Influence of climate and abundance on migration timing of adult Atlantic salmon (Salmo salar) among rivers in Newfoundland and Labrador

Abstract

Evidence mounts for the influence of climate variability on temporal trends in the phenology of many organisms including various species of fish. Accordingly, we examined variation in adult Atlantic salmon Salmo salar run timing in thirteen Newfoundland and Labrador rivers where returns were monitored at fishways or fishcounting fences. Run timing varied significantly among rivers with the median date of return differing by up to 5 weeks. Duration of runs was generally short with most adults returning over a period of three to 5 weeks. A mixed model analysis incorporating a first-order autoregressive error structure was used to generalise changes in run timing among all monitored rivers. Results indicated that the median date of return has advanced by almost 12 days over a 35-year interval from 1978 to 2012, while several individual rivers have advanced by almost 21 days. The influence of climate on median timing was evident when the simultaneous effects of both climate and salmon abundance were controlled. We found earlier runs associated with overall warmer climate conditions on the Newfoundland and Labrador Shelf. Results contrast with those from the north-east Atlantic where Atlantic salmon are returning later in some rivers coincident with warming climate conditions.

Atlantic salmon and sea trout display synchronised smolt migration relative to linked environmental cues

“…Models predict changes in several aspects of fish life history as a result of climate change, and several long-term studies have observed a shift in the distribution of marine stocks 35 and in the timing of key life history traits for salmonids 17,18,38 . While Byrne et al 20 found that the timing of smolt migration over a 30-year period in a river in western Ireland was consistent over time, a study by Dempson et al 39 found that migration timing of Atlantic salmon in several Canadian rivers had changed in relation to warmer climate conditions over a 35 year period. Similarly, Otero et al 38 found that the migration timing of Atlantic salmon across their North Atlantic range has changed in response to changing global climate in the last five decades.…”

Susceptibility of European freshwater fish to climate change: Species profiling based on life‐history and environmental characteristics

“…Riverine fish species losses due to climate change and reduced water discharge are predicted to reach 75% in some river basins, such as those of rivers Parnaíba (Brazil), Saloum (Senegal), and Cauvery (India; Xenopoulos et al, 2005). Phenological changes in fish behavior (Dempson et al, 2017;Hovel, Carlson, & Quinn, 2017;Otero et al, 2014) have been also detected and emphasize the powerful changes imposed by a changing climate. In Europe, there is a broad range of climatic conditions experienced across the landscape and a diverse ichthyofauna distributed throughout the lakes and rivers (Ficke et al, 2007).…”

Bioenergetic consequences of warming rivers to adult Atlantic salmon Salmo salar during their spawning migration

“…Sea trout ( Salmo trutta ) populations at high latitudes have less frequent iteroparity than do southern populations (Jonsson & L'Abée‐Lund, ), a trend that may also be true of the congeneric Atlantic salmon. Phenological changes such as shifts to later run timing could also buffer energetic costs of warming water, as has been observed for populations in Newfoundland and Labrador, Canada (Dempson et al., ). Entering rivers later may decrease the accumulated thermal units during migration and offset energetic costs of higher water temperatures (Katinic et al., ) and entering earlier and swimming upriver to holding sites before temperatures become elevated will avoid a collapse in aerobic scope (Farrell et al., ).…”

“…The Arctic is an area of relatively sparse human habitation and impact; therefore, climate change may present one of the most salient threats to salmon in the north. The phenotypic plasticity of salmon means that they may adjust either their body size through changes to maturation schedules or their behaviour by shifting run timing to adapt to changing demands associated with climate change (Clark et al., ; Dempson et al., ; Otero et al., ). Models predicting the energetic costs of size, activity and water temperature will therefore yield a better understanding of Atlantic salmon migration and potential responses to climate change.…”