Interactions between salmon farming and the ecosystem: Lessons from the Hardangerfjord, western Norway

Fjords are unique coastal landscape structures that require enhanced basic and applied biological research (Brattegard et al. 2011). In Norway, efforts have recently been made to study selected fjord systems more effectively and integratively. The current Thematic Issue presents results focusing on the Hardangerfjord in western Norway. The Hardangerfjord is approximately 180 km long and 2–10 km wide and is the second largest fjord in Norway. It was formed by glacial activity, has two moraine sills of around 150 m depth in the outer parts and extends to a maximum depth of 830 m in the fjord basin. In the inner part the main fjord splits into several narrow side fjords, the longest being Sørfjord which is 40 km long. Several large rivers run into the fjord and in the side fjords the surface water is permanently brackish. The rich populations of fish and shellfish have provided food and work since the times of the first recorded settlement, about 8000 years ago. The Hardangerfjord region provides good opportunities for industrial activities based on both the tributary freshwater systems and the main fjord. Consequently, the fjord basin may be affected by a number of local anthropogenic activities, such as agriculture, aquaculture, fisheries, hydroelectric power production, pollution from households and industry, and also through more indirect mechanisms such as climate change. Following the beginning of hydroelectric power plant constructions, the production of carbide and later dicyanamide was begun in the innermost part of the Sørfjord in 1908; later, other industrial plants began production in the fjord. The industrial activity resulted in strong pollution by heavy metals in the inner parts of the Hardangerfjord (Ruus et al. 2012). The discharges of black lime waste resulted in extremely low oxygen concentrations, high nitrate levels and toxic flagellate blooms in the late 1990s (Aure & Pettersen 1998). Piles of black lime waste still remain in the fjord, but the ecosystems are in recovery (Ruus et al. 2006). The massive hydroelectric power production in many rivers has provided much public revenue for local communities. The production clearly affects the habitats and life of Atlantic salmon and brown trout, while less is known about its effect on the fjord ecosystem. The Hardangerfjord is at present one of the regions in Norway with the highest density of salmon farms, with a production that exceeded 80,000 tonnes in 2011 (Knut Johnsen, The Norwegian Directorate of Fisheries, pers. comm.) or about 10,000 times the production of wild Atlantic salmon in the fjord. With high human activity in the coastal zone, the fast expansion of salmon farming along the Norwegian coast and particularly in the Hardangerfjord, the reports of massive salmon lice infection on anadromous brown trout (Salmo trutta), disease problems in many salmon farms and numerous of escapees in salmon rivers, there has been a strong concern among the public and management authorities for the wild salmon, the anadromous brown trout and the environment of the Hardangerfjord. Coincidentally, there are reports of excessive growth of filamentous macroalgae in the middle part of the fjord. The interdisciplinary research programme ‘Ecological Processes and Impacts Governing the Resilience and Alternations in the Porsangerfjord and the Hardangerfjord – EPIGRAPH’ was therefore initiated by the Ministry of Fisheries and Coastal Affairs in 2008 to learn more about the interactions between human activity and the ecosystems of the fjords. To distinguish between changes caused by local salmon farming and more general, large-scale trends related to climatic changes, the project was designed as an interdisciplinary project with eight work packages: (1) Physical oceanography and its importance for fjord ecology; (2) Nutrients, fluorescence and benthos; (3) Temporal changes in macroalgal vegetation in the intertidal and shallow subtidal zone; (4) Valuable and sensitive habitats; (5) Zooplankton and sprat diet; (6) Fish resources and predation; (7) Population structure and genetic relationship between fjord and open water components of sprat; and (8) Interactions between salmon farming and wild anadromous salmonids. The project was then linked up to other supplementary projects conducted at the Institute of Marine Research, Bergen, such as monitoring of salmon lice on wild and farmed salmonids, oceanography, Marine Biology Research, 2014 Vol. 10, No. 3, 199–202, http://dx.doi. org/10.1080/17451000.2013. 840730