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Atlantic Salmon Trust
Atlantic Salmon Trust

Ocean Silver conference - Fishmongers' Hall, London December 2011

‘Ocean Silver' attracted nearly 200 delegates, and feedback has been strongly supportive of AST's initiative to use SALSEA data to find ways of improving the efficacy of fisheries management. We hope that the conference raised awareness of the salmon's predicament in its ecosystem context and started the process of thinking through what measures we can take to help the wild Atlantic salmon as a species get through this challenging period of adapting to climate and oceanic changes.

SALSEA has delivered a database that will ultimately cover the whole range of salmon owning countries of the north Atlantic. These data include three distinct components, covering cruise data (biology, physio-chemical data, oceanography etc), scales data and genetic data. Historical data are included, enabling us to compare the lives of salmon in the early twentieth century with those of today. A full report on the SALSEA findings, as presented at the La Rochelle ‘Salmon Summit' in October 2011, can be seen on the AST or NASCO websites.

In the old Celtic cultures the salmon was a symbol of wisdom. As the secrets of the marine life of the Atlantic salmon are revealed by the international SALSEA project it has become clear that scientists and fishery managers need all the wisdom they can get to ensure that management of these fish and their habitats in fresh and salt water is informed and influenced by what we have learnt about their lives at sea. Understanding the whole life of the salmon gives us insights from which we can tease out implications for the manager on the riverbank whose job it is to apply what has been learned to practical measures.

Some people feel that new data on where salmon feed at sea, and what the constraints are on their survival, are beyond the capacity of man to intervene effectively. Fortunately, most people see merit in that the data provide us with a better understanding of the whole life history of salmon. The resulting increased empathy for this extraordinary animal should ultimately enable us to intervene on its behalf during the current period of climatic and environmental changes. It is the question of how we can respond to the new data to optimize the salmon's survival that was the subject of the ‘Ocean Silver' conference.

Perhaps the most important message from ‘Ocean Silver' was given by Dr Jens Christian Holst of Norway's Insitute of Marine Research in his scene-setting presentation when he placed the salmon firmly in the family of fish species in their pelagic environment context. He presented a cogent argument for increasing awareness and appreciation of the Atlantic salmon's role in the marine ecosystem, leading to an acceptance of salmon as a member of the pelagic family of fishes. He argued that an ecosystem-based approach necessitates an acceptance that surveys of the oceanic pelagic zone must in future include a migratory fish component. He also emphasized the importance of the underlying cyclical oceanic changes from the North Atlantic Oscillation and the Atlantic multidecadal cycle.

The mystery of when salmon return to their native rivers, either as 1SW (grilse) or MSW adults needs to be understood better than it is at present. Efforts must now shift to an assessment of the later years at sea. We need a better understanding of the mechanisms which control where fish are located during their first winter at sea; when maturing and non-maturing 1SW fish separate and what determines their decision to mature.

Remaining N Atlantic seas, such as the Irminger Sea and East Greenland, need to be surveyed and their role in marine recruitment better understood. More intensive studies are also required to separate out the areas of the oceans where salmon survival is poor in a continuing effort to understand when, where, why or how salmon are dying at sea.

Key messages from ‘Ocean Silver' built on the ‘Salmon Summit' outcomes:

  • We need to shift the emphasis from survivors to the 95% that die at sea. For too long we have limited our research efforts to studying the near shore and in-river survivors. We must now refocus on the fish that never return
  • Marine mortality is due to North Atlantic-wide factors. The factors governing mortality are common factors spread across the ocean. We need to take a much longer view, perhaps as long as 200 to 300 years, to appreciate the underlying cycles of oceanic changes. Changes in temperature attributed to man are an ‘overlay' above this natural, cyclical level. We need to be aware of the big picture and avoid being slave to seasonal or short period changes.
  • We need to know more about the migration patterns of post-smolts at sea. For example, Smolts may need to ‘jump' currents on several occasions to reach their destination. Where pelagic trawlers are fishing across salmon migration routes action is needed to minimise ‘collateral' damage to stocks. Little fish get mangled and spat out by trawlers, and therefore never achieve the status of by-catch. They are therefore extremely difficult to trace.
  • Salmon dive to 800 to 900m. Stable isotope and other chemical analysis methods are revealing new and extraordinary features of the lives of salmon at sea. Salmon may seek out the thermocline in spring and summer and dive to depths of 800m or more in winter, where they can stay for up to 24 hours, probably feeding on lantern fish. This surprising information enlarges our understanding of salmon as oceanic fish and should deepen our empathy for them.
  • Small post smolts are more vulnerable. If, because of poor feeding and reduced growth, post-smolts are forced to spend more time in smaller size slots they become vulnerable to far greater levels of predation.
  • Ocean systems have huge inherent inertia. Changes in ocean temperature are very slow to recover to ‘normal' levels. Salmon are a very resilient species and need time to adapt to environmental changes. It is vital that we work ‘with the grain of change' to find ways to help the fish adapt.
  • Younger smolts are migrating to sea. In some areas, particular in the southern range of the salmon, smaller younger smolts are migrating to sea. These fish are extremely vulnerable to predation and survive poorly at sea. We need to understand where the bottlenecks to survival Are and what we can do to mitigate them, particularly in the coastal zone.
  • Natural selection always imposes a cost. The greater the extent of the change, the greater the cost. Current climatic changes are ‘squeezing' the optimal areas for salmon at sea. We need to anticipate where the pressure points at sea will be, and take action to conserve stocks affected. There is every possibility that SALSEA has provided the tools to predict which stocks are likely to be under pressure and to enable managers to optimize their survival and natural production.
  • The condition of salmon stocks today is the product of past pressures. The SALSEA data are telling us what has already happened. We can and must plan on models for future change. The ability to predict future pressures and to put mitigation measures in place before the changes impact on salmon habitats requires sound data, good planning and above all commitment. SALSEA has given us the toolkit. We now need to use those tools wisely.
  • Reducing man's impacts on salmon stocks may be the key. There are only a few things we can do to mitigate the effects of climate and oceanic changes.
    A) We need to maximize natural smolt output from every catchment
    B) Reduce exploitation, especially of mixed stocks
    C) Reduce obstructions to migration, especially renewables
    D) Find ways to reduce damaging impacts of aquaculture
    E) Monitor stocks at sea by including salmon in pelagic fish surveys. Take action top protect stocks revealed as vulnerable
Atlantic Salmon Trust, Suite 3/11, King James VI Business Centre, Friarton Road, Perth PH2 8DG
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