Impacts of Open Pen Freshwater Aquaculture Production on Wild Fisheries

1 Introduction

1.1 Study overview

This report covers work undertaken on a Contract Research Fund study commissioned by Marine Scotland: "IMPACTS OF OPEN PEN FRESHWATER AQUACULTURE PRODUCTION ON WILD FISHERIES".

The study was undertaken by Homarus Ltd, a niche advisory firm in fisheries, aquaculture and the marine environment. It is being managed by the Performance and Aquaculture Division within Marine Scotland who have established a Steering Group to assist with oversight of the study.

The study was commissioned in late August 2011, with a start-up Steering Group meeting in early September 2011. Interim reporting and a Steering Group took place in late January and early February 2012, followed by a draft final report and Steering Group meeting in April 2012. This report is the final version and incorporates comments made by the Steering Group. Other outputs include a technical workshop for stakeholders which is planned for July 2012.

The study objectives and methods requested by Marine Scotland in the study brief are set out verbatim in Appendix 1.

1.2 Study background and rationale

The development of marine salmon farming in the northern and western fringes of Scotland has been rapid, with production rising to some 154,000 tonnes in 2010 ³ from small beginnings in the 1970's. The ex-farm value is £540m and global retail sales value of some £1 billion, (latest Scottish Government estimates). The industry is a major employer and investor in the economies in the remote rural fringes ⁴ .

To achieve this output, the ongrowing industry uses around 40 million smolts that are currently produced in tanks using river water or pens located in freshwater bodies, mostly in western and northern Scotland. The number of smolts stocked in marine sites has been relatively static or trending slightly downwards in recent years. However, there are medium to long term plans to expand the industry, provided that profitability can be maintained, with a prevailing view that EU and global demand will stay strong. With yields per smolt possibly near a realistic maximum, expansion of salmon production in Scotland is going to increase demand for smolts. Indeed, estimated smolt production in the latest Marine Scotland survey suggests a sharp upswing for 2011 and 2012. Recent smolt usage, trends and predictions in demand are discussed in more detail later in the study.

Just under half of Scotland's smolt production is from pens in freshwater bodies, while the remainder is derived from tank-based systems.

Concern in a number of stakeholder sectors has been expressed that freshwater pen production may lead to significant negative impacts on the character, productivity and viability of wild fish populations, and in particular those of Atlantic salmon, sea and brown trout. Concern is currently largely focused on the direct effect of escaped farm fish, through either ecological or reproductive interactions, the former encompassing both farmed salmon and rainbow trout and the latter focused on farmed salmon.

The concerns are also set out in the study brief and cover possible interbreeding, competition for habitat and alterations to behaviour. Both large episodic escapes and ongoing, low level, unrecorded escapes are perceived as being potentially problematic and contributing significantly to observed, documented declines in Scottish salmon and sea trout stocks observed over the past three decades. The status of Atlantic salmon stocks across the whole North Atlantic continues to give concern ⁵ , and whilst the rod-caught (released and retained) catch in Scotland has held up well, the overall abundance of fish has probably continued to decline, given that the catch (and effort) of coastal netting stations has significantly diminished. In some parts of Scotland, declines in sea trout appear even more marked than for salmon and significant differences appear to occur across regions.

In addition to their inherent conservation value, both salmon and sea trout are targeted by game anglers and any significant decline in their stocks risks declines in angler activities and spending in rural areas, as well as reduced capital values of game fishing waters and depressed amenity values of catchments. Expenditure on angling for salmon and sea trout in Scotland was estimated at £73m in the early 2000's ⁶ . This information is now somewhat old and inflationary factors mean this figure might currently be around £100m. Angling thus represents a significant economic activity and is a direct and indirect employer.

Concern also exists, though this is less widely or strongly expressed, with regard to the impacts of freshwater cage farms on the nutrient loading and the biological communities of lochs in which they are placed, as well as to local wild fish stocks feeding on farm pellets falling through and below cages. Increased nutrient levels have the potential to change the abundance of planktonic and benthic species with possible knock-on effects for the viability of some resident fish species. There is also concern that the presence of an additional, alternative food source may reduce the tendency of local trout stocks to undergo a marine migration thereby reducing local sea trout numbers. These concerns have become more focused since the introduction of new water body classifications, recommended by the UK Technical Advisory Group under the auspices of the Water Framework Directive and accepted by Scottish Ministers. This issue, of considerable interest to SEPA and other parts of the Scottish Government, is complex and largely outside the scope of this project, but reference has been made to aspects of it within the report, where they are relevant to any considerations or conclusions.

Any aquaculture operation involving pens involves risk of escapes, no matter how good the equipment. As such there is a call from some quarters that the risk should be removed completely by the transfer all of the freshwater phase of smolt to tanks and the replacement of freshwater pens for trout with conventional systems (ponds and raceways) or sea water pens. The economic costs of such changes are likely to be substantial, primarily in respect of capital expenditure but also in operational terms.

The study thus aims to address two fundamental questions:

What is the strength of evidence for negative effects on wild salmonid populations caused by freshwater pen culture?

What are the costs and benefits associated with partial or total phasing out of freshwater pen culture?

The study is therefore split into two main workstreams:

1. Evidence of effects on wild populations

This essentially addresses the state of knowledge concerning the interaction of farmed salmonids in freshwater pens and wild salmonids. It is achieved through a literature review of the situation both in Scotland and further afield. It also includes a synthesis of information on river systems where pen farms are located. This section finally includes a review of research activities and knowledge gaps in this field.

2. Mitigation options and economic and financial implications of a change to closed tank systems

This part of the study makes a brief review of "high level" mitigation options for reducing potential impacts to wild salmonids. It then goes on to make a more detailed analysis of the consequences of possible policy change regarding permitted production methods involving freshwater pens. Various scenarios are used to assess the economic costs associated with restriction on further expansion in the use of pens, as well as reduction from their current use and their total phasing out. The majority of this workstream concerns salmon smolt production, as the number of open pen sites currently used and their economic importance is considerably higher than those for trout. Implications of enforced changes in production technique are also assessed in financial terms as well as site and employment requirements.

1.3 Study implementation

Study team

The study was carried out by a team of three led by Patrick Franklin of Homarus Ltd. Members of the study team and their broad areas of responsibility are outlined below.

• Dr Eric Verspoor: One of the UK's leading salmon biologists and authorities on wild salmon genetics, with over 35 years experience in genetics and fisheries science, has authored over 150 peer reviewed papers, book chapters, and reports, and for the last 20 years worked in Scotland with the salmon aquaculture and wild fisheries sectors; led 2002-2005 EU SALGEN review of Atlantic salmon genetics related to their conservation management; member of steering committee for 2007-2009 EU GENIMPACT review of genetic impacts of cultivated native European species on wild stocks; recent work encompasses studies of loch fish biodiversity in Scotland and direct genetic impacts of smolt escapes from freshwater cages.
  
  Eric was responsible for the review of the state of national and international knowledge related to potential for impacts, examination of the evidentiary basis for impacts in Scotland and identification of research needs and priorities.

• Richard Slaski: Senior and established advisor in fisheries and aquaculture at strategic, policy and management levels in Scotland. Excellent existing working relationship with many of the stakeholder individuals and groups who need to be consulted and proven track record in stakeholder engagement in Scotland. Over 30 years experience of designing, building, operating and consulting on land-based aquaculture in the UK, Europe, Canada, Chile, Turkey, New Zealand and China.
  
  Richard led on assessment of current freshwater farming practices and developing capital and operational cost models for different methods of production.

• Patrick Franklin: Significant knowledge of the UK and Scottish aquaculture industry, technologies and economics. Long experience of leading impact studies in the fisheries and aquaculture sector on behalf of EU, government and private sector, leading researcher and author of several aquaculture-related studies on behalf of Scottish Government in recent years.
  
  Patrick led on scenario building and testing and in assessing the implications of a change in production method for the overall industry.

Structure of this report

The structure of this Final Report follows that set out in the Interim and Draft Final reports and was accepted as broadly meeting the needs of the study by the Steering Group. It is set out in a logical sequence with two main sections, one describing methods used in the study ( Section 2), followed by all the study findings in one substantive section ( Section 3). Each of these main sections is divided according to the two main workstreams of the study, i.e.

• biological aspects of interactions between open pen aquaculture in freshwater and wild salmonids
• costs and implications for restricting open pen aquaculture in freshwater in Scotland.

Section 2 thus describes information sources, approaches to the workstreams and methods used to analyse data. Section 3 covers all findings of the study, opening with a review of the evidence of impacts freshwater pen farming on wild populations, followed by an assessment of costs which might arise from a change in smolt production methods. Section 3 closes with an assessment of financial implications for the aquaculture industry of such changes.