Smallmouth bass (Micropterus dolomieu) and chain pickerel (Esox niger) identified as Atlantic salmon (Salmo salar) smolt predators in a reservoir system

Canadian Journal of Fisheries and Aquatic Sciences, Journal Year: 2025, Volume and Issue: 82, P. 1 - 15

Published: Jan. 1, 2025

Reservoir predation has been identified as a leading mortality source for smolts migrating through impounded river systems. We investigated smolt risk an endangered Atlantic salmon ( Salmo salar) population in the Weldon Dam reservoir Penobscot River, Maine, USA. In spring 2022, we characterized fates of 390 tethered smolts. Smolts were exclusively predated by two predator species not native to study area: chain pickerel Esox niger, n = 43) and smallmouth bass Micropterus dolomieu, 42). Using Cox-proportional hazard analysis, estimated that 23% (95% CI 15%–29%) expected be within one-hour deployment. Water temperature was primary driver probability increased from 10% 33% when 5 15 °C. also incurred above-average they 40 m shore. demonstrate non-native fish may drive patterns high impoundment is spatially temporally heterogeneous these Collectively, this offers direct evidence species-specific on illuminates potential strategies mitigate during migration.

Language: Английский

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Mesohabitat Evaluation Reveals Variable Abundances and Habitat Choice in Juvenile Atlantic Salmon Across Diverse Habitats in the Main Stem of a Large Sub‐Arctic River

Ecology Of Freshwater Fish, Journal Year: 2025, Volume and Issue: 34(3)

Published: May 7, 2025

ABSTRACT Large main stem rivers typically provide a variety of mesohabitat types, but their abundance, distribution and role in providing habitat for juvenile salmonids have rarely been analysed. The quantity meso‐scale habitats Atlantic salmon abundance was surveyed the large sub‐arctic River Teno northernmost Fennoscandia. Different types were mapped using Norwegian Mesohabitat Classification Method (NMCM). Juvenile different mesohabitats, on various substrates, depths lateral positions across channel estimated by electrofishing boat surveys. Most (67%) dominated fine substrate > 50 cm s −1 flow velocity. Typical salmon‐rearing habitats, such as rapids, riffles glides, comprised 32% riverbed. Data from NMCM surveys used generalised linear models to describe relationship between variables (YOY parr) abundance. varied lot within mesohabitats; general, higher areas with depth ≤ 70 than deeper areas, middle sections river compared those near shorelines. documented also sandy although low abundances, relatively high abundances considered important salmon. These should be assessing potential production. proved fast, cost‐effective method surveying assessment.

Language: Английский

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The use of predator tags to explain reversal movement patterns in Atlantic salmon smolts (Salmo salar L.)

Journal of Fish Biology, Journal Year: 2024, Volume and Issue: unknown

Published: Jan. 16, 2024

Abstract Acoustic telemetry has seen a rapid increase in utility and sophistication recent years is now used extensively to assess the behavior survival rates of many aquatic animals, including Atlantic salmon. As part salmon's complex life cycle, salmon smolts are thought make unidirectional migration from fresh water sea, which initiated by changes their physiology. However, some tag movement patterns do not conform with this can be difficult explain, particularly if tagged fish been eaten predator. This study combines use predator tags machine learning techniques understand fate migrating thereby improve estimates for success. Over 3 between 2020 2022, 217 (including wild hatchery‐reared ranched fish) were acoustically released into an embayment on west coast Ireland. Some observed return estuary back saline lagoon through they had already migrated. To distinguish smolt that predator, deployed 2021 2022. The addition temperature sensor 2022 enabled determination type causing returning movement. A significant number triggered, associated these triggered then two types algorithms (hierarchical cluster analysis random forest) identify validate without extra sensors. Both models produced same outputs, grouping additional sensors but showing similar movements. mammalian was identified as cause most reversal movement, found more likely predated upon than within lake estuary. overall success both fish. highlights value essential tool validation detection data.

Language: Английский

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Reintroducing Atlantic salmon in the river Rhine for decades: Why did it not result in the return of a viable population?

River Research and Applications, Journal Year: 2024, Volume and Issue: 40(7), P. 1164 - 1182

Published: April 21, 2024

Abstract Freshwater species biodiversity is under threat. The average global decline for migratory fish estimated to be more than 75% since 1970. Atlantic salmon one of these with a steep in north‐western Europe and it even went extinct the river Rhine 1950s. causes this have been posted habitat loss, pollution, climate change overfishing. Annual stocking late 1980s resulted an initial increase numbers after which collapsed again. In paper, we lay out recent decline, estimate losses smolts adults at different sections freshwater elaborate on potential losses. We found that population has declined rapidly over past two decades, current spawning only ~350–800 individuals. percentage returning as grounds 0.5%–0.6%, well below 3% supposedly needed maintain self‐sustaining population. Many individuals disappear during their migrations, highest disappearing German tributaries (44%) Dutch lower (71%), while both (74%) (78%) Rhine. Causes per section remain unclear possible threats, some specific Rhine, are being discussed. large inland waters, compared open sea losses, indicate restocking might result ecological restoration carried so far along intensively shipped highly regulated course associated high levels predation, increasingly limited by future change.

Language: Английский

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A Review of Factors Potentially Contributing to the Long-Term Decline of Atlantic Salmon in the Conne River, Newfoundland, Canada

Reviews in Fisheries Science & Aquaculture, Journal Year: 2024, Volume and Issue: 32(3), P. 479 - 504

Published: April 18, 2024

Species extinction and population extirpation are now widespread across aquatic ecosystems with many diadromous species, including Atlantic salmon (Salmo salar), in decline throughout much of the North Atlantic. Declines can occur simultaneously at both large small regional scales rendering factors driving decreases more elusive. On south coast Newfoundland abundance Conne River fell by 92% over a period almost four decades contrast most other populations region suggesting local may be contributing to decline. Here potentially long-term reviewed (1) examining trends survival different life stages, (2) presenting synopsis on presence absence impacting productivity this population, (3) using semi-quantitative two dimensional classification system, based expert opinion, rank decline, (4) utilizing quantitative Random Forest analysis complement opinion approach identifying possibly affecting population. Results from qualitative analyses identified associated aquaculture as possible driver Additional include influence climate change predation freshwater marine habitats. As various native range extirpation, results further highlight necessity river-specific addition monitoring fine-scale demographic threat information prioritization research necessary for conserving or restoring endangered populations.

Language: Английский

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Exploring predators of Pacific salmon throughout their life history: the case of Japanese chum, pink, and masu salmon

Reviews in Fish Biology and Fisheries, Journal Year: 2024, Volume and Issue: 34(3), P. 895 - 917

Published: May 17, 2024

Language: Английский

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Patterns of declining zooplankton energy in the northeast Atlantic as an indicator for marine survival of Atlantic salmon

ICES Journal of Marine Science, Journal Year: 2024, Volume and Issue: 81(6), P. 1164 - 1184

Published: June 22, 2024

Abstract Return rates of Atlantic salmon (Salmo salar) from the sea to European rivers have declined in recent decades. The first months at are critical for growth and survival; evidence suggests that reduced food availability may be a contributory factor observed declines. Here, zooplankton abundance data used derive measure prey energy available forage fish during early marine migration. This has significantly dramatically over much northeast Atlantic, specifically within key migration domains, past 60 years. Marine return set southern populations found exhibit clustering not entirely predictable geographical proximity. Variability grouped these is correlated with on range scales, demonstrating potential use as an indicator survival. Comparison environmental variables derived ocean model reanalysis regulated by combination climate change impacts ecosystem productivity multi-decadal variability water mass influence along routes.

Language: Английский

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Ephemeral piscivory in a mesopredator sunfish: Implications for pond food webs

Ecology, Journal Year: 2024, Volume and Issue: unknown

Published: Oct. 1, 2024

Language: Английский

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Determining early marine survival and predation by endothermic predators on acoustically tagged Atlantic salmon (Salmo salar) post-smolts

Canadian Journal of Fisheries and Aquatic Sciences, Journal Year: 2023, Volume and Issue: 81(4), P. 387 - 402

Published: Dec. 22, 2023

Many Atlantic salmon ( Salmo salar) populations have experienced significant declines for decades throughout North America and Europe. Mortality due to marine mammal predation during their early life could be an important factor contributing these limiting population recoveries. However, quantifying events, particularly the extent of on salmon, remains a challenge. In this study, we estimated contribution mesothermic endothermic species mortality post-smolts using acoustic telemetry. Predation events were inferred from changes in temperatures depths by acoustically tagged hatchery-reared smolts. No consumed predators, with most being classified as mammals. Post-smolt study period was low overall both years (13.1%–16.7%), accounting 33.1%–42.9% all (5.2%–5.6% mortality). Our results suggest that current return adult observed area recent not heavily influenced first weeks at sea.

Language: Английский

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Pinniped response to diadromous fish restoration in the Penobscot River Estuary

Frontiers in Conservation Science, Journal Year: 2024, Volume and Issue: 5

Published: Dec. 18, 2024

Successful conservation of pinnipeds in the northwest Atlantic has led to increasing populations harbor seals ( Phoca vitulina ) and gray Halichoerus grypus Gulf Maine. Within this region, habitat restoration diadromous fish Penobscot River have also been top priorities for past decade. To understand overlap between regional recovery aggregative response forage fish, we assessed how counts, distribution, behavior Estuary changed over time from 2012 2020 determined whether those changes were related biomass that are occurring as result restoration. We did not see increased counts hauled-out seals, but consistent with seal phenology, hauled out highest late spring declined throughout summer into fall. The number swimming analyzed a proxy behavior, showed stronger annual trend an increase study period. Fish was negatively associated total positively seals. documented potential displacement when present. Together, these results begin provide insights local efforts interact affect multiple trophic levels ecosystem. Continued monitoring predator-prey interactions, along diet movement studies, will further elucidate prey species system impact recovering predator on restored populations. Knowledge gained regarding pinniped important implications other systems ongoing measures aim improve habitat, decrease exploitation, or recover protected species. Studies like can be critical finding paths forward reconcile potentially competing objectives marine mammal protection

Language: Английский

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