Ecological correlates of diel activity in Arctic charr Salvelinus alpinus

Diel activity, the partitioning of time between periods of activity and rest, gives insights into how organisms compete for resources in time. Some species show plasticity in the rate and timing of their activity, which enables to study associations with ecological factors. Streamdwelling fishes like salmonids are a textbook example of animals with variable activity patterns. During this Ph.D., I studied the diel activity of individually tagged juvenile Arctic charr in several field experiments and studies, focusing on critical factors for salmonids ecology. I found that Arctic charr increased activity (i) with rising temperature, (ii) when shelters are limited, (iii) in fast current, (iv) under relatively stable waterflow and (v) at high population density. The distribution of activity in time was also affected by ecological conditions in all studies. Flexible activity patterns coincided with modifications of other behaviors (aggregation, foraging mode, habitat selection). Arctic charr sometimes appear to maintain growth under suboptimal conditions by modifying their activity (e.g. limited shelters), whereas in other situations they increase activity under conditions that yield higher growth (high current velocity). In all but one experiment, more active fish grew faster. This relationship depended on the environment. It was stronger in faster currents, and under stable waterflow. These results have important implications for biological fields such as behavioral ecology, by estimating behavioral flexibility, salmonids ecology via food intake and growth under different ecological scenarii, and conservation biology by using behavior to assess the effect of future changes in the physical habitat of stream fishes.Dægursveiflur í virkni lýsa því hvernig dýr deila sólarhringnum á milli virkni og hvíldar, og hvernig þau keppa um auðlindir í tíma. Sumar tegundir sýna sveigjanleika í því hversu virk þau eru og hvenær, og eru hentug til rannsókna á áhrifum vistfræðilegra þátta á virkni. Fiskar í ám, þá sérstaklega laxfiskar, eru skólabókardæmi um dýr sem sýna breytileika í virkni. Í doktorsnáminu rannsakaði ég dægursveiflur í virkni einstaklingsmerktra bleikjuseiða í tilraunum og rannsóknum við náttúrulegar aðstæður, þar sem athuguð voru áhrif þátta sem hafa mikilvæg áhrif á vistfræði laxfiska. Bleikjur voru virkari (i) við hærra hitastig, (ii) þar sem felustaðir voru takmarkaðir, (iii) við meiri straumhraða, (iv) þar sem vatnsrennsli var stöðugt, og (v) við hærri þéttleika. Í öllum rannsóknunum höfðu vistfræðilegir þættir líka áhrif á það hvernig virkni dreifðist í tíma. Sveigjanleiki í virkni tengdist líka breytileika í öðru atferli (t.d. árásarhneigð, fæðuháttum og búsvæðavali). Rannsóknirnar sýndu líka að stundum viðheldur bleikja vexti við óhagstæðar aðstæður (fáir felustaðir, hár þéttleiki) með því að breyta virkni sinni en stundum eru þær virkastar við aðstæður hagstæðar fyrir vöxt (meiri straumhraði). Í öllum tilraununum, nema einni, uxu virkari einstaklingar hraðar en þeir sem voru minna virkir. Þetta samband var þó háð aðstæðum, og var t.d. greinilegra við meiri straumhraða og jafnara vatnsrennsli. Niðurstöður þessa verkefnis eru mikilvægar fyrir t.d. (i) atferlisvistfræði (sveigjanleiki í atferli), (ii) vistfræði laxfiska, vegna áhrifa virkni á fæðunám og vöxt við ólíkar aðstæður, og (iii) verndun, vegna þess innsæis sem atferli veitir varðandi áhrif væntanlegra breytinga á búsvæðum fiska

Diel activity and foraging mode of juvenile Arctic charr in fluctuating water flow

Publisher's version (útgefin grein)Streams fluctuate in water flow because of natural (e.g., rain) and human‐induced events (e.g., hydropeaking). Magnitude, frequency, and predictability of these events can have drastic consequences for fish populations. We studied how rapid modifications of water flow affect diel activity and foraging mode of juvenile Arctic charr Salvelinus alpinus in stream enclosures exposed to either stable (intermediate) or fluctuating (low vs. high) water flow. Under stable conditions, Arctic charr showed limited activity (9.4%). In fluctuating water flow, charr increased activity during low flow periods, especially during the first hours after the flow decreased, but ceased activity almost completely at high flow. Charr were mostly nocturnal, and more nocturnal at low than intermediate water flow. Fish were more mobile and swam faster during prey search and attacked prey at longer distances at low water flow. Activity and foraging mode differed between the first and second day after reduced water flow, suggesting that Arctic charr require time to adjust their foraging behaviour. This study demonstrates the importance of behavioural flexibility for population ecology in fluctuating environments such as regulated rivers.This work was supported by the Icelandic Research Fund RANNIS (120235021) and The Energy Research Fund Landsvirkjun.Peer Reviewe

Elective cancer surgery in COVID-19-free surgical pathways during the SARS-CoV-2 pandemic: An international, multicenter, comparative cohort study

PURPOSE As cancer surgery restarts after the first COVID-19 wave, health care providers urgently require data to determine where elective surgery is best performed. This study aimed to determine whether COVID-19–free surgical pathways were associated with lower postoperative pulmonary complication rates compared with hospitals with no defined pathway. PATIENTS AND METHODS This international, multicenter cohort study included patients who underwent elective surgery for 10 solid cancer types without preoperative suspicion of SARS-CoV-2. Participating hospitals included patients from local emergence of SARS-CoV-2 until April 19, 2020. At the time of surgery, hospitals were defined as having a COVID-19–free surgical pathway (complete segregation of the operating theater, critical care, and inpatient ward areas) or no defined pathway (incomplete or no segregation, areas shared with patients with COVID-19). The primary outcome was 30-day postoperative pulmonary complications (pneumonia, acute respiratory distress syndrome, unexpected ventilation). RESULTS Of 9,171 patients from 447 hospitals in 55 countries, 2,481 were operated on in COVID-19–free surgical pathways. Patients who underwent surgery within COVID-19–free surgical pathways were younger with fewer comorbidities than those in hospitals with no defined pathway but with similar proportions of major surgery. After adjustment, pulmonary complication rates were lower with COVID-19–free surgical pathways (2.2% v 4.9%; adjusted odds ratio [aOR], 0.62; 95% CI, 0.44 to 0.86). This was consistent in sensitivity analyses for low-risk patients (American Society of Anesthesiologists grade 1/2), propensity score–matched models, and patients with negative SARS-CoV-2 preoperative tests. The postoperative SARS-CoV-2 infection rate was also lower in COVID-19–free surgical pathways (2.1% v 3.6%; aOR, 0.53; 95% CI, 0.36 to 0.76). CONCLUSION Within available resources, dedicated COVID-19–free surgical pathways should be established to provide safe elective cancer surgery during current and before future SARS-CoV-2 outbreaks

Elective Cancer Surgery in COVID-19-Free Surgical Pathways During the SARS-CoV-2 Pandemic: An International, Multicenter, Comparative Cohort Study.

PURPOSE: As cancer surgery restarts after the first COVID-19 wave, health care providers urgently require data to determine where elective surgery is best performed. This study aimed to determine whether COVID-19-free surgical pathways were associated with lower postoperative pulmonary complication rates compared with hospitals with no defined pathway. PATIENTS AND METHODS: This international, multicenter cohort study included patients who underwent elective surgery for 10 solid cancer types without preoperative suspicion of SARS-CoV-2. Participating hospitals included patients from local emergence of SARS-CoV-2 until April 19, 2020. At the time of surgery, hospitals were defined as having a COVID-19-free surgical pathway (complete segregation of the operating theater, critical care, and inpatient ward areas) or no defined pathway (incomplete or no segregation, areas shared with patients with COVID-19). The primary outcome was 30-day postoperative pulmonary complications (pneumonia, acute respiratory distress syndrome, unexpected ventilation). RESULTS: Of 9,171 patients from 447 hospitals in 55 countries, 2,481 were operated on in COVID-19-free surgical pathways. Patients who underwent surgery within COVID-19-free surgical pathways were younger with fewer comorbidities than those in hospitals with no defined pathway but with similar proportions of major surgery. After adjustment, pulmonary complication rates were lower with COVID-19-free surgical pathways (2.2% v 4.9%; adjusted odds ratio [aOR], 0.62; 95% CI, 0.44 to 0.86). This was consistent in sensitivity analyses for low-risk patients (American Society of Anesthesiologists grade 1/2), propensity score-matched models, and patients with negative SARS-CoV-2 preoperative tests. The postoperative SARS-CoV-2 infection rate was also lower in COVID-19-free surgical pathways (2.1% v 3.6%; aOR, 0.53; 95% CI, 0.36 to 0.76). CONCLUSION: Within available resources, dedicated COVID-19-free surgical pathways should be established to provide safe elective cancer surgery during current and before future SARS-CoV-2 outbreaks

Stratégies spatiales de reproduction du saumon atlantique

DUFAST Diplôme Unievrsitaire Formation Appliquée aux Sciences et Technique

Sex in space : how space use affects reproductive success of anadromous Atlantic salmon

International audienc

Individual reproductive success of Atlantic salmon male alternative mating tactics in the wild

International audienc

Data from: Density-dependent diel activity in stream-dwelling Arctic charr Salvelinus alpinus

Intraspecific competition plays a significant role in shaping how animals use and share habitats in space and time. However, the way individuals may modify their diel activity in response to increased competition has received limited attention. We used juvenile (age 1+) Arctic charr Salvelinus alpinus to test the prediction that individuals at high population density are more active and distribute their foraging activity over a greater portion of the 24-h cycle than individuals at low population density. Individually tagged fish were stocked in seminatural stream enclosures at low (2 fish/m2) and high (6 fish/m2) density. During each of two 2-week experimental rounds, activity of all fish within each enclosure was recorded every 3 h over seven 24-h cycles. At high density, fish were more active and distributed their activity over a greater portion of the 24-h cycle, with increased activity particularly at crepuscular times. Fluctuations in ecological conditions (e.g., water temperature and light intensity) also affected activity. Fish at high density grew as fast as fish at low density. This study demonstrates that individuals exhibit a degree of behavioral flexibility in their response to changes in ecological conditions and suggests that intraspecific competition can cause animals to modify temporal aspects of their activity to gain access to resources and maintain growth