Stressors

MARCIS

Project info

Marine spatial planning and cumulative impacts of blue growth on seabirds

Project period: 2021-2025

MARCIS is a collaborative research project where research institutes, together with industry and management authorities, will contribute to ecosystem-based management of marine spatial use and provide a decision-support tool for balancing interests and conflicts in planning processes.

Funding: The Research Council of Norway

Project leader: Tone Kristin Reiertsen (NINA)

Project partners:

Norwegian institute for nature research (NINA)

Environmental Research Institute – University of the Highlands and Islands (ERI-UHI)

Equinor

The UK Centre for Ecology & Hydrology

Total Energies

Aker Offshore Wind

RWE renewables Sweden

Norwegian Offshore Wind

Norwegian Polar Institute

Stakeholders: 

BirdLife Norway

Norwegian Fishermen's Association

Norwegian Oil and Gas Association

SalMar

Directorate of Fisheries 

Rogaland County Municipality

Norwegian Coastal Administration

Norwegian Environment Agency

Institute of Marine Research

Norwegian University of Science and Technology (NTNU)

Stressors

Human activities are increasingly exerting pressure on marine areas, and the need for knowledge that will help to reduce conflicts between these activities and natural processes, as well as to create sustainable solutions and protect marine biodiversity is great. 

To help close this knowledge gap, the MARCIS project will focus on different types of human activity (stressors) in marine areas, and study how they affect seabird populations. 

To date, the overall effect of different stressors on seabirds is deficient and can vary by species and region. MARCIS will focus mainly on stressors in offshore areas, and their combined effects on seabirds. For example, the transition from fossil fuels to renewable energy extraction increases the need for the development of offshore wind farms. Petroleum activity, fishing and ship traffic, along with the development of offshore aquaculture, are also important stressors. 

Finally, climate and ecosystem change can also affect seabird populations, both on their own, and in combination with each of the other stressors. Below is an overview of the various stressors that the MARCIS project will focus on, including background information on their effect on seabirds.

Offshore windfarms



Offshore windfarms

Climate change is considered one of the top threats to seabird survival (Dias et al. 2019). Paradoxically, while the development of the offshore wind industry plays a key role in reducing greenhouse gas emissions, offshore wind farms also represent a potentially novel stressor in the marine environment, and one of the major concerns for this growing industry is the risk of collisions between birds and wind turbines (Largey et al. 2021, May et al. 2015, Perveen et al. 2014). Although other bird groups also frequent the marine environment during migratory crossings, seabirds are at particular risk due to their almost obligate marine lifestyle.  

In addition to the risk of collision, seabirds might also be indirectly affected by offshore wind turbines. For example, seabirds may avoid them altogether, leading to potential displacement from important feeding areas. Conversely, some seabird species may actively seek out offshore wind farms because of increased food availability due to reduced local fishing pressure, and organic growth on turbine bases. Turbine bases may also be used as resting areas for gulls, cormorants and shags, thus further increasing collision risk (Dierschke et al. 2016, Drewitt & Langston 2006, Furness et al. 2013, Peschko et al. 2021). There is therefore pressing need to further understand the impact of offshore wind turbines on seabirds, as well as study their behaviour in response to wind farms to gain a better knowledge of the collision risk for different bird groups. 

The placement of offshore wind farms is vital when trying to avoid conflicts and reduce the number of bird collisions. However, the knowledge needed to inform optimal placement of wind farms is presently lacking. Behavioural responses to turbine proximity have a large influence on collision risk, as well as on energy expenditure due to displacement. More knowledge is also needed to quantify possible impacts from offshore wind farms on bird migration routes. By obtaining data and information on bird behaviour at different distances from wind farms, and at micro, meso and macro levels, more optimal wind farm placement can be made possible. 


References and further reading 

  • Dias, M.P., Martin, R., Pearmain, E.J., Burfield, I.J., Small, C., Phillips, R.A., Yates, O., Lascelles, B., Borboroglu, P.G. & Croxall, J.P. 2019. Threats to seabirds: a global assessment. Biological Conservation 237: 525-537. 
  • Dierschke, V., Furness, R.W. & Garthe, S. 2016. Seabirds and offshore wind farms in European waters: Avoidance and attraction. Biological Conservation 202: 59-68. 
  • Drewitt, A.L. & Langston, R.H. 2006. Assessing the impacts of wind farms on birds. Ibis 148: 29-42. 
  • Eaton, M., Aebischer, N., Brown, A., Hearn, R., Lock, L., Musgrove, A., Noble, D., Stroud, D. & Gregory, R. 2015. Birds of Conservation Concern 4: the population status of birds in the UK, Channel Islands and Isle of Man. British Birds 108(12): 708-746. 
  • Furness, R.W., Wade, H.M. & Masden, E.A. 2013. Assessing vulnerability of marine bird populations to offshore wind farms. Journal of environmental management 119: 56-66. 
  • Largey, N., Cook, A.S., Thaxter, C.B., McCluskie, A., Stokke, B.G., Wilson, B. & Masden, E.A. 2021. Methods to quantify avian airspace use in relation to wind energy development. Ibis 163(3): 747-764. 
  • Martin, G.R. 2011. Understanding bird collisions with man‐made objects: a sensory ecology approach. Ibis 153(2): 239-254. 
  • May, R., Reitan, O., Bevanger, K., Lorentsen, S.-H. & Nygård, T. 2015. Mitigating wind-turbine induced avian mortality: sensory, aerodynamic and cognitive constraints and options. Renewable and Sustainable Energy Reviews 42: 170-181. 
  • May, R., Nygård, T., Falkdalen, U., Åström, J., Hamre, Ø. & Stokke, B.G. 2020. Paint it black: Efficacy of increased wind turbine rotor blade visibility to reduce avian fatalities. Ecology and evolution 10(16): 8927-8935. 
  • Perveen, R., Kishor, N. & Mohanty, S.R. 2014. Off-shore wind farm development: Present status and challenges. Renewable and Sustainable Energy Reviews 29: 780-792. 
  • Peschko, V., Mendel, B., Mercker, M., Dierschke, J. & Garthe, S. 2021. Northern gannets (Morus bassanus) are strongly affected by operating offshore wind farms during the breeding season. Journal of Environmental Management 279: 111509. 

Petroleum activity



Petroleum activity

Petroleum activity can have various effects on seabirds, with acute oil spills from oil platforms being the most serious. Other negative effects can occur in the event of subsequent minor leaks from production areas, discharge of other chemicals used in production, or risk of collision with platforms (Christensen-Dalsgaard et al. 2008). Light pollution is a stressor that has received more attention in recent times, but we still have relatively little knowledge about its effects. For example, birds can be attracted by light from oil rigs or burning gas flames, which can lead to collision risk. Scavenging seabirds can also graze on waste from platforms, which can be contaminated by toxic chemicals or oil. 

The most serious way in which petroleum activity can affect seabirds is through oil spills on the surface of the water. Seabirds are very vulnerable to oil spills as they spend much of their time at sea. Even small amounts of oil in their plumage can have major and fatal consequences, as it is able to stick feathers together so that they lose their insulating ability. Furthermore, birds risk poisoning by getting oil in their digestive systems when they try to remove it from their plumage. The extent of the consequences of an oil spill depends on when and where a discharge occurs, as the density and species composition of seabirds varies by region and the time of year (Anker-Nilssen 1987). Diving species such as alcids, cormorants and marine diving ducks are considered the most vulnerable (Anker-Nilssen 1994). 

Studies from the North Atlantic have shown that large numbers of seabirds die annually as a result of oil pollution (Camphuysen 1989, Wiese 2002, Wiese & Ryan 2003). Both pelagic and coastal seabirds may be exposed to oil spills (Anker-Nilssen et al. 1988, Velando et al. 2005) depending on whether the oil spill occurs on the open sea or whether winds and currents direct the oil in towards the coast. There are several examples of accidental oil spills, both from offshore petroleum activities or from oil tankers, which have had serious consequences for seabirds (e.g. Castege et al. 2007, Munilla et al. 2011), and even small amounts of oil can have dire consequences for large numbers of seabirds (Anker-Nilssen et al. 1988, ICES 2005). Consequences are dependent on where and when in the year the oil spill occurs. For example, small amounts of oil in areas with high seabird densities have been shown to lead to high mortalities, while large oil spills in areas with low seabird densities can have less prominent effects (Goethe 1968, Camphuysen 1989, Burger 1993, Camphuysen 1998, ICES 2005). One example where a small oil spill was shown to have a large effect is the spill caused by the Greek oil tanker Stylis in the Skagerak in December 1980. The spill consisted of only 600 tonnes of ballast-water mixed with oil, but caused one of the greatest recorded numbers of seabird deaths (45 000; Anker-Nilssen & Røstad 1981). This can be attributed to the fact that the spill occurred in an area with a particularly high density of overwintering seabirds. 

One of the challenges in measuring the effects of oil spills on seabirds has been to estimate effects on populations through survival and juvenile production. However, Steven Votier and colleagues (2004) showed a doubling of the mortality of adult breeding birds on the island of Skomer in the UK after years of major oil spills from shipwrecks, but did not observe population changes. They explained this with increased recruitment of young birds due to reduced competition for nesting sites, which probably led to a compensation in the population as a result of the loss of the adult established nesting birds. These are effects that can hide the significance of high mortality in seabirds, and which show the importance of measuring the effects on demographic parameters such as annual variation in survival, and juvenile production. The challenge usually lies in not knowing which population the affected birds belong to. However, modelling the effects of drastic population reductions has shown that potential reductions as a result of oil spills, for example, can also have serious consequences at the population level (Reiertsen et al. 2019). Systad et al. (2018) recommend the use of time series data on demography and population trends (SEAPOP), together with distribution data from GLS studies (SEATRACK) in environmental risk analyses for the petroleum sector. In MARCIS, we will build on this knowledge; using the long time series data obtained through SEAPOP and SEATRACK, we will be able to provide a better knowledge basis to estimate population vulnerability in different regions and at different times of the year. 

References and further reading

  • Anker-Nilssen, T. 1987. Metoder til konsekvensanalyser olje/sjøfugl. - Viltrapport 44, 114s 
  • Anker-Nilssen, T., Jones, P. & Røstad, O.W. 1988. Age, sex and origins of Auks (Alcidae) killed in the Skagerrak oiling incident of January 1981. Seabird 11: 28–46.  
  • Anker-Nilssen, T. 1994. Identifikasjon og prioritering av miljøressurser ved akutte oljeutslipp langs norskekysten og på Svalbard. - NINA Oppdragsmelding 310, 18 s. 
  • Burger, A.E. 1993. Estimating the mortality of seabirds following oil spills: effects of spill volume. Marine Pollution Bulletin 26: 140–143. 
  • Camphuysen, C.J. 1989. Beached Bird Surveys in the Netherlands 1915–1988; Seabird Mortal[1]ity in the southern North Sea since the early days of Oil Pollution. Techn. Rapport Vo[1]gelbescherming 1, Werkgroep Noordzee, Amsterdam, 322 s. 
  • Camphuysen, C.J. 1998. Beached bird surveys indicate decline in chronic oil pollution in the North Sea. Marine Pollution Bulletin 36: 519–526. 
  • Castege, I., Lalanne, Y., Gouriou, V., Hemery, G., Girin, M., D’Amico, F., Mouchès, C., D’Elbee, J., Soulier, L., Pensu, J., Lafitte, D. & Pautrizel, F. 2007. Estimating actual seabirds mortality at sea and relationship with oil spills: lesson from the “Prestige” oilspill in Aquitaine (France). Arde[1]ola 54(2): 289–307. 
  • Christensen-Dalsgaard, S., Bustnes, J.O., Follestad, A., Systad, G.H., Eriksen, J.M., Lorentsen, S.-H. & Anker-Nilssen, T. 2008. Tverrsektoriell vurdering av konsekvenser for sjøfugl. Grun[1]nlagsrapport til en helhetlig forvaltningsplan for Norskehavet. NINA Rapport 338, 161 s 
  • Goethe, F. 1969. The effects of oil pollution on populations of marine and coastal birds. Hel[1]goländer Meeresuntersuchungen 17: 370–374. 
  • ICES. 2005. Report of the Working Group on Seabird Ecology (WGSE), 29 March – 1 April 2005, Texel, The Netherlands. ICES CM 2005/G:07, 49 s. 
  • Munilla, I., Arcos, J.M., Oro, D., Alvarez, D., Leyenda, P.M. & Velando, A. 2011. Mass mortality of seabirds in the aftermath of the Prestige oil spill. Ecosphere 2(7): 1–14. 
  • Reiertsen, T.K., Erikstad, K.E., Johansen, M.K., Sandvik, H., Anker-Nilssen, T., Barrett, R., Christensen-Dalsgaard, S., Lorentsen, S-H., Strøm, H. & Systad, G. 2019. Effects of acute pop[1]ulation declines in seabirds related to the Lofoten, Vesterålen and the Barents Sea. NINA Report 1547. Norwegian Institute for Nature Research. 
  • Systad, G.H.R., Bjørgesæter, A., Brude, O.W. & Skeie, G.M. 2018. Standardisering og tilrettelegging av sjøfugldata til bruk i konsekvens- og miljørisikoberegninger. NINA Rapport 1509. 
  • Velando, A., Alvarez, D., Mourino, J., Arcos, F. & Barros, A. 2005. Population trends and repro[1]ductive success of European Shag following the Prestige Oil spill in the Iberian Peninsula. Jour[1]nal of Ornithology 146: 116–120.  
  • Votier, S.C., Birkhead, T.R., Oro, D., Trinder, M., Grantham, M.J., Clark, J.A., McCleery, R.H., Hatchwell, B.J., Recruitment and survival of immature seabirds in relation to oil-spills and climate variability. Journal of Animal Ecology 2008, 77, 974–983 
  • Wiese, F.K. 2002. Seabirds and Atlantic Canada’s Ship-Source Oil Pollution. World Wildlife Fund Canada, Toronto, Canada.  
  • Wiese, F.K. & Ryan, P.C. 2003. The extent of chronic marine oil pollution in southeastern Newfoundland waters assessed through beached bird surveys 1984–1999. Marine Pollution Bulletin 46: 1090–1101 

Fisheries



Fisheries

Norway controls some of the richest fishing grounds in the world, and fisheries have always been a central component of Norwegian business and industry. Today Norway, is one of the world's largest exporters of fish and seafood (Johansen et al. 2019) and in 2020 the landing value of fish from the Norwegian commercial fisheries was ~22 billion NOK (https://www.fiskeridir.no/). The economic value of fisheries is estimated to increase in the years leading up to 2050, and overall catch volumes are estimated to either remain stable or be somewhat greater (Olafsen et al. 2012). It is thus crucial to take the implications of fishery into account in marine spatial planning.

Fisheries can lead to multiple pressures on marine biota, with the primary mortality being through incidental bycatch in fishing gear (Anderson et al. 2011, Zydelis et al. 2013) and change in availability of food through competition for resources (Gremillet et al. 2018)  . Fisheries can, however, also have a positive impact on seabirds by making food available to scavenging seabirds through fishing gear making fish available at the surface and from discards and offal from fishing vessels (Furness 2003). 

Incidental bycatch in fisheries is a worldwide conservation threat to many seabird species (Dias et al. 2019). Globally, an estimated range of 160,000–320,000 seabirds are killed annually as bycatch in longline fisheries (Anderson et al. 2011) and an estimated 400,000 seabirds are taken annually as bycatch in gillnet fishery, of which almost 200 000 were taken in the eastern North Atlantic (Zydelis et al. 2013). Incidental bycatch of seabirds in fishing gear has been reported in several fisheries in the North Atlantic region (Zydelis et al. 2009, Fangel et al. 2015, Bærum et al. 2019, Christensen-Dalsgaard et al. 2019, Dunn and Steel, 2001; Merkel, 2011;). Bycatch occur when seabirds and fishing activity occurs in the same area, for instance when the seabirds and the fish are targeting high concentrations of the same prey. In addition, opportunistic seabirds might be attracted to fishing vessels, increasing the risk of bycatch. What seabird species that are affected by different fishery types depends on the foraging behaviour of the birds. Gillnets are known to catch an array of species with the most susceptible seabird species being those that dive in pursuit of prey (e.g., seaducks, divers, alcids and cormorants) (Christensen-Dalsgaard et al. 2019), with some surface feeding species also being susceptible (Bærum et al. 2019). Longlines on the other hand are mainly a risk to surface feeding species such as gulls, fulmars   and gannets.   

As well as causing direct mortality, fisheries can affect seabirds through competition by changing the availability of food  . 

Seabirds represent top predators in marine ecosystems and are consequently potential competitors with commercial fisheries (Montevecchi et al. 2019). Fisheries are known to transform marine ecosystems and compete with top predators like seabirds (Pauly et al 1998). Competition with fishery has been documented to lead to shortages of prey for seabirds at a large scale (Croxall et al. 2012). Certain seabird species appear far more sensitive to competition with fisheries than others, for instance fish-eating and surface foraging species appear more vulnerable (Sydeman et al. 2021), especially in the Northern Hemisphere. The breeding performance of pelagic-feeding seabirds is shown to be reduced because of persistent depletion of forage fish (Cury et al. 2011).  Throughout the 20th century, many seabird species showed large population increases in the north-east Atlantic (Mitchell et al. 2004). This was likely, in part, explained by growing and changing human fisheries (Montevecchi 2001) through high fishing pressure on large predatory fish leading to increased availability of the smaller fish prey for seabirds (Furness 1982). Towards the end of the last century, harvesting small forage fish at an industrial scale has led to direct competition with foraging seabirds. Since then, regional declines have been observed in many seabird populations, some of which have been related to human fisheries (Anker-Nilssen et al. 1997).  Overexploitation has been suggested as the cause of population crashes of some forage fish species and concomitant declines in seabird populations during the last 50 years (Smith et al 2011). Landings of forage fish are predicted to increase in the future (Sydeman et al. 2017), at the same time as annual food consumption of seabirds decreases (Gremillet et al 2018). The consequences of continued commercial fishing for seabirds are likely severe and, despite declining seabird populations, competition with fishery has remained relatively constant (Grémillet et al. 2018). However, further studies on the impact of fisheries on seabirds, and especially on how much it contributes to changes in demographic rates and population declines are sorely needed.

Finally, fisheries can also have a positive impact on seabirds by making food available to scavenging seabirds that they could not naturally obtain for themselves. This can be either through offal discarded from boats where fish are gutted onboard the boats or making benthic or pelagic fish available at the surface through the fishing activity. In recent decades there has been reductions in offal discards from fishing vessels in Norwegian waters. This reduction in discard rates may have an unfortunate side-effect of forcing scavenging seabirds into finding alternative food sources such as killing of smaller seabirds, with drastic consequences for seabird community structure (Furness 2003).


References and further reading

  • Anderson, O. R. J., C. J. Small, J. P. Croxall, E. K. Dunn, B. J. Sullivan, O. Yates, and A. Black. 2011. Global seabird bycatch in longline fisheries. Endangered Species Research 14:91-106.
  • Anker-Nilssen T, Barrett R, and Krasnov J (1997). Long-and short-term responses of seabirds in the Norwegian and Barents Seas to changes in stocks of prey fish. Forage fishes in marine ecosystems. Alaska sea grant college program report:683-698.
  • Bærum, K. M., T. Anker-Nilssen, S. Christensen-Dalsgaard, K. Fangel, T. Williams, and J. H. Volstad. 2019. Spatial and temporal variations in seabird bycatch: Incidental bycatch in the Norwegian coastal gillnet-fishery. Plos One 14.
  • Christensen-Dalsgaard, S., Anker-Nilssen, T., Crawford, R., Bond, A., Sigurdsson, G.M., Glemarec, G., Hansen, E.S., Kadin, M., Kindt-Larsen, L., Mallory, M., Merkel, F.R., Petersen, A., Provencher, J. and Bærum, K.M. 2019. What's the catch with lumpsuckers? A North Atlantic study of seabird bycatch in lumpsucker gillnet fisheries. Biological Conservation 240.
  • Croxall JP, Butchart SH, Lascelles B, Stattersfield AJ, Sullivan B, Symes A, and Taylor P (2012). Seabird conservation status, threats and priority actions: a global assessment. Bird Conservation International 22:1-34.
  • Cury PM, Boyd IL, Bonhommeau S, Anker-Nilssen T, Crawford RJ, Furness RW, Mills JA, Murphy EJ, Österblom H, and Paleczny M (2011). Global seabird response to forage fish depletion—one-third for the birds. Science 334:1703-1706.
  • Dias, M.P., Martin, R., Pearmain, E.J., Burfield, I.J., Small, C., Yates, O., Phillips, R.A., Lascelles, B., Borboroglu, P.G. and Croxall, J. P. 2019. Threats to seabirds: A global assessment. Biological Conservation 237:525-537.
  • Dunn, E. and Steel, C., 2001. The impact of longline fishing on seabirds in the north-east Atlantic: recommendations for reducing mortality, NOF Rapportserie Report no 5-2001. RSPB, The Norwegian Ornithological Society, Sandy, UK, Trondheim, Norway.
  • Fangel, K., Aas, O., Volstad, J.H., Bærum, K.M., Christensen-Dalsgaard, S., Nedreaas, K., Overvik, M., Wold, L.C. and Anker-Nilssen, T. 2015. Assessing incidental bycatch of seabirds in Norwegian coastal commercial fisheries: Empirical and methodological lessons. Global Ecology and Conservation 4:127-136.
  • Furness, R.W. 2003. Impacts of fisheries on seabird communities. Scientia Marina 67: 33-45
  • Furness R (1982). Competition between fisheries and seabird communities. Adv Mar Biol 20:225-307. 
  • Garthe S, Camphuysen K, and Furness RW (1996). Amounts of discards by commercial fisheries and their significance as food for seabirds in the North Sea. Mar Ecol Prog Ser 136:1-11. 
  • Gjøsæter H, Bogstad B, and Tjelmeland S (2009). Ecosystem effects of the three capelin stock collapses in the Barents Sea. Mar Biol Res 5:40-53. 
  • Grémillet D, Ponchon A, Paleczny M, Palomares M-LD, Karpouzi V, and Pauly D (2018). Persisting worldwide seabird-fishery competition despite seabird community decline. Curr Biol 28:4009-4013. e4002.
  • Johansen, U., Bull-Berg, H., Vik, L.H., Stokka, A.M., Richardsen, R. and Winther, U. 2019. The Norwegian seafood industry – Importance for the national economy. Marine Policy 110: 103561. https://doi.org/10.1016/j.marpol.2019.103561
  • Merkel, F.R. 2011. Gillnet Bycatch of Seabirds in Southwest Greenland, 2003‒2008. Technical Report No. 85. Pinngortitaleriffik, Greenland Institute of Natural Resources.
  • Mitchell PI, Newton SF, Ratcliffe N, and Dunn TE (2004). Seabird populations of Britain and Ireland. T. & AD Poyser, London. 
  • Montevecchi WA (2001). Interactions between fisheries and seabirds. CRC Press. 
  • Montevecchi WA, Gerrow K, Buren AD, Davoren GK, Lewis KP, Montevecchi MW, and Regular PM (2019). Pursuit-diving seabird endures regime shift involving a three-decade decline in forage fish mass and abundance. Mar Ecol Prog Ser 627:171-178.
  • Olafsen, T., Winther, U., Olsen, Y. and Skjermo, J. 2012. Value created from productive oceans in 2050. Report prepared by a working group appointed by the Royal Norwegian Society of Sciences and Letters (DKNVS) and the Norwegian Academy of Technological Sciences (NTVA).
  • Pauly, D., Christensen, V., Dalsgaard, J., Froese, R., and Torres, F., Jr. (1998). Fishing down marine food webs. Science 279, 860–863.
  • Smith AD, Brown CJ, Bulman CM, Fulton EA, Johnson P, Kaplan IC, Lozano-Montes H, Mackinson S, Marzloff M, and Shannon LJ (2011). Impacts of fishing low–trophic level species on marine ecosystems. Science 333:1147-1150. 
  • Sydeman WJ, Thompson SA, Anker-Nilssen T, Arimitsu M, Bennison A, Bertrand S, Boersch-Supan P, Boyd C, Bransome NC, and Crawford RJ (2017). Best practices for assessing forage fish fisheries-seabird resource competition. Fisheries Research 194:209-221. 
  • Sydeman WJ, Schoeman DS, Thompson SA, Hoover BA, García-Reyes M, Daunt F, Agnew P, Anker-Nilssen T, Barbraud C, and Barrett R (2021). Hemispheric asymmetry in ocean change and the productivity of ecosystem sentinels. Science 372:980-983.
  • Zydelis, R., Small, C. and French, G. 2013. The incidental catch of seabirds in gillnet fisheries: A global review. Biological Conservation 162:76-88.
  • Zydelis, R., Wallace, B.P., Gilman, E.L. and Werner, T. B. 2009. Conservation of Marine Megafauna through Minimization of Fisheries Bycatch. Conservation Biology 23:608-616.

Climate change



Climate change

Globally, seabirds are among the most threatened groups of birds, and climate change is considered one of the top threats to their survival (Dias et al. 2019). In the oceans, increasing water temperatures lead to a more stable stratification of the water column, resulting in less nutrients in the surface waters. This can lead to a decrease in productivity and changes in the food web, leading to lower prey availability that can also affect top consumers (Schell, 2000; Hirons et al., 2001; Carroll 2015). Further, the increasing ocean temperatures can lead to changes in the distribution of species, with plankton and fish species from more temperate zones moving polewards. In the Barents Sea and European Arctic, one of the fastest warming areas on earth, we can already observe pronounced changes in the food web, a so-called “borealization” of the Arctic ecosystem.  Adapted to their specific prey, those seabird species that are more widespread are doing better than those that are typical high-Arctic species (Descamps & Strøm 2021) These processes may be helped further by a retraction of sea ice that go along with increasing temperatures in the polar ecosystems (Descamps & Ramírez 2021). 

Temperature is also an important trigger for phenology, i.e. the timing of seasonal activities such as the start of reproduction in animals or plants or the migration of birds. Across the globe, in marine as well as terrestrial species, there is a general trend to earlier timing of reproduction ascribed to global warming (Parmesan & Yohe 2003, Parmesan 2007, Poloczanska et al. 2013). A sufficient adaptation to climate change and variability appears particularly important in polar and subpolar regions, where the time window during which climatic conditions are suitable for reproduction is very short and strongly linked to the seasonal peak in temperature and light (Wiegolaski & Inouye 2013). Yet, species appear to react to the warming trend at different speeds, and within interacting species (e.g. predator−prey relationships), one can find more and more mismatches in timing, especially in high latitudes (Wiegolaski & Inouye 2013). Generally, lower trophic level prey species can advance their reproduction more than their predators and can. This leads to mismatches, for example in the timing of seabird reproduction and the peak of prey availability (e.g. Hipfner 2008, Shultz et al. 2009).  Recent analyses have highlighted the limited ability of birds in general, including seabirds, to adapt their phenology sufficiently to track the effects of climate change (Keogan et al. 2018; Radchuk et al. 2019). At closer detail,  it has been shown that advanced reproduction due to earlier spring onsets can be linked  to seabird’s foraging behaviour, with surface feeding species showing responses towards earlier reproduction, while diving seabird species showed a stable phenological response (Descamps et al. 2019).

Rising temperatures also lead to rising sea levels – both through thermic expansion and more water in the oceans. This can be regionally problematic for seabird colonies located on low-lying islands (Reynolds et al. 2015). However, the effects of climate change on seabirds are complex and not limited to effects of temperatures alone. Wind patterns are changing globally due to climate change, with the belts of westerly winds located in the boreal zones moving polewards, which can affect commuting costs for seabirds (Weimerskirch et al. 2012), but also impact migration costs for terrestrial migratory species (Nourani et al. 2017).

Climate change also leads to an acidification of the oceans due to dissolved CO2, which can affect food webs further. Many marine organisms have calcareous shells or skeletons, and these are disadvantaged under rising CO2 levels, leading to changes in marine communities and food webs (Kroeker et al. 2013; Riebesell et al. 2018). The pelagic swimming sea snail Limacina helicina, is among those species known to suffer from ocean acidification (Lischka et al. 2011).  These snails have a high fat content, and Black-legged kittiwakes rely on them as a food source during winter (Karnovsky et al 2008). As a result, kittiwake adult survival is reduced in winters with low amounts of pelagic sea snails in the Labrador Sea/Grand Banks area (Reiertsen et al. 2014). Ocean acidification may therefore indirectly affect seabirds through their diet.

Climate change further increases the risks for extreme weather events, such as heat waves and storms. While changes in the food web, and thus food availability and flight costs might lead to more indirect / subleathal effects, e.g. affecting breeding success, extreme weather events such as winter storms have the potential to kill adult birds (Reiertsen et al. 2021; Clairbaux et al. 2021). Due to seabirds being long-lived, their population trends are more sensitive to changes in adult survival compared to changes in chick production, and such impacts on adult survival will have much more severe impacts on population numbers than effects on breeding success. However, subsequent years with breeding failure can contribute and amplify population declines. Studies of which conditions affect seabirds outside of their breeding grounds are therefore important, in addition to causal studies within the breeding season.

References and further reading

  • Carroll, M.J., Butler, A., Owen, E., Ewing, S.R., Cole, T., Green, J.A., Soanes, L.M., Arnould, J.P.Y., Newton, S.F., Baer, J., Daunt, F., Wanless, S., Newell, M.A., Robertson, G.S., Mavor, R.A. & Bolton, M. (2015) Effects of sea temperature and stratification changes on seabird breeding success. Climate Research, 66, 75-89.  
  • Clairbaux, M., Mathewson, P., Porter, W., Fort, J., Strøm, H., Moe, B., Fauchald, P., Descamps, S., Helgason, H., Bråthen, V.S., Merkel, B., Anker-Nilssen, T., Bringsvor, I.S., Chastel, O., Christensen-Dalsgaard, S., Danielsen, J., Daunt, F., Dehnhard, N., Erikstad, K.E., Ezhov, A., Gavrilo, M., Krasnov, Y., Langset, M., Lorentsen, S.-H., Newell, M., Olsen, B., Reiertsen, T.K., Systad, G., Thórarinsson, T.L., Baran, M., Diamond, T., Fayet, A.L., Fitzsimmons, M.G., Frederiksen, M., Gilchrist, H.G., Guilford, T., Huffeldt, N.P., Jessopp, M., Johansen, K.L., Kouwenberg, A.L., Linnebjerg, J.F., Major, H.L., McFarlane Tranquilla, L., Mallory, M., Merkel, F.R., Montevecchi, W., Mosbech, A., Petersen, A. & Grémillet, D. (2021) North Atlantic winter cyclones starve seabirds. Current Biology 31: R1040-R1042  
  • Descamps S, Ramírez F, Benjaminsen S, Anker.Nilssen, T, Barrett, RT., Burr, Z., Christensen Dalsgaard, S., Erikstad, KE., Irons, DB., Lorentsen, S-H., Mallory, ML., Robertson. GJ., Reiertsen, TK., Strøm, H., Varpe, Ø., Lavergne, S. (2019) Diverging phenological responses of Arctic seabirds to an earlier spring. Global Change Biology 25:4081–4091. https://doi.org/10.1111/gcb.14780
  • Descamps, S. & Ramírez, F. (2021) Species and spatial variation in the effects of sea ice on Arctic seabird populations. Diversity and Distributions, 27, 2204– 2217. 
  • Descamps, S. & Strøm, H. (2021) As the Arctic becomes boreal: ongoing shifts in a high-Arctic seabird community. Ecology, 102, e03485. 
  • Dias, M.P., Martin, R., Pearmain, E.J., Burfield, I.J., Small, C., Phillips, R.A., Yates, O., Lascelles, B., Borboroglu, P.G. & Croxall, J.P. 2019. Threats to seabirds: a global assessment. Biological Conservation 237: 525-537. 
  • Hipfner, J.M. (2008) Matches and mismatches: ocean climate, prey phenology and breeding success in a zooplanktivorous seabird. Marine Ecology Progress Series, 368, 295-304. 
  • Hirons, A.C., Schell, D.M. & Finney, B.P. (2001) Temporal records of delta C-13 and delta N-15 in North Pacific pinnipeds: inferences regarding environmental change and diet. Oecologia, 129, 591-601.  
  • Karnovsky NJ, Hobson KA, Iverson S, Hunt GL Jr (2008) Seasonal changes in diets of seabirds in the North Water Polynya: a multiple-indicator approach. Marine Ecology Progress Series 357: 291−299
  • Keogan, K., Daunt, F., Wanless, S., Phillips, R.A., Walling, C.A., Agnew, P., Ainley, D.G., Anker-Nilssen, T., Ballard, G., Barrett, R.T., Barton, K.J., Bech, C., Becker, P., Berglund, P.-A., Bollache, L., Bond, A.L., Bouwhuis, S., Bradley, R.W., Burr, Z.M., Camphuysen, K., Catry, P., Chiaradia, A., Christensen-Dalsgaard, S., Cuthbert, R., Dehnhard, N., Descamps, S., Diamond, T., Divoky, G., Drummond, H., Dugger, K.M., Dunn, M.J., Emmerson, L., Erikstad, K.E., Fort, J., Fraser, W., Genovart, M., Gilg, O., González-Solís, J., Granadeiro, J.P., Grémillet, D., Hansen, J., Hanssen, S.A., Harris, M., Hedd, A., Hinke, J., Igual, J.M., Jahncke, J., Jones, I., Kappes, P.J., Lang, J., Langset, M., Lescroël, A., Lorentsen, S.-H., Lyver, P.O.B., Mallory, M., Moe, B., Montevecchi, W.A., Monticelli, D., Mostello, C., Newell, M., Nicholson, L., Nisbet, I., Olsson, O., Oro, D., Pattison, V., Poisbleau, M., Pyk, T., Quintana, F., Ramos, J.A., Ramos, R., Reiertsen, T.K., Rodríguez, C., Ryan, P., Sanz-Aguilar, A., Schmidt, N.M., Shannon, P., Sittler, B., Southwell, C., Surman, C., Svagelj, W.S., Trivelpiece, W., Warzybok, P., Watanuki, Y., Weimerskirch, H., Wilson, P.R., Wood, A.G., Phillimore, A.B. & Lewis, S. (2018) Global phenological insensitivity to shifting ocean temperatures among seabirds. Nature Climate Change 8, 313. 
  • Kroeker, K., Micheli, F. & Gambi, M. Ocean acidification causes ecosystem shifts via altered competitive interactions. Nature Climate Change 3, 156–159 (2013). 
  • Lischka S, Buedenbender J, Boxhammer T, Riebesell U (2011) Impact of ocean acidification and elevated temperatures on early juveniles of the polar shelled pteropod Limacina helicina:mortality, shell degradation, and shell growth. Biogeosci Discuss 7: 8177−8214
  • Reynolds, M.H., Courtot, K.N., Berkowitz, P., Storlazzi, C.D., Moore J. & Flint, E. (2015) Will the Effects of Sea-Level Rise Create Ecological Traps for Pacific Island Seabirds? PLOS ONE 10: e0136773. 
  • Riebesell, U., Aberle-Malzahn, N., Achterberg, E.P., Algueró-Muñiz, M., Alvarez-Fernandez, S. Arístegui, J., Bach, L.T., Boersma, M., Boxhammer, T., Guan, W., Haunost, M., Horn, H.G., Löscher, C.R., Ludwig, A., Spisla, C., Sswat, M., Stange, P. & Taucher, J. (2018) Toxic algal bloom induced by ocean acidification disrupts the pelagic food web. Nature Climate Change 8: 1082–1086  
  • Parmesan, C. (2007) Influences of species, latitudes and methodologies on estimates of phenological response to global warming. Global Change Biology 13: 1860-1872. 
  • Parmesan, C. & Yohe, G. (2003) A globally coherent fingerprint of climate change impacts across natural systems. Nature 421: 37-42. 
  • Poloczanska, E.S., Brown, C.J., Sydeman, W.J., Kiessling, W., Schoeman, D.S., Moore, P.J., Brander, K., Bruno, J.F., Buckley, L.B., Burrows, M.T., Duarte, C.M., Halpern, B.S., Holding, J., Kappel, C.V., O'Connor, M.I., Pandolfi, J.M., Parmesan, C., Schwing, F., Thompson, S.A. & Richardson, A.J. (2013) Global imprint of climate change on marine life. Nature Climate Change 3: 919-925. 
  • Radchuk, V., Reed, T., Teplitsky, C., van de Pol, M., Charmantier, A., Hassall, C., Adamík, P., Adriaensen, F., Ahola, M.P., Arcese, P., Miguel Avilés, J., Balbontin, J., Berg, K.S., Borras, A., Burthe, S., Clobert, J., Dehnhard, N., de Lope, F., Dhondt, A.A., Dingemanse, N.J., Doi, H., Eeva, T., Fickel, J., Filella, I., Fossøy, F., Goodenough, A.E., Hall, S.J.G., Hansson, B., Harris, M., Hasselquist, D., Hickler, T., Joshi, J., Kharouba, H., Martínez, J.G., Mihoub, J.-B., Mills, J.A., Molina-Morales, M., Moksnes, A., Ozgul, A., Parejo, D., Pilard, P., Poisbleau, M., Rousset, F., Rödel, M.-O., Scott, D., Senar, J.C., Stefanescu, C., Stokke, B.G., Kusano, T., Tarka, M., Tarwater, C.E., Thonicke, K., Thorley, J., Wilting, A., Tryjanowski, P., Merilä, J., Sheldon, B.C., Pape Møller, A., Matthysen, E., Janzen, F., Dobson, F.S., Visser, M.E., Beissinger, S.R., Courtiol, A. & Kramer-Schadt, S. (2019) Adaptive responses of animals to climate change are most likely insufficient. Nature Communications 10: 3109. 
  • Reiertsen, T.K., Layton-Matthews, K., Erikstad, K.E., Hodges, K., Ballesteros, M., Anker-Nilssen, T., Barrett, R.T., Benjaminsen, S., Bogdanova, M., Christensen-Dalsgaard, S., Daunt, F., Dehnhard, N., Harris, M.P., Langset, M., Lorentsen, S.H., Newell, M., Bråthen, V.S., Støyle-Bringsvor, I., Systad, G.H. & Wanless, S. (2021) Inter-population synchrony in adult survival and effects of climate and extreme weather in non-breeding areas of Atlantic puffins. Marine Ecology Progress Series 676: 219-231. 
  • Reiertsen, T.K., Erikstad, K.E., Anker-Nilssen, T., Barrett, R.T., Boulinuer, T., Frederiksen, M., Johns, D., Moe, B., Ponchon, A., Skern-Mauritzen, M., Sandvik, H. and Yoccoz, N.G. 2014. Prey density in nonbreeding areas affects adult survival of Black-legged Kittiwakes Rissa tridactyla breeding in the southern Barents Sea. Mar Ecol Prog Series 509: 289–302.doi: 10.3354/meps10825
  • Schell, D.M. (2000) Declining carrying capacity in the Bering Sea: isotopic evidence from whale baleen. Limnology and Oceanography 45: 459-462. 
  • Shultz, M.T., Piatt, J.F., Harding, A.M.A., Kettle, A.B. & van Pelt, T.I. (2009) Timing of breeding and reproductive performance in murres and kittiwakes reflect mismatched seasonal prey dynamics. Marine Ecology Progress Series 393: 247-258. 
  • Weimerskirch, H., Louzao, M., de Grissac, S. & Delord, K. (2012) Changes in wind pattern alter albatross distribution and life-history traits. Science 335: 211-214. 
  • Wiegolaski, F.E. & Inouye, D.W. (2013) Phenology at high latitudes. Phenology: an intregrative environmental science (ed. M.D. Schwartz), pp. 225-247. Springer, Doordrecht, The Netherlands. 

Ship traffic



Commercial and industrial ship traffic

Commercial and industrial ship traffic (hereafter simply referred to as ship traffic) has been identified as one of the anthropogenic stressors that contribute most to the global cumulative impacts on marine ecosystems (Halpern et al. 2015). Ship traffic has increased substantially since the mid-1950s, and the trend seems to have accelerated in the last two decades (Tournadre 2014, Kaplan and Solomon 2016). This phenomenon has occurred at global scale, both near- and offshore, as well as in remote polar areas where the retreating sea-ice is creating opportunities for new shipping routes (Dawson et al. 2018, Gunnarsson 2021). Short- and long-term projections suggest that global ship traffic will keep increasing in the decades to come (Sardain et al. 2019), and it is therefore critical to take this stressor into account in marine spatial planning.

Ship traffic contributes to multiple pressures on the biota in marine ecosystems, such as direct disturbance (Schwemmer et al. 2011), underwater noise (Celi et al. 2016), chemical and light pollution (Merkel and Johansen 2011), marine litter (Grøsvik et al. 2018), and the introduction of alien species (Ware et al. 2016). While certain pressures (e.g., emissions of sulphur- and nitrogen-oxides) have been quantified to some extent (Jonson et al. 2020), other pressures (e.g., the effects of wastewater discharges, the impact of noise on marine organisms, or the direct disturbance caused by moving ships) remain poorly understood (Jägerbrand et al. 2019). There is a paucity of data regarding which of the pressures that are generated by ship traffic specifically apply to seabirds. It has however been documented that for some species such pressures include direct disturbance (Dehnhard et al. 2019, Fliessbach et al. 2019) and strikes due to light-pollution (Merkel and Johansen 2011). Although this not yet been documented, to our knowledge, it is also likely that other pressures such as noise and chemical pollution can have negative effects.

 

References and further reading

  • Celi, M., F. Filiciotto, G. Maricchiolo, L. Genovese, E. M. Quinci, V. Maccarrone, S. Mazzola, M. Vazzana, and G. Buscaino. 2016. Vessel noise pollution as a human threat to fish: assessment of the stress response in gilthead sea bream (Sparus aurata, Linnaeus 1758). Fish Physiology and Biochemistry 42:631-641.
  • Dawson, J., L. Pizzolato, S. E. L. Howell, L. Copland, and M. E. Johnston. 2018. Temporal and Spatial Patterns of Ship Traffic in the Canadian Arctic from 1990 to 2015. Arctic 71:15-26.
  • Dehnhard, N., J. Skei, S. Christensen-Dalsgaard, R. May, D. Halley, T. H. Ringsby, and S.-H. Lorentsen. 2019. Boat disturbance effects on moulting common eiders Somateria mollissima. Marine Biology 167:12.
  • Fliessbach, K. L., K. Borkenhagen, N. Guse, N. Markones, P. Schwemmer, and S. Garthe. 2019. A Ship Traffic Disturbance Vulnerability Index for Northwest European Seabirds as a Tool for Marine Spatial Planning. Frontiers in Marine Science 6.
  • Grøsvik, B. E., T. Prokhorova, E. Eriksen, P. Krivosheya, P. A. Horneland, and D. Prozorkevich. 2018. Assessment of Marine Litter in the Barents Sea, a Part of the Joint Norwegian–Russian Ecosystem Survey.  5.
  • Gunnarsson, B. 2021. Recent ship traffic and developing shipping trends on the Northern Sea Route—Policy implications for future arctic shipping. Marine Policy 124:104369.
  • Halpern, B. S., M. Frazier, J. Potapenko, K. S. Casey, K. Koenig, C. Longo, J. S. Lowndes, R. C. Rockwood, E. R. Selig, K. A. Selkoe, and S. Walbridge. 2015. Spatial and temporal changes in cumulative human impacts on the world’s ocean. Nature Communications 6:7615.
  • Jonson, J. E., M. Gauss, M. Schulz, J. P. Jalkanen, and H. Fagerli. 2020. Effects of global ship emissions on European air pollution levels. Atmos. Chem. Phys. 20:11399-11422.
  • Jägerbrand, A. K., A. Brutemark, J. Barthel Svedén, and I.-M. Gren. 2019. A review on the environmental impacts of shipping on aquatic and nearshore ecosystems. Science of the Total Environment 695:133637.
  • Kaplan, M. B., and S. Solomon. 2016. A coming boom in commercial shipping? The potential for rapid growth of noise from commercial ships by 2030. Marine Policy 73:119-121.
  • Merkel, F. R., and K. L. Johansen. 2011. Light-induced bird strikes on vessels in Southwest Greenland. Marine Pollution Bulletin 62:2330-2336.
  • Sardain, A., E. Sardain, and B. Leung. 2019. Global forecasts of shipping traffic and biological invasions to 2050. Nature Sustainability 2:274-282.
  • Schwemmer, P., B. Mendel, N. Sonntag, V. Dierschke, and S. Garthe. 2011. Effects of ship traffic on seabirds in offshore waters: implications for marine conservation and spatial planning. Ecological Applications 21:1851-1860.
  • Tournadre, J. 2014. Anthropogenic pressure on the open ocean: The growth of ship traffic revealed by altimeter data analysis. Geophysical Research Letters 41:7924-7932.
  • Ware, C., J. Berge, A. Jelmert, S. M. Olsen, L. Pellissier, M. Wisz, D. Kriticos, G. Semenov, S. Kwaśniewski, and I. G. Alsos. 2016. Biological introduction risks from shipping in a warming Arctic. Journal of Applied Ecology 53:340-349.

Offshore aquaculture



Offshore aquaculture

Offshore aquaculture is one of the up-and-coming new blue industries which might overlap with seabird habitats and cause a range of different conflicts related to area-use. Since offshore aquaculture is a comparatively new business concept and very few installations are in place today , the knowledge base with regards to effects on and interactions with seabirds remains scarce. However, some knowledge can be transferred from either other offshore installations or from aquaculture-installations closer to shore. 

Offshore installations in general might attract seabirds as roosting places, for example gulls, shags and cormorants (Dierschke et al. 2016). In addition, offshore aquaculture may be attractive as a food source for seabirds, dependent on the kind of production. Shellfish farms might be visited by feeding sea ducks as is also the case in coastal areas (Varennes et al. 2013; Žydelis et al. 2008), while fish farming facilities could attract seabirds hunting for the fish itself, for the fish food and for wild fish gathering around the facility (Quick et al. 2004; Follestad 2015). All types of offshore facilities have the potential to be attractive as roosting places and even breeding sites (Christensen-Dalsgaard et al. 2019a, 2019b). This can lead to considerable human-wildlife conflicts, especially when seabirds cause damage to farmed (shell-)fish, and may lead to concessions to shoot birds (Bregnballe et al. 2014; BirdLife International 2016). There is also a potential for accidental entanglement in the nets and drowning of seabirds in aquaculture facilities (Varennes et al. 2013). 

Depending on the species, seabirds can have wide foraging ranges of several hundred kilometres, even during the breeding season (e.g. Christensen-Dalsgaard et al. 2018). Thus, activities at offshore aquaculture facilities may come into conflict with seabirds breeding in nearby colonies, because of disturbance, both at the facilities and as a result of increased boat traffic in the area due to maintenance of the facilities, as is also the case for coastal aquaculture installations (Follestad et al. 2015). 

While some species may be attracted to offshore aquaculture, large facilities may form barriers for other species and displace birds from feeding in the area. Similar observations have been made for common guillemots avoiding offshore wind installations (Peschko et al. 2020), and for coastal seabird species avoiding coastal aquaculture installations (Follestad 2015).  Offshore aquaculture facilities might also change the species composition in the food web in the area due to food spills and fertilizing effects (Beveridge 2001), and thus change the food availability for different species of seabirds. 


References and further reading

  • Beveridge, M.C.M. (2001). "Aquaculture and wildlife interactions," in Environmental impact assessment of Mediterranean aquaculture farms, eds. A. Uriarte & B. Basurco.  (Zaragoza: CIHEAM: Cahiers Options Méditerranéennes), 57-66.
  • BirdLife International (2016). Summary of National Hunting Regulations: Norway. http://datazone.birdlife.org/userfiles/file/hunting/HuntingRegulations_Norway.pdf [Accessed December 1, 2021].
  • Bregnballe, T., Hyldgaard, A.M., Clausen, K.K. and Carss, D.N. (2015), What does three years of hunting great cormorants, Phalacrocorax carbo, tell us? Shooting autumn-staging birds as a means of reducing numbers locally. Pest Management Science 71: 173-179.  
  • Christensen-Dalsgaard, S, Dehnhard, N, Moe, B., Systad, G. H.R., Follestad, A. (2019b). Unmanned installations and birds. A desktop study on how to minimize area of conflict. NINA Rapport 1731. Norwegian Institute for Nature Research, Trondheim, Norway.
  • Christensen-Dalsgaard, S., Langset, M., Anker-Nilssen, T. (2019b). Offshore oil rigs - a breeding refuge for Norwegian black-legged kittiwakes Rissa tridactyla? Seabird 32:20-32.
  • Christensen‐Dalsgaard S, May R, Lorentsen SH (2018). Taking a trip to the shelf: Behavioral decisions are mediated by the proximity to foraging habitats in the black‐legged kittiwake. Ecology and Evolution 8: 866-878. 
  • Dierschke V, Furness RW, Garthe S (2016). Seabirds and offshore wind farms in European waters: Avoidance and attraction. Biological Conservation 202: 59-68.
  • Follestad, A. (2015). Effekter av forstyrrelser på fugl og pattedyr fra akvakulturanlegg i sjø - en litteraturstudie. - NINA Rapport 1199. Norwegian Institute for Nature Research, Trondheim, Norway. 
  • Peschko V, Mercker M, Garthe S (2020). Telemetry reveals strong effects of offshore wind farms on behaviour and habitat use of common guillemots (Uria aalge) during the breeding season. Marine Biology 167: 118. 
  • Quick NJ, Middlemas SJ, Armstrong JD (2004). A survey of antipredator controls at marine salmon farms in Scotland. Aquaculture 230: 169-180. 
  • Varennes É, Hanssen SA, Bonardelli J, Guillemette M (2013) Sea duck predation in mussel farms: the best nets for excluding common eiders safely and efficiently. Aquaculture Environment Interactions 4:31-39. 
  • Žydelis R, Esler D, Kirk M, Boyd SW (2009), Effects of off-bottom shellfish aquaculture on winter habitat use by molluscivorous sea ducks. Aquatic Conservation: Marine and Freshwater Ecosystems 19: 34-42.

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