain air by swimming faster, generating hydrodynamic lift, to maintain buoyancy. It is understood that SINTEF and the Norwegian Institute of Marine Research (Havforskingsinstituttet) have undertaken research looking at the physiological impact of salmon being farmed in submersible cages (2009, SINTEF, pers. comm.). There is also a European Commission funded project research project entitled Subfish Cage, Development of a cost effective submersible cage system (Teknologisk Institutt AS, undated). Subfish Cage is coordinated by the Norwegian National Institute of Technology (Teknologisk Institutt AS); it is not thought that there are yet any reports available from this project. Closed Containment At present, all Scottish finfish farming on loch sites (marine and freshwater) is undertaken in cage nets. With few exceptions, this is a situation mirrored worldwide. However, some stakeholders have raised the notion of farming in closed containment systems whereby stock is reared in enclosures with an impermeable physical barrier between the stock and the environment using water pumped from outside. The provision of a physical barrier in closed containment systems brings the benefit of helping to contain stock as well as giving the opportunity for the treatment of discharge. It also allows control over the growing environment, including temperature and oxygen, although there are also potential environmental (and economic) costs in terms of energy use and emissions. A conceptual study of a marine closed containment system examined a system of floating rigid containment units composed of layers of concrete and foam which would provide secure containment. The study considered the effects on this containment structure of local environmental conditions, drag forces on multiple containment units, wave loading, undamped heave-motions, mooring gear components and material stresses on a rigid containment structure. The study concluded that wave forces could be substantial and that little is known about how closely spaced heavy containment units would respond individually and as a whole farm to surface waves. Potential capital and operational costs were not considered (Fredriksson et al, 2008). A Canadian study of over forty closed saltwater containment systems from around the world found that none was producing Atlantic salmon (Canadian Science Advisory Secretariat, 2008). It examined four types of system conventional net-pen; floating, closed-confinement systems with rigid walls; floating, closed-confinement systems with flexible walls, and, flow-through and recirculation land-based systems. It found that only land-based recirculation systems could achieve the complete isolation of Thistle Environmental 10

16 Literature Review farmed fish from the environment and that previous attempts at closed salt water system production of adult Atlantic salmon had all failed. The main reasons for failure were mechanical breakdown, poor fish performance, management failure, declines in market price and inadequate financing (Canadian Science Advisory Secretariat, 2008). Closed containment is a well used technique in salmon aquaculture for the freshwater juvenile phase, both in Scotland and overseas. No examples of the use of closed containment systems for freshwater cage sites or the on growing sea water phase of salmon aquaculture at a commercial scale were identified in this literature review, although it is understood that representation has been made to the Scottish government to promote the use of such systems by non-industry stakeholders (2009, SSPO, pers. comm.). A Canadian marine conservation organisation reports on its website that there have been successful trials of the use of flexible bag closed-cell containment systems in British Columbia and Norway for salmon in the sea water environment (undated, Living Oceans Society). However, the fish farming company Marine Harvest reports on its website that its trials of closed containment systems in Canada were disappointing as they offered no environmental or biological advantages but operational expense was greater (Marine Harvest, undated). Nevertheless, Marine Harvest says it will investigate, encourage and fund research into closed containment salmon farms. Marine Harvest s website also reports that it has partnered with the Coastal Alliance for Aquaculture Reform (CAAR) to discuss issues including the economic feasibility of commercial scale closed containment salmon farms; their framework document includes a commitment to closed containment when it becomes economically viable (Coastal Alliance for Aquaculture Reform and Marine Harvest Canada, 2006). AgriMarine Holdings Inc has announced the development of a site with ten solid wall tanks in China for freshwater trout framing (FishnewsEU.com, undated) which will hence constitute closed containment approach to commercial fish farming. It is understood that the site development has commenced and when complete will comprise 24m diameter tanks with an estimated annual output of 1,000 tonnes. At the present time, there is a European Union funded project on closed containment finfish farming which is looking into the development of closed cell technology. It is understood that this project is considering different materials and cell designs. Cage Nets Net design is based on fishing industry technologies and construction from ropes and netting with the former carrying all the major forces (from wind, waves, current, net weights and handling) and the netting containing the fish. Nylon has been the traditional material used for cage nets but in recent years there has been some interest in nets made from high modulus polyethylene (HMPE) and in particular from Dyneema an HMPE material made by DSM Dyneema (FFI, 2006). Predator nets are rarely used in Scotland, but when used they are generally made from polypropylene. Thistle Environmental 11

17 Literature Review The cage/net interface has long been identified as a problem area where tears and chafing occur providing the opportunity for escape incidents (Smith, 1990). Waves and particularly currents produce net deformation which can lead to chafing and net damage through abrasion on cages, moorings, weights, equipment used within the net and from propeller damage. Early research on the drag on nets caused by currents was based on wind engineering which were found to be inaccurate. But models developed since the late 1980s, using different net solidity factors (mesh sizes and fouling), velocity measurement within cage systems and current force measurements from different types of cage systems, have been used to estimate the weights required to keep nets in position (Aarsnes et al, 1990). Recent work in Norway looked at developing methods of strength testing nets and at different net designs (Moe, 2009). Net tears could result from several factors: A worn net with weak spots, Unfavourable handling of the net cage, Weak construction, mainly due to few cross ropes in the bottom, Large loads during handling due to gravity, drag and mass forces (e.g. from biofouling), heavy weights and powerful lifting equipment, Stress concentrations in the netting due to the net production, or, Abrasion from adjacent equipment such as weights, cage collar and mooring system. (Moe, 2009). When lifting a net by hand, any snagging is detected is relatively easily detected. When lifting with a crane there is little control and the sea motion between cage and crane makes the situation worse (Moe, 2009). The study looked at seven different net designs using standard netting materials (nylon netting and polypropylene / polyethylene ropes) for a 24 x 24 x 12 metre cage. The designs differed in roping (straight or inclined) and mesh direction (square or diamond). The most promising design was the net with a twisted bottom which also had extra side ropes and weights (Moe, 2009). It is well known that UV light reduces net strength. Without UV stabiliser intensive sunlight can reduce the breaking strength of a net dramatically within weeks (Christenson, 2000). In a commercial comparison trial of nylon and HMPE nets both types were of equal strength (Fish Farming International, 2006). The HMPE (Dyneema ) net twine was proportionately thinner and lighter than the nylon net because the material is stronger than nylon. This allowed for greater flow of water through the mesh and therefore lesser distortion and greater residual volume when the nets were subjected to increased current speeds. In turn this reduced the (plastic) cage deformation and wave stress on the cage. This reduces the likelihood of escapes due to tears and, because of the toughness of the material, it is more resistant to seal biting and resultant net holes and escape (Fish Farming International, 2006). These nets are, however twice as expensive as conventional (nylon) netting (Fish Farmer, 2009). Thistle Environmental 12

18 Literature Review The SSPO and the Scottish Government are currently funding trials using Dyneema and this has been welcomed by environmental groups such as the Rivers and Fisheries Trusts of Scotland (Fish Farmer, 2009). Whilst the results of these trials are not yet available, this topic is discussed further in Annex 5. In 2007 the Scottish Executive (2007a) suggested that nets should be inspected from day one. Deliberate damage to nets from vandalism has been a cause of escapes in Scotland but is a rare occurrence (Scottish Executive, 2007a) (see also Annex 4). No literature in this regard was identified. Various species, such as blue mussels (e.g. Mytilus edulis) algae (e.g. Sugar kelp, Laminaria saccharina) and barnacles (e.g. Balanus crenatus), attach themselves to a substrate to grow. Cages, nets and moorings as well as rocks and shells provide an ideal infrastructure on which to attach. Biofouling increases the forces on the net particularly when it is handled. Fouling also increases the likelihood of net chafe from abrasion on moorings and cages with marine growth. The Collective Research on Biofouling project (CRAB) project looked at various methods of managing biofouling (cleaning and changing nets, antifoulants, biological controls and new infrastructure designs) and concluded that there were no sustainable and cost-effective solutions to the biofouling problem in aquaculture (Willemsen, 2005). No literature relating to the effects of different cleaning methods on cage net integrity was found. Predation Fish farms in Scotland attract various predators principally herons, diving birds, otters, mink and seals. All predators can cause fish mortalities through attacking fish through the nets. Attacks by mammalian predators in particular can cause holes in the nets, whilst birds can cause tears in the mesh which may become a containment issue should several occur in a small area. Otters and mink are a particular concern to freshwater farms and seals are obviously a sea water issue. Further information on farmers experiences in respect of predation is given in Annex 5. Farmers have three basic strategies to exclude seals: 1. Acoustic deterrent devices (ADDs) for protection against seals; 2. The use of a second (predator) net around the cage net to keep seals (although it could be used for other predators) from gaining access to the cage net, and 3. Tensioning the cage net which helps prevent seals from being able to bite through to the fish (Hambrey Consulting, 2005). ADDs are underwater sound devices designed to deter marine mammals. A recent study looked at the effectiveness of ADDs in estuaries and rivers. Devices were deployed in the River Conon and North Esk to assess their effectiveness in deterring seals (from predating on migratory salmonids) from a specific area of river and as a barrier to the upstream movement of seals. The density of seals was unaffected but upstream movement was reduced considerably by up to 50% (Graham et al, 2009). Thistle Environmental 13

19 Literature Review The use of ADDs is not without wider concern. ADDs may exclude cetaceans (dolphins, porpoises and whales) from a much larger area due to their greater sensitivity to noise (Scottish Executive 2002). Substantial long-term exclusion from habitat and a corresponding reduction in the density of cetaceans through the use of ADDs has been observed. (Gordon, G., Northridge, S., 2001). Maintaining the net at high tension is thought to assist in preventing seals chewing holes in the net (SSPO, 2009) although no formal research in this respect was found. Seals are said to attack slack areas of net in order to bite fish and can then suck the flesh of the fish through the net mesh without necessarily holing the net (Fish Farmer, 2009). At some locations whole cage predator nets are used, elsewhere no special predator netting is used, whilst at others a seal blind or heavy central net weight is used (SSPO, 2009). For halibut, one commentator considered that sinker tubes are essential to enable the base of the net to be tensioned like a trampoline by divers attaching and tensioning the sinker tube (Fish Farmer 2009). There are no consistent metrics used to measure seal predation which might reveal management approaches that work and which could be shared (Natural Environment Research Council, 2008). A study into predation at fish farms was undertaken by the Fisheries Research Services (FRS) in 2001/2. They noted that 55% of Scottish finfish sites which returned a questionnaire on marine predation considered predation to be a problem (i.e. predation was causing loss or damage at the site), while 21% did not (24% did not answer this question) (Quick et al, 2002). The survey identified seal scarers as the most widely used form of deterrent (used at just over 100 sites), whilst predator nets were used at about 25 sites, false bottom nets at about 23 sites, box nets at about 15 sites and cone nets at two sites 4. Seal blinds were in use at seven sites. In respect of weighting, tensioned nets were used at five sites and sinker tubes at four. In the 2002 FRS report, site managers were asked for their thoughts on the effectiveness of different predator deterrent measures. The most effective controls were seen as cone nets, tensioned nets, seal blinds and sinker tubes, with all site managers using these measures considering them to be very effective. While there was some variation in how effective false bottom cages, box nets and curtain nets were thought to be, false bottom cages and box nets were thought to be more effective than curtain nets. Only 23% of site managers considered seal scarers to be very effective, but most did consider them to be at least moderately effective. In six cases they were thought to be ineffective. The report compared its findings to two previous studies and considered that while there had been a significant increase in seal damage between 1985 and 1987, there had not been further increase since then. European Commission Research Project: Escape Proof Net 4 Note that the survey identified top nets in use at over 170 sites and shooting in use at nearly 100 sites; however, for the purposes of this report, there is greater interest in measures being taken to prevent seals (and other predators) from causing escape incidents through making holes in the net. Thistle Environmental 14

20 Literature Review The European Commission is currently funding a research programme entitled Escape Proof Net. This project is particularly aimed at finfish species known to exhibit more aggressive behaviour towards the cage net including sea bass, sea bream and cod. The aim of the project is to develop a sea cage net system suitable for the farming of such species which resists their aggressive behaviour and hence should reduce the likelihood of escapes. This project is particularly focusing on the net materials and net design and, possibly, the use of repulsive coatings. Any resulting designs need to be cost effective. This project is coordinated by the Norwegian National Institute of Technology (Teknologisk Institutt AS) and includes a number of participating organisations which, from Scotland, includes Ocean Nets Ltd. No outcomes have yet to be reported on the website. Scottish Aquaculture Research Forum Research The Sea Mammal Research Unit (SMRU) is currently undertaking a project for the Scottish Aquaculture Research Forum (SARF) entitled: Assessment of the impacts and utility of acoustic deterrent devices. It is understood that this project has not yet reported. A summary of the project is provided in the box below. The use of ADDs in Scottish fish farms has become controversial due to a perceived acoustic impact on cetaceans. Uncertainties about the extent to which ADDs are effective in minimising seal damage also remain. This study proposes to examine the extent to which porpoises are affected by different ADD models, and specifically under different duty cycles. We will also use existing acoustic data collected over five years from the West Coast to examine how porpoise distribution is influenced by ongoing ADD use. In collaboration with the industry we will use daily records from farms where ADDs have been used to collate descriptive information on the effectiveness or otherwise of ADDs. We will on an opportunistic basis deploy acoustic and video equipment around the pens of a salmon farm where seal attacks are ongoing to try to understand more about the nature of such attacks, while also testing the effectiveness of triggers used by one of the manufacturers as indicators of seal attack. Finally we will use the results of this work to elaborate guidelines for best practice use of ADDs. A1.6 Managerial Issues This section considers managerial issues relating to containment. Matters relating to insurance are discussed in Annex 6. Stock Inventories This review did not identify research relating to the accuracy of fish counters, stock inventories and reconciliation data. Where a site is stocked with large number of fish, not uncommonly a half or one million, a stock reconciliation exercise occurs, either as stock are input to sea water, or after all the sea water fish have been harvested. This entails the deduction of fish mortalities, transferred or harvested fish and any known escapee numbers from the original stocked figure. The resulting balance should be zero. Not uncommonly unaccounted losses will occur which could be due to several Thistle Environmental 15

21 Literature Review reasons including unidentified fish mortalities, unidentified stock escaping or an incorrect initial stocking count. Accurate fish counts are very important, not only to the accountant but also to the farmer in order to accurately calculate feeding quantities, appropriate medicine dose rates and accurate stock insurance. During transfer, grading and harvesting operations fish counters are used. These claim an accuracy of % for larger fish and over 98% at maximum capacity for fish of a very small size 0.2g (VAKI, undated). The counters are capable of counting one million 1g fry per hour according to the manufacturers (VAKI). Whilst the level of accuracy of counting machines is remarkable it is nevertheless the case that there could be an unaccounted 1% or 10,000 fish per hour. Management Systems and Policies The use of externally verified management systems is common in Scottish salmonid aquaculture. Some Scottish companies operate under the requirements of BS EN ISO 9001: 2001 and many companies under the requirements of BS EN ISO 14001:2004 (ISO14001). The operational procedures required by such standards would be expected to cover containment risks and issues and, therefore, reduce such risks. Likewise, customer specifications, product certification schemes and other protocols may also directly or indirectly relate to containment. Many company policies are driven by the management systems and protocols the company subscribes to. To conform to ISO 14001, for example, the company must have an environmental policy and operational procedures to address the causes of significant impacts such as those resulting from an escape of fish. These regulatory and non-regulatory protocols and, where relevant, their audit, are examined in Annex 2. This review did not find any literature relating such management systems and protocols to the subject of containment. In 2007 the Scottish Executive suggested that step by step operational procedures and checks should be prepared and shared by the industry to avoid escape incidents and the use of unsuitable equipment (Scottish Executive, 2007a). A1.7 Training Whilst training in operational procedures is identified as an important factor in relation to the physical containment of farmed fish (Wong et al, 2008; Rist et al, 2004 WWF, 2005) the literature has little more to say on the subject. Training was raised at several of the SSPO regional workshops on containment undertaken during 2007/9 (SSPO 2009). These workshops were a Scottish industry initiative aimed at sharing best practice. It is understood that proceedings of the workshop have not been published or made available to farmers; however, Table A1.2 outlines the key points raised by farmers at the workshops which took place in Orkney, Shetland, the Western Isles, Fort William and Argyll. Table A1.2 Summary of SSPO Containment Workshop findings Cage systems Manufacturers guidance/instructions are not often provided. Manufacturers do not specify what moorings are required for Thistle Environmental 16

22 Literature Review Moorings Nets their cage system. Steel cage systems require more maintenance than plastic ones. All farmers do not carry out wave height analysis. Wave height analysis is carried out for all new sites but is very expensive, particularly for small companies. There should be more guidance in the Code of Good Practice for Scottish Finfish Aquaculture (CoGP, 2006) on the development of a moorings maintenance plan and on the frequency of checks rather than...inspected according to a regular and recorded plan. (CoGP ). A time frame should be specified. Divers are unable to inspect moorings on sites deeper than 30m due to health and safety regulations. What was the original source of CoGP net strengths? No satisfactory net strength testing method; e.g. destructive testing not representative of the net as a whole. CoGP Minimum net strengths are too low. CoGP net strengths need updating. CoGP geared towards sea water. A specification for freshwater nets should be formalised. Sinker tubes provide for a stable net. Double netting around top 2 metres is being used by some farmers to protect against chafing. If dive inspections every 60 days were required by CoGP it would reduce competitiveness. CoGP net mesh size should be a must (CoGP ). Dyneema nets do stay cleaner. Anti-fouling increases longevity. Weighting ring inside cage net reduce the risk of escapes. One company does a full net check, by divers, monthly. Use of divers is costly per day. Frequency of net checks should be specified in CoGP ( & 5). Propeller guards are not fitted as standard. Operations Are transfer and handling risk assessments done? (CoGP ) Predators There is little awareness of the SSGA CoP Salmon Farming and predatory wildlife. (CoGP ). Weighting down the centre of the net reduces predator attacks. Are risk assessments being carried out on a site by site basis? (COGP ). There is uncertainty regarding this clause: are most companies undertaking a generic rather than site by site risk assessment? Little use of predator nets. Full predator nets used by one company in the Northern Isles. Thistle Environmental 17