Impact of early salmon louse, Lepeophtheirus salmonis, infestation and differences in survival and marine growth of sea-ranched Atlantic salmon, Salmo salar L., smolts 1997-2009

The impact of salmon lice on the survival of migrating Atlantic salmon smolts was studied by comparing the adult returns of sea-ranched smolts treated for sea lice using emamectin benzoate or substance EX with untreated control groups in the River Dale in western Norway. A total of 143500 smolts were released in 35 release groups in freshwater from 1997 to 2009 and in the fjord system from 2007 to 2009. The adult recaptures declined gradually with release year and reached minimum levels in 2007. This development corresponded with poor marine growth and increased age at maturity of ranched salmon and in three monitored salmon populations and indicated unfavourable conditions in the Norwegian Sea. The recapture rate of treated smolts was significantly higher than the controls in three of the releases performed: the only release in 1997, one of three in 2002 and the only group released in sea water in 2007. The effect of treating the smolts against salmon lice was smaller than the variability in return rates between release groups, and much smaller that variability between release years, but its overall contribution was still significant (P<0.05) and equivalent to an odds ratio of the probability of being recaptured of 1.17 in favour of the treated smolts. Control fish also tended to be smaller as grilse (P=0.057), possibly due to a sublethal effect of salmon lice

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

Large-effect loci mediate rapid adaptation of salmon body size after river regulation

Understanding the potential of natural populations to adapt to altered environments is becoming increasingly relevant in evolutionary research. Currently, our understanding of adaptation to human alteration of the environment is hampered by lack of knowledge on the genetic basis of traits, lack of time series, and little or no information on changes in optimal trait values. Here, we used time series data spanning nearly a century to investigate how the body mass of Atlantic salmon (Salmo salar) adapts to river regulation. We found that the change in body mass followed the change in waterflow, both decreasing to ∼1/3 of their original values. Allele frequency changes at two loci in the regions of vgll3 and six6 predicted more than 80% of the observed body mass reduction. Modeling the adaptive dynamics revealed that the population mean lagged behind its optimum before catching up approximately six salmon generations after the initial waterflow reduction. Our results demonstrate rapid adaptation mediated by large-effect loci and provide insight into the temporal dynamics of evolutionary rescue following human disturbance.publishedVersio

The operationalisation of sustainability: Sustainable aquaculture production as defined by certification schemes

Sustainability certification has become an increasingly important feature in aquaculture production, leading to a multitude of schemes with various criteria. However, the large number of schemes and the complexity of the standards creates confusion with respect to which sustainability objectives are targeted. As a result, what is meant by ‘sustainability’ is unclear. In this paper, we examine the operationalisation of the concept from the vantage point of the certifying authorities, who devise standards and grant or withhold certification of compliance. We map the criteria of eight widely-used certification schemes using the four domains of the Wheel of Sustainability, a reference model designed to encompass a comprehensive understanding of sustainability. We show that, overall, the sustainability certifications have an overwhelming focus on environmental and governance indicators, and only display scattered attempts at addressing cultural and economic issues. The strong focus on governance indicators is, to a large degree, due to their role in implementing and legitimising the environmental indicators. The strong bias implies that these certification schemes predominantly focus on the environmental domain and do not address sustainability as a whole, nor do they complement each other. Sustainability is by definition and by necessity a comprehensive concept, but if the cultural and economic issues are to be addressed in aquaculture, the scope of certification schemes must be expanded. The Wheel of Sustainability can serve as a valid lexicon and asset to guide such efforts.publishedVersio

Under the sea: How can we use heart rate and accelerometers to remotely assess fish welfare in salmon aquaculture?

Recent advances in bio-sensing technologies open for new possibilities to monitor and safeguard the welfare of fishes in aquaculture. Yet before taken into practice, the applicability of all novel biosensors must be validated, and the breadth of their potential uses must be investigated. Here, we investigated how ECG and accelerometryderived parameters measured using bio-loggers, such as heart rate, acceleration and variance of acceleration, relate to O2 consumption rate (MO2) and blood borne indicators of stress and tissue damage to determine how biologgers may be used to estimate stress and welfare. To do this, we instrumented 13 fish with a biologger and an intravascular catheter and subjected them to a swimming protocol followed by a stress protocol throughout which the physiological parameters were measured and analyzed a posteriori. Additionally, based on the empirical data obtained, we calculated the mathematical relationships between the bio-logger data and the other parameters and tested the relationship between the calculated parameters using the linear regression algorithms and the measured parameters. Our results show that acceleration is a good proxy for swimming activity as it is closely related to tail beat frequency. In addition, we show that heart rate, acceleration and variance of acceleration all can be used as predictors for metabolic rate. Accelerometry based data, especially variance of acceleration, significantly explain some of the variation in venous partial pressure of O2, blood lactate and plasma cortisol concentration. Variance of acceleration also significantly explains some of the variation in pH and mean corpuscular hemoglobin concentration. These relationships are explained by variance of acceleration being a good indicator of the onset of burst-swimming activity, which is often followed by acid-base imbalances and release of catecholamines. The results herein indicate that bio-logger data can be used to extrapolate a range of stress-related physiological events when these are accompanied by increases in activity and highlight the great potential of biosensors for monitoring fish welfare. Biologger Acceleration Heart rate Stress MetabolismpublishedVersio

En vurdering av lakselusinfestasjonen i produksjonsområdene i 2018 og 2019 - Basert på data fra den nasjonale overvåkingen av lakselus på vill laksefisk (NALO)

Sammendrag Lakselus er en ektoparasitt som lever av mucus, skinn, muskel og blod til laksefisk. Er antall lakselus høyt vil dette negativt påvirke vill laksefisk. For å estimere smittepresset av lakselus på vill laksefisk undersøkes smittepresset både med fangst av vill laksefisk samt at smittepresset estimeres basert på koblede biologisk-hydrodynamiske modeller. For å estimere smittepresset i fjordene og langs kysten under smoltutvandringen, gjennomføres årlig en undersøkelse basert på fangst av sjøørret og sjørøye med garn og ruse av lakselus på vill laksefisk på 3-6 stasjoner i hver av de 13 produksjonsområdene. Det er i tillegg både i 2018 og 2019 trålt i 6 fjordsystemer (Boknafjorden, Hardangerfjorden, Sognefjorden, Romsdalsfjorden, Trondheimsfjorden og i Altafjorden), i 2019 er det i tillegg trålt noe i Nordfjord, på Møre og i Namsen. Det er også benyttet vaktbur hvor det settes ut oppdrettssmolt i noen av samme fjordene som det tråles i, samt i Namsen/Vikna området. Denne rapporten summerer dataene fra 2018 og 2019, og er i stor grad basert på data innsamlet gjennom NALO. Posisjonene er vist i disse rapportene. Rapportene kan lastes ned her: https://www.hi.no/radgivning/akvakultur/nb-no.publishedVersio

Fremdriftsrapport til Mattilsynet over lakselusinfestasjon på vill laksefisk langs norskekysten i mai og juni 2016

Havforskningsinstituttet (HI) har på oppdrag fra Mattilsynet (MT) og Nærings- og fiskeridepartementet (NFD) ansvaret for å koordinere overvåkning, forskning og rådgivning vedrørende lakselusinfestasjon på vill laksefisk langs norskekysten (NALO-programmet). Overvåkningen ble fra 2015 lagt om til en risikobasert adaptiv overvåkning, og i 2016 kjøres Havforskningsinstituttets hydrodynamiske spredningsmodeller for lakselus operativt. Modellresultatene blir brukt til fastsettelse av fiskelokaliteter sammen med NINA og UNI Research Miljø. Lakselusinfestasjon på vill laksefisk blir undersøkt med garn- og rusefiske i to perioder à 14 dager, der første periode så langt det er mulig blir lagt til forventet utvandringsperiode for laksesmolten i området. Tråling etter utvandrende laksepostsmolt og smoltbur blir også benyttet i overvåkingen. Antallet stasjoner har økt vesentlig i 2016 sammenlignet med tidligere år. Resultatene i denne fremdriftsrapporten er foreløpige, og det presiseres at resultatene ikke er analysert. I denne rapporten er det tatt med data fra 21 stasjoner. Kontrollokalitetene på Sørlandet viser som tidligere lite lus på fisken og få fisk med lus. For de andre lokalitetene er det generelle bildet noe mer lus på fisken sammenlignet med 2015. Det er også noe mer fisk med så mye lus at det forventes en fysiologisk effekt

Impact of parasites on salmon recruitment in the Northeast Atlantic Ocean

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