Inferring individual marine migration from otolith ecogeochemical signatures of a wide-ranging fish

Despite technical advances in archival tag attachment and functional longevity, long-term tracking of individuals of some fish species remains prohibitively difficult. Here we combined high resolution stable isotope sampling of otoliths, genetic assignment, growth increment analyses and a simple movement model to inform a hidden Markov model of the location of individual wild Atlantic salmon (Salmo salar L.) at sea. The model provided a reconstruction of North Atlantic migration for a species which is extremely difficult to track throughout its marine life-stage. We show that plausible emigration and return migration patterns can be achieved from wild fish. Simulations of simplified northward and westward movement patterns in the North Atlantic were used to quantify precision and accuracy of the model which differed between these two directional scenarios. Because otolith-derived migratory information does not rely on capture, release and subsequent recapture of the individual, this can be retrieved from any fish. Thus these techniques offer a powerful tool for improving our understanding of the processes that govern movement and survival of individual fish during a protracted and largely unobservable life-stage in the oceanic environment

Quantifying the Ocean, Freshwater and Human Effects on Year-to-Year Variability of One-Sea-Winter Atlantic Salmon Angled in Multiple Norwegian Rivers

Many Atlantic salmon, Salmo salar, populations are decreasing throughout the species' distributional range probably due to several factors acting in concert. A number of studies have documented the influence of freshwater and ocean conditions, climate variability and human impacts resulting from impoundment and aquaculture. However, most previous research has focused on analyzing single or only a few populations, and quantified isolated effects rather than handling multiple factors in conjunction. By using a multi-river mixed-effects model we estimated the effects of oceanic and river conditions, as well as human impacts, on year-to-year and between-river variability across 60 time series of recreational catch of one-sea-winter salmon (grilse) from Norwegian rivers over 29 years (1979–2007). Warm coastal temperatures at the time of smolt entrance into the sea and increased water discharge during upstream migration of mature fish were associated with higher rod catches of grilse. When hydropower stations were present in the course of the river systems the strength of the relationship with runoff was reduced. Catches of grilse in the river increased significantly following the reduction of the harvesting of this life-stage at sea. However, an average decreasing temporal trend was still detected and appeared to be stronger in the presence of salmon farms on the migration route of smolts in coastal/fjord areas. These results suggest that both ocean and freshwater conditions in conjunction with various human impacts contribute to shape interannual fluctuations and between-river variability of wild Atlantic salmon in Norwegian rivers. Current global change altering coastal temperature and water flow patterns might have implications for future grilse catches, moreover, positioning of aquaculture facilities as well as the implementation of hydropower schemes or other encroachments should be made with care when implementing management actions and searching for solutions to conserve this species

What should I eat? Experimental evidence for prey selection in grey seals

Understanding the responses of predators, such as seals, to variations in prey availability is key to understanding their role in marine ecosystems. Individual variation in prey preference is likely to be important but we have little information on this aspect of predator behaviour. Operant conditioning techniques and an underwater feeding apparatus were used to test the prey species and size preferences of five captive grey seals, Halichoerus grypus, in a series of paired choice trials. The experimental procedure was designed to present simple foraging choices to remove as many potentially confounding variables as possible. Results suggest that individual grey seals exhibit prey preferences. When presented with different numbers of items of the same species, seals generally selected the larger number of prey items. When presented with choices between two species, seals apparently showed consistent preferences for particular species. However, the apparent species preferences may be simply explained in terms of size selection

Identification of a single genomic region associated with seasonal river return timing in adult Scottish Atlantic salmon (Salmo salar L.) identified using a genome-wide association study.

Examination of the genetic basis of the timing of the return migration of Atlantic salmon (Salmo salar L.) to freshwater from the sea, a trait of economic and conservation interest, was carried out using a genome-wide association study. Genotype data from 52,731 single nucleotide polymorphic (SNP) markers from 73 early and 49 late running two sea-winter salmon from five rivers in eastern Scotland was examined. A single region of the Atlantic salmon chromosome Ssa09 was identified, containing nine SNP markers significantly associated with run timing, a region previously linked to variation in sea age at maturity. Validation of the markers in a group of 233 one and two sea-winter fish, including adults from a novel river, again showed significant associations between the trait and the Ssa09 region, explaining ~24% of the trait variance. The SNP loci identified provide the ability to examine trait variation in populations of Atlantic salmon and so help facilitate conservation management of the differing run timing phenotypes.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Inferring individual marine migration from otolith ecogeochemical signatures of a wide-ranging fish

Despite technical advances in archival tag attachment and functional longevity, long-term tracking of individuals of some fish species remains prohibitively difficult. Here we combined high resolution stable isotope sampling of otoliths, genetic assignment, growth increment analyses and a simple movement model to inform a hidden Markov model of the location of individual wild Atlantic salmon (Salmo salar L.) at sea. The model provided a reconstruction of North Atlantic migration for a species which is extremely difficult to track throughout its marine life-stage. We show that plausible emigration and return migration patterns can be achieved from wild fish. Simulations of simplified northward and westward movement patterns in the North Atlantic were used to quantify precision and accuracy of the model which differed between these two directional scenarios. Because otolith-derived migratory information does not rely on capture, release and subsequent recapture of the individual, this can be retrieved from any fish. Thus these techniques offer a powerful tool for improving our understanding of the processes that govern movement and survival of individual fish during a protracted and largely unobservable life-stage in the oceanic environment.</p

Perceptions and costs of seal impacts on Atlantic salmon fisheries in the Moray Firth, Scotland: Implications for the adaptive co-management of seal-fishery conflict

The Moray Firth Seal Management Plan (MFSMP) was introduced in Scotland in 2005 as a pilot for resolving conflict between Atlantic salmon fisheries and conservation imperatives for protected harbour and grey seals. This adaptive co-management model is now being applied nationally through the Marine (Scotland) Act (2010). However, no information exists on salmon fishery stakeholders' perceptions of seal predation impacts and related costs, which could influence the success of the MFSMP and other similar initiatives. In 2006 a questionnaire survey of the 95 salmon rod fisheries in seven major Moray Firth rivers was undertaken, and all 20 active salmon netting stations in the Firth. Forty-five fishery owners, 39 ghillies, 120 anglers and 11 netsmen (representing 17 netting stations) responded. The majority (81%) believed that seals had a significant or moderate impact on stocks and catches, 77% believed that all seals were responsible and 47% supported seal culling. Seals were sighted by 38% of rod fisheries, and 18% lost angler days from seal interference. Overall, 0.2% of total reported angler days were lost annually. The estimated direct cost of seal interference for responding rod fisheries was £14,960 annum-1, and losses of catches and damage to nets was £16,500 annum-1 for responding netsmen. Stakeholders' perceptions were largely inconsistent with their low direct costs and the aims of the MFSMP. Possible reasons for this are discussed, and implications for the governance of future adaptive co-management initiatives for seal-fishery conflict.Atlantic salmon Adaptive co-management Grey seal Harbour seal Livelihoods Special Area of Conservation

Presentation_1_Inferring individual marine migration from otolith ecogeochemical signatures of a wide-ranging fish.pptx

Despite technical advances in archival tag attachment and functional longevity, long-term tracking of individuals of some fish species remains prohibitively difficult. Here we combined high resolution stable isotope sampling of otoliths, genetic assignment, growth increment analyses and a simple movement model to inform a hidden Markov model of the location of individual wild Atlantic salmon (Salmo salar L.) at sea. The model provided a reconstruction of North Atlantic migration for a species which is extremely difficult to track throughout its marine life-stage. We show that plausible emigration and return migration patterns can be achieved from wild fish. Simulations of simplified northward and westward movement patterns in the North Atlantic were used to quantify precision and accuracy of the model which differed between these two directional scenarios. Because otolith-derived migratory information does not rely on capture, release and subsequent recapture of the individual, this can be retrieved from any fish. Thus these techniques offer a powerful tool for improving our understanding of the processes that govern movement and survival of individual fish during a protracted and largely unobservable life-stage in the oceanic environment.</p