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Hawley KL, Urke HA, Kristensen T, Haugen TO. Balancing risks and rewards of alternate strategies in the seaward extent, duration and timing of fjord use in contemporary anadromy of brown trout (Salmo trutta). BMC Ecol Evol 2024; 24:27. [PMID: 38418991 PMCID: PMC10903050 DOI: 10.1186/s12862-023-02179-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2023] [Accepted: 11/25/2023] [Indexed: 03/02/2024] Open
Abstract
BACKGROUND Anadromy comprises a successful life-cycle adaptation for salmonids, with marine migration providing improved feeding opportunities and thus improved growth. These rewards are balanced against costs from increased energy expenditure and mortality risk. Anthropogenic-induced environmental changes that reduce benefits and/or increase costs of migration e.g., aquaculture and hydropower, may therefore result in adaptations disfavouring anadromy. We tagged brown trout (Salmo trutta) smolts (N = 175) and veteran migrants (N = 342), from five adjacent riverine populations located in Sognefjorden, the longest Norwegian fjord-system supporting anadromous brown trout populations (209 km). Over four years, 138 acoustic telemetry receivers were deployed to track migrations of tagged individuals from freshwater and throughout Sognefjorden. Detected movements were used to fit migration models and multi-state mark-recapture models of survival and movement for each life-stage. Seaward migration distance was modelled to examine the fitness consequences from alternate migration strategies, with these models used to simulate the extent of fjord-use by individuals and accompanying growth, fecundity and survival consequences. We compared these findings with mark-recapture data collected prior to aquaculture and hydropower development. RESULTS The telemetry data revealed that the outermost-fjord region was utilised by all populations albeit by few individuals. However, historical recaptures were located at a greater distance from the river mouth (87.7 ± 70.3 km), when compared to maximum migration distances of present-day counterparts (58.6 ± 54.9 km). River of origin influenced observed migratory behaviour and differential survival was estimated for each population and life-stage. The simulations based on telemetry-data models revealed a 30% and 23% difference in survival among populations for smolts and veteran migrants, respectively. At the individual-level, a long-distance migration strategy was rewarded with enhanced fecundity. However, the main contribution to population-level fecundity was overwhelmingly derived from middle-distance migrants, due to higher mortality rates and limited numbers of long-distant migrants. CONCLUSIONS We conclude that present-day anadromy is precarious, but potential risk varies considerably between life-stages and populations, even within a single fjord system. Our findings suggest that selection for extended migration is under pressure, we therefore stress the importance of monitoring and management actions to secure genetic variation pertinent to preserve fitness gains of anadromy.
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Affiliation(s)
- K L Hawley
- Faculty of Environmental Sciences and Natural Resource Management, The Norwegian University of Life Sciences, Høgskoleveien 12, 1433, Ås, Norway.
| | - H A Urke
- AquaLife R&D, Havnegata 9, 7010, Trondheim, Norway
| | - T Kristensen
- Faculty of Biosciences and Aquaculture, Nord University, Universitetsalléen, 8049, Bodø, Norway
| | - T O Haugen
- Faculty of Environmental Sciences and Natural Resource Management, The Norwegian University of Life Sciences, Høgskoleveien 12, 1433, Ås, Norway
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Lilly J, Honkanen HH, Rodger JR, Del Villar D, Boylan P, Green A, Pereiro D, Wilkie L, Kennedy R, Barkley A, Rosell R, Maoiléidigh NÓ, O'Neill R, Waters C, Cotter D, Bailey D, Roche W, McGill R, Barry J, Beck SV, Henderson J, Parke D, Whoriskey FG, Shields B, Ramsden P, Walton S, Fletcher M, Whelan K, Bean CW, Elliott S, Bowman A, Adams CE. Migration patterns and navigation cues of Atlantic salmon post-smolts migrating from 12 rivers through the coastal zones around the Irish Sea. JOURNAL OF FISH BIOLOGY 2024; 104:265-283. [PMID: 37843923 DOI: 10.1111/jfb.15591] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2023] [Revised: 10/07/2023] [Accepted: 10/13/2023] [Indexed: 10/18/2023]
Abstract
The freshwater phase of the first seaward migration of juvenile Atlantic salmon (Salmo salar) is relatively well understood when compared with our understanding of the marine phase of their migration. In 2021, 1008 wild and 60 ranched Atlantic salmon smolts were tagged with acoustic transmitters in 12 rivers in England, Scotland, Northern Ireland and Ireland. Large marine receiver arrays were deployed in the Irish Sea at two locations: at the transition of the Irish Sea into the North Atlantic between Ireland and Scotland, and between southern Scotland and Northern Ireland, to examine the early phase of the marine migration of Atlantic salmon smolts. After leaving their natal rivers' post-smolt migration through the Irish Sea was rapid with minimum speeds ranging from 14.03 to 38.56 km.day-1 for Atlantic salmon smolts that entered the Irish Sea directly from their natal river, to 9.69-39.94 km.day-1 for Atlantic salmon smolts that entered the Irish Sea directly from their natal estuary. Population minimum migration success through the study area was strongly correlated with the distance of travel, populations further away from the point of entry to the open North Atlantic exhibited lower migration success. Post-smolts from different populations experienced different water temperatures on entering the North Atlantic. This was largely driven by the timing of their migration and may have significant consequences for feeding and ultimately survivorship. The influence of water currents on post-smolt movement was investigated using data from previously constructed numerical hydrodynamic models. Modeled water current data in the northern Irish Sea showed that post-smolts had a strong preference for migrating when the current direction was at around 283° (west-north-west) but did not migrate when exposed to strong currents in other directions. This is the most favorable direction for onward passage from the Irish Sea to the continental shelf edge current, a known accumulation point for migrating post-smolts. These results strongly indicate that post-smolts migrating through the coastal marine environment are: (1) not simply migrating by current following (2) engage in active directional swimming (3) have an intrinsic sense of their migration direction and (4) can use cues other than water current direction to orientate during this part of their migration.
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Affiliation(s)
- Jessie Lilly
- Scottish Centre for Ecology and the Natural Environment, School of Biodiversity, One Health and Veterinary Medicine, University of Glasgow, Glasgow, UK
| | - Hannele H Honkanen
- Scottish Centre for Ecology and the Natural Environment, School of Biodiversity, One Health and Veterinary Medicine, University of Glasgow, Glasgow, UK
| | - Jessica R Rodger
- Scottish Centre for Ecology and the Natural Environment, School of Biodiversity, One Health and Veterinary Medicine, University of Glasgow, Glasgow, UK
- Atlantic Salmon Trust, Perth, UK
| | | | - Patrick Boylan
- Scottish Centre for Ecology and the Natural Environment, School of Biodiversity, One Health and Veterinary Medicine, University of Glasgow, Glasgow, UK
| | - Amy Green
- Scottish Centre for Ecology and the Natural Environment, School of Biodiversity, One Health and Veterinary Medicine, University of Glasgow, Glasgow, UK
| | | | | | | | | | - Robert Rosell
- Agri-food and Biosciences Institute, Hillsborough, UK
| | | | | | | | | | - David Bailey
- School of Biodiversity, One Health and Veterinary Medicine, University of Glasgow, Glasgow, UK
| | | | | | | | - Samantha V Beck
- Galloway Fisheries Trust, Newton Stewart, UK
- Institute for Biodiversity and Freshwater Conservation, UHI Inverness, Inverness, UK
| | - Jim Henderson
- The Nith Catchment Fishery Trust and Nith District Salmon Fishery Board, Dumfries, UK
| | - Debbie Parke
- The Nith Catchment Fishery Trust and Nith District Salmon Fishery Board, Dumfries, UK
| | | | | | | | | | | | | | - Colin W Bean
- Scottish Centre for Ecology and the Natural Environment, School of Biodiversity, One Health and Veterinary Medicine, University of Glasgow, Glasgow, UK
- NatureScot, Clydebank Business Park, Clydebank, UK
| | - Sophie Elliott
- Game & Wildlife Conservation Trust, Salmon & Trout Research Centre, Wareham, UK
| | - Adrian Bowman
- School of Mathematics & Statistics, University of Glasgow, Glasgow, UK
| | - Colin E Adams
- Scottish Centre for Ecology and the Natural Environment, School of Biodiversity, One Health and Veterinary Medicine, University of Glasgow, Glasgow, UK
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Wynne R, Kaufmann J, Coughlan J, Phillips KP, Waters C, Finlay RW, Rogan G, Poole R, McGinnity P, Reed TE. Autumn outmigrants in brown trout (Salmo trutta) are not a demographic dead-end. JOURNAL OF FISH BIOLOGY 2023; 102:1327-1339. [PMID: 36911993 DOI: 10.1111/jfb.15377] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2023] [Accepted: 03/10/2023] [Indexed: 06/09/2023]
Abstract
Genetic identity analysis and PIT (passive integrated transponder) tagging were used to examine the freshwater return rates and phenotypic characteristics of n = 1791 downstream migrating juvenile Salmo trutta in the Burrishoole catchment (northwest Ireland) across the period September 2017 to December 2020. In this system, juveniles out-migrate (move from freshwater into brackish or marine habitats) in every month of the year, with distinct seasonal peaks in spring (March through June; mostly silvered smolts) and autumn (September through December; mostly younger, unsilvered fry or parr). Both types exhibited a sex-bias towards females, which was stronger in spring (78% females) than in autumn outmigrants (67%). Sixty-nine returning fish were matched back to previous juvenile outmigrants, and similar return rates were found for spring outmigrants (5.0%), autumn outmigrants (3.3%) and fish that out-migrated outside of spring or autumn (2.8%). Spring and autumn outmigrants returned at similar dates (typically mid to late July), but autumn fish were away for longer periods (median = 612 days; spring outmigrants = 104 days). Autumn outmigrants were 25% smaller than spring outmigrants at outmigration and 6% smaller on their return, and within both groups smaller/younger outmigrants spent longer away than larger/older outmigrants. Autumn outmigrants were more likely to return unsilvered as "slob" trout (84%) than spring outmigrants (31%), suggesting they make greater use of brackish habitats that might be safer, but less productive, than fully marine habitats. Nonetheless, both types also produced silvered "sea trout" (≥1+ sea-age), implying neither is locked into a single life-history strategy. The findings emphasise that autumn outmigrants and the transitional habitats that support their persistence should not be overlooked in salmonid management and conservation.
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Affiliation(s)
- Robert Wynne
- School of Biological, Earth and Environmental Sciences, University College Cork, Cork, Ireland
- Environmental Research Institute, University College Cork, Cork, Ireland
| | | | - Jamie Coughlan
- School of Biological, Earth and Environmental Sciences, University College Cork, Cork, Ireland
- Environmental Research Institute, University College Cork, Cork, Ireland
| | - Karl P Phillips
- Canadian Rivers Institute, University of New Brunswick, Fredericton, New Brunswick, Canada
| | | | - Ross W Finlay
- School of Biological, Earth and Environmental Sciences, University College Cork, Cork, Ireland
- Environmental Research Institute, University College Cork, Cork, Ireland
- Marine Institute, Furnace, Newport, Co. Mayo, Ireland
| | - Ger Rogan
- Marine Institute, Furnace, Newport, Co. Mayo, Ireland
| | - Russell Poole
- Marine Institute, Furnace, Newport, Co. Mayo, Ireland
| | - Philip McGinnity
- School of Biological, Earth and Environmental Sciences, University College Cork, Cork, Ireland
- Environmental Research Institute, University College Cork, Cork, Ireland
- Marine Institute, Furnace, Newport, Co. Mayo, Ireland
| | - Thomas E Reed
- School of Biological, Earth and Environmental Sciences, University College Cork, Cork, Ireland
- Environmental Research Institute, University College Cork, Cork, Ireland
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