MOVEMENT AND DISPERSAL OF FARMED ATLANTIC SALMON (Salmo salar) FOLLOWING SIMULATED ESCAPES IN FORTUNE BAY, NEWFOUNDLAND (CANADA).
The objective of this three year study is to determine the residency time, locations, migratory routes, and survival of escaped farmed Atlantic salmon by monitoring the movements of groups of smolts, post smolts, and adults in a simulated escape, at different times of the year. A total of five releases are planned as part of this project. Four releases were completed in August 2014, October 2014, May 2015, and August 2015 while the last one is planned for September 2015. Farmed Atlantic salmon are tagged with acoustic transmitters (Vemco V9 and V13) and released from cage sites in Fortune Bay, Newfoundland. A network of 54 Acoustic Receivers (Vemco VR2W) were strategically deployed throughout the inner bay area (700km2) at all cage sites, along headlands, and mouths of salmon rivers to monitor movement (Figure 1). In each release 90 individuals of different sizes are tagged including 15 with temperature sensors. Thirty fish from each of the following size classes were represented at most of the releases: 100g-400g, 400-1.5kg and 1.5-5 kg.
Preliminary data analyses (August and October 2014) suggest that fish remained around cages an average of 2.5 days after release independent of their size with 25% of the fish swimming in the vicinity of other cage sites in the area. For both releases, temperature sensor transmitters recorded higher than ambient water temperature values within days after release for 11 sensors (73%), and 13 sensors (87%) for August and October releases, respectively. These data suggest that fish were preyed upon by sharks, tuna, or seals that were observed near release sites. Analyses of swimming patterns are still ongoing and will be discussed in more details. This project will provide useful information to assist in designing potential recapture strategies in case of escapes.