Faroe Marine Research Institute

Tórshavn, Faroe Islands

Faroe Marine Research Institute

Tórshavn, Faroe Islands
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Letessier T.B.,University of St. Andrews | Falkenhaug T.,Norwegian Institute of Marine Research | Debes H.,Faroe Marine Research Institute | Bergstad O.A.,Norwegian Institute of Marine Research | Brierley A.S.,University of St. Andrews
Journal of Plankton Research | Year: 2011

New baseline information is presented on biogeography, abundance and distribution of euphausiids from discrete depth samples collected throughout the water column to 3000 m at 42 locations along the Mid-Atlantic Ridge (MAR) between Iceland and the Azores. Eighteen species were recorded, with Euphausia krohni and Thysanoessa longicaudata being most abundant. Eight species had not been recorded in the area previously. The Subpolar Front is a northern boundary to some southern species, but not a southern boundary to northern ubiquitous species that show submergence. Four major species assemblages were identified and characterized in terms of spatial distribution and species composition. Numerical abundance was highly variable but decreased logarithmically with depth. The greatest average abundance and the greatest spatial variation in abundance occurred in northern waters, over the Reykjanes Ridge. Abundance declined less with depth in the sub-Arctic Intermediate Water/North Atlantic Current Water than in other areas and water masses. The near bottom layer (0200 m from the seabed) had typically low density of euphausiids. The MAR is generally deeper than the usual depth distribution of euphausiids (0300 m), but many species conduct vertical migrations to ridge crest depths. Euphausiid distribution and abundance patterns appeared only weakly affected by the MAR. © 2011 The Author.

Olafsdottir A.H.,Faroe Marine Research Institute | Slotte A.,Norwegian Institute of Marine Research | Jacobsen J.A.,Faroe Marine Research Institute | Oskarsson G.J.,Iceland Marine Research Institute | And 2 more authors.
ICES Journal of Marine Science | Year: 2016

Weight-at-length and length-/weight-at-age were analysed for mature 3- to 8-year-old Northeast Atlantic mackerel (Scomber scombrus; n= 26 084) collected annually in autumn (September and October) at the end of the annual feeding season during 1984-2013 in the northern North Sea. The age range represented 92% of the mackerel stock size (age 3+). During the most recent decade, mackerel length- and weight-at-age continually declined. In 2013, the average mackerel was 3.7 cm shorter and weighed 175 g less than the average individual in 2002. Individual weight-at-length, demonstrating annual summer feeding success, continually declined during the most recent 5 years, whereas somatic growth of cohorts aged 3-8 continually declined for the last 11 of 25 cohorts investigated. Growth of the latest cohort was 34% of the maximum cohort growth recorded. Both weight-at-length and cohort growth were negatively affected by mackerel stock size and Norwegian spring-spawning herring (Clupea harengus) stock size (weight-at-length: r2 = 0.89; growth (length): r2 = 0.68; growth (weight): r2 = 0.78), while temperature was not significant. Conspecific density-dependence was most likely mediated via intensified competition associated with greater mackerel density. Negative effects of herring were likely mediated by exploitative competition for shared food resources rather than direct competition due to limited spatio-temporal overlap between mackerel and herring during the feeding season. Herring begin their seasonal feeding migration at least a month before mackerel; therefore, herring consumption influences prey availability for the later-arriving mackerel. Record low mackerel growth and negative effects of mackerel and herring stock size suggest that the carrying capacity of the Norwegian Sea and adjacent areas for plankton-feeding fish stocks have been reached. However, compounding effects of a less productive Norwegian Sea during the 30-year period cannot be excluded. © 2015 International Council for the Exploration of the Sea.

Hansen B.,Faroe Marine Research Institute | Hatun H.,Faroe Marine Research Institute | Kristiansen R.,Faroe Marine Research Institute | Olsen S.M.,Danish Meteorological Institute | Osterhus S.,University of Bergen
Ocean Science | Year: 2010

The flow of Atlantic water across the Greenland-Scotland Ridge (Atlantic inflow) is critical for conditions in the Nordic Seas and Arctic Ocean by importing heat and salt. Here, we present a decade-long series of measurements from the Iceland-Faroe inflow branch (IF-inflow), which carries almost half the total Atlantic inflow. The observations show no significant trend in volume transport of Atlantic water, but temperature and salinity increased during the observational period. On shorter time scales, the observations show considerable variations but no statistically significant seasonal variation is observed and even weekly averaged transport values were consistently uni-directional from the Atlantic into the Nordic Seas. Combining transport time-series with sea level height from satellite altimetry and wind stress reveals that the force driving the IF-inflow across the topographic barrier of the Ridge is mainly generated by a pressure gradient that is due to a continuously maintained low sea level in the Southern Nordic Seas. This implies that the relative stability of the IF-inflow derives from the processes that lower the sea level by generating outflow from the Nordic Seas, especially the thermohaline processes that generate overflow. The IF-inflow is an important component of the system coupling the Arctic region to the North Atlantic through the thermohaline circulation, which has been predicted to weaken in the 21st century. Our observations show no indication of weakening. © Author(s) 2010.

Jansen T.,Technical University of Denmark | Campbell A.,Marine Institute of Ireland | Kelly C.,Marine Institute of Ireland | Hatun H.,Faroe Marine Research Institute | And 2 more authors.
PLoS ONE | Year: 2012

It has been suggested that observed spatial variation in mackerel fisheries, extending over several hundreds of kilometers, is reflective of climate-driven changes in mackerel migration patterns. Previous studies have been unable to clearly demonstrate this link. In this paper we demonstrate correlation between temperature and mackerel migration/distribution as proxied by mackerel catch data from both scientific bottom trawl surveys and commercial fisheries. We show that mackerel aggregate and migrate distances of up to 500 km along the continental shelf edge from mid-November to early March. The path of this migration coincides with the location of the relatively warm shelf edge current and, as a consequence of this affinity, mackerel are guided towards the main spawning area in the south. Using a simulated time series of temperature of the shelf edge current we show that variations in the timing of the migration are significantly correlated to temperature fluctuations within the current. The proposed proxies for mackerel distribution were found to be significantly correlated. However, the correlations were weak and only significant during periods without substantial legislative or technical developments. Substantial caution should therefore be exercised when using such data as proxies for mackerel distribution. Our results include a new temperature record for the shelf edge current obtained by embedding the available hydrographic observations within a statistical model needed to understand the migration through large parts of the life of adult mackerel and for the management of this major international fishery. © 2012 Jansen et al.

Eigaard O.R.,Technical University of Denmark | Rihan D.,Bord Iascaigh Mhara | Graham N.,Marine Institute of Ireland | Sala A.,National Research Council Italy | Zachariassen K.,Faroe Marine Research Institute
Fisheries Research | Year: 2011

Based on information from an international inventory of gears currently deployed by trawlers in five European countries, the relationship between vessel engine power and trawl size is quantified for different trawl types, trawling techniques and target species. Using multiplicative modelling it is estimated that the fishing circle (or circumference) of trawls targeting shoaling species such as mackerel (Scomber scombrus) and herring (Clupea harengus) increases approximately 44.1. m with each 100. hp increase, whereas the increase for trawls targeting demersal species such as Nephrops (Nephrops norvegicus) and monkfish (Lophius piscatorius) is only approximately 9.4. m per 100. hp. Trawling technique also affects the relationship between vessel horsepower and fishing circle in that trawls used for pair trawling have a significantly (P< 0.001) lower rate of fishing circle increase with hp of a factor 0.56 of that of both twin and single trawls. Underlying these results is the definition of four geometrically different trawl typologies and corresponding target species, driven by the assumption that fishing mortality for a trawl gear is governed by its geometry and proportional to its size, as understood by existing knowledge of the interactions between trawl gear and target species. The modelling results have implications for the reliability of kilowatt days as descriptor of effective effort and point to the need of including metrics relating to the size and geometry of gear deployed in routine monitoring of fishing effort. © 2011 Elsevier B.V.

Kristiansen I.,Faroe Marine Research Institute | Gaard E.,Faroe Marine Research Institute | Hatun H.,Faroe Marine Research Institute | Jonasdottir S.,Technical University of Denmark | Ferreira A.S.A.,Technical University of Denmark
ICES Journal of Marine Science | Year: 2016

The southwestern Norwegian Sea is characterized by an inflow of warm and saline Atlantic water from the southwest and cold and less saline East Icelandic Water (EIW), of Arctic origin, from the northwest. These two water masses meet and form the Iceland-Faroe Front (IFF). In this region, the copepod Calanus finmarchicus plays a key role in the pelagic ecosystem. Time-series of C. finmarchicus and Calanus hyperboreus in May and September, extending back to the early 1990s, were studied in relation to phytoplankton bloom dynamics and hydrography. The main reproductive period of C. finmarchicus started consistently earlier south of the IFF, resulting in different life cycles and stage compositions in the two water masses. In 2003, a sudden shift occurred north of the IFF, resulting in a similar phenology pattern to south of the IFF. Before this, only one generation of C. finmarchicus was produced in the Arctic water, but the earlier reproduction enabled the species to produce two generations after 2003. Simultaneously, C. hyperboreus, an expatriate in the EIW, largely disappeared. Food availability is unlikely the reason for the phenological differences observed across the front, as the typical pattern of the phytoplankton spring bloom showed an earlier onset north of the IFF. Temperature and salinity peaked at record high values in 2003 and 2004, and therefore possible links to oceanography are discussed. The dominant role of Calanus spp. and the potential linkages to water mass exchanges may herald strong effects on the ecosystem and pelagic fish in this subpolar Atlantic region under expected climate change. © International Council for the Exploration of the Sea 2015. All rights reserved.

Larsen K.M.H.,Faroe Marine Research Institute | Htn H.,Faroe Marine Research Institute | Hansen B.,Faroe Marine Research Institute | Kristiansen R.,Faroe Marine Research Institute
ICES Journal of Marine Science | Year: 2012

The inflow of Atlantic water (AW) across the GreenlandScotland Ridge and into the Nordic Seas controls both physical and biological conditions in the northeastern Atlantic through its transport of heat, salt, and other properties. The two main branches of this flow pass through the IcelandFaroe Gap and the FaroeShetland Channel, respectively. Regular monitoring along four standard sections crossing these flows provides time-series of the AW temperature and salinity variability since the late 1980s. The analysis of these series presented shows a persistent increasing trend in both temperature and salinity, modulated by smaller subdecadal oscillations. Using SUPPL.ementary data sources, the previously established link between the large-scale circulation in the North Atlantic and Atlantic inflow properties is supported. Salinity is also impacted by large changes in the Bay of Biscay source waters, and upstream airsea heat fluxes modulate temperature. Relationships between changes in transport and associated residence time, and the modifying strength of the airsea interaction and mixing, are also discussed. © 2012 International Council for the Exploration of the Sea.

Steingrund P.,Faroe Marine Research Institute | Ofstad L.H.,Faroe Marine Research Institute
ICES Journal of Marine Science | Year: 2010

The natural production of cod on the Faroe Plateau depends on the spatial overlap between cod and their prey. However, cod tend to be distributed shallower than the bulk of their prey fish, such as Norway pout and blue whiting. We used commercial and survey catch per unit effort (cpue) data to investigate the distribution of cod in the deep water (150-400 m) on the Faroe Plateau. Cod often move to deep water when they are 4 or 5 years old. The extent of this habitat shift was positively correlated with the total biomass of 3- or 4-year-old cod on the Faroe Plateau, whereas prey densities in the shallow and deep areas, respectively, seemed to have much less influence. Hence, year classes that were a year older than strong year classes were distributed deeper than normal, and vice versa. The cpue in deep water for all ages pooled was strongly correlated with the age 3-6 biomass of cod on the entire Faroe Plateau. These findings are discussed in relation to food utilization and management. © 2009 International Council for the Exploration of the Sea.

Homrum E.I.,Faroe Marine Research Institute | Hansen B.,Faroe Marine Research Institute | Steingrund P.,Faroe Marine Research Institute | Hatun H.,Faroe Marine Research Institute
Marine Biology Research | Year: 2012

Saithe (Pollachius virens) in Faroese waters is a stock that is very important for the Faroese economy. Previous studies have provided information on juvenile saithe, but only sporadic information on the general biology of adult saithe is available in the published literature. Here, we present the basic biology of Faroe saithe based on data from Faroese groundfish surveys. Spawning appears presently to occur earlier in the year than in the early twentieth century, and the main spawning seems to occur on the eastern part of the Faroe Plateau. There is a gradual movement of saithe into deeper water with increasing size, which may well reflect a shift in diet with age. Together with changes associated with maturation, this may explain the change observed in the growth pattern around the age of 4 years. The diet of adult Faroe saithe is dominated by young blue whiting in August, whereas Norway pout, sandeel and blue whiting are equally important in March, but the stomach fullness is substantially higher in summer. © 2012 Copyright Taylor and Francis Group, LLC.

Gaard E.,Faroe Marine Research Institute | Nori G.A.,Faroe Marine Research Institute | Simonsen K.,University of the Faroe Islands
Journal of Plankton Research | Year: 2011

Primary production in the fjords of the Faroe Islands is usually high. Results of productivity measurements in a typical Faroese fjord (Kaldbaksfjord) in 2006 and 2007 reveal values of about 335 g C m-2 year -1, which is two to three times higher than reported from neighboring regions, such as Icelandic, west Norwegian and west Scottish fjords. The causal mechanism is high flushing rate of the euphotic zone and high influx of nutrients, relative to the surface area. On average, the majority of the production is based on new production. The productive season is from late March to early April until October. It is controlled by irradiance and occurs when the critical depth extends below the halocline. The system is highly dynamic and the plankton productivity is largely influenced by short-term fluctuations in horizontal flow and vertical mixing, influencing vertical as well as temporal variability in P/B ratio and f-ratio. Fast repetition rate fluorescence profiles revealed that Fv/Fm decreases below 0.5 when the light intensity is above 200 E m-2 s-1 or when the nitrate + ammonium concentrations were below a threshold between 0.8 and 2 M. © 2011 The Author.

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