Genetic evidence of farmed straying and introgression in Swedish wild salmon populations

Escaped farmed Atlantic salmon represent a well-documented and ongoing threat to wild conspecific populations. In Norway, the world-leading producer of farmed salmon, annual monitoring of straying and genetic introgression by farmed escapees in wild salmon rivers has been carried out since the late 1980s. In this study, we applied molecular and statistical methods routinely used in the Norwegian monitoring programme to investigate the magnitude of escaped farmed salmon and genetic introgression in salmon rivers on the west coast of Sweden, where suspected escapees have been observed. Our results confirm that escaped farmed salmon stray, successfully spawn, and produce offspring at levels similar to those observed in neighbouring Norway. These findings raise concerns over population productivity and long-term viability and highlight the need for more permanent monitoring of the presence and consequences of escaped farmed salmon in Swedish salmon rivers. Our results further illustrate that farmed gene flow may constitute a transboundary problem with potential international implications

Utviklingen i levekår for mottakere av sykepenger og uførepensjon

Målet for oppgaven er å studere levekårene til mottakere av de helserelaterte trygdeytelsene sykepenger og uførepensjon, og undersøke hvordan levekårsforskjellene mellom trygdede og ikke-trygdede utvikler seg. Som mål på levekår bruker jeg inntekt og utdanning. I en deskriptiv analyse, gjort på anonymiserte data med informasjon om norske individer observert mellom 1992 og 2007, ser jeg på utviklingen i gjennomsnittlig inntektsnivå og gjennomsnittlig utdanningsnivå for grupper med ulik status når det kommer til trygd, og presenterer differansene mellom ikke-trygdede og trygdede. Jeg deler utvalget i datasettet inn i referansegruppene uførepensjonist, ikke-uførepensjonist, sykmeldt, sykmeldt i under to måneder, sykmeldt i over seks måneder og ikke-sykmeldt. Jeg kommenterer hvordan kjønn har en innvirkning på levekårsforskjellene, og diskuterer hvilke andre faktorer man kan anta at har en innvirkning på hva som skiller ikke-trygdedes og trygdedes levekår. Når man sammenligner gjennomsnittlige levekår for ikke-uførepensjonister og uførepensjonister, er hovedresultatet at levekårene er betydelig bedre for de ikke-trygdede, både når det gjelder inntekt og utdanning. Men forskjellene utvikler seg i hver sin retning i analyseperioden. Differansen i inntektsnivå blir større, samtidig som differansen i utdanningsnivå blir mindre. Når man sammenligner ikke-sykmeldte og sykmeldte kvinner er levekårsforskjellene svært små og avtakende - med innslag av “gevinst” for trygdede - dersom man ser bort fra de med lengst sykefravær. Og når man sammenligner ikke-sykmeldte og sykmeldte menn er levekårsforskjellene litt større enn for kvinner, og alltid positive, men samtidig avtagende utover perioden.MasteroppgaveECON391PROF-SØKMASV-SØ

Modernisation of the Norwegian Tide Gauge Network

The modernization of the Norwegian Tide Gauge Network using technologies of the 1980s is presented. Technical and organizational challenges are described in detail together with cost-estimates and possible future developments

Statistical and ecological challengesof monitoring parasitic salmon lice infestationsin wild salmonid fish stocks

-Ecological monitoring programmes should provide precise data to inform management, but the data quality is often limited by methodological challenges and the need for cost-effective sampling. Parasite infestations are particularly challenging to monitor due to complex interactions among hosts, parasites and the environment. In Norway, salmon lice infestations on wild salmonid fish have been monitored since 1992 to survey the potential transmission between farmed and wild salmonids. Here, we compared spatiotemporal variation in salmon lice levels with variations in local fjord conditions, including salinity, temperature and infestation pressure from salmon farms (measured as mean abundance of mature female lice × number of farmed fish). We tested 3 different measures of infestation with different statistical properties. Our results confirm that, even after correcting for temperature and salinity effects, in - festation pressure from salmon farms significantly increases the probability of lice infestation in wild salmonids. The probability of infestation increases with fish body length, salmon farm infestation pressure and tem perature, and decreases with increasing freshwater influence. Furthermore, we found a significant interaction between temperature and infestation pressure from salmon farms. When the infestation pressure from farms is low, temperature has a strong increasing effect on the probability of infestation, but as the infestation pressure from farms increases, temperature gradually becomes less important. The exact results vary somewhat depending on the measure of lice infestations used, but the same trend can be seen in all models. We discuss the statistical and biological complexities that make monitoring of salmon lice in wild populations challenging

Modelling the effect of hydropeaking‐induced stranding mortality on Atlantic salmon population abundance

Studies of hydropeaking‐induced stranding mortality on fish populations have been confined to analysis of empirical data and/or short‐term hydraulic‐habitat modelling of individual events and are thus limited as to how they may be used to infer long‐term effects in fish populations. In this study, the effects of stranding mortality on an Atlantic salmon population were simulated using an individual‐based Atlantic salmon population model with the objective of determining the sensitivity of population dynamics to stranding. It was found that density‐dependent mortality (an alternative source of mortality in juvenile Atlantic salmon) partially compensated for stranding mortality, acting as a negative feedback mechanism that dampened change in population abundance. Stranding caused a perturbation in population dynamics, and effects of individual stranding events persisted in time across the life stages of the population. Effects on population abundance depended on the time of year when stranding was applied, both because of intra‐annual changes in stranding mortality probability and because of intra‐annual changes in the ability of density‐dependent mortality to compensate for stranding mortality. We concluded that empirical measurements of stranding mortality have limited potential for inference of overall effects on the population, and a more dynamic modelling approach, incorporating system feedback, allows for a better modelling of the impact of stranding. Sensitivity analysis showed that population abundance was highly sensitive to density‐dependent mortality, and we suggest that this area should be prioritized for further research when investigating the effects of hydropeaking on rivers.acceptedVersio

An Ecological-Economic Simulation Model of Genetic interaction Between Farmed and Wild Salmon

The paper is the first attempt to explore the ecological and economic impacts of genetic interaction between farmed and wild salmon over generations. An age- and stage-structured bioeconomic model is developed. The biological part of the model includes age-specific life history traits such as survival rate, fecundity, spawning success for both wild and farmed salmon and their hybrids, while the economic part takes account of market and non-market values of fish stock. The model is constructed based on the Atlantic salmon fishery and salmon farming in Norway. The discounted profits are estimated given the current fishing practice over 50 years. The sensitivity analysis is also performed. It is expected that wild salmon stock will be gradually replaced with hybrid ones, while the total discounted profit will decline, but not significantly. The analysis will provide some new insights for designing effective management strategies to protect wild salmon stocks from genetic intrusion of farmed escapees.Keywords: Fisheries Economics, Aquaculture, Aquaculture and EnvironmentKeywords: Fisheries Economics, Aquaculture, Aquaculture and Environmen

Density-Dependence as a Size-Independent Regulatory Mechanism

The growth function of populations is central in biomathematics. The main dogma is the existence of density dependence mechanisms, which can be modelled with distinct functional forms that depend on the size of the population. One important class of regulatory functions is the $\theta$-logistic, which generalises the logistic equation. Using this model as a motivation, this paper introduces a simple dynamical reformulation that generalises many growth functions. The reformulation consists of two equations, one for population size, and one for the growth rate. Furthermore, the model shows that although population is density-dependent, the dynamics of the growth rate does not depend either on population size, nor on the carrying capacity. Actually, the growth equation is uncoupled from the population size equation, and the model has only two parameters, a Malthusian parameter $\rho$ and a competition coefficient $\theta$. Distinct sign combinations of these parameters reproduce not only the family of $\theta$-logistics, but also the van Bertalanffy, Gompertz and Potential Growth equations, among other possibilities. It is also shown that, except for two critical points, there is a general size-scaling relation that includes those appearing in the most important allometric theories, including the recently proposed Metabolic Theory of Ecology. With this model, several issues of general interest are discussed such as the growth of animal population, extinctions, cell growth and allometry, and the effect of environment over a population.Comment: 41 Pages, 5 figures Submitted to JT

Article Taxonomy and distribution of the Pygmy Eagle Aquila (Hieraaetus) weiskei (Accipitriformes: Accipitridae)

Abstract We re-evaluated the taxonomic status of the New Guinean subspecies weiskei of the Little Eagle Aquila morphnoides and confirmed that it differs considerably from the Australian A. morphnoides in multiple morphological and plumage characters. Genetic differentiation in published mitochondrial cyt-b and ND2 sequences between the nominate subspecies and weiskei is equivalent to that found between other accipitrid taxa at the species level, as are pairwise divergences between each Little Eagle taxon and their sister species, the Booted Eagle A. pennata. The available morphological and genetic evidence thus strongly and unambiguously supports the specific distinctness of A. weiskei. We propose the English name Pygmy Eagle, as this is the world's smallest known eagle. We show that the distribution of A. weiskei includes the western part of New Guinea (Vogelkop) and the Moluccas (Halmahera, Ternate and Seram), based on our new observations

The future looks like the past: Introgression of domesticated Atlantic salmon escapees in a risk assessment framework

Escapes of domesticated fish from aquaculture, followed by interbreeding with wild conspecifics, represent a threat to the genetic integrity and evolutionary trajectory of natural populations. Approximately fifty years of Atlantic salmon production has left an unprecedented legacy of widespread introgression of domesticated escapees in wild Norwegian populations. A major question, however, is whether current aquaculture practice will lead to additional introgression in the near future. As part of the updated Norwegian risk assessment of fish farming, we conducted a risk assessment for further introgression of domesticated escapees in wild populations in Norway. Extensive data of reported numbers of escapees, observed proportions of escapees in rivers, removal of escapees pre‐spawning, and the resilience of wild populations through demographic and genetic status informed the risk assessment. The analysis revealed that rivers in 10 of the 13 aquaculture production zones covering Norway display a moderate or high risk of further introgression of domesticated escapees. This comes in addition to widespread introgression that is already documented. We therefore conclude that so long as aquaculture production continues at its present level and form, there is a moderate‐to‐high risk of further introgression of domesticated salmon in many native populations throughout much of Norway.publishedVersio

Theoretical biology - Comparing models of species abundance

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/62867/1/nature04826.pd