Thermal habitat experienced by Atlantic salmon (Salmo salar L.) kelts in coastal Newfoundland waters

Thermal habitat was recorded by data storage tags (DSTs) applied to Atlantic salmon (Salmo salar L.) kelts during their seaward migration in the spring of 1998 at enumeration facilities in Highlands River, Humber River, Western Arm Brook, and Campbellton River, Newfoundland. In total, 139 DSTs were applied and data were downloaded from eleven of the recovered tags. The recovered tags had been applied at Highlands, Campbellton and Western Arm rivers and recovered in the coastal waters of Newfoundland and Quebec and at the enumeration facilities at Highlands and Campbellton rivers. Water temperatures experienced by the fish were recorded for periods of 62-118 days at resolutions of 15-30 min. The data from the sea record on the DSTs were analysed for temperature patterns in relation to migration behaviour and diurnal movement of the fish. A variety of patterns were exhibited on the temperature records suggesting that the fish were behaving in various ways at different times. For Campbellton and Highlands fish over the course of some 24 h periods, night-time temperatures changed little and were among the highest daily temperatures experienced by the fish, whereas daytime temperatures often showed dramatic and frequent shifts in temperature presumably as the fish rapidly and frequently changed depth. For the Western Arm Brook fish, rapid fluctuations in temperature occurred sometimes during the day and night without a consistent diurnal pattern. We also considered large-scale aspects of the data by examining oceanographic conditions in relation to the temperatures recorded by the tags.