O'Briain R.,Inland Fisheries Ireland |
Shephard S.,Inland Fisheries Ireland |
Coghlan B.,Inland Fisheries Ireland
Ecological Engineering | Year: 2017
Macrophyte responses to disturbance provide a short-term opportunity to document and interpret plant succession and related hydrogeomorphological interactions relative to the long-term, concomitant evolution of river morphology. Macrophyte colonisation may drive changes, e.g., increasing heterogeneity, in physical characteristics that define broad-scale hydrogeomorphology. Relationships between macrophyte presence and key physical descriptors were investigated within channelized river reaches of a low gradient river. Plant species within two morphotypes sharing similar traits were the most abundant colonisers of the wetted channel. The standard deviation of depth, flow velocity and substrate were used in turn as response variables expressing physical heterogeneity across the channel. A second substrate response variable was the summed coarseness score based on substrate size (fines = 1, gravel = 2 and cobble = 3) across the channel. Macrophyte presence showed strong fine-scale relationships to heterogeneity in flow velocity and depth but not to heterogeneity in substrate. Substrate coarseness score was positively related to increasing heterogeneity in flow velocity, with increased presence of coarse substrate indicative of greater heterogeneity in velocity. Certain macrophyte species appear to play an important pioneer role in initiating and driving physical changes that underlie hydrogeomorphological processes. Likely mechanisms are flow manipulation, sediment interception and sorting. © 2017 Elsevier B.V.
Kelly F.L.,Inland Fisheries Ireland |
Harrison T.D.,Environment and Rural Affairs DAERA
Biology and Environment | Year: 2016
The Water Framework Directive (WFD) has established the concept of ecological quality as a method to improve European Union (EU) surface and ground waters. Ecological quality status is based on the composition and abundance of different biological quality elements, including fish fauna, with the supporting elements of hydromorphology and chemical and physico-chemical parameters. Monitoring for fish for the WFD began in Ireland in 2007. In parallel, classification tools were developed or refined for each surface water type (lakes, rivers and transitional waters) and then intercalibrated in a cross-Europe exercise to ensure consistency across all EU states. The development and basic concepts of three WFD-compliant ecological classification tools for fish and the cross-Europe intercalibration exercise are described for rivers, lakes and transitional waters. © Royal Irish Academy.
News Article | May 11, 2017
Returns of wild adult salmon can be reduced by more than 50% in years following high lice levels on nearby salmon farms during the smolt out-migration, according to the results of a new study. The study, published in the international journal Aquaculture Environment Interactions, used 30 years of data from the Erriff river (National Salmonid Index Catchment) in the West of Ireland to evaluate the effect of sea lice from salmon aquaculture on wild Atlantic salmon. Entitled “Quantifying the contribution of sea lice from aquaculture to declining annual returns in a wild Atlantic salmon population” it examined sea lice production from salmon farming in Killary harbour and its effect on the return of wild salmon to the Erriff river, at the head of the harbour, in the following year. Sea lice from salmon farming have long been implicated in the collapse of sea trout stocks along the west coast of Ireland. However, according to Inland Fisheries Ireland (IFI), this new study, authored by the organisation’s own Dr Samuel Shephard and Dr Paddy Gargan, is the first to clearly demonstrate significant losses of wild Atlantic salmon due to infestation with sea lice from salmon farms. Dr Shephard stated: “There has been a lot of discussion as to the importance of the sea lice impact in the context of environmental variation and changing ocean conditions. We find that the predicted 50% reduction in 1SW salmon returns following a high lice year is greater than the average year-to-year variation attributable to environmental effects”. Modelled lice impact levels and a fitted stock-recruitment relationship were used to estimate how annual returns of Erriff salmon might have looked over the last 30 years in the absence of a serious impact of sea lice from aquaculture. Results suggest that Erriff salmon returns could now be twice as large as without observed anthropogenic lice impacts, but would probably show a similar long-term decline. The River Erriff is designated as a Special Area of Conservation (SAC) for Atlantic salmon under the European Union Habitats Directive (92/43/EEC). Dr Gargan commented: “Increased mortality of wild salmon due to the impact of sea lice from salmon farming can result in salmon stocks not reaching spawning targets or not being at favourable conservation status as required under the EU Habitats Directive. It is critical therefore that sea lice levels are maintained at a very low level on farmed salmon in spring and where this has not been achieved that farmed fish are harvested before the wild salmon smolt migration period.” The authors conclude that: “Many Atlantic salmon populations are already under pressure from (possibly climate-mediated) reductions in marine survival. The addition of significant lice-related mortality during the coastal stage of smolt out-migration could be critical.”
Krkosek M.,University of Otago |
Revie C.W.,University of Prince Edward Island |
Gargan P.G.,Inland Fisheries Ireland |
Skilbrei O.T.,Norwegian Institute of Marine Research |
And 2 more authors.
Proceedings of the Royal Society B: Biological Sciences | Year: 2013
Parasites may have large effects on host population dynamics, marine fisheries and conservation, but a clear elucidation of their impact is limited by a lack of ecosystem-scale experimental data. We conducted a meta-analysis of replicated manipulative field experiments concerning the influence of parasitism by crustaceans on the marine survival of Atlantic salmon (Salmo salar L.). The data include 24 trials in which tagged smolts (totalling 283 347 fish; 1996-2008) were released as paired control and parasiticide-treated groups into 10 areas of Ireland and Norway. All experimental fish were infectionfree when released into freshwater, and a proportion of each group was recovered as adult recruits returning to coastal waters 1 or more years later. Treatment had a significant positive effect on survival to recruitment, with an overall effect size (odds ratio) of 1.29 that corresponds to an estimated loss of 39 per cent (95% CI: 18-55%) of adult salmon recruitment. The parasitic crustaceans were probably acquired during early marine migration in areas that host large aquaculture populations of domesticated salmon, which elevate local abundances of ectoparasitic copepods-particularly Lepeophtheirus salmonis. These results provide experimental evidence from a large marine ecosystem that parasites can have large impacts on fish recruitment, fisheries and conservation. © 2012 The Author(s) Published by the Royal Society. All rights reserved.
Wahlberg M.,University of Southern Denmark |
Westerberg H.,Institute of Freshwater Research |
Aarestrup K.,Technical University of Denmark |
Feunteun E.,French National Center for Scientific Research |
And 2 more authors.
Deep-Sea Research Part I: Oceanographic Research Papers | Year: 2014
Temperature and depth logging tags were implanted into adult eels released on Atlantic west coasts of France and Ireland to study their oceanic migration behavior. For three of the tags, 25 to 256 days after release there was a dramatic rise in temperature from 10. °C to 36. °C and the dive profile changed from depths of 300-1000. m to repeated ascents to the surface. This indicated that the eels carrying the tags had been eaten by a mammalian predator. Two of the tags had sufficient sampling rate to resolve the dives in detail. They recorded a total of 91 dives to maximum depths of 250-860. m lasting 11-12. min and with surface intervals of 5-7. min. More than two thirds of the dives included a rapid descent from approximately 500. m to 600-700. m. From this we infer that the predator was most likely a deep-diving toothed whale. The dives logged while the tags were inside the predator revealed that the temperature usually decreased during dives, and increased again during surface periods. The temperature drops during dives were probably caused by the ingestion of prey or water. These observations provide insights into the behavior of toothed whales foraging in the mesopelagic zone. © 2014 Elsevier Ltd.
Pedreschi D.,University College Dublin |
Kelly-Quinn M.,University College Dublin |
Caffrey J.,Inland Fisheries Ireland |
O'Grady M.,Inland Fisheries Ireland |
And 2 more authors.
Journal of Biogeography | Year: 2014
Aim: We investigated genetic variation of Irish pike populations and their relationship with European outgroups, in order to elucidate the origin of this species to the island, which is largely assumed to have occurred as a human-mediated introduction over the past few hundred years. We aimed thereby to provide new insights into population structure to improve fisheries and biodiversity management in Irish freshwaters. Location: Ireland, Britain and continental Europe. Methods: A total of 752 pike (Esox lucius) were sampled from 15 locations around Ireland, and 9 continental European sites, and genotyped at six polymorphic microsatellite loci. Patterns and mechanisms of population genetic structure were assessed through a diverse array of methods, including Bayesian clustering, hierarchical analysis of molecular variance, and approximate Bayesian computation. Results: Varying levels of genetic diversity and a high degree of population genetic differentiation were detected. Clear substructure within Ireland was identified, with two main groups being evident. One of the Irish populations showed high similarity with British populations. The other, more widespread, Irish strain did not group with any European population examined. Approximate Bayesian computation suggested that this widespread Irish strain is older, and may have colonized Ireland independently of humans. Main conclusions: Population genetic substructure in Irish pike is high and comparable to the levels observed elsewhere in Europe. A comparison of evolutionary scenarios upholds the possibility that pike may have colonized Ireland in two 'waves', the first of which, being independent of human colonization, would represent the first evidence for natural colonization of a non-anadromous freshwater fish to the island of Ireland. Although further investigations using comprehensive genomic techniques will be necessary to confirm this, the present results warrant a reappraisal of current management strategies for this species. © 2013 John Wiley & Sons Ltd.
Gargan P.G.,Inland Fisheries Ireland |
Forde G.,Inland Fisheries Ireland |
Hazon N.,University of St. Andrews |
Russell D.J.F.,University of St. Andrews |
Todd C.D.,University of St. Andrews
Canadian Journal of Fisheries and Aquatic Sciences | Year: 2012
Sea trout (Salmo trutta) stock collapses in coastal areas of western Ireland subject to salmon aquaculture were contemporaneous with high abundances of larval sea lice (Lepeophtheirus salmonis) on juvenile sea trout. Whereas sea trout remain in near-shore waters throughout their marine migration, Atlantic salmon (Salmo salar) smolts typically move quickly offshore into oceanic waters. It might therefore be predicted that salmon smolts would be less vulnerable to coastal stressors and less likely to be negatively affected by infestations of sea lice early in their marine phase. Groups of microtagged, hatchery-reared Atlantic salmon smolts were fed either untreated pellets or pellets incorporating the in-feed sea louse treatment SLICE (emamectin benzoate) prior to eight experimental releases in three marine locations over a 3-year period. In total, 74 324 smolts were released and analysis of tag recaptures from returning adult salmon showed that emamectin-treated smolts experienced increased survivorship and were 1.8 times more likely to return compared with control fish. These results suggest that sea lice-induced mortality on adult Atlantic salmon returns in Ireland can be significant, and that sea lice larvae emanating from farmed salmon may influence individual survivorship and population conservation status of wild salmon in these river systems.
King J.J.,Inland Fisheries Ireland
Biology and Environment | Year: 2015
There is a small international scientific literature, principally from North America, on recovery of fish communities following substantial fish kill events and a smaller literature on monetary assessment of losses in such events. A chemical discharge led to over 90% loss of brown trout (Salmo trutta L.) and Atlantic salmon (Salmo salar L.) age classes in 31km of the River Boyne catchment, a major Irish salmon-producing and angling fishery in July 1997. Subsequent investigations permitted a novel study that examined both the changes in the fish community composition over time and also a monetary assessment of losses. The population structure and density of 1 and older brown trout took four to five years to recover. The population of 1 salmon increased substantially during the recovery period, to levels threefold higher than those recorded prior to the pollution event. Financial loss assessment was examined through ‘replacement cost’ and through consequential loss models. An examination of the monetary modelling, in the light of the fish community recovery, showed there was an ecological justification for the potential loss model used. This approach to appraisal of loss is considered to have an international relevance, in the context of ecosystem processes and the ‘polluter pays’ principle. © ROYAL IRISH ACADEMY.
Gargan P.G.,Inland Fisheries Ireland |
Stafford T.,Inland Fisheries Ireland |
Okland F.,Norwegian Institute for Nature Research |
Thorstad E.B.,Norwegian Institute for Nature Research
Fisheries Research | Year: 2015
The practice of catch and release (C&R) in salmon rod fisheries has become increasingly common due to the widespread decline in salmon abundance in the North Atlantic over the past two decades. Many Irish Atlantic salmon rivers are only open for catch and release (C&R) angling since a change in salmon management in 2006. Success of Atlantic salmon surviving to contribute to the spawning stock following C&R was studied in three rivers. In total, 76 fish were tagged with radio transmitters post C&R angling. Survival to spawning was greater for fly caught (98%) than lure caught fish (55%). Hence, survival after C&R was dependent on gear type. Hook location may have influenced C&R mortality in the lure captured fish. All fish bleeding at the hook wound or hooked in the throat died. Simultaneous hooking in the upper and lower mouth may also have contributed to reduced survival. There was an overall net upstream movement post release with many salmon moving more than 10. km upstream. Results demonstrated that, when conducted using proper guidelines, survival of salmon after C&R can be high. Opening rivers to C&R angling can be successful as a tool to provide information on salmon stock status while not significantly impacting on salmon survival. © 2014 Elsevier B.V.
Caffrey J.M.,Inland Fisheries Ireland |
Evers S.,Inland Fisheries Ireland |
Millane M.,Inland Fisheries Ireland |
Moran H.,Inland Fisheries Ireland
Aquatic Invasions | Year: 2011
The Asian clam Corbicula fluminea was first discovered in Ireland in the Rivers Barrow and Nore in 2010. Scuba diving surveys were the primary sampling method used to determine the detailed distribution of this species in the two rivers. Sustainable populations of Asian clam were present in the tidal freshwater reaches of both rivers. No clams were present upstream of the tidal limit. A maximum density of 9,636 individuals m-2 was recorded in the River Barrow. This paper presents some basic metrics in relation to the populations present in these two connected river systems. © 2011 The Author(s).