Characteristics of early Atlantic cod (Gadus morhua L.) catches based on otoliths recovered from archaeological excavations at medieval to early modern sites in northern Norway

We compared stock origin, size- and age-distributions, and length growth rates derived from Atlantic cod otoliths from archaeological excavations at two sites in northern Norway: Vágar in Lofoten (68◦12 N, ad 1156–1285) and the Værbukta site (70◦57 N, ad 1450–1680). For comparison, modern otoliths were sampled during 1993–2001 from areas situated close to Vágar and Værbukta. Length-at-age from pre-20th century samples was back-calculated from otolith growth increments. The pre-20th century cod from Vágar was dominated by northeast Arctic cod (NEAC) of age 9–16 years and were much older and larger than the pre-20th century cod from Værbukta, which were dominated by coastal cod of age 2–6 years. Cod from Vágar had smaller increments and a shorter back-calculated length-at-age than modern cod from Lofoten. In contrast, the predominantly coastal cod from Værbukta had similar increments width and length-at-age as in modern samples. Age-distributions and mortality rates of the pre-20th century Vágar cod and NEAC from Lofoten in the 1930s were similar, indicating that both age at maturity and longevity were similar for these time periods. This contrasts with truncated and young age-distributions of spawning NEAC in the 1980s and 1990s following the strong increase in fishing and total mortality rate in the period 1955–2000

Growth rates and age distributions of capelin (Mallotus villosus) larvae in the Barents Sea investigated by otolith increment analysis

In order to investigate age distributions and growth rates, otoliths from capelin larvae collected from the Barents Sea during the summers 2001-2003 were analysed using otolith microstructure analysis. Stations were selected to represent areas with different water masses and temperature regimes. One hundred forty larvae from two stations in 2001 and 2002 and three stations in 2003 were analysed. Water temperature in the upper 50 m differed by up to 1.5o C between stations within years. Before the otolith increment analysis, the otoliths were coded and analysed together with otoliths from larvae of known age from bag rearing experiments. The average change in body length was 0.33 mm per increment. Except for 2002, there were no differences between stations within years with respect to increment number distributions and body length distributions. Average increment width differed between years. The larvae collected in 2002 had on average far fewer increments (average 14) than those collected in 2003 (average 24) at the same time of year. The average change in body length per increment (0.33 mm) corresponds to bag-reared larvae that deposit about one zone per day in the otoliths. This suggests that otolith increment analysis of capelin larvae may provide valuable information about age distributions and growth rates in capelin larvae. The implications of the results for assessment of factors affecting mortality rates and drift patterns of capelin larvae will be discussed

Growth rates and age distributions of capelin (Mallotus villosus) larvae in the Barents Sea investigated by otolith increment analysis

In order to investigate age distributions and growth rates, otoliths from capelin larvae collected from the Barents Sea during the summers 2001-2003 were analysed using otolith microstructure analysis. Stations were selected to represent areas with different water masses and temperature regimes. One hundred forty larvae from two stations in 2001 and 2002 and three stations in 2003 were analysed. Water temperature in the upper 50 m differed by up to 1.5o C between stations within years. Before the otolith increment analysis, the otoliths were coded and analysed together with otoliths from larvae of known age from bag rearing experiments. The average change in body length was 0.33 mm per increment. Except for 2002, there were no differences between stations within years with respect to increment number distributions and body length distributions. Average increment width differed between years. The larvae collected in 2002 had on average far fewer increments (average 14) than those collected in 2003 (average 24) at the same time of year. The average change in body length per increment (0.33 mm) corresponds to bag-reared larvae that deposit about one zone per day in the otoliths. This suggests that otolith increment analysis of capelin larvae may provide valuable information about age distributions and growth rates in capelin larvae. The implications of the results for assessment of factors affecting mortality rates and drift patterns of capelin larvae will be discussed

Modelling the spatial shifts of functional groups in the Barents Sea using a climate-driven spatial food web model

We built a dynamic, spatial food web model for the Barents Sea, developed with Ecospace by including species’ habitat requirements and ecological interactions. The model was used to test the spatial shifts of different functional groups due to warming. We compared model-predicted and field-surveyed biomass of functional groups (FGs) spatial distributions in relatively cold and warm years. The Ecospace model included habitat foraging capacities for environmental parameters such as water temperature and bottom depth for 74 FGs out of a total of 108 FGs. We created two plausible scenarios, one representing a relatively cold year (2004) and another representing a warm year (2013) with differences of ca. 0.3 °C in bottom temperature, 0.6 °C in surface temperature, and 7% less ice coverage between them. Comparison of centre of gravity, inertia, and spatial overlap of the modelled and surveyed spatial distributions in warm and cold years showed that the model represented the past distributions of the functional groups satisfactorily. We observed poleward shifts of 41 and 68 km for the modelled and observed distributions, respectively, in the average centre of gravity position for the 35 FGs with lowest sampling uncertainty. The model predicted that the whole community had shifted distribution towards the northeast at an average rate of 4.4 km year−1 and 67 km °C-1 between 2004 and 2013. We conclude that our Ecospace model represents past observed species distributions in the Barents Sea satisfactorily, and may predict the direction and magnitude of temperature-driven changes in spatial distributions. This ability may be useful for predicting the impact of climate changes on species and FG distributions in future scenarios.publishedVersio

Future trajectories of change for an Arctic deep-sea ecosystem connected to coastal kelp forests

Environmental stressors related to climate change and other anthropogenic activities are impacting Arctic marine ecosystems at exceptional rates. Within this context, predicting future scenarios of deep-sea ecosystems and their consequences linked with the fate of coastal areas is a growing need and challenge. We used an existing food-web model developed to represent the outer basin of the Malangen fjord, a northern Norwegian deep-sea ecosystem, to assess the potential effects of plausible future trajectories of change for major drivers in the area, including links to coastal kelp forests. We considered four major drivers (kelp particulate organic matter [POM] production entering the deep sea, fishing effort, king crab invasion, and ocean warming) to project 12 future scenarios using the temporal dynamic module of Ecopath with Ecosim approach. Overall, we found that the impact of warming on the deep-sea ecosystem structure and functioning, as well as on ecosystem services, are predicted to be greater than changes in kelp forest dynamics and their POM production entering the deep sea and the king crab invasion. Yet, the cumulative impacts are predicted to be more important than noncumulative since some stressors acted synergistically. These results illustrate the vulnerability of sub-Arctic and Arctic marine ecosystems to climate change and consequently call for conservation, restoration, and adaptation measures in deep-sea and adjacent ecosystems. Results also highlight the importance of considering additional stressors affecting deep-sea communities to predict cumulative impacts in an ecosystem-based management and global change context and the interlinkages between coastal and deep-sea environments.acceptedVersio

Ulv og utmarksressurser: Økonomiske konsekvenser av ulv på inntekter fra småviltjakt

Sentralisert forvaltning av store rovdyr fører ofte til konflikter med lokale interesser og bruk av skogslandskapet. Jakt og jakthunder er viktige både økonomisk og kulturelt. Tilstedeværelse av ulv kan føre til at jegere med hund velger å jakte i andre områder, dersom de frykter at jakthunden kan bli tatt av ulv. Vi undersøkte om rettighetshaveres inntekter fra småviltjakt indirekte reduseres av tilstedeværelse av ulv. Vi kontaktet rettighetshavere for tilgang på data på inntekter fra småviltjakt i årene 1990 til 2009 i Hedmark og Oppland fylker, i områder med og uten ulv. Rettighetshaverne fikk i gjennomsnitt halverte inntekter fra småviltjakt de årene hvor ulven var tilstede. Vi fant også at mellomårsvariasjonen i jaktinntekter økte jo nærmere man kom et ulverevir. Ulike kompensasjons-ordninger har blitt benyttet for å dekke økonomiske tap som rettighetshavere har på grunn av ulv. Det er likevel viktig å merke seg at selv om rettighetshaverne kan bli økonomisk kompensert for de tapene de har, vil påvirkningen ulv har på lokalbefolkningen og jegernes frykt for å miste jakthunden fortsatt være kontroversiell.English: Centralized management of large carnivore populations in rural and remote landscapes used by local people often leads to conflicts between the objectives of wildlife conservation and rural development. We tested the hypotheses that the presence of wolves indirectly reduces landowner revenues from traditional small game hunting, and that landowner revenues are more variable closer to wolf territories. The assumed mechanism is that hunters fear that their economically and culturally valuable hunting dogs may be killed by wolves, which results in reduced hunting and thus reduced revenues for landowners where and when wolves occur. To determine the effect of wolf presence on revenues from sport hunting, we obtained data from 1990 to 2009 on income from small game management areas, in Hedmark and Oppland Counties in Norway, as well as the spatial and temporal variations in wolf presence. Small game management areas experienced higher sport hunting revenue in years when wolves were absent compared to when they were present. When testing for the effect of distance between small game management areas and wolf territories, inter-annual variation in revenue decreased with increasing distance from wolf territories. Thus, wolf presence may reduce landowners’ revenues from small game hunting, and cause higher economic variability in rural communities. It is important to note that while the economic impacts of wolves may be compensated where governments have the will and the economic resources, the impacts on the lifestyles of rural people (e.g. hunter’s fear of losing prized dogs to wolves) will remain controversial.Glommen Skog SA, finansiert av Høgskolen i Hedmark, Høgskolen i Innlandet, Skogtiltaksfondet, Forskningsrådet för miljö, areella näringar och samhällsbyggande (FORMAS

Vegetation Type and Demography of Low Density Willow Ptarmigan Populations

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Community structure of deep fjord and shelf benthic fauna receiving different detrital kelp inputs in northern Norway

Kelp forests produce large amounts of macroalgal detritus, ranging from whole plants to small particles (1 mm). The role of this kelp detritus in fueling deep-sea communities adjacent to healthy kelp forests was investigated in a region in the north of Norway by comparing the community structure and biodiversity of meio-, macro-, and megafauna in two deep (450 m) areas with different expected input of kelp detritus: a deep fjord basin surrounded by kelp forests and the adjacent continental shelf 15 km offshore from the kelp forests. The results showed that, although the fjord received a significantly higher amount of large kelp detritus (i.e. blades) than the shelf area, the amount of small kelp detritus available on the sediment was similar in both areas. There were significant differences in the multidimensional scaling analyses on the community structure for meio-, macro-, and megafauna between the fjord and the shelf. Significant differences were also found in biomass, abundance and biodiversity indices for some groups. However, no clear pattern emerged in the community structure and biodiversity between the fjord and the shelf, and the observed differences could not be linked directly to kelp detritus availability. The similar amounts of small particles of kelp detritus in the fjord and shelf area suggest that kelp detritus can provide organic matter to ecosystems further away than initially hypothesized, thus potentially shaping the structure and functioning of deep benthic communities distant from the kelp forests. Yet, the direct (trophic) links of kelp detritus and the studied benthic fauna need to be further analysed. The results are discussed in relation to current global changes in kelp forest, including regime shifts from healthy kelp reefs to turfs or barren areas, which reduce drastically the amount of macroalgal detritus produced and exported.publishedVersio

Overexploitation, Recovery, and Warming of the Barents Sea Ecosystem During 1950–2013

The Barents Sea (BS) is a high-latitude shelf ecosystem with important fisheries, high and historically variable harvesting pressure, and ongoing high variability in climatic conditions. To quantify carbon flow pathways and assess if changes in harvesting intensity and climate variability have affected the BS ecosystem, we modeled the ecosystem for the period 1950–2013 using a highly trophically resolved mass-balanced food web model (Ecopath with Ecosim). Ecosim models were fitted to time series of biomasses and catches, and were forced by environmental variables and fisheries mortality. The effects on ecosystem dynamics by the drivers fishing mortality, primary production proxies related to open-water area and capelin-larvae mortality proxy, were evaluated. During the period 1970–1990, the ecosystem was in a phase of overexploitation with low top-predators’ biomasses and some trophic cascade effects and increases in prey stocks. Despite heavy exploitation of some groups, the basic ecosystem structure seems to have been preserved. After 1990, when the harvesting pressure was relaxed, most exploited boreal groups recovered with increased biomass, well-captured by the fitted Ecosim model. These biomass increases were likely driven by an increase in primary production resulting from warming and a decrease in ice-coverage. During the warm period that started about 1995, some unexploited Arctic groups decreased whereas krill and jellyfish groups increased. Only the latter trend was successfully predicted by the Ecosim model. The krill flow pathway was identified as especially important as it supplied both medium and high trophic level compartments, and this pathway became even more important after ca. 2000. The modeling results revealed complex interplay between fishery and variability of lower trophic level groups that differs between the boreal and arctic functional groups and has importance for ecosystem management