Incidence and impacts of escaped farmed Atlantic salmon Salmo salar in nature

• Main Authors: Thorstad, Eva B., Fleming, Ian A., McGinnity, Philip, Soto, Doris, Wennevik, Vidar, Whoriskey, Fred
• Format: Book
• Language: English
• Published: Norwegian Institute for Nature Research (NINA) 2008
• Subjects: Atlantic salmon; Salmo salar; Aquaculture; Fish farming; Farmed salmon; Escaped salmon; Escapees; Geographical and temporal trends; Genetic interactions; Canada; Norway
• Online Access: https://hdl.handle.net/11250/2725676

Since the mid-1960s, Atlantic salmon Salmo salar farming has grown into a large industry within and beyond the native range of the species. Norway, Chile, Scotland and Canada are the largest producers (46, 31, 10 and 7% of total production in 2005). A number of environmental concerns have arisen from the phenomenal growth of the industry. This report from the Technical Working Group on Escapes of the Salmon Aquaculture Dialogue aims at examining and evaluating i) the incidence and impacts of escaped farmed salmon in nature, and ii) the technologies and efforts to prevent escapes and to reduce their impacts upon wild salmon and the environment. This document: • reviews the status of current research and our understanding of the issues, • identifies significant conclusions/issues resolved by past research, and • documents specific knowledge gaps and research needs. Detailed information on salmon production, reported escapes from fish farms and monitoring of escaped farmed salmon in nature is given for each of the salmon producing countries. Escapes from fish farms occur from marine net pens in all salmon producing countries, as both repeated “trickle” losses of relatively small numbers of fish, and through large-scale episodic events. Numbers of farmed salmon escaping to the wild are large relative to the abundance of their wild conspecifics. Nearly all salmon producing countries have established routines for reporting at least large-scale escapes from sea cage sites, but the magnitude of unreported escapes is unknown. Information on low-level leakage and escapes from freshwater hatcheries remains uniformly poor. Negative effects by escaped farmed salmon on wild Atlantic salmon populations have been scientifically documented. Negative effects include both ecological interactions and genetic impacts of inter-breeding. A large number of studies point to negative effects, and outcomes for wild populations are either mostly negative and at best neutral. It has been shown that inter-breeding of farm with wild salmon ...