Assessing Efficacy of Non-Lethal Harassment of Double-Crested Cormorants to Improve Atlantic Salmon Smolt Survival

Hawkes, James P.; Saunders, Rory; Vashon, Adam D.; Cooperman, Michael S.

doi:10.1656/045.020.0101

Cited by 19 publications

(9 citation statements)

References 24 publications

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“…However, reversal behavior may be (1) an adaptive strategy to aid in successfully exiting this reach, (2) a stress response, or (3) a missed opportunity to pass through constricted passages during optimal tidal conditions, as suggested by others (Lacroix et al 2005;Kocik et al 2009;Martin et al 2009; Dempson et al 2011;Halfyard et al 2012Halfyard et al , 2013Stich et al 2015b). By contrast, it is expected that increased exposure to predators (Blackwell et al 1997;Blackwell and Juanes 1998;Beland et al 2001;Hawkes et al 2013) will increase predation rates and mortality (Hvidsten and Lund 1988;Jepsen et al 2006). Therefore, if the positive relationship between reversals and survival was solely an artifact of prolonged time at large, then we would expect a priori a neutral or even inverse relationship between the number of reversals and survival.…”

Section: Discussionmentioning

confidence: 97%

Assessment of Early Migration Dynamics of River‐Specific Hatchery Atlantic Salmon Smolts

2017

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Many Atlantic Salmon Salmo salar populations within the southern extent of the species’ range are at critically low abundances, while others have been extirpated. The focus of many ongoing recovery efforts is on maximizing the number of smolts that reach the ocean, where marine survival is low, primarily through hatchery supplementation and improvement of in‐river hydropower system management. However, estuaries also are known to be sites of high mortality, although in many cases the correlates of this mortality are poorly characterized. We acoustically tagged hatchery smolts (n = 666) during 2001–2005 to evaluate migration performance through freshwater, estuarine, and bay reaches of the small but tidally dynamic Dennys River, Maine, USA, to investigate potential drivers contributing to low returns within the system. Migration behaviors (e.g., migration timing and tidal use) were typical for Atlantic Salmon smolts, but reversals during migration were observed upon entry into the estuary environment more frequently in this system than in regional rivers. We used Cormack–Jolly–Seber mark–recapture models to estimate apparent survival within the study environment during this period. We found two distinct periods of survival, with much lower survival in 2003–2005 than in 2001 and 2002 (more than a 40% decrease). Among the variables considered, temperature and migratory behavior had the largest effects on survival. We found that survival increased by about 28% across the range of temperatures observed during these years; additionally, survival increased by about 15% for fish that reversed direction during migration compared to fish that did not. These results indicate that extreme environmental changes during the transition through this coastal system constitute a significant obstacle to Atlantic Salmon restoration stocking efforts.

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Section: Discussionmentioning

confidence: 97%

Assessment of Early Migration Dynamics of River‐Specific Hatchery Atlantic Salmon Smolts

2017

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“…However, proximate causes of mortality, such as predation (J€ arvi 1990;Handeland et al 1997;Hawkes et al 2013) or acidosis due to synergies between osmoregulatory stress and other forms of stress (J€ arvi 1989;Price and Schreck 2003;Berli et al 2014), have the potential to dramatically increase when the osmoregulatory capacity of smolts is suboptimal (McCormick et al 2009). Research targeting the relationships between smolt physiology and the sources of direct mortality (e.g., predation) in estuaries might help to further unravel the links between physiology and the proximate causes of mortality in the wild.…”

Section: Modelmentioning

confidence: 99%

“…This period is marked by high predation risk (Hvidsten and Lund 1988;Kocik et al 2009;Hawkes et al 2013), physiological stresses (Handeland et al 1997), and novel environmental conditions . In response to these challenges, the process of smolting involves a synchronous suite of changes in physiology, morphology, and behavior that, in concert, enhance the probability of survival following successful saltwater entry .…”

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confidence: 99%

“…The transition of Atlantic Salmon smolts to saltwater is recognized as a period of high mortality in estuaries (Lacroix 2008;Kocik et al 2009;Dempson et al 2011) and fjords (Gudjonsson et al 2005;Svenning et al 2005; Thorstad et al 2012b). This period is marked by high predation risk (Hvidsten and Lund 1988; Kocik et al 2009;Hawkes et al 2013), physiological stresses (Handeland et al 1997), and novel environmental conditions . In response to these challenges, the process of smolting involves a synchronous suite of changes in physiology, morphology, and behavior that, in concert, enhance the probability of survival following successful saltwater entry .…”

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Linking Behavior, Physiology, and Survival of Atlantic Salmon Smolts During Estuary Migration

et al. 2015

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Decreased marine survival is identified as a component driver of continued declines of Atlantic Salmon Salmo salar. However, estimates of marine mortality often incorporate loss incurred during estuary migration that may be mechanistically distinct from factors affecting marine mortality. We examined movements and survival of 941 smolts (141 wild and 800 hatchery‐reared fish) released in freshwater during passage through the Penobscot River estuary, Maine, from 2005 to 2013. We related trends in estuary arrival date, movement rate, and survival to fish characteristics, migratory history, and environmental conditions in the estuary. Fish that experienced the warmest thermal history arrived in the estuary 8 d earlier than those experiencing the coolest thermal history during development. Estuary arrival date was 10 d later for fish experiencing high flow than for fish experiencing low flow. Fish released furthest upstream arrived in the estuary 3 d later than those stocked further downstream but moved 0.5 km/h faster through the estuary. Temporally, movement rate and survival in the estuary both peaked in mid‐May. Spatially, movement rate and survival both decreased from freshwater to the ocean. Wild smolts arrived in the estuary later than hatchery fish, but we observed no change in movement rate or survival attributable to rearing history. Fish with the highest gill Na+, K+‐ATPase activity incurred 25% lower mortality through the estuary than fish with the lowest gill Na+, K+‐ATPase activity. Smolt survival decreased (by up to 40%) with the increasing number of dams passed (ranging from two to nine) during freshwater migration. These results underscore the importance of physiological preparedness on performance and the delayed, indirect effects of dams on survival of Atlantic Salmon smolts during estuary migration, ultimately affecting marine survival estimates. Received October 25, 2014; accepted January 8, 2015

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“…High mortality of S. salar smolts has been observed during passage through estuaries (Kocik et al, 2009;Holbrook et al, 2011), fjords (Dempson et al, 2011;Thorstad et al, 2012a) and near-coastal waters (Lacroix, 2008;Thorstad et al, 2012b). This mortality recently has been related to physiology, experiences during FW migration and behaviour of individual smolts (Schreck et al, 2006;Halfyard et al, 2013;Stich et al, 2015) as well as predation upon smolts (Hawkes et al, 2013) during the early marine phase of migration. The results of these studies underscore the importance of physiological, morphological and behavioural preparations for successful estuary passage.…”

Section: Introductionmentioning

confidence: 99%

Physiological preparedness and performance of Atlantic salmon Salmo salar smolts in relation to behavioural salinity preferences and thresholds

Stich

Zydlewski

2015

Journal of Fish Biology

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This study investigated the relationships between behavioural responses of Atlantic salmon Salmo salar smolts to saltwater (SW) exposure and physiological characteristics of smolts in laboratory experiments. It concurrently described the behaviour of acoustically tagged smolts with respect to SW and tidal cycles during estuary migration. Salmo salar smolts increased their use of SW relative to fresh water (FW) from April to June in laboratory experiments. Mean preference for SW never exceeded 50% of time in any group. Preference for SW increased throughout the course of smolt development. Maximum continuous time spent in SW was positively related to gill Na(+), K(+)-ATPase (NKA) activity and osmoregulatory performance in full-strength SW (measured as change in gill NKA activity and plasma osmolality). Smolts decreased depth upon reaching areas of the Penobscot Estuary where SW was present, and all fish became more surface oriented during passage from head of tide to the ocean. Acoustically tagged, migrating smolts with low gill NKA activity moved faster in FW reaches of the estuary than those with higher gill NKA activity. There was no difference in movement rate through SW reaches of the estuary based on gill NKA activity. Migrating fish moved with tidal flow during the passage of the lower estuary based on the observed patterns in both vertical and horizontal movements. The results indicate that smolts select low-salinity water during estuary migration and use tidal currents to minimize energetic investment in seaward migration. Seasonal changes in osmoregulatory ability highlight the importance of the timing of stocking and estuary arrival.

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Assessing Efficacy of Non-Lethal Harassment of Double-Crested Cormorants to Improve Atlantic Salmon Smolt Survival

Cited by 19 publications

References 24 publications

Assessment of Early Migration Dynamics of River‐Specific Hatchery Atlantic Salmon Smolts

Assessment of Early Migration Dynamics of River‐Specific Hatchery Atlantic Salmon Smolts

Linking Behavior, Physiology, and Survival of Atlantic Salmon Smolts During Estuary Migration

Physiological preparedness and performance of Atlantic salmon Salmo salar smolts in relation to behavioural salinity preferences and thresholds

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