Browsing by Author "Kennedy, Richard"

Now showing 1 - 12 of 12
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    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.
    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.
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    Behavioural traits of rainbow trout and brown trout may help explain their differing invasion success and impacts
    (Nature Research (Springer), 2022-02-02) McGlade, Ciara L. O.; Dickey, James W. E.; Kennedy, Richard; Donnelly, Shannon; Nelson, Clare‑Ann; Dick, Jaimie T. A.; Arnott, Gareth
    Animal behaviour is increasingly recognised as critical to the prediction of non-native species success and impacts. Rainbow trout and brown trout have been introduced globally, but there appear to be differences in their patterns of invasiveness and ecological impact. Here, we investigated whether diploid rainbow trout and diploid and triploid brown trout differ among several key behavioural measures linked to invasiveness and impact. We assessed activity, boldness, aggression, and feeding, using open field, novel object, shelter, mirror, feeding, and functional response experiments. We also tested within each fish type for behavioural syndromes comprising correlations among activity, boldness and aggression. Rainbow trout were more active and aggressive but less bold than diploid and triploid brown trout. In small groups, however, rainbow trout were bolder than both types of brown trout. Diploid brown trout were more active and bolder than triploids when tested individually, and had a higher functional response than both rainbow trout and triploid brown trout. In terms of behavioural syndromes, there was no association between activity and boldness in rainbow trout, however, there was in both brown trout types. The increased activity and aggression of rainbow trout may reflect an increased stress response to novel situations, with this response reduced in a group. These results suggest that rainbow trout do not manage their energy budgets effectively, and may explain why they have limited survival as invaders. In addition, the lower functional response of rainbow trout may explain why they are implicated in fewer ecological impacts, and the triploidy treatment also appears to lower the potential impact of brown trout. Comparative analyses of multiple behaviours of invasive species and genetic variants may thus be key to understanding and predicting invader success and ecological impacts.
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    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
    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.
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    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.
    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.
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    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.
    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
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    Investigating the phenology of juvenile potamodromous brown trout (Salmo trutta L.) in two large lake catchments
    (Wiley, 2022-01-05) Kennedy, Richard; Rosell, Robert; Allen, Michelle
    There is growing interest in the phenology of juvenile Salmo trutta and evidence of significant downstream migration during the autumn in some anadromous populations. The present study used acoustic telemetry to examine the phenology of potamodromous trout parr across a region encompassing two large lake catchments. One hundred sixty-seven trout parr were tagged in late summer across four lake tributaries between 2018 and 2020. In total, 75 tagged parr migrated into the lakes with 67 (89%) migrating between September and December and 8 (11%) migrating between March and June. Autumn migration was highly prevalent across all the tributaries, with 16%–66% of each tagged sample exhibiting autumn migration, and 0%–15% of each tagged sample exhibiting spring migration. Autumn migrants were significantly longer and heavier than spring migrants, but condition factor was similar. Autumn migrants were associated with higher river discharge levels and lower water temperatures than spring migrants. The management challenges posed by extensive autumn migration behaviour in migratory trout stocks are examined and discussed.
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    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.
    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.
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    Long term retention of dummy acoustic transmitters in adult brown trout
    (Wiley, 2020-08-26) Kennedy, Richard; Evans, Derek W.; Allen, Michelle M.
    A group of 36 1+ age class Salmo trutta were surgically implanted with dummy acoustic tags and monitored for 370 days. In total 13 tags were expelled through-out the experiment with an overall tag loss rate of c. 0.035 tag/d. Fish length was the only explanatory variable which had a significant association with subsequent tag expulsion. The estimated probability of retaining a tag for a year for a fish of length 32 cm was 0.76, 34 cm was 0.60 and 36 cm was 0.38. The long term tag loss patterns were examined and discussed.
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    Programmed acoustic tags reveal novel information on late-phase marine life in Atlantic salmon, Salmo salar
    (Wiley, 2022-12-30) Kennedy, Richard; Rosell, Robert; Hunter, Ewan; del Villar-Guerra, Diego
    This pilot study used programmed acoustic tags implanted into Salmo salar smolts, in conjunction with an extensive offshore marine receiver array, to investigate latestage migratory behaviour and survival of returning adult salmon. A total of 100 smolts were tagged in 2020, and a number of individuals were successfully detected as returning adults in 2021. After detection efficiency was accounted for, 5–9 adults were estimated to have returned to the offshore array c. 45 km from the river mouth. A total of three fish were subsequently detected in the river. Losses of between 40% and 66% were evident during the final stages of ocean migration, and one tagged fish provided direct evidence of a predation event.
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    River lamprey present an unusual predation threat to Atlantic salmon smolts in Lough Neagh, Northern Ireland.
    (Wiley, 2020-09-18) Kennedy, Richard; Campbell, W.; Gallagher, K.; Evans, Derek W.
    A new monitoring programme on the Lough Neagh catchment has documented a high incidence of river lamprey, Lampetra fluviatilis L., predation on Atlantic salmon smolts, Salmo salar L.,. In total 470 smolts were examined during the 2020 emigration period with 168 fish (36%) exhibiting lamprey scars of which 57 were lightly scarred and 111 were classed as heavily scarred. Lamprey predation was not size selective on Lough Neagh S. salar smolts.
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    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.
    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.