Section 8.3: Ontogeny of a Sonic Telemetry Program for Atlantic Salmon Salmo salar
Fred G. Whoriskey
The Atlantic salmon Salmo salar is an iconic anadromous species of great social and cultural importance (Dunfield 1985; Beland and Bielak 2002). The potential value of the annual recreational fishery for Atlantic salmon in North America probably exceeds CAN $175 million (Whoriskey and Glebe 2002). In addition, salmon are important for subsistence in some communities and for food and ceremonial purposes for First Nations and Tribes. Atlantic salmon spawn and rear as juveniles in rivers draining to the North Atlantic Ocean in both Europe and North America. After 1–5 years in freshwater, the juveniles become “smolts” and undertake feeding migrations to sea that can last for 1–5 years before returning to home rivers to spawn. Atlantic salmon from North America can return from the ocean to home rivers for their first spawning after one (termed “grilse,” or 1 Sea Winter (SW) fish) or two or more (Multi Sea Winter fish (MSW)) years. In southern portions of North America, the MSW fish are predominantly female, whereas the 1 SW fish are mostly males (O’Connell et al. 2006). Atlantic salmon do not necessarily die after spawning, and postspawn adults can migrate back to the sea and return to home rivers for repeat spawnings in subsequent years. Conservation-oriented management efforts for Atlantic salmon are targeted at ensuring that enough females survive to spawn to seed freshwater habitats with target levels of egg depositions (Chaput et al. 1998).
Atlantic salmon populations are at historic low levels, especially in North America (WWF 2001; Amiro 2003; ICES 2009). There were multiple contributors to the declines, including lost productive capacity in freshwater habitat, blocked freshwater migration routes, and overfishing. More recently, the survival rates of salmon during their ocean feeding migration have dropped precipitously and have stayed low, for unknown reasons (O’Neill et al. 2000; Cairns 2001). This recent increase in at-sea mortality rates has severely impacted Atlantic salmon across the species’ range, but especially in southern North America where a number populations have been listed or are being considered for listing as endangered by national authorities (Federal Register 2009; DFO 2009).