About the Likely Suspects Framework:
An Evidence-based Approach to Support Salmon Management
As the flagship project of the Missing Salmon Alliance, this project represents the development of a guiding vision to help boost adult Atlantic salmon returns.
Atlantic salmon are an impressive fish, overcoming extraordinary challenges and threats as they struggle to complete their life-cycle.
As they grow and migrate, they compete with a changing suite of species for food, and remain extremely susceptible to subtle changes in relationships between their environment, predators and food species.
The species that make up their food, competition and predators vary depending upon where the salmon are, and also on how large they are in relation to others.
The interactions amongst salmon, competitors and predators that may result in mortality are themselves being continually shaped by subtle changes in their physical environments.
The Likely Suspects Framework Project
Decades of research shows us the pattern of survival and how background levels vary greatly throughout the Atlantic salmon life cycle. The species is highly adapted to a level of losses occurring in certain stages of its life cycle, but in recent decades the pattern of survival has been changing, particularly during the marine phase. Whilst the overall output of smolts to the sea has not reduced markedly, typically there are now fewer and smaller adults returning to our rivers from the ocean phase that can provide the next generation.
Image: A representation showing typical variation in the current survival rates associated with the various stages of the Atlantic salmon life-cycle. This is based on an example life history comprising of 2 years of freshwater growth followed by one year of marine growth.
The Likely Suspects Framework (LSF) aims to provide an intellectual and resourcing framework to assist cooperative research into salmon mortality drivers. LSF will provide managers with access to high value decision-support advice that considers the efficacy of their activities within the context of other factors at play (i.e. taking a full lifetime survival view). It will
A) Encourage data mobilisation B) Provide an underlying modelling framework and C) Enable users to interact with the model via an online tool giving future scenario-testing functions.
Image: Conceptual outline of how the components of the Likely Suspects Framework process could facilitate the development of new river stock-specific management guidance and support, linking the processes of stock assessment and catch advice for Atlantic salmon (at the stock-complex scales) and wider Integrated Ecosystem Assessments. ICES J Mar Sci, fsac099, https://doi.org/10.1093/icesjms/fsac099
The Likely Suspects Framework Approach
There are a number of candidate “suspects” that impact salmon survival, ranging from the obvious (e.g. being eaten by something) to the less obvious (e.g. poor feeding due to water temperature changes). We all hold opinions as to which “suspects” are probably responsible for salmon losses, but salmon management actions need support based on more than just strength of opinion.
Salmon management is frequently impeded by poor access to information and evidence to support decisions. The Likely Suspects Framework is working to change this through the mobilisation of available physical and biological data (see Mobilising Knowledge Sources) to help address key scientific questions on what is driving salmon mortality. An ambitious data management system is under development to collect and collate this available data from various ecosystems across the North Atlantic. For more information please see the Salmon Ecosystem Data Hub
Drawing on existing data resources from a multitude of sources, the project will attempt to describe the mechanisms behind changes in the Atlantic salmon’s ecosystem at key points in the lifecycle (see The Lifecycle) where survival fluctuates.
By interrogating the mechanisms influencing salmon stocks in the past, we can begin to address key questions about the drivers of mortality (see Key Mortality Questions: Hypotheses) and direct future actions to protect wild salmon.
Image: Conceptual overview of the life cycle of the Atlantic salmon showing hierarchical scaling of primary environmental drivers influencing stock dynamics across the marine and freshwater life stages. Processes leading to salmon mortality (red negative symbols) arise from multiple natural (dark blue circles) and anthropogenic (light blue circles) sources. Focused management strategies (green circles) intending to counter these losses (green positive symbols) and enhanced stock status benefit from knowledge of the processes acting across the life-cycle to optimise their effectiveness. ICES J Mar Sci, fsac099, https://doi.org/10.1093/icesjms/fsac099
International Workshops
NASCO-ICES WKSALMON workshop participants, Copenhagen June 2019.
The success of the Likely Suspects Framework approach is largely dependant upon cooperation, communication and building partnerships amongst a large number of organisations.
To date, there have been several important international workshops with the Likely Suspects Framework as their focus and there are more being planned:
Edinburgh: November 2017 Atlantic Salmon Trust Likely Suspects Workshop
Copenhagen: June 2019 NASCO-ICES WKSALMON Ocean Data Workshop
Online: May 2020 MSA Likely Suspects Framework Roadmap Workshop
Vancouver: 2022 International Year of the Salmon Symposium
Seattle: 2023 World Fisheries Congress
AST Likely Suspects Framework workshop participants, Edinburgh, Nov 2017
The ‘usual suspects’ of international expert scientists gathered at workshops in support of the project. The input from internationally-recognised expert scientists is invaluable to this process and we are extremely fortunate that so many individuals and organisations support the project and remain so actively engaged with us. We are grateful for on-going support to facilitate this knowledge exchange.
Meet The Team
“Atlantic salmon management needs adaptive strategies based on knowledge of the past and of the mechanisms behind changing mortality rates”
Likely Suspect Framework Work Packages
The LSF programme will focus on combining existing data resources with newly derived data to expand our understanding of what is driving salmon mortality in the individual stages of their life cycle where survival rates have been declining in recent years. In time (and where possible) this level of guidance can be translated into developing more river-specific advice.
Facing the scale of the knowledge gaps requiring immediate attention, and the availability of data sources, it is not a realistic prospect for the LSF programme to focus on formulating river-specific management advice. It is a reality that river-specific advice is critically dependant on the availability of appropriate local data and these are available for only a minority of salmon rivers. The delivery of the LSF hinges on progressing four areas through five work packages (WP) over five years:
Image: Phasing the delivery of LSF work packages.
Developing a salmon data library as a state-of-the-art knowledge exchange hub mobilising environmental and biological data for salmon science and management (WP1).
Developing a salmon mortality (i.e. suspects) framework as a statistical tool representing mechanisms behind fluctuations in stock abundance that provides new information across the life-cycle and evidential support for salmon management (WP2).
Integrating new and emerging knowledge in ways that provide interactive decision support tools for salmon managers (WP3).
Catalysing strategic research into conditions that lead to salmon mortality and development of new indicators of the state of ecosystems linked to salmon survival. This will support regional scale guidance and a greater understanding of the efficacy of existing management activities (WP4 & 5).
Likely Suspects Framework News:
