Browsing by Author "Rosell, Robert S."

Now showing 1 - 6 of 6

Open Access
Atlantic salmon smolts in the Irish Sea: First evidence of a northerly migration trajectory
(Wiley, 2020-06-09) Barry, James; Kennedy, Richard; Rosell, Robert S.; Roche, William K.; Fisheries and Aquatic Ecosystems
Results from an acoustic telemetry study revealed for the first time a northerly migration route for Atlantic salmon (Salmo salar L.) smolts leaving the east coast of Ireland. Atlantic salmon smolts were tagged in spring 2019 in the Castletown and Boyne rivers. Three tagged smolts registered on disparate deep‐water offshore marine receivers as they travelled northwards out of the Irish Sea through the North Channel. One fish had migrated an estimated 250 km in a period of 32 days. The remaining two individuals were detected on receivers located off the Northern Ireland coast, further corroborating the northward migration of salmon smolts through the Irish Sea.
Open Access
A comparison of the behaviour and survival of angling vs. trap-sampled S. salar smolts.
(Wiley, 2022-06-15) Kennedy, Richard; Rosell, Robert S.; Campbell, Warren; Allen, Michelle M.; Del Villar-Guerra, diego; Fisheries and Aquatic Ecosystems
An experiment was undertaken, using acoustic telemetry, to compare the survival and migratory timing of Salmo salar L. smolts sampled, under optimal conditions, in a traditional fixed Wolf trap against a sample of rod-caught fish captured using a sensitive angling technique. No significant difference was evident in survival with 83% of both samples detected in the river outflow, 67% of the trap and 76% of the rod samples were detected in coastal waters and finally 43% of the trap and 35% of the rod samples were detected on an offshore array c. 50 km from the river outlet. No significant difference was evident in the time taken for trap- and rod-sampled fish to reach either the river outflow, coastal or offshore waters. Angling, if undertaken sensitively, can provide an effective, resource-efficient and ethically justifiable sampling tool for juvenile salmonid age classes.
Open Access
Evidence of Long-Distance Coastal Sea Migration of Atlantic Salmon, Salmo Salar, Smolts from Northwest England (River Derwent).
(Springer, 2022-01-26) Green, Amy; Honkanen, Hannele M.; Ramsden, Philip; Shields, Brian; Villar-Guerra, Diego del; Fletcher, Melanie; Walton, Silas; Kennedy, Richard; Rosell, Robert S.; O'Maoileidigh, Niall; Barry, James; Roche, William; Whoriskey, Fred; Klimley, Peter; Adams, Colin E.; Fisheries and Aquatic Ecosystems
Background Combining data from multiple acoustic telemetry studies has revealed that west coast England Atlantic salmon (Salmo salar L.) smolts used a northward migration pathway through the Irish Sea to reach their feeding grounds. Hundred Atlantic salmon smolts were captured and tagged in May 2020 in the River Derwent, northwest England as part of an Environment Agency/Natural England funded project. Results Three tagged smolts were detected on marine acoustic receivers distributed across two separate arrays from different projects in the Irish Sea. One fish had migrated approximately 262 km in 10 days from the river mouth at Workington Harbour, Cumbria to the northernmost receiver array operated by the SeaMonitor project; this is the longest tracked marine migration of an Atlantic salmon smolt migrating from the United Kingdom. This migrating fish displayed behaviours which resulted in fast northward migration. The remaining two fish were detected on a receiver array operated by a third project: the Collaborative Oceanography and Monitoring for Protected Areas and Species (COMPASS). Conclusion These detections further provide evidence that migration to reach marine feeding grounds of at least a proportion of salmon smolts from rivers draining into the Irish Sea is northerly, though without a southern marine array it is impossible to conclude that this is the only route. The pattern of these detections would not have been possible without the collaborative efforts of three distinct and separately funded projects to share data. Further work is required to fully understand migration trajectories in this species on the west coast of the British Isles.
Open Access
In-river behaviour and freshwater return rates of sea trout, Salmo trutta L., from two coastal river populations
(Wiley, 2022-07-22) Kennedy, Richard; Barry, James; Roche, William; Rosell, Robert S.; Allen, Michelle M.; Fisheries and Aquatic Ecosystems
The effective management of anadromous Salmo trutta resources is challenging because long-term data on life history, phenology and survival are sparse and most stocks across the range are highly diverse and data-limited. The current study employed acoustic telemetry to tag 448 sea trout across three life stages, to describe the phenology, spawning behaviour and return rates of smolts, finnock (0+ sea age) and adult (≥1+ sea age) sea trout in two Irish river systems during 2018–2021. Tagged smolts (n = 206) exhibited river to sea transition rates of 78%–92% and a number of surviving smolts returned to their natal river as 0+ sea age finnock, exhibiting overall smolt to finnock return rates of between 6% and 17%. Short-term vagrancy occurred among smolts, and 14 individuals were detected in adjacent nonnatal rivers. Finnock tagged during the late summer (n = 205) exhibited a range of behaviours with a minority (<30%) ascending upstream to spawning areas. Tagged adult sea trout (n = 37) ascended upstream to the spawning grounds and between 50% and 80% successfully returned to sea as kelts after spawning. Subsequent return rates of kelts back to the river in the following year ranged from 9% to 40%. The current study indicated that body size was an influential predictor of behaviour and survival across all three life stages. Increased body size was positively associated with marine transition success in smolts, long-term marine survival in kelts and spawning behaviour in finnock. This work further demonstrates the complexity of sea trout life-history dynamics and provides a comparative perspective across different age classes. An understanding of life-history variation, behaviour and survival is f
Open Access
Long term abundance patterns of potamodromous brown trout in a large lacustrine catchment in County Fermanagh
(Royal Irish Academy, 2021-09-29) Kennedy, Richard; Rosell, Robert S.; McElarney, Yvonne; Gallagher, Kevin; Allen, Michelle M.; Fisheries and Aquatic Ecosystems
Long-term survey data detailing brown trout abundance in the Lough Erne catchment in Co. Fermanagh were tabulated from 1968–2016. These data included redd counts and electric fishing surveys across three key spawning tributaries in addition to gill-net surveys of the lake. The abundance of spawning adults fluctuated widely across the time-series and were examined in relation to various pressures, including a major disease epidemic and the invasion of the catchment by zebra mussels. A functional stock-recruitment relationship between adult spawners and young-of-year juveniles in the spawning tributaries was identified and described. Redd counts were significantly lower for the post-zebra mussel time-series (2000–16) than the pre-zebra mussel time-series (1968–99). The post-zebra mussel invasion period was associated with increased water clarity, reduced plankton productivity and changes to the balance of coarse fish species in the lake. The significance of these changes is discussed in relation to the trout stock.
Open Access
Some observations on the behaviour of lake-dwelling brown trout in Lower Lough Erne
(Royal Irish Academy, 2021-02-23) Kennedy, Richard; Rosell, Robert S.; Allen, Michelle M.; Fisheries and Aquatic Ecosystems
Acoustic telemetry was utilised to track a sample of 80 adult wild brown trout across an extensive array of 30 receivers in Lower Lough Erne during 2016 and 2017. The mean detection duration across the array was 142 days, and the majority of tagged fish were detected consistently in the northern basin of the lake. One year after tagging, c.40% of larger fish (>45cm LF) were still actively detected, while only 5-10% of smaller fish (<45cm LF) were detected on the array. In total, nine trout were recaptured by anglers between 2 and 1,152 days post-tagging, with a mean liberty time of 152 days, and a minimum angling exploitation rate of 11.25%. A high proportion of surviving tagged trout (>50%) did not undertake spawning migrations into an influent tributary and remained active within the lake during the reproductive period in November. In total, fourteen tagged trout undertook spawning migrations into a range of tributaries; the mean spawning sojourn was 54 days, and five fish (36%) did not return to the lake post spawning.