Radgivende Biologer AS

Bergen, Norway

Radgivende Biologer AS

Bergen, Norway
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Otero J.,University of Oslo | Otero J.,CSIC - Institute of Marine Research | L'Abee-Lund J.H.,Norwegian Water and Energy Directorate | Castro-Santos T.,U.S. Geological Survey | And 44 more authors.
Global Change Biology | Year: 2014

Migrations between different habitats are key events in the lives of many organisms. Such movements involve annually recurring travel over long distances usually triggered by seasonal changes in the environment. Often, the migration is associated with travel to or from reproduction areas to regions of growth. Young anadromous Atlantic salmon (Salmo salar) emigrate from freshwater nursery areas during spring and early summer to feed and grow in the North Atlantic Ocean. The transition from the freshwater ('parr') stage to the migratory stage where they descend streams and enter salt water ('smolt') is characterized by morphological, physiological and behavioural changes where the timing of this parr-smolt transition is cued by photoperiod and water temperature. Environmental conditions in the freshwater habitat control the downstream migration and contribute to within- and among-river variation in migratory timing. Moreover, the timing of the freshwater emigration has likely evolved to meet environmental conditions in the ocean as these affect growth and survival of the post-smolts. Using generalized additive mixed-effects modelling, we analysed spatio-temporal variations in the dates of downstream smolt migration in 67 rivers throughout the North Atlantic during the last five decades and found that migrations were earlier in populations in the east than the west. After accounting for this spatial effect, the initiation of the downstream migration among rivers was positively associated with freshwater temperatures, up to about 10 °C and levelling off at higher values, and with sea-surface temperatures. Earlier migration occurred when river discharge levels were low but increasing. On average, the initiation of the smolt seaward migration has occurred 2.5 days earlier per decade throughout the basin of the North Atlantic. This shift in phenology matches changes in air, river, and ocean temperatures, suggesting that Atlantic salmon emigration is responding to the current global climate changes. © 2013 John Wiley & Sons Ltd.


Skaala O.,Norwegian Institute of Marine Research | Johnsen G.H.,Radgivende biologer AS | Lo H.,Norwegian Veterinary Institute | Borgstrom R.,Norwegian University of Life Sciences | And 5 more authors.
Marine Biology Research | Year: 2014

Extensive use of aquatic habitats, mainly for hydropower and aquaculture, has a negative impact on anadromous salmonid populations of the Hardangerfjord region, western Norway. High infection levels of salmon lice, and high proportions of escaped farmed salmon in spawning rivers, appear to violate the goals in the 'Strategy for an Environmentally Sustainable Aquaculture Industry' set by the Norwegian government. An overview of the anadromous populations in the fjord, their status and the major threats are presented. A conservation plan with mitigation efforts consisting of seven steps is presented: (1) genetic assessment of Atlantic salmon and anadromous brown trout populations, (2) reducing gene flow from escapees, (3) reducing infection pressure from salmon lice, (4) conduct an assessment of the freshwater habitats for anadromous salmonids and then implement it in order to restore smolt production, (5) efforts to reduce risk of river pollution from agriculture and industry and minimize impacts from hydropower production, (6) when and where necessary and practical, plant out eyed eggs from the Norwegian Genebank to increase parr and smolt production, and finally, (7) monitor spawning populations and parr densities to evaluate potential effects of the mitigation efforts. Experience and knowledge gained through the plan will be useful for other regions with similar challenges. We call for an initiative to establish a national fund under democratic and public control, where funding can be obtained for projects which focus on mitigation efforts and conservation of salmonid populations. © 2014 The Author(s).


Arechavala-Lopez P.,Norwegian Institute for Nature Research | Arechavala-Lopez P.,University of Alicante | Thorstad E.B.,Norwegian Institute for Nature Research | Todd C.D.,University of St. Andrews | And 8 more authors.
Revista de Biologia Marina y Oceanografia | Year: 2015

Salmon lice are external parasites on salmonids in the marine environment. During recent years, sea lice abundance has been increased due to the presence of salmon farming using on-growing floating seas-cages. Amongst salmonids, sea trout is especially vulnerable to salmon lice infestations, because during their marine residence they typically remain in coastal waters, where open net cage Atlantic salmon farms typically are situated. In this report the existing knowledge about the effects of salmon lice on sea trout populations in the NE Atlantic coastal waters has been reviewed, assessing the current situation of this problematic. Salmon aquaculture increase the salmon lice abundance, which affect negatively on sea trout populations as an increase in marine mortality, changes in migratory behaviour and reduction of marine growth. These conclusions are based on published studies that range from those investigating the effects of salmon lice on individual fish, both in the laboratory and the field, to analyses of their impacts on populations in the wild. In sum, the combined knowledge from the reviewed studies provides evidence of a general and pervasive negative effect of salmon lice on sea trout populations, especially in intensively farmed areas. The effects induced by elevated salmon lice levels inevitably imply a reduction in numbers and body size of sea trout returning to freshwater for spawning, affecting the local population dynamic and recreational and commercial fisheries in the most impacted areas. © Universidad de Valparaiso. All rights reserved.


Glover K.A.,Norwegian Institute of Marine Research | Glover K.A.,University of Bergen | Bos J.B.,Norwegian Institute of Marine Research | Urdal K.,Radgivende Biologer AS | And 8 more authors.
Biological Invasions | Year: 2016

Each year, hundreds of thousands of farmed Atlantic salmon escape from fish farms into the wild. Some of these escapees enter freshwater, and manage to interbreed with native populations. To hinder further genetic introgression in native populations, the use of sterile triploid salmon within commercial aquaculture is being examined. However, if triploid escapees migrate into freshwater, they may still have ecological impacts on local populations. In the present study, we used microsatellite DNA genotyping to determine the ploidy of 3794 farmed escapees captured in 17 Norwegian rivers in the period 2007–2014. Although a previous study has reported an average of 2 % triploids in Norwegian fish farms during this exact period, here, we only observed 7 (0.18 %) triploids among the escapees captured in freshwater. In addition, we identified three trisomic escapees. For the triploids where the within-river capture location was determined, they were only observed in the lower reaches and not on the spawning grounds. It is concluded that propensity for triploid Atlantic salmon to migrate into freshwater following escape from a fish farm is significantly lower than for normal diploid salmon escapees. Therefore, commercial production of triploids should not only be seen as an effective way of stopping genetic introgression, it will also significantly reduce the numbers of escapees entering rivers, which in turn limits ecological interactions and potential disease transmission. © 2016 The Author(s)


Thorstad E.B.,Norwegian Institute for Nature Research | Todd C.D.,University of St. Andrews | Uglem I.,Norwegian Institute for Nature Research | Bjorn P.A.,Norwegian Institute of Marine Research | And 6 more authors.
Aquaculture Environment Interactions | Year: 2015

Salmon farming increases the abundance of salmon lice, which are ectoparasites of salmonids in the sea. Here we review the current knowledge on the effects of salmon lice on wild sea trout. Salmon lice feed on host mucus, skin and muscle, and infestation may induce osmoregulatory dysfunction, physiological stress, anaemia, reduced feeding and growth, increased susceptibility to secondary infections, reduced disease resistance and ultimately mortality of individual sea trout. Wild sea trout in farm-free areas generally show low lice levels. In farm-intensive areas, lice levels on wild sea trout are typically higher, and more variable than in farm-free areas. Lice on wild sea trout are found at elevated levels particularly within 30 km of the nearest farms but can also extend to further ranges. Salmon lice in intensively farmed areas have negatively impacted wild sea trout populations by reducing growth and increasing marine mortality. Quantification of these impacts remains a challenge, although population-level effects have been quantified in Atlantic salmon by comparing the survival of chemically protected fish with control groups, which are relevant also for sea trout. Mortality attributable to salmon lice can lead to an average of 12-29% fewer salmon spawners. Reduced growth and increased mortality will reduce the benefits of marine migration for sea trout, and may also result in selection against anadromy in areas with high lice levels. Salmon lice-induced effects on sea trout populations may also extend to altered genetic composition and reduced diversity, and possibly to the local loss of sea trout, and establishment of exclusively freshwater resident populations. © The authors 2015.


Skilbrei O.T.,Norwegian Institute of Marine Research | Finstad B.,Norwegian Institute for Nature Research | Urdal K.,Radgivende Biologer AS | Bakke G.,Norwegian Institute of Marine Research | And 2 more authors.
Journal of Fish Diseases | Year: 2013

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 143 500 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. © 2013 Blackwell Publishing Ltd.


Thorstad E.B.,Norwegian Institute for Nature Research | Todd C.D.,University of St. Andrews | Uglem I.,Norwegian Institute for Nature Research | Bjorn P.A.,Norwegian Institute of Marine Research | And 6 more authors.
Marine Biology | Year: 2016

An understanding of when and where sea trout Salmo trutta L. are located at sea is essential to the effective management of local populations and in evaluating their vulnerability to salmon lice and other anthropogenic threats. Here we review the available literature on sea trout life-history strategies, behaviour and habitat use in the marine environment, including feeding, growth, survival and homing. There is considerable variation in life-history strategies among individuals and populations and in the timing and duration of marine migration(s). Females tend to adopt the anadromous strategy more than do males. Smolts typically leave rivers in spring (March–June in European rivers), but also at other times of the year. Post-smolts may remain at sea during the summer and return to freshwater to over-winter; adults thereafter spend summers at sea and winters in freshwater, or they can remain at sea until they later return to freshwater for spawning. Sea trout frequently are recorded at sea during winter and can tolerate full-salinity sea water at water temperatures as low as 1–2 °C. Sea trout often remain within 80 km of their river of origin, but also may undertake longer-distance marine migrations (>500 km). The duration and timing of marine migration both are likely governed by trade-offs between mortality risk and growth potential in different habitats, and the most beneficial strategy may vary among individuals and populations. Reduced marine growth and increased marine mortality will reduce the benefit of marine migrations and may result in selection against anadromy. © 2016, Springer-Verlag Berlin Heidelberg.


Passos F.D.,University of Campinas | Correa P.V.F.,University of Campinas | Todt C.,Radgivende Biologer AS | Todt C.,University of Bergen
Marine Biodiversity | Year: 2016

Falcidens australocaudatus sp. nov. is described from the southeastern Brazilian coast, based on characters of external anatomy, including size, shape, and ornamentation of the sclerites, and on the structure of the radula. It bears a tail characteristically distinct from the trunk, a U-shaped oral shield, and the sclerites of the trunk and shank are slender, without an obvious separation between a blade and base; it differs from all other tailed species of Falcidens, which have sclerites that are flared at the base. Externally, it is very similar to F. caudatus, recorded from the northeastern coast of the USA; the sclerites of this species are illustrated here and are characterized as being larger, slightly flared, and with a different ornamentation as compared to those of the new Brazilian species. Based on the examination of a large collection, the new species can be characterized as very abundant at the southeastern Brazilian coast, with a wide bathymetric distribution, but mainly occurring in the upper continental slope. © 2016 Senckenberg Gesellschaft für Naturforschung and Springer-Verlag Berlin Heidelberg


Plotkin A.,University of Bergen | Morrow C.,National University of Ireland | Gerasimova E.,Radgivende Biologer AS | Rapp H.T.,University of Bergen
Journal of the Marine Biological Association of the United Kingdom | Year: 2016

All polymastiid sponges displaying ornamented exotyles are reviewed and their morphological affinities are reconsidered. The study embraces all known species of Proteleia, Sphaerotylus, Trachyteleia and Tylexocladus as well as several species of Polymastia. A new genus, Koltunia, is established for the Antarctic species Proteleia burtoni based on the unique shape of distal ornamentations of its giant exotyles and on the absence of a spicule palisade in its cortex, a rare feature among the polymastiids. Three new species of Sphaerotylus are described – S. renoufi from the British Isles, S. strobilis from South Africa and S. tjalfei from West Greenland. Transfer of one New Zealand species from Polymastia to Proteleia and of one Chilean species from Polymastia to Sphaerotylus is proposed. The present study provides a background for future integrative phylogenetic analyses based on comprehensive molecular and morphological datasets which should reveal the natural relationships between the polymastiid taxa. Copyright © Marine Biological Association of the United Kingdom 2016


Finstad A.G.,Norwegian Institute for Nature Research | Einum S.,Norwegian Institute for Nature Research | Einum S.,Norwegian University of Science and Technology | Saettem L.M.,County Governor in More og Romsdal | Hellen B.A.,Radgivende Biologer AS
Canadian Journal of Fisheries and Aquatic Sciences | Year: 2010

The spatial distribution of breeders within populations may have important implications for offspring habitat availability in species where mobility of early life stages is restricted. Here we address this issue using time series of spawner distributions from eight Norwegian Atlantic salmon (Salmo salar) populations. Whereas spawners distribute themselves uniformly along the length of the rivers in some populations, others show a heavily skewed distribution. Linear mixed models identified pronounced and temporally consistent among-population differences in spawner distributions. Using a model of limited juvenile dispersal from nests following emergence, we show that the observed spawner distributions are predicted to result in significant proportions of rivers being inaccessible for young of the year during early life stages, and the magnitude of this effect differs among populations (e.g., ranging from 27% to 59% for dispersal distance of 250 m). Thus, assuming population regulation during early but not later juvenile stages, consistent differences in spawner istributions among populations such as those observed here may translate into differences in productivity (i.e., carrying capacity) as well as egg densities required for populations to reach their spawning targets.

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