Salmon Watch Ireland endeavors to keep our support base informed of scientific studies concerning ecological changes in both freshwater and in the marine phase of the Atlantic salmon life cycle. To this end we are initiating a periodical posting which examines such diverse topics as predation, marine ecosystem change , impacts of salmon aquaculture on wild salmonids and freshwater changes resulting from a changing climate. This posting examines the changing marine environment and how these changes may impact on salmon survival at sea. There is also some interesting video content which examines telemetry and highlights the work carried out by the salmon research station on the River Bush.
Distribution shifts of marine species
The first study does not specifically relate to Atlantic salmon but does demonstrate that with a warming ocean certain movements of phytoplankton, zooplankton and fish are occurring with an anticipated negative effect on Atlantic salmon from Ireland and UK in particular. We are currently nearing the southern limit of Atlantic salmon distribution with stocks severely depleted further south.
- Increases in regional sea temperatures have triggered a major northwards expansion of warmer water plankton and a northwards retreat of colder water plankton in the North-east Atlantic. This northerly movement has amounted to about 10 ° latitude (1 100 km) over the past 40 years, and it seems to have accelerated since 2000.
- Sub-tropical species are occurring with increasing frequency in Europe’s seas, and sub-Arctic species are receding northwards.
- Wild fish stocks are responding to changing temperatures and food supply by changing their distribution. This can have impacts on those local communities that depend on those fish stocks.
- Further changes in the distribution of marine species, including fish stocks, are expected with the projected climate change, but quantitative projections of these distribution changes are not widely available.
Atlantic salmon in a rapidly changing environment—Facing the challenges of reduced marine survival and climate change.
This study concerns management actions that are required to address decreasing survival indices for wild stocks
- Atlantic salmon populations have declined in recent decades. Many of the threats to the species during its freshwater and coastal residency periods are known, and management approaches are available to mitigate them. The global scale of climate change and altered ocean ecosystems make these threats more difficult to address.
- Managers need to be aware that promoting strong, healthy, and resilient wild populations migrating from rivers is the optimal approach currently to reduce the impacts of changing ecosystems and low marine survival. We argue that a fundamental strategy should be to ensure that the highest number of wild smolts in the best condition leave from rivers and coastal areas to the ocean. There is great scope for water quality, river regulation, migration barriers, and physical river habitat improvements.
- Maintenance of genetic integrity and diversity of wild populations by eliminating interbreeding with escaped farmed salmon, eliminating poorly planned stocking, and reducing impacts that reduce population sizes to dangerously low levels will support the ability of Atlantic salmon to adapt to changing environments. Reducing the impacts from aquaculture and other human activities in coastal areas can greatly increase marine survival in affected areas.
- As most of the threats to wild salmon are the result of human activities, a focus on human dimensions and improved communication, from scientific and management perspectives, needs to be increasingly emphasized. When political and social will are coupled with adequate resources, managers often have the tools to mitigate many of the threats to wild salmon.
Atlantic salmon in a rapidly changing environment—Facing the challenges of reduced marine survival and climate change - Thorstad - 2021 - Aquatic Conservation: Marine and Freshwater Ecosystems - Wiley Online Library
Impacts of a Changing Ecosystem on the Feeding and Feeding Conditions for Atlantic Salmon During the First Months at Sea
The second study is very relevant to Ireland as there are strong indications that post 2007 contents of smolt stomachs off the west coast of Ireland were seriously impacted. This factor may have contributed to decreased marine survival which appears to have accelerated after 2007. It is important to understand that if post smolts do not gain adequate feeding on leaving our shores, they are more likely to be predated as size is very important in their first period at sea. There should also be alarm at present trawling activities may also be affecting near coastal ecosystems.
West of Ireland and Scotland
"The dominating prey were sand eel and fish from the cod family. The years with the lowest FR values were 2008 and 2009, which were the last 2 years with data sampling in the region. In contrast to previous years, gadoids and sandeel were in general absent from the diet these 2 years, even though the small proportion of unidentified fish larvae could belong to these groups."
ICES Report to North Atlantic Salmon Conservation Organisation 2022
This report is a comprehensive overview of the status of Atlantic Salmon. There are some very relevant points raised concerning the impact of Pink Salmon. A long read but well worthwhile to understand the many challenges facing Atlantic salmon.
The following video illustrates a behind the scenes look at the River Bush research station in Northern Ireland which includes the use of telemetry to conduct their important research.