Marine feeding areas and vertical movements of Atlantic salmon (Salmo salar) as inferred from recoveries of data storage tags

Abstract

We released 598 Atlantic salmon (Salmo salar) hatchery smolts in a river in Iceland in 2005 and 2006 tagged with data storage tags recording temperature and (depth) continuously. Five salmon returned in 2006 and two in 2007, all spending 1 year at sea. The complete temperature and depth profiles of the whole ocean migration were measured. The salmon stayed close to the surface most of the time and showed diurnal behavior, staying at slightly deeper waters during day. The salmon were in temperatures from 6 to 15 °C, with warmer temperatures in the summer. We compared the fish-recorded temperature with sea surface temperature from an available National Oceanic and Atmospheric Administration database to locate the fish at different times. Utilizing the diurnal behavior of the salmon, we estimated solar noon each day during winter. Sea surface temperatures and diurnal activity were used to estimate daily locations using established Hidden Markov Model for fish geolocation. The salmon in the study stayed southwest of Iceland in the Irminger Sea during the first summer months, but in the fall they moved towards the Faroes Islands and then back to the Irminger Sea where they stayed, until returning to the river. The salmon also took shorter and deeper dives (>100 m) during the latter part of their ocean migration.

Revealing the full ocean migration of individual Atlantic salmon

“…Previous electronic tagging studies on the horizontal migration of Atlantic salmon have either been limited by only describing the first part of the ocean migration [7,8] or by describing coarse spatial distributions [12,13]. The current study is therefore the first to provide detailed information about the continuous horizontal migration of individual Atlantic salmon throughout the entire ocean residency, providing indispensable information about the habitat occupancy for the winter and spring period.…”

“…However, as PSATs eventually detach from the tagged fish and transmit archived data to passing satellites, detailed descriptions of the entire horizontal migration are difficult to obtain. Studies using archival tags, which require recapture of the fish to retrieve the data, have succeeded in describing the depth use of individuals during the entire ocean migration [10,11]; however, they have not been able to provide detailed descriptions of individual migrations [12,13]. Therefore, information on the continuous horizontal migration of individual Atlantic salmon during the entire ocean residency is lacking.…”

Environmental change influences the life history of salmonSalmo salarin the North Atlantic Ocean

“…Fishes living in temperate waters often encounter habitats colder than their optimal temperature for growth (Forseth et al, 2009). For instance, in the North Atlantic Ocean, post-smolts of Atlantic salmon Salmo salar L. 1758 typically exploit habitats that are colder than their optimal temperature (Gudjonsson et al, 2015;Minke-Martin et al, 2015), which for post-smolts is about 14 ∘ C according to the study by Handeland et al (2008). Thus, growth typically increases with increasing ambient temperature given that the fish find enough high-quality food.…”

Spatial synchrony in the response of a long range migratory species (Salmo salar) to climate change in the North Atlantic Ocean

“…We also assumed that the space-time domains sequentially occupied by salmon during the first year at sea have not changed over the 1971-2014 period. However, both the timing of smolt migration (Otero et al, 2012;Satterthwaite et al, 2014), and the boundaries of favorable habitat at sea (Cheung et al, 2009;Poloczanska et al, 2013) have changed which may have altered salmon migration routes (Guðjónsson et al, 2015). In addition, spring plankton blooms and therefore the peak of higher trophic resources available for salmon may be advanced in the season and may occur in different places (Edwards et al, 2010;Malick, Cox, Mueter, Peterman, & Bradford, 2015;Parmesan & Yohe, 2003), thus potentially creating a mismatch between salmon migration and available resources (Cushing, 1990).…”